inorganic syntheses volume 35the ﬁrst chemistry monograph that i ever bought was inorganic...

INORGANIC SYNTHESES

Volume 35

.......

Board of Directors

THOMAS B. RAUCHFUSS, president University of Illinois at Urbana-Champaign

DIMITRI COUCOUVANIS University of Michigan

MARCETTAY. DARENSBOURG Texas A&M University

JOHN R. SHAPLEY University of Illinois at Urbana-Champaign

Secretary to the Corporation

STANTON CHING Connecticut College

Future Volumes

36 GREGORY S. GIROLAMI and ALFRED P. SATTELBERGER University of Illinois

at Urbana-Champaign and Argonne National Laboratory

37 PHILIP P. POWER University of California at Davis

International Associates

MARTIN A. BENNETT Australian National University

FAUSTO CALDERAZZO University of Pisa

M. L. H. GREEN Oxford University

JACK LEWIS Cambridge University

RENE POILBLANC University of Toulouse

HERBERT W. ROESKY University of Gottingen

WARREN R. ROPER University of Auckland

F. G. A. STONE Baylor University

JAN REEDIJK Leiden University

H. VAHRENKAMP University of Freiburg

AKIO YAMAMOTO Tokyo Institute of Technology

Editor-in-Chief

THOMAS B. RAUCHFUSS

University of Illinois at Urbana-Champaign

.................................................................

INORGANIC

SYNTHESES

Volume 35

Copyright � 2010 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada

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Library of Congress Catalog Number: 39:23015

ISBN 978-0471-68255-4

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

PREFACE

This volume presents procedures to compounds that illustrate the scope of modern

inorganic and organometallic synthesis. Following the tradition of Inorganic

Syntheses, emphasis has been placed on useful compounds and methods. Reflect-

ing my own interests, transition metal derivatives are featured.

The largest chapter concerns NacNac complexes. Such complexes represent

versatile platforms for a variety of transformations. The NacNac ligands have

many desirable features, not the least of which is the scope of their substituted

derivatives. The set of procedures was organized by three leaders in this area,

Professors Daniel J. Mindiola, Patrick L. Holland, and Timothy H. Warren. In

addition to their own contributions, they recruited other colleagues so that the

chapter consists of procedures for NacNac complexes of all metals from scandium

to zinc.

The remaining sections of the book reflect several areas of contemporary

activity. Routes are described to a selection of platinummetal reagents that straddle

the inorganic and organometallic domains, including some complexes that are of

interest in the area of solar energy research. A chapter highlights important

complexes from the area of bioorganometallic chemistry. We present an excellent

selection of electronically and stereochemically unusual ligands that are easily

prepared and adaptable to many metals, for example, the NHCs, bispidines, and

Kl€aui’s metalloligand. There is little question that metal-organic frameworks

(MOFs)will emerge as an important area of research and possibly applications.We

are fortunate to have detailed procedures for importantmembers of this new family

of molecule-based materials provided by the leading group in this area. As is our

tradition, the volume includes a series of procedures that do not neatly fit into any

category, such as salts of the remarkable radical [B12Me12]� and the hydrophilic

[B12(OH)12]2�. Finally, we include a collection of versatile classical coordination

and organometallic complexes.

Inorganic Syntheses has benefited from outstanding contributions from across

the globe, so I thank these authors and checkers first. Of the many people who

helped produce this volume, I wish to recognized my graduate and undergraduate

students, several ofwhom are listed as checkers.My colleaguesGregGirolami and

Scott Denmark were sources of advice and encouragement in this venture as they

have been throughout my career at Illinois. Finally, I wish to acknowledge the

previous editors of Inorganic Syntheses who have inspired me by their example.

v

The first chemistry monograph that I ever bought was Inorganic Syntheses,

Volume XIII, edited by F. A. Cotton.

I dedicate this volume to the memory of Alan M. Sargeson, a frequent

contributor to Inorganic Syntheses, inspired chemist, and gentleman.

THOMAS B. RAUCHFUSS

University of Illinois at Urbana-Champaign, Urbana, IL

vi Preface

CONTRIBUTORS

Debashis Adhikari, Department of Chemistry and Molecular Structure Center,

Indiana University, Bloomington, IN 47405

Enzo Alessio, Dipartimento di Scienze Chimiche, Universita di Trieste, 34127

Trieste, Italy

NicoleL.Armanasco,ChemistryM313, School ofBiomedical, Biomolecular and

Chemical Sciences, The University of Western Australia, Crawley, WA 6009,

Australia

YosraM.Badiei,Department of Chemistry, GeorgetownUniversity,Washington,

DC 20057-1227

Murray V. Baker, Chemistry M313, School of Biomedical, Biomolecular and


Australia

Alison G. Barnes, Chemistry M313, School of Biomedical, Biomolecular and


Australia

Stefan Bernhard, Department of Chemistry, Princeton University, Princeton, NJ

08544

Soledad Betanzos-Lara, Department of Chemistry, University of Warwick,

Coventry CV4 7AL, UK

Steven M. Bischof, The Scripps Energy Laboratories, The Scripps Research

Institute, Jupiter, FL 33458

Karen J. Blackmore, Department of Chemistry, University of California, Irvine,

CA 92697

Ioannis Bratsos,Dipartimento di Scienze Chimiche, Universita di Trieste, 34127

Trieste, Italy

David H. Brown, Chemistry M313, School of Biomedical, Biomolecular and


Australia

Gloria Sanchez Cabrera, Centro de Investigaciones Quımicas, Universidad

Autonoma del Estado de Hidalgo, Pachuca, Estado de Hidalgo 42184, Mexico

vii

Maria Caporali, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei

CompostiOrganometallici (ICCOM-CNR),50019SestoFiorentino(Firenze), Italy

Chien-Hong Chen, School of Applied Chemistry, Chung Shan Medical Univer-

sity, Taichung, Taiwan

Anthony R. Chianese, Department of Chemistry, Yale University, New Haven,

CT, 06520-8107

Karen P. Chiang, Department of Chemistry, University of Rochester, Rochester,

NY 14627

Young Keun Chung,Department of Chemistry, Seoul National University, Seoul

151-742, Korea

Joshua R. Clayton, Department of Chemistry and Biochemistry, University of

Colorado, Boulder, CO 80309

Eric D. Cline, Department of Chemistry, Princeton University, Princeton, NJ

08544

Peter Comba, Anorganisch-Chemisches Institut, Universitat Heidelberg,

D-69120 Heidelberg, Germany

Timothy R. Cook, Department of Chemistry, Massachusetts Institute of Tech-

nology, Cambridge, MA 02139-4307

Ryan E. Cowley, Department of Chemistry, University of Rochester, Rochester,

NY 14627

Robert H. Crabtree,Department of Chemistry, Yale University, New Haven, CT

06520-8107

Keying Ding, Department of Chemistry, University of Rochester, Rochester, NY

14627

Anders Døssing,Department of Chemistry, University of Copenhagen, DK-2100

Copenhagen Ø, Denmark

Christos Douvris, Department of Chemistry and Biochemistry, University of


Daniel L. DuBois, Chemical and Materials Sciences Division, Pacific Northwest

National Laboratory, Richland, WA 99352

Mary Rakowski DuBois, Chemical and Materials Sciences Division, Pacific

Northwest National Laboratory, Richland, WA 99352

Lisa Dudek, Department of Chemistry and Biochemistry, University of

California, Los Angeles, CA 90095-1569

viii Contributors

ThomasR.Dugan,Department of Chemistry, University ofRochester, Rochester,

NY 14627

Celine Fellay, Institut des Sciences et Ingenierie Chimiques, Ecole Polytechnique

Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

Matthew G. Fete, Department of Chemistry and Biochemistry, University of


Anne Mette Frey, Department of Chemistry, University of Copenhagen, DK-

2100 Copenhagen Ø, Denmark

Benjamin R. Garrett,Department of Chemistry, University of Illinois at Urbana-

Champaign, Urbana, IL 61801

Starla D. Glover, Department of Chemistry and Biochemistry, University of

California at San Diego, San Diego, CA 92093

John C. Goeltz, Department of Chemistry and Biochemistry, University of


Luca Gonsalvi, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei

Composti Organometallici (ICCOM-CNR), 50019 Sesto Fiorentino (Firenze),

Italy

Abraha Habtemariam, Department of Chemistry, University of Warwick, Cov-

entry CV4 7AL, UK

James Hauk, Department of Chemistry and Biochemistry, University of


M. Frederick Hawthorne, International Institute of Nano and Molecular Medi-

cine, University of Missouri, Columbia, MO 65211

Paul G. Hayes, Department of Chemistry and Biochemistry, University of

Lethbridge, Lethbridge, Alberta, Canada T1K 3M4

Valerie J. Hesler, Chemistry M313, School of Biomedical, Biomolecular and


Australia

Alan F. Heyduk, Department of Chemistry, University of California, Irvine, CA

92697

YutakaHitomi,Department ofMolecular Chemistry andBiochemistry, Doshisha

University, Kyotanabe, Kyoto 610-0321, Japan

Patrick L. Holland, Department of Chemistry, University of Rochester,

Rochester, NY 14627

Contributors ix

Maik Jakob,Anorganisch-Chemisches Institut, Universitat Heidelberg, D-69120

Heidelberg, Germany

Satish S. Jalisatgi, International Institute of Nano and Molecular Medicine,

University of Missouri, Columbia, MO 65211

Yuuji Kajita, Department of Molecular Chemistry and Biochemistry, Doshisha

University, Kyotanabe, Kyoto 610-0321, Japan

Marion Kerscher, Anorganisch-Chemisches Institut, Universitat Heidelberg,

D-69120 Heidelberg, Germany

SangBokKim,Department ofChemistry, BrownUniversity, Providence, RI 02912

Benjamin T. King, Department of Chemistry and Biochemistry, University of


Yoshihisa Kishima, Department of Molecular Chemistry and Biochemistry,

Doshisha University, Kyotanabe, Kyoto 610-0321, Japan

Wolfgang Klaui, Lehrstuhl I: Bioanorganische Chemie und Katalyse, Heinrich-

Heine-Universitat Dusseldorf, 40225 Dusseldorf, Germany

Masahito Kodera, Department of Molecular Chemistry and Biochemistry,


Elzbieta Kogut, Department of Chemistry, Georgetown University, Washington,

DC 20057-1227

Clifford P. Kubiak, Department of Chemistry, University of California at San

Diego, San Diego, CA 61801

Peter C. Kunz, Lehrstuhl I: Bioanorganische Chemie und Katalyse, Heinrich-

Heine-Universitat Dusseldorf, 40225 Dusseldorf, Germany

Gabor Laurenczy, Institut des Sciences et Ingenierie Chimiques, Ecole Poly-

technique Federale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

Mark W. Lee, Jr., International Institute of Nano and Molecular Medicine,


Christopher S. Letko,Department of Chemistry, University of Illinois at Urbana-


Chin Hin Leung, Department of Chemistry, Yale University, New Haven, CT

06520-8107

Wen-Feng Liaw, Department of Chemistry, National Tsing Hua University,

Hsinchu 30043, Taiwan

x Contributors

Simon Lotz, Department of Chemistry, University of Pretoria, Pretoria 0002,

South Africa

Leonard A.MacAdams,Department of Chemistry and Biochemistry, University

of Delaware, Newark, DE 19716

Amanda E. Mack, Department of Chemistry, University of Illinois at Urbana-


Neal D.McDaniel,Department of Chemistry, Princeton University, Princeton, NJ

08544

Marie M. Melzer, Department of Chemistry, Georgetown University, Washing-

ton, DC 20057-1227

JosefMichl,Department of Chemistry and Biochemistry, University of Colorado,

Boulder, CO 80309; Institute of Organic Chemistry and Biochemistry, Academy

of Sciences of the Czech Republic, 16610 Prague 6, Czech Republic

Daniel J. Mindiola, Department of Chemistry and Molecular Structure Center,

Indiana University, Bloomington, IN 47405

Tomoyuki Nakagawa, Department of Molecular Chemistry and Biochemistry,


Andy I. Nguyen, Department of Chemistry, University of California, Irvine, CA

92697

Daniel G. Nocera, Department of Chemistry, Massachusetts Institute of Tech-

nology, Cambridge, MA 02139-4307

Michael R. North, Chemistry M313, School of Biomedical, Biomolecular and


Australia

Yasuhiro Ohki, Department of Chemistry, Graduate School of Science, and

Research center for Materials science, Nagoya University, Nagoya 464-8602,

Japan

Shun Ohta,Department of Chemistry, Graduate School of Science, and Research

center for Materials science, Nagoya University, Nagoya 464-8602, Japan

RoyA.Periana,TheScripps EnergyLaboratories, TheScrippsResearch Institute,

Jupiter, FL 33458

Maurizio Peruzzini, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei


Italy

Contributors xi

Warren E. Piers, Department of Chemistry, University of Calgary, Calgary,

Alberta, Canada T2N 1N4

Robert D. Pike, Department of Chemistry, College of William and Mary,

Williamsburg, VA 23187

Chuleeporn Puttnual,Department of Chemistry and Biochemistry, University of

Delaware, Newark, DE 19716

Udo Radius, Institut fur Anorganische Chemie der Universitat Wurzburg, 97074

Wurzburg, Germany

Thomas B. Rauchfuss, Department of Chemistry, University of Illinois at

Urbana-Champaign, Urbana, IL 61801

Herbert W. Roesky, Institut fur Anorganische Chemie, Universitat Gottingen,

D-37077 Gottingen, Germany

D. Ruckerbauer, Institute of Chemistry, Inorganic Department, Karl-Franzens-

University, 8010 Graz, Austria

Peter J. Sadler,Department of Chemistry, University ofWarwick, Coventry CV4

7AL, UK

Alexander V. Safronov, International Institute of Nano andMolecular Medicine,


Thomas Schaub, BASF SE, 67056 Ludwigshafen, Germany

Bryan D. Stubbert, Department of Chemistry, University of Rochester,

Rochester, NY 14627

Shouheng Sun, Department of Chemistry, Brown University, Providence, RI

02912

DwightA. Sweigart,Department of Chemistry, BrownUniversity, Providence, RI

02912

Yoshimitsu Tachi, Department of Molecular Chemistry and Biochemistry,


Kazuyuki Tatsumi, Department of Chemistry, Graduate School of Science, and

Research Center for Materials Science, Nagoya University, Nagoya 464-8602,

Japan

Thomas S. Teets, Department of Chemistry, Massachusetts Institute of Technol-

ogy, Cambridge, MA 02139-4307

Klaus H. Theopold, Department of Chemistry and Biochemistry, University of

Delaware, Newark, DE 19716

xii Contributors

Leonard L. Tinker, Department of Chemistry, Princeton University, Princeton,

NJ 08544

Ba L. Tran, Department of Chemistry and Molecular Structure Center, Indiana

University, Bloomington, IN 47405

David J. Tranchemontagne, Department of Chemistry and Biochemistry, Uni-

versity of California, Los Angeles, CA 90095-1569

Michal Valasek, Institute of Organic Chemistry and Biochemistry, Academy of

Sciences of the Czech Republic, 16610 Prague 6, Czech Republic

Matthew S. Varonka, Department of Chemistry, Georgetown University,

Washington, DC 20057-1227

Victoria Volkis, Department of Chemistry and Biochemistry, University of


AdelinaM. Voutchkova,Department of Chemistry, Yale University, NewHaven,

CT 06520-8107

Timothy H. Warren, Department of Chemistry, Georgetown University,

Washington, DC 20057-1227

J. W. Wielandt, Institute of Chemistry, Inorganic Department, Karl-Franzens-

University, 8010 Graz, Austria

Stefan Wiese, Department of Chemistry, Georgetown University, Washington,

DC 20057-1227

Omar M. Yaghi, Department of Chemistry and Biochemistry, University of

California, Los Angeles, CA 90095-1569

Fabrizio Zanobini, Consiglio Nazionale delle Ricerche, Istituto di Chimica dei


Italy

IlyaZharov,Department of Chemistry andBiochemistry, University of Colorado,

Boulder, CO 80309

Francisco J. Zuno-Cruz, Centro de Investigaciones Quımicas, Universidad

Autonoma del Estado de Hidalgo, Pachuca, Estado de Hidalgo 42184, Mexico

Contributors xiii

DEDICATION

This volume is dedicated to the memory of four eminent chemists who made

outstanding contributions to inorganic chemistry in general and to Inorganic

Syntheses in particular. We mourn their passing, but we celebrate their

achievements.

ROBERT W. PARRY (EDITOR-IN-CHIEF, VOLUME XII, 1970)

Bob was born on October 1, 1917 in Ogden, UT, and died on December 1, 2006 in

Salt Lake City, UT, at the age of 89, following a stroke. He received his B.S. degree

in soil chemistry fromUtah StateAgricultural College (nowUtah StateUniversity)

(1940), his M.S. degree in soil chemistry from Cornell University (1942), and his

Ph.D. in inorganic coordination chemistry under John C. Bailar, Jr. (Editor-in-

Chief, Inorganic Syntheses, Volume IV, 1953) from the University of Illinois

(1946). He served on the chemistry faculties of the University of Michigan

(1946–1969) and the University of Utah (Distinguished Professor of Chemistry,

1969–1997).

An extraordinary teacher, Bob coauthored the widely used high school text,

Chemistry: Experimental Foundations (1970), was senior author of Prentice-

Hall’s high school chemistry curriculum program (CHEM STUDY), and was

coeditor of Prentice-Hall’s paperback series, Foundations of General Chemistry.

He mentored more than 60 Ph.D. students and postdoctoral fellows. His honors

include first recipient of the ACS Award for Distinguished Service in Inorganic

Chemistry (1965), Manufacturing Chemists Award for Excellence in the Teaching

of College Chemistry (1972), ACS Award in Chemical Education (1977),

Alexander von Humboldt Senior U.S. Scientist Award (1980, 1983), first State

of Utah Governor’sMedal in Science and Technology (1987), honorary doctorates

from the Utah State University (1985) and the University of Utah (1997), and the

ACS’s highest honor, the Priestley Medal (1993).

Bob authored more than 150 publications, not only on the boron hydrides but

also on gallium, phosphines, and the thermodynamics of chelation. Long active in

the ACS, he served as President (1982), member of the Council for more than 45

years and of the Board of Directors (1973–1983), and Associate Editor of the

Journal of the American Chemical Society (1966–1968, 1971–1980), and a

member of its Editorial Board (1969–1980). He was the founding editor of

Inorganic Chemistry (1960–1964) and a member of its Editorial Board

(1962–1979) and President of Inorganic Syntheses, Inc. (1969–1972). One of the

early leaders of the Gordon Research Conferences, hewas a member (1965–1972)

xv

and Chairman (1967–1968) of the GRC Board of Trustees. He was Executive

Secretary, Chairman, and Councilor of the American Association for the Ad-

vancement of Science between 1980 and 1995, and he held offices in the

International Union of Pure and Applied Chemistry between 1965 and 1982.

FRANK ALBERT COTTON (EDITOR-IN-CHIEF, VOLUME XIII, 1973)

Al, one of the twentieth century’smost prolific, creative, and influential inorganic

chemists and chemical educators, was born on April 9, 1930 in Philadelphia, PA,

and died following a violent attack on February 20, 2007 in College Station, TX,

at the age of 76. He received his primary, secondary, and undergraduate education

in Philadelphia, enrolling in the Drexel Institute of Technology, intending to

major in chemical engineering. He switched to chemistry and received his B.S.

degree from Temple University (1951). He began graduate study at Harvard

University, where he joined the research group of future (1973) Nobel chemistry

laureate Geoffrey Wilkinson and worked on ferrocene and other metallocenes.

After receiving his Ph.D. (1955), he became an Instructor at the Massachusetts

Institute of Technology. In 1961, at the age of 3l, he became MIT’s youngest full

Professor.

As one of the small number of chemists credited with initiating the renaissance

of inorganic chemistry that began in the 1950s, Al researched metal carbonyls,

ligand field theory, organometallic compounds, phosphine oxide and sulfide

complexes, metal complexes with high coordination numbers, protein X-ray

crystallography, fluxional organometallic molecules, and application of such

physicochemical techniques as infrared and ultraviolet spectroscopies to transition

metal complexes. His synthesis and characterization of the [Re2Cl8]� (1964)

opened a new field of research in multiple metal-metal bonds, metal clusters, and

extended solids. He proposed the hapto (h) nomenclature to indicate the structures

of p-bonded hydrocarbon ligands.

In 1971, Al became Robert A. Welch Professor of Chemistry and shortly

thereafter W. T. Doherty-Welch Distinguished Professor of Chemistry at Texas

A&M University, where he worked on the synthesis and characterization of

compounds with multiple and/or single metal–metal bonds and other unusual

species. He and his 118 Ph.D. students and more than 150 postdoctoral fellows

from over 30 countries produced more than 1600 publications. He was an ardent

and articulate advocate of ‘‘curiosity-driven’’ basic research.

Al received many awards from American and foreign societies, including the

U.S. National Medal of Science (1982), Robert A. Welch Award (1994), and

Israel’s Wolf Prize (2000). His major ACS honors include the Award in Inorganic

Chemistry (first recipient, 1962), Award for Distinguished Service in the Ad-

vancement of Inorganic Chemistry (1974), Award in Organometallic Chemistry

(2001), F. Albert Cotton Medal for Excellence in Chemical Research (first

recipient, 1995), George C. Pimentel Award in Chemical Education (2005), and

xvi Dedication

the ACS’s highest award, the Priestley Medal (1998). The ACS’s F. Albert Cotton

Award in Synthetic Inorganic Chemistry bears his name. He also received 29

honorary doctorates from universities around the world.

Al was a prominent scientific educator and textbook author. His Advanced

Inorganic Chemistry, coauthoredwith GeoffWilkinson, became a standard text. It

underwent six editions (1962–1999), sold more than half a million copies, and was

translated into 15 foreign languages. From his lecture notes, he wrote Chemical

Applications of Group Theory (1963, 1971, 1990). His Chemistry—An Investiga-

tive Approach (1973, 1976) was intended for high schools, and hisBasic Inorganic

Chemistry (1976, 1987, 1995) was an entry-level text.

FRED BASOLO (EDITOR-IN-CHIEF, VOLUME XVI, 1976)

Fredwas born of Italian immigrant parents on February 11, 1920 in Coello, a small

coal mining town in southern Illinois, and died on February 27, 2007 in Skokie, IL,

at the age of 87. Until he attended school, he spoke the Piedmontese dialect,

understanding but speaking little English. The first Coello resident to attend

college, he earned his B.Ed, degree from Southern Illinois Normal School (now

Southern Illinois University) (1940), intending to teach high school. However, he

pursued graduate studies at the University of Illinois on platinum complexes under

John C. Bailar, Jr. (Editor-in-Chief, Inorganic Syntheses, Volume IV, 1953),

earning his M.S. (1942) and Ph.D. (1943) degrees. After 3 years of war-related

research at Rohm and Haas near Philadelphia, PA, he joined the faculty of

Northwestern University as Instructor. He rose through the ranks, becoming

Charles E. and Emma H. Morrison Professor of Chemistry (1980–1990). He

served as Chairman of the Chemistry Department (1969–1972).

Fred realized that thework on kinetics andmechanisms of substitution reactions

on carbon being investigated by organic chemists could be applied to inorganic

coordination compounds such as those of cobalt(III) and platinum(II). He con-

vinced his colleagueRalphG. Pearson to join him in such studies, and the two soon

became leaders in the field, and their monograph, Mechanisms of Inorganic

Reactions (1958, 1967), became a classic. Their postulation of a SN1CB mecha-

nism for the base hydrolysis of cobalt(III) complexes led to a controversy with

Christopher K. Ingold and Ronald S. Nyholm that was resolved in Basolo and

Pearson’s favor and garnered them and Northwestern University a global

reputation.

Fred maintained an international perspective, spending sabbatical leaves

with Jannik Bjerrum (1954–1955) and Vincenzo Caglioti (1961–1962). He

regarded Italy as a second home and was elected to the Accademia Nazionale

dei Lincei (1987), the world’s oldest scientific society. He coauthored Coordi-

nation Chemistry (1964, 1986) with former student Ronald C. Johnson.

Fred cofounded the Inorganic Gordon Research Conference, which continues

today.

Dedication xvii

In the ACS, Fred was elected Chairman of the Division of Inorganic Chemistry

(1970), a member of its Executive Committee, and President of the society (1983).

He received the following ACS honors—Award in Inorganic Chemistry (1964),

Award for Distinguished Service in the Advancement of Inorganic Chemistry

(1975), George C. Pimentel Award in Chemical Education (1993), and the

Priestley Medal, the society’s highest honor (2001).

ALAN G. MACDIARMID (EDITOR-IN-CHIEF, VOLUME XVII, 1977)

Alan was born onApril 14, 1927 inMasterton, NewZealand, and died on February

7, 2007 in Philadelphia, PA, after falling in his home. His youth was spent in

poverty (his father lost his job because of the Great Depression), and he left high

school at the age of 16 to help support the family. As a part-time student with a low-

paying ‘‘lab boy’’ (janitor) job in the Chemistry Department of Victoria University

College at Wellington, he earned his B.Sc. degree (1947) and then became a

demonstrator and worked as an assistant. His first publication (in Nature, 1949)

dealt with S4N4, a molecule that played a role in his later Nobel-winning research.

After graduating with a M.Sc. degree with first class honors (1951), Alan

received a Fulbright Fellowship that enabled him to study the rate of exchange in14C-tagged metal cyanide complexes at the University of Wisconsin, Madison,

from which he received his M.S. (1952) and Ph.D. (1953) degrees. With a New

Zealand Shell graduate scholarship, he then studied silicon hydrides underHarry J.

Emel�eus at Cambridge University, earning his second Ph.D. degree (1955).

Following short stints at Queen’s College and the University of St. Andrews, he

joined the Department of Chemistry at the University of Pennsylvania, where he

spent the remainder of his career, rising through the ranks and becomingBlanchard

Professor of Chemistry (1988). In 2002, he became James Von Ehr Distinguished

Professor of Science & Technology at the University of Texas, Dallas.

After devoting himself to silicon chemistry for two decades, Alan began a

fruitful collaborationwith his colleagueAlan J.Heeger on the conducting polymer,

(SN)x, the precursor to which he had studied in Wellington. While a Visiting

Professor at Kyoto University, Alan visited the Tokyo Institute of Technology,

where Hideki Shirakawa showed him a silvery film of polyacetylene. Shirakawa

accepted Alan’s invitation to spend a year with him studying this substance. They

discovered that the impurity in polyacetylene served as a dopant and increased its

conductivity. By adding bromine to the (CH)x films, they increased the conduc-

tivity by many millions of times. The two collaborated with Heeger, and in 2000

the trio shared theNobel Prize inChemistry ‘‘for the discovery and development of

conductive polymers.’’ Alan wrote more than 600 articles and held 20 patents. His

honors include the ACS’s Frederic Stanley Kipping Award in Silicon Chemistry

(1971) and Award in the Chemistry ofMaterials (1999); the RutherfordMedal, the

Royal Society of New Zealand’s highest honor (2000); election to the U.S.

NationalAcademyof Sciences (2002) and theOrder ofNewZealand, the country’s

xviii Dedication

highest honor (2002); and the fellowship in the Royal Society (2003). His alma

mater, Victoria University, awarded him an honorary doctorate (1999), created a

chair in physical chemistry in his name (2001), and named an Institute for

Advanced Materials and Nanotechnology after him (2003). Institutes named after

him include those at Jilin University in China (2001) and the University of Texas,

Dallas (2007).

STANLEY KIRSCHNER (EDITOR-IN-CHIEF, VOLUME XXIII, 1985)

Stan was born on December 17, 1927 in Brooklyn, New York and died on July 16,

2008. Stan attended New York City’s renowned Stuyvesant High School. He had

decided on a career in chemistry after his father, a pharmacist, presented himwith a

chemistry set when he was 11 years old.

After graduation Stan enlisted in the U.S. Navy (1944–1945), but then attended

Brooklyn College, from which he received his B.S. degree in 1950. Following a

brief stint with theMonsanto Chemical Company, he attendedHarvard University,

where hewon a departmental award as the best teaching fellow and fromwhich he

received his A.M. degree in 1952. He studied inorganic chemistry at theUniversity

of Illinois under John C. Bailar, Jr. (one of the founders of Inorganic Syntheses and

Editor-in-Chief of Volume 4, 1953). After receiving his Ph.D. in 1954, Stan joined

the faculty of Wayne State University in Detroit, Michigan, where he spent his

entire career, rising through the ranks and retiring as Professor Emeritus in 1992.

Stan was a longtime Secretary of the Editorial Board of Inorganic Syntheses.

His awards and honors include the Wayne State University President’s Award for

Excellence in Teaching (1969), Heyrovsk�y Medal of the Czechoslovak Academy

of Sciences (1978), the ACS Detroit Section’s Distinguished Service Award

(1980), the ChemicalManufacturers Award for Excellence in Chemistry Teaching

(1984), and the ACS Henry Hill Award and Engineering Society of Detroit’s Gold

Award (both in 1995),

Stan’s some one hundred articles dealt with the synthesis, structure, stereo-

chemistry, and biological properties of coordination compounds, including the

anticancer activity of platinum complexes; optical rotatory dispersion; circular

dichroism; the Pfeiffer Effect inmetal complexes; inorganic nomenclature; and the

application of computer techniques to chemical and information problems. A

prominent educator, he edited three books on inorganic and coordination

chemistry.

Because of his ebullient personality, organizational talent, and interest in

foreign languages, Stan held visiting professorships and similar honorary appoint-

ments across the globe. Among his many positions, he held positions at University

College, London (with Ronald S. Nyholm), University of S~ao Paolo in Brazil, theCentrul de Chimie in Timisoara and Institutul de Chimie in Cluj-Napoca in

Romania; the University of Florence, Tohoku University, and both the Technical

University and the University of Porto in Portugal. He held honorary membership

Dedication xix

in the national societies of most of these countries. Stan was an omnipresent

participant at the International Conference on Coordination Chemistry, the longest

running conference dedicated to inorganic chemistry. He attended every meeting

from 1959 to 2002 and serving as Permanent Secretary and Permanent Secretary

Emeritus.

GEORGE B. KAUFFMAN

California State University, Fresno, CA

xx Dedication

NOTICE TO CONTRIBUTORSAND CHECKERS

The Inorganic Syntheses series is published to provide all users of inorganic

substances with detailed and reliable procedures for the preparation of important

and timely compounds. Thus, the series is the concern of the entire scientific

community. The Editorial Board hopes that many chemists will share in the

responsibility of producing Inorganic Syntheses by offering their advice and

assistance in both the formulation and the laboratory evaluation of outstanding

syntheses. Help of this kind will be invaluable in achieving excellence and

pertinence to current scientific interests.

There is no rigid definition of what constitutes a suitable synthesis. The major

criterion by which syntheses are judged is the potential value to the scientific

community. An ideal synthesis is one that presents a new or revised experimental

procedure applicable to a variety of related compounds, at least one of which is

critically important in current research. Syntheses of individual compounds that

are of interest or importance are, however, also acceptable. Syntheses of com-

pounds that are readily available commercially at reasonable prices are ordinarily

not acceptable. Corrections and improvements of syntheses already appearing in

Inorganic Syntheses are suitable for inclusion.

The Editorial Board lists the following criteria of content for submitted

manuscripts. Style should conform with that of previous volumes of Inorganic

Syntheses. The introductory section should include a concise and critical summary

of the available procedures for synthesis of the product in question. It should also

include an estimate of the time required for the synthesis, an indication of the

importance and utility of the product, and an admonition if any potential hazards

are associated with the procedure. The Procedure section should present detailed

and unambiguous laboratory directions and bewritten so that it anticipates possible

mistakes and misunderstandings on the part of the person who attempts to

duplicate the procedure. Unusual equipment or procedure should be clearly

described. Line drawings should be included when they can be helpful. Safety

measures should be stated clearly. Sources of unusual starting materials must be

given, and, if possible, minimal standards of purity of reagents and solvents should

be stated. The scale should be reasonable for normal laboratory operation, and

problems involved in scaling the procedure either up or down should be discussed.

The criteria for judging the purity of the final product should be delineated clearly.

The Properties section should supply and discuss those physical and chemical

characteristics that are relevant to judging the purity of the product and to

xxi

permitting its handling and use in an intelligent manner. Under References,

pertinent literature citations should be listed in order. The style sheet is available

at www.inorgsynth.com.

The Editorial Board determines whether submitted syntheses meet the general

specifications outlined above. Every procedure will be checked in an independent

laboratory, and publication is contingent on satisfactory duplication of the

syntheses. For online access to information and requirements, see www.inorg-

synth.com.

Each manuscript should be submitted to the Secretary of the Editorial Board,

Professor Stanton Ching, [email protected]. The manuscript should be type-

written in English. Nomenclature should be consistent and should follow the

recommendations presented in Nomenclature of Inorganic Chemistry, 2nd ed.,

Butterworths&Co, London, 1970 and inPure and Applied Chemistry,Volume 28,

No. 1 (1971). Abbreviations should conform to those used in publications of the

American Chemical Society, particularly Inorganic Chemistry.

Chemistswilling to check syntheses should contact the editor of a future volume

or make this information known to Professor Ching.

xxii Notice to Contributors and Checkers

TOXIC SUBSTANCES ANDLABORATORY HAZARDS

Chemicals and chemistry are by their very nature hazardous. The obvious hazards

in the syntheses reported in this volume are delineated, where appropriate, in the

experimental procedure. It is impossible, however, to foresee every eventuality,

such as a new biological effect of a common laboratory reagent. As a consequence,

all chemicals used and all reactions described in this volume should be viewed as

potentially hazardous. Care should be taken to avoid inhalation or other physical

contact with reagents and solvents used in this volume. In addition, particular

attention should be paid to avoiding sparks, open flames, or other potential sources

that could set fire to combustible vapors or gases.

The following sources are especially recommended for guidance:

NIOSH Pocket Guide to Chemical Hazards (U.S. by the National Institute for

Occupational Safety and Health) is available free at http://www.cdc.gov/niosh/

npg/ and can be purchased inexpensively in paperback format. It contains

information and data for 677 common compounds and classes of compounds.

Organic Syntheses, which is freely available online (http://www.orgsyn.org/),

has a concise but useful section ‘‘Handling Hazardous Chemicals.’’

Prudent Practices in the Laboratory: Handling and Disposal of Chemicals

(National AcademyPress, 1995, ISBN 0-309-05229-7). This classic book presents

guidelines for laboratory practices. The contents can be read freely online at http://

www.nap.edu/catalog.php?record_id=4911.

Purification of Laboratory Chemicals by D. D. Perrin, W. L. F. Armarego, and

D. R. Perrin (Pergamon, 2009, ISBN978-1-85617-567-8) is the standard reference

for the purification of reagents and solvents. Special attention should be paid to the

purification and storage of ethers.

xxiii

CONTENTS

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Dedication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xv

Notice to Contributors and Checkers . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi

Toxic Substances and Laboratory Hazards. . . . . . . . . . . . . . . . . . . . . . xxiii

Chapter One COMPLEXES OF BULKY

b-DIKETIMINATE LIGANDS 1

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

2. b-Diketiminate Precursors HLMe,Me3 and

TlLMe,Me3 (LMe,Me3 ¼ 2,4-Bis-(Mesitylimido)Pentyl) . . . . . . . . . . . . . 4

A. 2,4-Bis-(Mesitylimido)Pentane (HLMe,Me3) . . . . . . . . . . . . . . . . . . 5

B. Thallium 2,4-Bis-(Mesitylimido)Pentyl (TlLMe,Me3) . . . . . . . . . . . . 6

3. b-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x,

and [LtBu,iPr2K]x (LMe,iPr2¼2,4-Bis-(2,6-

Diisopropylphenylimido)Pentyl; LtBu,iPr2¼2,2,6,6-

Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido)Heptyl) . . . . . . . . . 8

A. 2,4-Bis-(2,6-Diisopropylphenylimido)Pentane

(LMe,iPr2H) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

B. Lithium 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl

([LMe,iPr2Li]x). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

C. Potassium 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-

Diisopropylphenylimido)Heptyl ([LtBu,iPr2K]x). . . . . . . . . . . . . . . 11

4. b-Diketiminate Precursors LtBu,iPr2H and

LtBu,iPr2Li(THF) (LtBu,iPr2¼2,2,6,6-Tetramethyl-3,5-

Bis-(2,6-Diisopropylphenylimido)Heptyl) . . . . . . . . . . . . . . . . . . . . . 13

A. N-Pivaloyl-2,6-Diisopropylanilide (DIPPNHC(O)tBu) . . . . . . . . . 14

B. DIPPN¼C(Cl)tBu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

C. DIPPN¼C(Me)tBu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

D. 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido)

Heptane ([DIPPN¼C(tBu)]2CH2, LtBu,iPrH) . . . . . . . . . . . . . . . . . 17

xxv

E. Lithium 2,2,6,6-Tetramethyl-3,5-Bis-

(2,6-Diisopropylphenylimido)Heptyl

(LtBu,iPr2Li, THF Adduct) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5. Scandium Trichloride Tris(Tetrahydrofuran) and

b-Diketiminate-Supported Scandium Chloride Complexes. . . . . . . . . 20

A. Scandium Trichloride Tris(Tetrahydrofuran), ScCl3(THF)3. . . . . . 20

B. Scandium 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl

Dichloride Tetrahydrofuran, (LMe,iPr2)ScCl2(THF) . . . . . . . . . . . . 21

C. Scandium 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-

Diisopropylphenylimido)Heptyl Dichloride,

(LtBu,iPr2)ScCl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

6. b-Diketiminate-Supported Titanium and Vanadium

Dichloride Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

A. Synthesis of (LMe,iPr2)TiCl2(THF) . . . . . . . . . . . . . . . . . . . . . . . . 25

B. Synthesis of (LtBu,iPr2)TiCl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

C. Synthesis of (LMe,iPr2)VCl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

7. b-Diketiminate-Supported Vanadium and

Chromium Chloride Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

A. Synthesis of LMe,Me2VCl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

B. Synthesis of LMe,Me2CrCl2(THF)2 . . . . . . . . . . . . . . . . . . . . . . . . 32

8. b-Diketiminate-Supported Manganese and Zinc Complexes. . . . . . . . 34

A. LMe,iPr2MnI(THF). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

B. The THF-Free Dimer (LMe,iPr2MnI)2 . . . . . . . . . . . . . . . . . . . . . . 35

C. LMe,iPr2ZnCl2Li(OEt2)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

9. Iron 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl

Chloride (LMe,iPr2FeCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

10. Iron 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-

Diisopropylphenylimido)Heptyl Chloride

(LtBu,iPr2FeCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

11. Cobalt 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido)

Heptyl Chloride (LtBu,iPr2CoCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

12. b-Diketiminate-Supported Nickel(II) and Nickel(I)

Complexes of LMe,Me3 (LMe,Me3¼2,4-Bis-(Mesitylimido)Pentyl) . . . . 45

A. LMe,Me3NiI(2,4-Lutidine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

B. LMe,Me3Ni(2,4-Lutidine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

xxvi Contents

13. Nickel 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl

Chloride Dimer, [LMe,iPr2Ni(m-Cl)]2 . . . . . . . . . . . . . . . . . . . . . . . . . 48

14. Bis[Copper 2,4-Bis-(2,4,6-Trimethylphenylimido)Pentyl]

Toluene, (LMe,Me3Cu)2(m-h2:h2-C7H8) . . . . . . . . . . . . . . . . . . . . . . . 50

A. Copper tert-Butoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

B. Bis[Copper 2,4-Bis-(2,4,6-

Trimethylphenylimido)pentyl] Toluene . . . . . . . . . . . . . . . . . . . . 52

15. Copper 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl

Chloride (LMe,iPr2CuCl) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Chapter Two BORON CLUSTER COMPOUNDS 56

16. Salts of Dodecamethylcarba-closo-Dodecaborate(�)

Anion, CB11Me12�, and the Radical Dodecamethylcarba-

closo-Dodecaboranyl, CB11Me12 . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

A. Cesium 1-Methylcarba-closo-Dodecaborate(�),

Cs[1-Me-CB11H11] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

B. Cesium, Tetramethylammonium, and Lithium

Dodecamethylcarba-closo-Dodecaborates(�),

Cs[CB11Me12], [NMe4][CB11Me12], and Li[CB11Me12] . . . . . . . . 58

C. Dodecamethylcarba-closo-Dodecaboranyl Radical,

CB11Me12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

17. Cesium Dodecahydroxy-closo-Dodecaborate,

Cs2[B12(OH)12] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Chapter Three COORDINATION COMPOUNDS 67

18. Pentaaquanitrosylchromium Sulfate . . . . . . . . . . . . . . . . . . . . . . . . . 67

A. Pentaaquanitrosylchromium Sulfate . . . . . . . . . . . . . . . . . . . . . . 68

19. The Tetradentate Bispidine Ligand Dimethyl-(3,7-Dimethyl-

9-oxo-2,4-bis(2-pyridyl)-3,7-Diazabicyclo[3.3.1]nonane)-1,

5-dicarboxylate and Its Copper(ll) Complex . . . . . . . . . . . . . . . . . . . 70

A. Piperidone (pI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

B. Bispidone 3,7-dimethyl-9-oxo-2,4-bis(2-pyridyl-3,7-

diazabicyclo[3.3.1]nonane-1,5-dicarboxylate

dimethylester (L) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

C. Copper(II) Bispidone Chloride (CuLCl) . . . . . . . . . . . . . . . . . . . 72

Contents xxvii

20. Tris(2-Picolinyl)Methane and Its Copper(I) Complex . . . . . . . . . . . . 74

A. Bis(2-Picolinyl)Methane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

B. Tris(2-Picolinyl)Methane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

C. Copper(I) (Tris(2-Picolinyl)Methane)Acetonitrile

Hexafluorophosphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

Chapter Four CARBENE LIGANDS AND COMPLEXES 78

21. 1,3-Dialkyl-Imidazole-2-Ylidenes . . . . . . . . . . . . . . . . . . . . . . . . . . 78

A. 1,3-DI-n-Propyl-Imidazolium Chloride (nPr2ImHCl)

and 1,3-Diisopropyl-Imidazolium Chloride ( iPr2ImHCl) . . . . . . . 79

B. 1,3-Dimethyl-Imidazolium Iodide (Me2ImHI)

and 1-Methyl-3-Isopropyl-Imidazolium Iodide

(MeiPrImHI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

C. 1,3-DI-n-Propyl-Imidazol-2-Ylidene (nPr2Im)

and 1,3-Diisopropyl-Imidazol-2-Ylidene ( iPr2Im) . . . . . . . . . . . . 80

D. 1,3-Dimethyl-Imidazol-2-Ylidene (Me2Im) and

1-Methyl-3-Isopropyl-Imidazol-2-Ylidene (MeiPrIm). . . . . . . . . . 82

22. A Chelating Rhodium N-Heterocyclic Carbene

Complex by Transmetallation from a Silver–NHC

Intermediate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

A. Methylenebis(N-(t-Butyl)Imidazolium) Bromide . . . . . . . . . . . . . 84

B. {Methylenebis(N-(t-Butyl)Imidazol-2-Ylidene)}

(1,5-Cyclooctadiene)Rhodium(I)

Hexafluorophosphate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

23. Rhodium and Iridium N-Heterocyclic Carbene

Complexes from Imidazolium Carboxylates . . . . . . . . . . . . . . . . . . . 88

A. N,N0-Dimethylimidazolium-2-Carboxylate. . . . . . . . . . . . . . . . . . 88

B. Chloro(1,5-Cyclooctadiene)(1,3-Dimethylimidazolium-

2-Ylidene) Rhodium(I) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

C. (h4-1,5-Cyclooctadiene)(Bis-1,3-Dimethylimidazole-

2-Ylidene)Iridium(I) Hexafluorophosphate. . . . . . . . . . . . . . . . . . 90

Chapter Five FUNCTIONAL LIGANDS AND COMPLEXES 92

24. N-tert-Butyl ortho-Aminophenol, ortho-Iminoquinone, and

a Zirconium(IV) bis(Aminophenolate) Complex . . . . . . . . . . . . . . . . 92

A. 2,4-Di-tert-Butyl-6-(tert-Butylamino)Phenol . . . . . . . . . . . . . . . . . . 93

B. 2,4-Di-tert-Butyl-6-(tert-Butylimino)Quinone . . . . . . . . . . . . . . . 94

C. ZrIV(ap)2(THF)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

xxviii Contents

25. Synthesis of the Water-Soluble Bidentate (P, N) Ligand

PTN(Me) (PTN(Me) ¼ 7-Phospha-3-methyl-1,3,5-

triazabicyclo[3.3.1]nonane) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

A. Dehydration of Tetrakis(Hydroxymethyl)Phosphonium

Chloride, THPC, [P(CH2OH)4]Cl . . . . . . . . . . . . . . . . . . . . . . . . 97

B. Tris(Hydroxymethyl)Phosphine, P(CH2OH)3 . . . . . . . . . . . . . . . . 98

C. Tris(Hydroxymethyl)Methyl Phosphonium Iodide,

[PCH3(CH2OH)3]I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

D. 7-Methyl-1,3,5-Triaza-7-Phosphoniaadamantane Iodide . . . . . . . 100

E. 7-Phospha-3-Methyl-1,3,5-Triazabicyclo[3.3.1]nonane,

PTN(Me) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

26. Synthesis of Metal-Organic Frameworks: MOF-5

and MOF-177 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

A. MOF-5: Zn4O(Terephthalate)3 (Solvothermal) . . . . . . . . . . . . . 103

B. MOF-5: Zn4O(Terephthalate)3 (Room Temperature). . . . . . . . . . 105

C. MOF-177: Zn4O(1,3,5-Benzenetribenzoate)2(Room Temperature) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Chapter Six ORGANOMETALLIC REAGENTS 109

27. Tricarbonyl 1,3,5-Trimethyl-1,3,5-Triazacyclohexane

Complexes of Chromium(0), Molybdenum(0), and Tungsten(0)

[M(CO)3(Me3TACH) (M ¼ Cr, Mo, W)] . . . . . . . . . . . . . . . . . . . . . . 109

A. Tricarbonyl(1,3,5-Trimethyl-1,3,5-Triazacyclohexane)

Chromium(0), fac-Cr(CO)3(Me3TACH) . . . . . . . . . . . . . . . . . . . 111

B. Tricarbonyl(1,3,5-Trimethyl-1,3,5-Triazacyclohexane)

Molybdenum(0), fac-Mo(CO)3(Me3TACH) . . . . . . . . . . . . . . . . . 112

C. Tricarbonyl(1,3,5-Trimethyl-1,3,5-Triazacyclohexane)

Tungsten(0), fac-W(CO)3(Me3TACH) . . . . . . . . . . . . . . . . . . . . . 113

28. Manganese Tricarbonyl Transfer (MTT) Agents . . . . . . . . . . . . . . . 114

A. Acenaphthene(Tricarbonyl)Manganese(I) . . . . . . . . . . . . . . . . . 117

B. Naphthalene(Tricarbonyl)Manganese(I) . . . . . . . . . . . . . . . . . . 118

C. Synthesis of h6-N,N-Dimethylaniline(Tricarbonyl)-

Manganese(I) Tetrafluoroborate, [Mn(h6-C6H5NMe2)

(CO)3]BF4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

29. Bis(1,5-Cyclooctadiene)Nickel(0) . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

A. Hexakis(Acetylacetonato)Trinickel(II). . . . . . . . . . . . . . . . . . . . 121

B. Di(n-Butyl)Magnesium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

C. Bis(1,5-Cyclooctadiene)Nickel(0) . . . . . . . . . . . . . . . . . . . . . . . 123

Contents xxix

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)

Cobaltate(III), Na[(C5H5)Co{P(O)(OMe)2}3] . . . . . . . . . . . . . . . . . 125

A. [Co((C5H5)Co{P(O)(OMe)2}3)2], Co(LOMe)2 . . . . . . . . . . . . . . . . 126

B. Na[(C5H5)Co{P(O)(OMe)2}3], NaLOMe . . . . . . . . . . . . . . . . . . . 126

Chapter Seven BIO-INSPIRED IRON AND NICKEL

COMPLEXES 129

31. Iron–Cyanocarbonyl Complexes [PPN][Fe(CO)4(CN)] and

[PPN][FeBr(CO)3(CN)2] . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

A. Bis(Triphenylphosphoranylidene)Ammonium

Tetracarbonylcyanoferrate(0), [PPN][Fe(CO)4(CN)] . . . . . . . . . . . 130

B. Bis(Triphenylphosphoranylidene)Ammonium

Bromotricarbonylcyanoferrate(II), [PPN][FeIIBr(CO)3(CN)2] . . . 131

32. Nickel Complexes of Bis(Diethylphosphinomethyl)

Methylamine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

A. Bis(Diethylphosphinomethyl)Methylamine . . . . . . . . . . . . . . . . 133

B. Bis(Bis(Diethylphosphinomethyl)Methylamine)

Nickel(0), Ni(PNP)2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134

C. Hydridobis(PNP)Nickel(II) Hexafluorophosphate . . . . . . . . . . . . 134

D. Bis(PNP)Nickel(II) Tetrafluoroborate . . . . . . . . . . . . . . . . . . . . 135

33. Monomeric Iron(II) Complexes Having Two Sterically

Hindered Arylthiolates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

A. Bis[Bis(Trimethylsilyl)Amido]Iron(II) . . . . . . . . . . . . . . . . . . . 138

B. 2,6-Di(Mesityl)Benzenethiol . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

C. Fe[SC6H3-2,6-(Mesityl)2]2 (Mesityl ¼ C6H2-2,4,6-Me3). . . . . . . 141

34 (1,3-Propanedithiolato)-Hexacarbonyldiiron

and Cyanide Derivatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

A. (1,3-Propanedithiolato)Hexacarbonyldiiron . . . . . . . . . . . . . . . . 144

B. Tetraethylammonium (1,3-Propanedithiolato)

Tetracarbonyldiiron Dicyanide . . . . . . . . . . . . . . . . . . . . . . . . . 145

C. Tetraethylammonium (1,3-Propanedithiolato)

Pentacarbonyldiiron Cyanide . . . . . . . . . . . . . . . . . . . . . . . . . . 146

Chapter Eight RUTHENIUM COMPLEXES 148

35. Ruthenium(II)-Chlorido Complexes of Dimethylsulfoxide . . . . . . . . 148

A. cis-Dichloridotetrakis(dimethylsulfoxide)ruthenium(II) . . . . . . . 150

B. trans-Dichloridotetrakis(dimethylsulfoxide)ruthenium(II) . . . . . 151

xxx Contents

36. Synthesis of Chloride-Free Ruthenium(II) Hexaaqua

Tosylate, [Ru(H2O)6]tos2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

37. Basic Ruthenium Acetate and Mixed Valence Derivatives . . . . . . . . 156

A. Tri(Aquo)-m3-Oxo-Hexakis(m-Acetate)TrirutheniumAcetate, [Ru3(m3-O)(m-OAc)6(H2O)3]OAc . . . . . . . . . . . . . . . . . 156

B. Tri(Pyridine)-m3-Oxo-Hexakis(m-Acetate)Triruthenium,

Ru3(m3-O)(m-OAc)6(py)3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

C. Di(Aquo)-m3-Oxo-Hexakis(m-Acetate)Carbonyl-Triruthenium(II, III, III), Ru3(m3-O)(m-OAc)6(CO)(H2O)2. . . . . . 158

38. Di-m-Chloro(Ethylbenzoate)Diruthenium(II),

[(h6-etb)RuCl2]2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

A. Ethyl-1,4-Cyclohexadiene-3-Carboxylate . . . . . . . . . . . . . . . . . 161

B. Chloro(Ethylbenzoate)Diruthenium(II),

[(h6-etb)RuCl2]2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162

Chapter Nine IRIDIUM COMPLEXES 164

39. The Diphosphine tfepma and its Diiridium Complex

Ir20,II(tfepma)3Cl2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

A. Bis(dichlorophosphino)methylamine . . . . . . . . . . . . . . . . . . . . . 165

B. Bis(bis(trifluoroethoxy)phosphino)methylamine (tfepma) . . . . . . 166

C. Ir20,II(tfepma)3Cl2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

40. Heteroleptic Cyclometalated Iridium(III) Complexes . . . . . . . . . . . 168

A. Di-m-chlorotetrakis[2-(2-pyridinyl-N)phenyl-C]diiridium(III), [Ir(ppy)2Cl]2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

B. (2,20-bipyridine-kN1, kN10)Bis[2-(2-pyridinyl-kN)phenyl-kC]–iridium(III) hexafluorophosphate,

[Ir(ppy)2bpy]PF6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

C. 2-(4-Fluorophenyl)-5-methyl-pyridine, F–mppy . . . . . . . . . . . . . 171

D. Di-m-Chlorotetrakis[5-Fluoro-2-(5-Methyl-2-Pyridinyl-N)

Phenyl-C]Diiridium(III), [Ir(F–mppy)2Cl]2 . . . . . . . . . . . . . . . . 171

41. Oxygen and Carbon Bound Acetylacetonato

Iridium(III) Complexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173

A. trans-Bis-(Acetylacetonato-O,O)(Acetylacetonato-C3)Aquo

Iridium(III), (acac-O,O)2Ir(acac-C3)(H2O). . . . . . . . . . . . . . . . . 174

B. Bis-(m-Acetylacetonato-O,O,C3)-Bis-(Acetylacetonato-

O,O)-Bis-(Acetylacetonato-C3) Diiridium(III),

[Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 . . . . . . . . . . . . . . . . . 175

Contents xxxi

C. trans-Bis-(Acetylacetonato-O,O)(Acetylacetonato-C3)

Pyridine Iridium(III), (acac-O,O)2Ir(acac-C3)Pyridine . . . . . . . . 176

Contributor Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

Formula Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

xxxii Contents

Chapter One

COMPLEXES OF BULKY b-DIKETIMINATELIGANDS

1. INTRODUCTION

by DANIEL J. MINDIOLA,� PATRICK L. HOLLAND,� and

TIMOTHY H. WARRENz

In the past decade, b-diketiminates1 have experienced a dramatic renaissance.2

These scaffolds are structurally analogous to the ubiquitous acac (acetylacetonate)

ligand, forming a six-membered chelate ring with nitrogen atoms in place of the

oxygen atoms of acac. Like the popular cyclopentadienyl ligand, the monoanionic

b-diketiminate ligand forms complexes with a wide variety of main-group and

d-block metals, lanthanides, and actinides.2 Moreover, b-diketiminates often

serve as a robust framework for supporting metal-containing functional groups

owing to their relatively strong donating properties and chelating nature. As such,

b-diketiminate complexes rarely suffer from decomplexation pathways that

often plague monodentate ligands such as amides, amines, and neutral diimines.

Although b-diketiminates typically bind in a bidentate fashion, the delocalization

of charge about the NCCCN ring renders it possible for metals to coordinate to the

face of the ligand with hapticities up to h5. In such cases, the coordination

geometry is highly dependent on both the metal and ligand substituents.2

Inorganic Syntheses, Volume 35, edited by Thomas B. RauchfussCopyright � 2010 John Wiley & Sons, Inc.

*Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN

47405.�Department of Chemistry, University of Rochester, Rochester, NY 14627.zDepartment of Chemistry, Georgetown University, Washington, DC 20057-1227.

1

The availability of straightforward, multigram syntheses for many classes of

b-diketiminates has generated widespread popularity of the ligand for coordina-

tion and organometallic chemistry. Prototypical b-diketimines with N-aryl sub-

stituents can be synthesized in one step from commercially available anilines and

diones through simple condensation reactions.1,3 b-Diketiminate ligands with

aliphatic nitrogen substituents can also be prepared by related condensation routes,

but often require harsh reagents such as oxonium salts for complete diimine

formation.4 More sterically encumbered derivatives possessing tert-butyl groups

on the b-carbons of the NCCCN backbone require a multistep, but high-yielding,

synthesis (described herein).5 Other variants of the b-diketiminate scaffold have

been recently discussed in a comprehensive review.2

This chapter focuses on theN-aryl b-diketiminates, which have a high degree of

modularity of the R and R0 positions of the NCCCN backbone, and of the N-aryl

ortho substituents (R00 andR000) (Fig. 1, left). Steric and electronic factors can easilybe fine-tuned via the R, R0, and R00 groups. For instance, the steric demands of the

coordination wedge in b-diketiminatometal complexes (Fig. 1, right) can be

modified by judicious choice of R and R00 substituents, while the electronic

properties of the ligand are influenced predominantly by the backbone substituents

R0, and to a lesser extent, R. In this chapter, we describe complexes of four different

b-diketiminate ligands using a notation that specifies R and R00/R000 substituents(R0 ¼H in all syntheses described here). Thus, LMe,Me2 indicates R¼R00 ¼Me

and R000 ¼H; LMe,Me3 indicates R¼R00 ¼R000 ¼Me; LMe,iPr2 indicates R¼Me,

R00 ¼ iPr, and R000 ¼H; and LtBu,iPr2 indicates R¼ tBu, R00 ¼ iPr, and R000 ¼H.

An important application for b-diketiminates is the generation of low-coordi-

nate metal complexes. This propensity for stabilizing complexes with low

coordination numbers has proven particularly useful for the isolation of systems

with unprecedented oxidation states, especially low oxidation state main-group

species.6 Such complexes often serve as precursors for group-transfer reactions to

Figure 1. Left: General structure of a b-diketiminate ligand with aryl substituted nitrogen

groups. Right: The coordination wedge of a metal complex with LMe,iPr2 (R¼Me, R0 ¼H,

R00 ¼ iPr, R000 ¼H), depicting how the R00 groups block the axial sites of the metal atom

(shown in black).

2 Complexes of Bulky b-Diketiminate Ligands

afford reactive, metal-bound functional groups. Low-coordinate b-diketiminate

complexes also play host to a variety of reactive functionalities including

hydrides,7 alkyls,2,8 alkylidenes/carbenes,9,10 alkylidynes,11 imides/nitrenes and

nitrides,12–15 and phosphinidenes.9,16 Many of these functionalities find applica-

tion in catalysis such as copolymerization,17 ring-opening polymerization,18

alkene and alkyne polymerization,5,8,11,19 olefin metathesis,20 intramolecular

hydroamination,21 carboamination,22 intermolecular hydrophosphination,16c car-

bene and nitrene group transfer,9,10 and hydrodefluorination.23 In biomimetic

chemistry, b-diketiminate ligands have been used in type 1 ‘‘blue’’ copper sites,24

the study of dioxygen activation by cobalt10a and copper,25 the binding of nitric

oxide by nickel,26 and the binding of nitrogenase substrates to iron.27

In this chapter we collect representative procedures for the preparation of the

most popular family of N-aryl b-diketiminate ligands, and of alkali metal and

thallium salts that are especially useful precursors to transition metal complexes.

We then describe the preparation of a series of useful b-diketiminato metal

complexes with 3d transition metals from Sc to Zn, each of which serves as

a template for further elaboration.

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1. Introduction 3

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2. b-DIKETIMINATE PRECURSORS HLMe,Me3 and TlLMe,Me3

(LMe,Me3 ¼ 2,4-BIS-(MESITYLIMIDO)PENTYL)

Submitted by MATTHEW S. VARONKA� and TIMOTHY H. WARREN�

Checked by THOMAS R. DUGAN,� RYAN E. COWLEY,�

and PATRICK L. HOLLAND�

*Department of Chemistry, Georgetown University, Washington, DC 20057-1227.�Department of Chemistry, University of Rochester, Rochester, NY 14627.


The b-diketiminate ligand HLMe,Me3 was first reported by Budzelaar via

condensation of acetylacetone with 2,4,6-trimethylaniline in 12N HCl at

120–140�C.1 We find that the milder procedure below for HLMe,Me3 adapted from

Budzelaar’smethod forHLMe,Me2offers a simpleworkupand is alsoversatile for the

synthesis of other HLMe,R derivatives.2 We also include spectroscopic information

for HLMe,Me2 that was prepared analogously. The synthesis of the thallium deriva-

tive TlLMe,Me3 was adapted from the published literature procedures for TlLMe,Me2

and TlLMe,Me3.3,4

General Procedures

Experiments requiring air-free techniques were carried out in a dry nitrogen

atmosphere using a glovebox and/or standard Schlenk techniques. Diethyl ether

and tetrahydrofuran (THF) were first sparged with nitrogen and then dried by

passing through activated alumina columns.5 Pentane was first washed with conc.

HNO3/H2SO4 to remove olefins, stored over CaCl2, sparged with nitrogen, and

then dried by passing through activated alumina columns.5 Deuterated solvents

were sparged with nitrogen, dried over activated 4A�molecular sieves, and stored

under nitrogen.

2,4,6-Trimethylaniline, 2,4-pentanedione, p-toluenesulfonic acid, and thallous

acetate were purchased from Acros Organics. These reagents were used as

received. Potassium hydride was obtained from Aldrich as a dispersion in mineral

oil; using air-free techniques, it was filtered and washed with pentane to afford

a dry powder.

A. 2,4-BIS-(MESITYLIMIDO)PENTANE (HLMe,Me3)

MeCðOÞCH2CðOÞMeþ 2 2; 4; 6-Me3C6H2NH2

þHOTs!½H2LMe;Me3�OTsþ 2 H2O

½H2LMe;Me3�OTsþNa2CO3 !HLMe;Me3 þNaOTsþNaHCO3

To a suspension of p-toluenesulfonic acid monohydrate (18.6 g, 0.098mol) in

300mL of toluene is added 2,4-pentanedione (9.75 g, 0.098mol) and 2,4,6-

trimethylaniline (26.6 g, 0.196mol). Using a Dean–Stark trap, the mixture is

refluxed with stirring for 4 h until no further water is collected. Cooling the

resulting solution gives a solid, the protonated b-diketimine as its tosylate salt,

which is filtered and the solid is air-dried. This solid is taken up in 300mL of

CH2Cl2 and stirred with 200mL of saturated Na2CO3 solution for 1 h. The organic

layer is separated and dried over MgSO4. The volatiles are removed in vacuo to

2. b-Diketiminate Precursors HLMe,Me3 and TlLMe,Me3 5

yield a yellow oil.* Addition of 200mL of ice-cold MeOH to the yellow oil

followed by vigorous shaking for 1min causes a white solid to precipitate. The

slurry is stored at �35�C overnight to encourage further crystallization. The

product is isolated by filtration, washed with cold methanol, and dried to yield

30.3 g (93%) of product.

1H NMR (CDCl3): d 12.20 (s, 1, N-H), 6.89 (s, 4, Ar-H), 4.89 (s, 1, backbone-CH),2.29 (s, 6, Ar-p-CH3), 2.16 (s, 12, Ar-o-CH3), 1.72 (s, 6, backbone-CH3);

13C{1H}

NMR (CDCl3): d 161.62, 141.81, 134.16, 132.46, 129.09, 93.93 (backbone-CH),

21.50 (Ar-o-CH3), 20.96 (Ar-p-CH3), 18.95 (backbone-CH3).

Properties

The white microcrystalline solid forms colorless needles upon careful crystalliza-

tion attempts. It is soluble in common organic solvents.

The b-diketimine HLMe,Me2 may be prepared analogously by substituting 2,6-

dimethylaniline for 2,4,6-trimethylaniline in the above synthesis.3 1H NMR

(CDCl3): d 12.17 (s, 1, N-H), 7.02 (d, 4, Ar-m-H), 6.93 (t, 2, Ar-p-H), 4.86

(s, 1, backbone-CH), 2.14 (s, 6, Ar-CH3), 1.67 (s, 6, backbone-CH3);13C{1H}

NMR (CDCl3): d 160.72, 143.69, 132.06, 127.67, 124.19, 93.20 (backbone-CH),

20.25 (Ar-o-CH3), 18.29 (backbone-CH3).

B. THALLIUM 2,4-BIS-(MESITYLIMIDO)PENTYL (TlLMe,Me3)

HLMe;Me3 þKH!KLMe;Me3 þH2

KLMe;Me3 þTlOAc!TlLMe;Me3 þKOAc

& Caution. Air-free procedures are required for use of potassium hydride,

which can explosively generate hydrogen gas upon uncontrolled hydrolysis.

Hydrogen gas is generated in the procedure and should not be performed in

a sealed flask.

Procedure

A solution of HLMe,Me3 (8.00 g, 23.9mmol) in 40mL of THF is treated with

1.3 equiv. of dryKH (1.25 g, 31.1mmol). The reaction is stirred overnight and then

filtered through Celite to remove excess KH to yield a bright yellow filtrate. The

filter cake is washedwith a small amount of THF that is added to the filtrate; TlOAc

(6.31 g, 23.9mmol) is then added to this solution, which is stirred overnight in the

* The checkers obtained a solid at this step, which was treated identically and gave a 68% yield.


dark. The resulting dark green solution is filtered through Celite to yield a bright

yellow filtrate. Removal of all volatiles in vacuo gives a dry yellow solid.

Dissolving this solid in ca. 25mL diethyl ether followed by chilling to �35�Cresults in the formation of yellow crystals, which are isolated by decanting the

mother liquors to yield 8.50 g (66%) of the product after drying in vacuo.�

1H NMR (C6D6): d 6.86 (s, 4, Ar-H), 4.84 (s, 1, backbone-CH), 2.22 (s, 6, Ar-p-

CH3), 2.14 (s, 12, Ar-o-CH3), 1.71 (s, 6, backbone-CH3).13C{1H} NMR (C6D6):

d 161.87, 147.28, 132.15, 130.39, 129.31, 100.12 (backbone-CH), 24.93 (Ar-o-

CH3), 21.36 (Ar-p-CH3), 19.59 (backbone-CH3).

Properties

The compound is both light and air sensitive and is best stored in the dark.

Decomposition by light, air, or water results in black solutions or solids in which

the free b-diketimine HLMe,Me3 may be detected by observation of its N-H1H NMR signal at d 12.20 (benzene-d6). Thallium b-diketiminates exhibit low

coordination numbers in the solid state.6–8 Owing to their soft, relatively nonre-

ducing nature and the insolubility of resulting metal halides, thallium reagents

favor complete removal of the exchanged halide from the metal’s coordination

sphere; thallium b-diketiminates have found use as transmetallation agents in the

preparation of Co,9,10 Ni,5,11 Cu,4,12,13 and Au14 b-diketiminate complexes.

Acknowledgments

The authors thank Georgetown University, the Petroleum Research Fund (PRF-G

and PRF-AC awards to T.H.W), and the U.S. National Science Foundation

(CHE-0716304 and CHE-0135057, CAREER Award to T.H.W.) for support of

this research.

References


2. P. H. M. Budzelaar, N. N. P. Moonen, R. de Gelder, J. M. M. Smits, and A. W. Gal, Eur. J. Inorg.

Chem. 753 (2000).

3. X. Dai and T. H. Warren, Chem. Commun. 1998 (2001).

4. E.Kogut,H. L.Wiencko, L. Zhang,D.E. Cordeau, andT.H.Warren, J. Am.Chem. Soc. 127, 11248

(2005).

5. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers,Organometallics

15, 1518 (1996).

6. M. S. Hill, R. Pongtavornpinyo, and P. B. Hitchcock, Chem. Commun. 3720 (2006).

�The checkers obtained a yield of 48% from the first crop of crystals. Concentrating the mother liquor

afforded additional crystals (total over 2 crops: 59%)

2. b-Diketiminate Precursors HLMe,Me3 and TlLMe,Me3 7

7. M. S. Hill, P. B. Hitchcock, and R. Pongtavornpinyo, Dalton Trans. 273 (2005).

8. Y. Cheng, P. B. Hitchcock, M. F. Lappert, and M. Zhou, Chem. Commun. 752 (2005).

9. P. L. Holland, T. R. Cundari, L. L. Perez, N. A. Eckert, and R. J. Lachicotte, J. Am. Chem. Soc. 124,

14416 (2002).

10. X. Dai, P. Kapoor, and T. H. Warren, J. Am. Chem. Soc. 126, 4798 (2004).

11. H. L. Wiencko, E. Kogut, and T. H. Warren, Inorg. Chim. Acta 345, 199 (2003).

12. X. Dai and T. H. Warren, J. Am. Chem. Soc. 126, 10085 (2004).

13. L. D. Amisial, X. Dai, R. A. Kinney, A. Krishnaswamy, and T. H. Warren, Inorg. Chem. 43, 6537

(2004).

14. H. V. R. Dias and J. A. Flores, Inorg. Chem. 46, 5841 (2007).

3. b-DIKETIMINATE PRECURSORS LMe,iPr2H, [LMe,iPr2Li]x,and [LtBu,iPr2K]x (L

Me,iPr2¼2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL; LtBu,iPr2¼2,2,6,6-

TETRAMETHYL-3,5-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)HEPTYL)

Submitted by DEBASHIS ADHIKARI,� BA L. TRAN,�

FRANCISCO J. ZUNO-CRUZ,� GLORIA SANCHEZ CABRERA,�

and DANIEL J. MINDIOLA�

Checked by KAREN P. CHIANG,z RYAN E. COWLEY,z THOMAS R. DUGAN,z

and PATRICK L. HOLLANDz

The following procedure has been slightly modified from the literature by

inclusion of a few more synthetic details as well as an increment in the scale

for consistency of yield.4,5 Potassium salts of LMe,iPr2 have been reported byMair6

and Winter7 by using KN(SiMe3)2 and KH, respectively. Likewise, in Chapter 8,

Roesky describes the synthesis of LMe,iPr2K from KH and LMe,iPr2H. We have,

however, encountered low yields and irreproducible results in syntheses that start

from potassium diketiminate salts prepared in this way, presumably because of the

variable quality of commercial KH. We describe here a reproducible and facile

synthesis that uses benzylpotassium3 as the potassium source, thus avoiding the

use of potentially dubious KH and the hazards of explosion from the production of

H2 gas.

*Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN

47405.�Centro de Investigaciones Qu�ımicas, Universidad Autonoma del Estado de Hidalgo, Pachuca, Estado

de Hidalgo, 42184, Mexico.zDepartment of Chemistry, University of Rochester, Rochester, NY 14627.


General Procedures

All manipulations (unless otherwise mentioned) were performed under a nitrogen

atmosphere using standard Schlenk line or glovebox techniques. THF was dried

over Na/Ph2CO and distilled into an evacuated vacuum flask equipped with a gas

adapter and under a positive flow of N2 or Ar. The THF-filled flask was taken into

the glovebox and stored over metallic Na (thin films). Anhydrous toluene and

pentanewere purchased fromAldrich in a sure-sealed reservoir (18 L) and dried by

passing through two columns of activated alumina and aCuQ-5 column underN2.1

Before use, a 5mL aliquot of each solvent was tested, qualitatively, with a drop of

Na/benzophenone ketyl radical in a THF solution (1–2 drops in 3–5 mL of solvent

must give a blue to purple solution). Celite was dried under reduced pressure at

180�C for 24 h. TiCl3(THF)3 was purchased from Strem and also prepared

according to the literature procedure.2 All 1H NMR spectra were referenced to

solvent resonances (residual C6D5H inC6D6, 7.16 ppm). C6D6was purchased from

Cambridge Isotope Laboratories, degassed and dried over CaH2, and then vacuum

transferred to 4A�molecular sieves. Benzylpotassiumwas prepared by a procedure

reported in the literature.3

A. 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTANE (LMe,iPr2H)

MeCðOÞCH2CðOÞMeþ 2 2; 6-ði-PrÞ2C6H3NH2 þHCl

!½H2LMe;Me3�Clþ 2H2O

½H2LMe;iPr2�ClþNa2CO3 !HLMe;iPr2 þNaClþNaHCO3

Procedure

Manipulations are performed in the air. In a two-neck 500-mL round-bottomed

flask, 1,4-pentanedione (6.68 g, 0.067mol) is mixed with 300mL of ethanol and

2,6-diisopropylaniline (28.67 g, 0.162mol). To the mixture is added 7.5mL of

conc. hydrochloric acid (�12M) and the solution is refluxedwith vigorous stirring

at 100�C for 3 days. After 6 h, a white precipitate begins to form, but the reaction

must be continued for the full 3 days for complete conversion. The slurry is allowed

to cool to room temperature and then filtered. The filtered solid is dried under

reduced pressure, and the filtrate is evaporated on a rotary evaporator. The dried

mass is combined with the filtrate residue and the mixture is refluxed in 250mL

hexane at 80�C for 1 h. After cooling themixture, the slurry is filtered, and the solid

residue is treated with 300mL of a saturated aqueous solution of Na2CO3 and

500mL of CH2Cl2. The slurry is stirred until the solid dissolves, giving a yellowish

organic solution and a pale yellow aqueous layer. The organic layer is separated

3. b-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x 9

using a separatory funnel and the solution is dried over MgSO4. The solution is

filtered again and dried under reduced pressure to yield a slightly yellow residue

that uponwashingwith 50mL of cold methanol (�20�C) yields white LMe,iPr2H as

a fluffy powder (21.42 g, 0.051mol, 77% yield).* The compound is characterized

by 1H NMR spectroscopy that was compared with that reported in the literature.5

1H NMR (C6D6): d 12.44 (s, 1H, N-H), 7.14–7.09 (m, 6H, Ar-H), 4.85 (s, 1H, CH),

3.27 (m, 4H, CH(CH3)2), 1.63 (s, 6H, NC(CH3)), 1.18 (d, JH�H¼ 7Hz, 12H, CH

(CH3)2), 1.12 (d, JH�H¼ 7Hz, 12H, CH(CH3)2).

Properties

LMe,iPr2H is a white crystalline solid that is soluble in organic solvents including

n-pentane and n-hexane. LMe,iPr2H is not soluble in water and is poorly soluble in

other polar solvents such as MeOH and EtOH. Solids are indefinitely stable in air

and readily form the iminium salt [LMe,iPr2H2]Cl upon exposure to 12MHCl. As a

solid, LMe,iPr2H gradually turns pale yellow in air, but the material can be purified

by recrystallization by concentrating an Et2O solution followed by cooling to

�20�C for >12 h. It is recommended, however, to store the pure white free base

under an inert atmosphere (or under vacuum) to avoid gradual tainting.

B. LITHIUM 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL

([LMe,iPr2Li]x)

HLMe;iPr2 þBuLi!½LMe;iPr2Li�x þBuH

& Caution. Butyllithium is pyrophoric in air and should be handled exclu-

sively under dry nitrogen or argon. This reaction is extremely exothermic, so the

addition of n-BuLi should be performed at low temperatures and not be rushed.

Procedure

In a 250-mL round-bottomed flask, LMe,iPr2H (5.00 g, 0.012mol) is dissolved in

100mLof hexane and the solution cooled to�35�C.To the cooled solution a 1.6Mn-BuLi solution in hexane (7.84mL, 0.013mol) is added dropwise, and the

solution is stirred for 12 h at room temperature.

During the course of this time, a white precipitate gradually appears. The

suspension is cooled to �35�C over 12 h, and the solid is collected by filtration,

washed with 10mL of cold hexane, and then dried under reduced pressure. The

filtrate collected from the first batch is concentrated to �30mL under reduced

* The checkers omitted the stepwhere the residuewas refluxed in hexane, obtaining a final yield of 72%.


pressure and the solution is cooled again to �35�C. After 12 h, a second batch ofsolid is collected via filtration, washed with cold hexane, and dried under reduced

pressure. The combined yield for the two batches is 2.85 g (0.007mol, 56%yield).�

Compound [LMe,iPr2Li]x is characterized by1H NMR spectroscopy by comparison

to that reported in the literature.4 The structural chemistry of lithium diketiminate

complexes has been investigated.4

1H NMR (C6D6): d 7.21–7.18 (m, 6H, Ar-H), 4.90 (s, 1H, g-CH), 3.15 (m, 4H, CH

(CH3)2), 1.83 (s, 6H, NC(CH3)), 1.21 (d, JH�H¼ 7Hz, 12H, CH(CH3)2), 1.18 (d,

JH�H¼ 7Hz, 12H, CH(CH3)2).

Properties

Compound [LMe,iPr2Li]x is a white amorphous solid, which is soluble in donor

solvents such as Et2O and THF. The salt has very low solubility in hydrocarbons

such as n-pentane and n-hexane but can be dissolved in copious amounts of

benzene and toluene. The compound [LMe,iPr2Li]x decomposes rapidly in haloge-

nated solvents and upon exposure to air. It is recommended that solids not be stored

for extended periods of time, even if inside a glovebox. For the preparation of its

transition metal derivatives, it is preferable to use fresh [LMe,iPr2Li]x or generate it

in situ before use. In the presence of donor solvents such as Et2O and THF, [LMe,

iPr2Li]x forms yellow adducts.4 The binding is exothermic, and it is therefore

recommended to add the salt to the solution and not the reverse.

C. POTASSIUM 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-

DIISOPROPYLPHENYLIMIDO)HEPTYL ([LtBu,iPr2K]x)

LtBu;iPr2HþKCH2Ph!½LtBu;iPr2K�x þ PhMe

Procedure

& Caution.KCH2Ph is a highly pyrophoric that should be handled only in an

inert atmosphere. Upon contact with O2 or H2O, solid benzylpotassium will

immediately deflagrate. This reaction to produce [LtBu,iPr2K]x is extremely

exothermic, so it is recommended that the addition of KCH2Ph be performed

slowly and at low temperatures.

A solution of LtBu,iPr2H (2.15 g, 4.27mmol) in 40mL of diethyl ether is placed

in a 250-mL round-bottomed flask and frozen in a cold well for 0.5 h. To the

thawing solution is added benzylpotassium3 (557mg, 4.27mmol) in portions. The

� The checkers performed the reaction on a larger scale (27mmol) and obtained a yield of 75%.

3. b-Diketiminate Precursors LMe,iPr2H, [LMe,iPr2Li]x 11

suspension is slowly warmed to room temperature, and the orange solids gradually

dissolve to give a yellow solution. After stirring the solution at room temperature

for 1.5 h, removal of the ethereal solution affords a canary yellow solid, which is

triturated with 25mL of cold pentane and vacuum filtered through a porous frit to

afford a pale yellow product. The product is further washed with 15mL of cold

pentane, dried, and stored at �37�C. Yield: 91% (2.10 g, 3.88mmol).� 1H NMR

spectra of [LtBu,iPr2K]x indicate the absence of solvent. The degree of aggregation

of this material was not investigated.

1H NMR (C6D6): d 7.00 (d, 4H, J¼ 7Hz,m-Ar-H), 6.81 (t, 2H, J¼ 7Hz, p-Ar-H),

4.93 (s, 1H, a-H), 3.26 (m, 4H, CH(CH3)2, 1.37 (s, 18H, C(CH3)3), 1.32 (d, 12H,

J¼ 7Hz, CH(CH3)2, 0.94 (d, 12H, J¼ 7Hz, CH(CH3)2).13C NMR (C6D6): d

166.0 (ArN(C(CH3)3)CCHC(C(CH3)3)NAr), 151.4 (Ar), 144.8 (Ar), 135.7 (Ar),

133.2 (Ar), 123.4 (Ar), 118.1 (Ar), 89.6 (ArN(C(CH3)3)CCHC(C(CH3)3)NAr),

44.0 (ArN(C(CH3)3)CCHC(C(CH3)3)NAr), 32.5 (ArN(C(CH3)3)CCHC(C

(CH3)3)NAr), 31.6 (Ar-2,6-(CH(CH3)2), 27.0 (Ar-2,6-(CH(CH3)2), 24.8 (Ar-

2,6-(CH(CH3)2), 23.4 (Ar-2,6-(CH(CH3)2), 22.69 (Ar-2,6-(CH(CH3)2).

Properties

Compound [LtBu,iPr2K]x is a pale yellow amorphous solid that is soluble in THF.

The salt is insoluble in hydrocarbons such as n-pentane and n-hexane, and partially

soluble in benzene, toluene, and Et2O. Compound [LtBu,iPr2K]x decomposes

rapidly in halogenated solvents such as CH2Cl2 and CCl4 and also upon exposure

to air. It is also recommended that solids not be stored for extended periods of time,

even if inside a glovebox. It is preferable to isolate fresh [LtBu,iPr2K]x for

subsequent use.

Acknowledgments

The authors thank Indiana University-Bloomington, the Camille and Henry

Dreyfus Foundation (New Faculty and Teacher-Scholar Awards to D.J.M.), the

Alfred P. Sloan Foundation (fellowship to D.J.M.), and the U.S. National Science

Foundation (CHE-0348941, PECASE Award to D.J.M.) for support of this

research.

� The checkers obtained a yield of 93% using the method described. The checkers also performed the

reaction on a similar scale at room temperature and obtained a solid having identical properties, with a

yield of 95%. It is difficult to remove the final traces of toluene from the solid under vacuum, as is evident

from 1H NMR spectra.


References

1. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics

15, 1518 (1996).

2. N. A. Jones, S. T. Liddle, C. Wilson, and P. L. Arnold, Organometallics 26, 755 (2007).

3. P. J. Bailey, R. A. Coxall, C.M. Dick, S. Fabre, L. C. Henderson, C. Herber, S. T. Liddle, D. Lorono-

Gonzalez, A. Parkin, and S. Parsons, Chem. Eur. J. 9, 4820 (2003).

4. M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead, H. B. Roesky, and P. P. Power,


5. J. Feldman, S. J. McLain, A. Parthasarathy, W. J. Marshall, J. C. Calabrese, and S. D. Arthur,

Organometallics 16, 1514 (1997).

6. W. Clegg, E. K. Cope, A. J. Edwards, and F. S. Mair, Inorg. Chem. 37, 2317 (1998).

7. H. M. El-Kaderi, M. J. Heeg, and C. H. Winter, Polyhedron 25, 224 (2006).

4. b-DIKETIMINATE PRECURSORS LtBu,iPr2H ANDLtBu,iPr2Li(THF) (LtBu,iPr2¼2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)HEPTYL)

Submitted by RYAN E. COWLEY,� KAREN P. CHIANG,�


Checked by DEBASHIS ADHIKARI,� FRANCISCO J. ZUNO-CRUZ,z

GLORIA SANCHEZ CABRERA,z and DANIEL J. MINDIOLA�

The b-diketiminate ligand with tert-butyl substituents on the backbone (LtBu,iPr2)

gives especially extreme hindrance in late transition metal complexes. Studies on

the vanadium chemistry of bulky b-diketiminates showed that this ligand did not

coordinate to vanadium or titanium.1 Only under the right conditions can this

ligand be coordinated to Ti(III), albeit in low yields.2

In iron(II) and nickel(II) complexes, the LtBu,iPr2 ligand gives three-coordinate

monomers LtBu,iPr2MCl, even though LMe,iPr gives [LMe,iPr2M(m-Cl)]2 under

identical conditions.3 At first glance, this distinct increase in sizemay be surprising

because the location of the large t-butyl groups is far from the metal binding site,

and directed away from the metal. However, steric interactions between the tert-

butyl groups and the neighboring 2,6-diisopropylphenyl groups push the latter

toward the ‘‘open’’ side of the ligand and increase the extent to which the metal is

blocked from additional ligands. This size difference has been shown by side-to-

*Department of Chemistry, University of Rochester, Rochester, NY 14627.�Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN

47405.zCentro de Investigaciones Qu�ımicas, Universidad Autonoma del Estado de Hidalgo, Pachuca, Estado

de Hidalgo, 42184, Mexico.

4. b-Diketiminate Precursors LtBu,iPr2H AND LtBu,iPr2 13

side comparison of three-coordinate iron alkyl complexes of the two diketiminate

ligands.4

Because of the hindrance near the imine carbon atoms, the diimine LtBu,iPr2H

cannot be synthesized through a double condensation, as in the other ligands.

Budzelaar sidestepped this problem using a convergent synthesis that couples the

two sides of the ligand.1 Both sides derive from a common intermediate, an

imine chloride which is prepared from pivaloyl chloride. Half of this imine

chloride is methylated to give a methyl tert-butyl imine, which is then

deprotonated and treated with the remaining half of the imine chloride to give

the final ligand. The synthesis below, which is very little changed from that

reported by Budzelaar, gives the ligand in a total yield of 58% in four steps.1 The1H NMR spectrum of the final ligand has broad signals at room temperature,

presumably from exchange between diimine and imine–enamine tautomers,

which has a rate similar to the NMR timescale.

A method for preparing the lithium salt of this ligand is given here; please refer

to the previous chapter to find a method for preparing the potassium salt of this

ligand.

General Procedures

All materials were purchased from Aldrich and used as received, unless otherwise

specified. NMR spectra are referenced to residual C6D5H at 7.16 ppm or CHCl3 at

7.26 ppm. Solvents for the final two steps were dried by passing HPLC-grade

solvents through columns of activated alumina and Cu Q-5 (Glass Contour Co.).

A. N-PIVALOYL-2,6-DIISOPROPYLANILIDE (DIPPNHC(O)tBu)

Me3CðOÞClþ 2; 6-ði-PrÞ2C6H3NH2 þEt3N

! 2; 6-ði-PrÞ2C6H3NHCðOÞCMe3 þEt3NHCl

Procedure

2,6-Diisopropylaniline (97.5 g, 0.55mol), triethylamine (70mL, 0.50mol), di-

chloromethane (200mL), and a large stir bar are added to a 1000-mL round-

bottomed flask to give a colorless solution. A solution of pivaloyl chloride (62mL,

0.50mol) in dichloromethane (200mL) is added to a pressure-equalizing addition

funnel, and this solution is added dropwise to the vigorously stirring aniline

solution over 2 h. Although pivaloyl chloride is sensitive to water, predrying the

triethylamine and dichloromethane is not required. The reaction is exothermic, so


slow addition is necessary. The solution has a pale pink or green color, and a white

precipitate is evident. After stirring the mixture for an additional 30min, the slurry

is chilled to 0�C, and the fluffy solid is collected by filtration.* The solid is washedwith diethyl ether (3� 150mL) to remove excess aniline and with copious

amounts of water (4� 200mL) to remove triethylammonium chloride. Finally,

the solid is dried under vacuum for at least 12 h to afford DIPPNH(C¼O)(tBu)

(121 g, 93% yield). Typical isolated yields are greater than 90%, and the product is

stable to air and water. Purity is determined by 1H NMR spectroscopy.

1H NMR (CDCl3): d 7.29 (m, 2H, p-Ar), 7.15 (d, 2H, m-Ar, J¼ 7.6Hz), 6.80

(br, 1H, N-H), 3.00 (sept, 2H, CH(CH3)3, J¼ 6.8Hz), 1.36 (s, 9H, C(CH3)3), 1.18

(d, 12H, CH(CH3)2, J¼ 6.8Hz).

B. DIPPN¼C(Cl)tBu

2; 6-ði-PrÞ2C6H3NHCðOÞCMe3 þ PCl5

! 2; 6-ði-PrÞ2C6H3N¼CðClÞCMe3 þHClþ POCl3

Procedure

A 2000-mL three-necked flask containing a slurry of DIPPNH(C¼O)(tBu)

(121 g, 0.46mol) in 1000mL of benzene (predrying benzene is not necessary)

is fitted with a glass stopper and two hose adapters. One hose attaches to a N2 inlet,

and the other is allowed to bubble through saturated sodium carbonate to neutralize

gaseousHCl produced in the reaction. The headspace of the flask is purgedwithN2

for 10min, and the flow rate is reduced to a slow bubble. Solid PCl5 (106 g,

0.51mol) is added in small portions (5–10 g) over a 90-min period by opening the

stoppered joint against a positive N2 flow, adding the solid, and replacing the

stopper. Slow addition of PCl5 is necessary because the reaction is exothermic.

During the course of the reaction all solids dissolve, and the solution develops

a yellowish color. The mixture is stirred for an additional 1 h after the addition of

PCl5 is complete. The two hose adapters are removed from the flask and replaced

with ground glass stoppers. The third neck is fitted with a distillation head and

benzene and POCl3 are removed by distillation directly from the reaction flask at

ambient pressure under a N2 atmosphere. (Caution: POCl3 produces gaseous HCl

upon contact with moisture or moist air.) The residue is then transferred into

a smaller single-necked flask and chloroimine is distilled under vacuum (82�C,

* Using 2,6-diisopropylaniline from Acros Organics, the checkers conducted the reaction at a lower

concentration and obtained a tacky product.


0.10mbar) through a Vigreux column.� The product (100 g, 83%) is a colorless oil

and is best stored under an atmosphere of N2 to prevent reaction with moisture,

which converts it to DIPPNH(C¼O)(tBu). Purity is established by 1H NMR

spectroscopy. Occasionally, the distillate contains traces of DIPPNH(C¼O)(tBu)

(up to 10% based on 1H NMR integration), in which case a second distillation

through a Vigreux column is necessary.

1H NMR (CDCl3): d 7.14 (m, 3H, m- and p-Ar), 2.74 (sept, 2H, CH(CH3)2,

J¼ 6.8Hz), 1.43 (s, 9H, C(CH3)3), 1.18 (d, 12H, CH(CH3)3, J¼ 6.8Hz).

C. DIPPN¼C(Me)tBu

2; 6-ði-PrÞ2C6H3N¼CðClÞCMe3 þMeLi

! 2; 6-ði-PrÞ2C6H3N¼CðMeÞCMe3 þLiCl

Procedure

& Caution. Methyllithium is pyrophoric in air and should be handled

exclusively under dry nitrogen or argon. This reaction is extremely exothermic,

so the addition should be performed carefully at low temperatures.

An oven-dried (150 �C) 500-mL Schlenk flask is charged with DIPPN¼C(Cl)

(tBu) (45.3 g, 0.16mol), rigorously dry diethyl ether (200mL), and a stir bar under

a N2 atmosphere to give a colorless solution, and the flask is sealed with a septum

and removed from the glovebox. (It is easier to perform the reaction in a cold well

in a drybox, if the equipment is available.) The solution is chilled to�78�C in a dry

ice/acetone cold bath, and methyllithium (121mL, 1.6M solution in diethyl ether,

0.19mol) is added to the stirring reaction mixture in�5-mL portions over 30min.

Themixture is allowed to slowlywarm and stirred at ambient temperature, upon

which a white precipitate is observed. (Caution: A slow flow of N2 through the

septum and out to an oil bubbler is necessary to ensure that the reaction vessel does

not develop pressure since the reaction is exothermic and the ether solvent is quite

volatile.) After 12 h,� the mixture is exposed to air by removing the septum and ice

(about 5 g) is carefully added in small portions until effervescence ceases.

Water (100mL) is added, and the mixture is transferred to a separatory funnel

where the aqueous layer is removed. The organic layer is extracted twicemorewith

� The checkers distilled at 125–127�C at 7mbar.� The checkers report that a 3-h reaction time is sufficient for full conversion.


water (2� 100mL), dried with anhydrous MgSO4, and filtered through coarse

filter paper. The volatile materials are removed under vacuum to afford a light

yellow oil. Pure DIPPN¼C(Me)(tBu) is distilled through a Vigreux column under

vacuum (72�C, 0.02mbar) as a colorless oil (36.0 g, 86%).� The oil is stable formonths to air and moisture. Purity is established by 1H NMR spectroscopy.

1H NMR (CDCl3): d 6.97–7.09 (m, 3H, Ar-H), 2.68 (sept, 2H, CH(CH3)2,

J¼ 6.9Hz), 1.66 (s, 3H, CH3), 1.28 (s, 9H, C(CH3)3), 1.13 (d, 6H, CH(CH3)3,

J¼ 6.9Hz), 1.11 (d, 6H, CH(CH3)3, J¼ 6.9Hz).

D. 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-

DIISOPROPYLPHENYLIMIDO)HEPTANE

([DIPPN¼C(tBu)]2CH2, LtBu,iPrH)

2; 6-ði-PrÞ2C6H3N¼CðMeÞCMe3 þBuLi

! 2; 6-ði-PrÞ2C6H3N¼CðCH2LiÞCMe3 þBuH

2; 6-ði-PrÞ2C6H3N¼CðClÞCMe3

þ 2; 6-ði-PrÞ2C6H3N¼CðCH2LiÞCMe3 !LtBu;iPrHþLiCl

Procedure

In a N2 glovebox, an oven-dried (150�C) 500-mL Schlenk flask is charged with

DIPPN¼C(Me)(tBu) (48.6 g, 0.18mol), rigorously dry diethyl ether (250mL,

pentane can also be used), dried N,N,N0,N0-tetramethylethylenediamine (40mL,

0.26mol), and a stir bar to give a colorless solution. The solution is chilled to

�78�C and n-butyllithium (76mL, 2.5M in hexanes, 0.19mol) is added slowly in

5-mL portions over 15min. (Note: Although using a glovebox cold well is

convenient, sealing the flask with a septum, removing the flask from the glovebox,

and chilling in a dry ice/acetone bath under dynamic N2 is also appropriate.) The

flask is sealed with a ground glass stopper and the stopcock is left open to allow

butane to escape. The mixture is allowed to slowly warm to ambient temperature

for 16 h. The mixture is then cooled to �78�C and a solution of DIPPN¼C(Cl)

(tBu) (50.4 g, 0.18mol) in diethyl ether (50mL) is added. The resulting slurry is

allowed to slowlywarm and stirred at ambient temperature for 18 h, whereupon the

� The checkers conducted the reaction at 0�C and did not distill the product. The crude product was

assayed by 1H NMR spectrum and was used in subsequent steps without further purification.


solution develops a yellowish color and a white precipitate forms. The mixture is

removed from the glovebox and heated at reflux in an oil bath for 2 h under N2.

The slurry is cooled and exposed to air where it is carefully quenched with ice

and water (200mL). The mixture is transferred to a separatory funnel, and the

aqueous layer is discarded. The organic layer is extracted twice more with water

(2� 200mL), dried with anhydrous MgSO4, and filtered through coarse filter

paper. The volatile materials are removed under vacuum to afford a sticky

yellow solid. This solid is dissolved in 400mL of boiling hexanes, and the

extract is slowly cooled to �25�C to give colorless block-shaped crystals of

LtBu,iPrH in two crops (79.1 g, 87%).

When stored in air, LtBu,iPrH slowly turns yellow over a period of weeks;

therefore, keeping LtBu,iPrH under an atmosphere of N2 is appropriate for long-

term storage. Purity is established by 1H NMR spectroscopy.

1H NMR (CDCl3): d 7.07–6.97 (m), 3.21 (br), 2.68 (br), 1.21 (s), 1.09 (s), 1.05 (br)

ppm. The 1H NMR spectrum of LtBu,iPrH shows overlapped and broadened peaks

due to themixture of bis(imine) and imine–enamine tautomers. At 70�C in CDCl3,

the spectrum is better resolved. The major component (ca. 95%) is the bis(imine)

tautomer: d 7.04–6.92 (m, 6H, m- and p-Ar), 3.26 (s, 2H, a-CH2), 2.61 (broad m,

4H, CH(CH3)2), 1.19 (d, 12H, CH(CH3)3, J¼ 8Hz), 1.07 (s, 18H, C(CH3)3), 1.03

(d, 12H, CH(CH3)3, J¼ 8Hz) ppm. The minor (ca. 5%) component is assigned to

the imine–enamine tautomer: d 11.0 (s, 1H, N-H), 5.43 (s, 1H, a-CH), 3.15 (sept,1H, CH(CH3)2). The remaining alkyl and aryl resonances from the imine–enamine

tautomer overlap with the major component.

E. LITHIUM 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-

DIISOPROPYLPHENYLIMIDO)HEPTYL (LtBu,iPr2Li, THF

ADDUCT)

LtBu;iPr2HþBuLi!LtBu;iPr2LiðTHFÞþBuH

Procedure

& Caution. Butyllithium is pyrophoric in air and should be handled

exclusively under dry nitrogen or argon. This reaction is extremely exothermic,

so n-BuLi should be added slowly. It is important to vent the reaction. This

manipulation is also possible outside of the glovebox by adding n-butyllithium

through a septum and allowing butane to escape through an oil bubbler.

In a N2 glovebox, an oven-dried (150�C) 500-mL Schlenk flask is charged

with LtBu,iPrH (24.5 g, 54.6mmol), anhydrous THF (150mL), and a stir bar to


give a colorless solution. The flask is kept open while a solution of n-butyllithium

(22.5mL, 2.5M solution in hexanes, 56.3mmol) is slowly added to the stirring

solution, causing effervescence and a color change to dark yellow-orange.

Following addition of butyllithium, the mouth of the flask is sealed with a ground

glass stopper and the stopcock is left open to allow additional butane to vent.

After stirring the solution for 30min, the flask is closed, removed from the

glovebox, and the solution is heated in a 60�Coil bath for 3 h. Thevolatilematerials

are removed in vacuum, leaving a yellow residue. The flask is returned to the

glovebox. The solid is freed from any excess butyllithium by briefly shaking with

pentane (100mL) and decanting the supernatant. This wash is repeated with an

additional portion of pentane (100mL), and the yellow solid is dried under vacuum

to give LtBu,iPr2Li(THF) (26.6 g). Additional product is obtained by reducing

the volume of the combined pentane washes to 30mL and cooling to�45�C. Thissolid is collected on an oven-dried fritted glass funnel and washed with cold

pentane (10mL, �45�C) to obtain additional LtBu,iPr2Li(THF) (2.60 g, combined

yield 92%). Purity is established by 1H NMR spectroscopy.

1H NMR (C6D6): d 6.94–7.03 (m, 6H,Ar-H), 5.25 (s, 1H,a-H), 3.49 (sept, 4H, CH(CH3)2, J¼ 7.0Hz), 2.31 (br, 4H, OCH2CH2), 1.38 (s, 18H, C(CH3)3), 1.37

(d, 12H, CH(CH3)2, J¼ 7.0Hz), 1.11 (s, 12H, CH(CH3)2, J¼ 7.0Hz), 0.92

(br, 4H, OCH2CH2).

Properties

Solid LtBu,iPr2Li(THF) is air and moisture sensitive but stable indefinitely when

stored under N2. It is suitable for most further syntheses, but recrystallization is

recommended to ensure complete removal of traces of butyllithiumbefore usewith

metal salts that are prone to reduction, for example, copper(I) derivatives.5

References


2. (a) F. Basuli, B. C. Bailey, L. A. Watson, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola,

Organometallics 24, 1886 (2005). (b) F. Basuli, R. L. Clark, B. C. Bailey, D. Brown, J. C. Huffman,

and D. J. Mindiola, Chem. Commun. 2250 (2005).

3. (a) J. M. Smith, R. J. Lachicotte, and P. L. Holland,Chem. Commun. 1542 (2001). (b) N. A. Eckert,

E. M. Bones, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 42, 1720 (2003). (c) N. A. Eckert, J.

M. Smith, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 43, 3306 (2004).

4. J. Vela, S. Vaddadi, T. R. Cundari, J. M. Smith, E. A. Gregory, R. J. Lachicotte, C. J. Flaschenriem,

and P. L. Holland, Organometallics 24, 5494 (2005).

5. D. J. E. Spencer, N. W. Aboelella, A. M. Reynolds, P. L. Holland, andW. B. Tolman, J. Am. Chem.

Soc. 124, 2108 (2002).


5. SCANDIUM TRICHLORIDE TRIS(TETRAHYDROFURAN)AND b-DIKETIMINATE-SUPPORTED SCANDIUM

CHLORIDE COMPLEXES

Submitted by PAUL G. HAYES� and WARREN E. PIERS�

Checked by DEBASHIS ADHIKARIz and DANIEL J. MINDIOLAz

General Procedures

All manipulations were performed either in an inert atmosphere glovebox or on

a doublemanifold high-vacuum line equipped with Teflon needle valves.1 Toluene

and hexanes were dried and purified using the Grubbs/Dow purification system2

and stored in evacuated bombs.Diethyl ether and benzene-d6were dried and stored

over sodium/benzophenone ketyl. Compounds [LMe,iPr2Li]x3–5 (LMe,iPr2¼ [ArNC

(Me)]2CH�, Ar¼ 2,6-iPr2C6H3) and [L

tBu,iPr2Li]x5 (LtBu,iPr2¼ [ArNC(tBu)]2CH

�,Ar¼ 2,6-iPr2C6H3) were prepared according to literature procedures. 1H and13C NMR spectra were referenced to SiMe4 through the residual solvent signals.

A. SCANDIUM TRICHLORIDE TRIS(TETRAHYDROFURAN),ScCl3(THF)3

*

Sc2O3 þ 6 HClþ 9 H2O! 2 ScCl3ðH2OÞ6ScCl3ðH2OÞ6 þ 6 SOCl2 þ 3 THF! ScCl3ðTHFÞ3 þ 6 SO2 þ 12 HCl

Procedures

& Caution. This reaction is extremely exothermic, so the SOCl2/THF

solution should be added carefully.

ScCl3(THF)3 is prepared by a modified literature procedure.6 A 1-L round-

bottomed flask equipped with a condenser is charged with Sc2O3 (20.3 g,

*Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada,

T1K 3M4.�Department of Chemistry, University of Calgary, Calgary, Alberta, Canada, T2N 1N4.zDepartment of Chemistry and Molecular Structure Center, Indiana University,

Bloomington, IN 47405.

§ The checkers converted commercially available ScCl3(H2O)6 (Strem Chemicals) to ScCl3(THF)3using the protocol in Ref. 6. It should be noted that the checkers did not use a swivel frit, but rather,

conducted manipulations inside a glovebox using a commercially available microporous frit (medium

porosity).


0.147mol) and 6M HCl (300mL). The reaction mixture is heated at reflux for 3 h

duringwhich period themixture changes from a cloudywhite suspension to a clear

yellow solution. The solvent is removed by rotary evaporation to give ScCl3(H2O)6as a thick yellow oil. A solution of SOCl2 (350mL) in THF (250mL) is added

dropwise to the oil over 2 h, during which time a large quantity of gas (HCl and

SO2) evolves. Precipitation of awhite solid, followed by a gradual change to a clear

yellow solution, also occurs during this period. The reactionmixture is then heated

at 86�C for 18 h, and the solvent is removed by rotary evaporation to afford an oily

yellow solid. The moisture-sensitive mixture is quickly attached to a swivel-frit1

apparatus and evacuated. Et2O (200mL) is added to the residue, which is then

stirred for 20min and filtered. The fine white powder is washed with Et2O

(4� 50mL) and the solvent is removed in vacuo. Yield: 100.8 g, 0.274mol,

93%. IR (neat):6 1004 (s), 846 (s) cm�1.

Properties

The product is a finewhite powder that must be stored under an inert atmosphere as

it rapidly absorbs moisture from air.

B. SCANDIUM 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL

DICHLORIDE TETRAHYDROFURAN, (LMe,iPr2)ScCl2(THF)

ScCl3ðTHFÞ3 þLMe;iPr2Li!ðLMe;iPr2LiÞScCl2ðTHFÞþ 2 THFþLiCl

A 250-mL round-bottomed flask is attached to a swivel-frit1 assembly and charged

with [LMe,iPr2Li]x (5.00 g, 11.8mmol) and ScCl3(THF)3 (5.00 g, 13.6mmol).�

Toluene (90mL) is vacuum distilled into the evacuated flask at �78�C, and the

mixture is heated with stirring at reflux for 16 h. During this period, the solution

gradually changes from almost colorless to pale yellow. The reactionmixture is hot

filtered to remove LiCl and excess ScCl3(THF)3, and the toluene is removed from

the filtrate in vacuo. The residue is sonicated for 10min in hexanes (60mL),

followed by cold (�78�C) filtration.�� After exposure to vacuum for 6 h, (LMe,iPr2)

ScCl2(THF) is isolated in 94% yield (6.72 g, 11.1mmol).

Anal. Calcd. for C33H49N2Cl2OSc: C, 65.44; H, 8.15; N, 4.63. Found: C, 65.35; H,

8.61; N, 4.61. 1H NMR (benzene-d6): d 7.21 (m, 6H, C6H3), 5.32 (s, 1H, CH), 3.56

(sp, 4H,CHMe2, JHH¼ 6.8Hz), 3.48 (m, 4H,OCH2CH2), 1.65 (s, 6H,NCMe), 1.48

� The checkers performed the same reaction inside an N2 filled glovebox equipped with a cold well.

Similar yields were obtained as long as the glassware is oven dried and the N2 atmosphere contains

<1 ppm of O2 and is virtually free of moisture�� The checkers performed an alternative method to sonication by vigorously stirring the mixture for

5–6 hours in 80–100 mL of hexanes. Similar yields were obtained.

5. Scandium Trichloride Tris(Tetrahydrofuran) and b-Diketiminate 21

(m, 4H, OCH2CH2), 1.39 (d, 12H, CHMe2, JHH¼ 6.8Hz), 1.17 (d, 12H, CHMe2,

JHH¼ 6.8Hz). 13C{1H}NMR (benzene-d6): d 162.3 (NCMe), 143.3 (Cipso), 143.3,

126.6, 124.2 (C6H3), 99.8 (CH), 28.6 (CHMe2), 25.0, 24.7 (CHMe2), 24.4 (Me).

Properties

Complex (LMe,iPr2)ScCl2(THF) is an off-white solid that is soluble in most organic

solvents, such as diethyl ether, THF, hexanes (slightly), toluene, and bromoben-

zene; however, prolonged exposure to chlorinated solvents such as dichloro-

methane or chloroform results in decomposition. Although (LMe,iPr2)ScCl2(THF)

rapidly decomposes upon exposure to even trace air or moisture, samples can be

stored indefinitely under an inert atmosphere.

Related Compounds

Complex (LMe,iPr2)ScCl2(THF) can be alkylated by reaction with lithium or

potassium reagents. With LiMe, the resulting complex retains one THF molecule

(LMe,iPr2)ScMe2(THF), but larger groups (e.g., LiCH2EMe3 (E¼C, Si), KCH2Ph)

afford THF-free complexes.7 It is also possible to remove THF directly from (LMe,

iPr2)ScCl2(THF) via heating to 130�C under dynamic vacuum (10�4 Torr) for 18 h.

The resultant chloride-bridged dimer, [(LMe,iPr2)ScCl2]2, is largely insoluble in

alkane solvents, although reaction with LiMe to yield themethyl-bridged complex

[(LMe,iPr2)ScMe2]2 proceeds in toluene.8

C. SCANDIUM 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-

DIISOPROPYLPHENYLIMIDO)HEPTYL DICHLORIDE,

(LtBu,iPr2)ScCl2

ScCl3ðTHFÞ3 þLtBu;iPr2Li!ðLtBu;iPr2ÞScCl2 þ 3 THFþLiCl

Method A: A thick-walled round-bottomed pressure vessel (Fig.1) equippedwith a

Teflon valve1 is charged with [LtBu,iPr2Li]x (11.1 g, 21.9mmol) and ScCl3(THF)3(9.38 g, 25.7mmol) and evacuated.� Toluene (400mL) is condensed into the

vessel, which is then sealed and heated at 110�C for 3 days. It is necessary that the

mixture be constantly stirred. Quiescent mixtures generally require an additional

3–4 days. During this time, the color changes from pale to deep yellow.�� The

* The checkers performed the same reaction inside an N2 filled glovebox equipped with a heating stir

plate and obtained similar yields.** Minute quantities of water (usually from inadequately dried ScCl3(THF)3) will cause a black or dark

green color during early stages of the reaction. Such colors are generally supplanted by the usual deep

yellow as time progresses. If dark colors are observed during (or persist throughout) the reaction, the

normalworkupprotocoloutlined abovewill still give the desiredproduct, albeit in somewhat loweryields.


reaction mixture is transferred via cannula into a 500mL round-bottomed flask,

which is attached to a swivel-frit1 apparatus.Ahot filtration is performed to remove

LiCl, and excess ScCl3(THF)3, followed by removal of toluene under reduced

pressure.� The bright yellow residue is sonicated for 10min in hexanes (100mL)

and cooled to �78�C, and the slurry is filtered. The resultant yellow solid is dried

under vacuum for 12 h to afford (LtBu,iPr2)ScCl2 in 86% yield (11.7 g, 18.9mmol).

MethodB: The abovemethod is usedwith the exception that the reactionmixture is

heated at 180�C for approximately 30min and (LtBu,iPr2)ScCl2 is obtained in 68%

yield.

Anal. Calcd. for C35H53N2Cl2Sc: C, 68.06; H, 8.65; N, 4.54. Found: C, 68.54; H,

7.98; N, 4.92. 1H NMR (benzene-d6): d 7.05 (m, 6H, C6H3), 6.01 (s, 1H, CH), 3.10

(sp, 4H, CHMe2, JHH¼ 6.8Hz), 1.43 (d, 12H, CHMe2, JHH¼ 6.8Hz), 1.26 (d,

12H, CHMe2, JHH¼ 6.8Hz), 1.17 (s, 18H, NCCMe3).13C{1H} NMR (benzene-

d6): d 174.3 (NCCMe3), 142.8 (Cipso), 141.1, 127.0, 124.3 (C6H3), 90.8 (CH), 44.7

(CMe3), 32.3 (CMe3), 29.9 (CHMe2), 26.9, 24.4 (CHMe2).

Properties

Complex (LtBu,iPr2)ScCl2 is a pale yellow solid that is soluble in most organic

solvents, such as diethyl ether, THF, hexanes (slightly), toluene, and bromoben-

zene. Unlike (LMe,iPr2)ScCl2(THF), (LtBu,iPr2)ScCl2 does not retain THF, although

it does share a similar sensitivity toward air and moisture.

* The checkers performed the reaction inside an N2 filled glovebox equipped with a cold well and

filtered the product using an oven dried medium porosity filter frit. Similar yields were obtained.

Figure 1. Heavy-walled reactor used in this procedure.

5. Scandium Trichloride Tris(Tetrahydrofuran) and b-Diketiminate 23

Related Compounds

Complex (LtBu,iPr2)ScCl2 can be dialkylated using a wide array of Grignard and

lithium reagents.6 Substitution of only one chloride group can be accomplished

by reaction with LiCH2SiMe3 at �78�C to afford (LtBu,iPr2)ScCl(CH2SiMe3).7

Alternatively, it is possible to prepare (LtBu,iPr2)ScCl(Me) by the ligand redistri-

bution of (LtBu,iPr2)ScCl2 and (LtBu,iPr2)ScMe2. Upon reaction with methylalu-

moxane (MAO) orB(C6F5)3, (LtBu,iPr2)ScMe2 is an active ethylene polymerization

catalyst.9 If activated with MAO, complex (LtBu,iPr2)ScCl2 is also catalytically

active; however, larger polydispersities and lower activity, in comparison to the

dimethyl analogue, are observed.9

Acknowledgments

The authors thank the Natural Sciences and Engineering Research Council of

Canada for support in the form of Discovery Grants to P.G.H. and W.E.P. P.G.H.

also thanks theCanada Foundation for Innovation and theUniversity of Lethbridge

for financial support.

References

1. For a description of the equipment and techniques used in conducting this chemistry, see: B. J.

Burger and J. E. Bercaw, in Experimental Organometallic Chemistry: A Practicum in Synthesis

and Characterization, A. L. Waydaand M. Y. Darensbourg, eds., American Chemical Society,

Washington, DC, 1987, Vol. 357, p. 79.

2. A. B. Pangborn, M. A. Giardello, R. H. Grubbs, R. K. Rosen, and F. J. Timmers, Organometallics

15, 1518 (1996).

3. J. Feldman, S. J. McLain, A. Parthasarathy, W. J. Marshall, J. C. Calabrese, and S. D. Arthur,





6. L. E. Manzer, Inorg. Synth. 21, 135 (1982).

7. P. G. Hayes, W. E. Piers, L. W. M. Lee, L. K. Knight, M. Parvez, M. R. J. Elsegood, and W. Clegg,


8. P. G. Hayes, W. E. Piers, and M. Parvez, J. Am. Chem. Soc. 125, 5622 (2003).

9. P. G. Hayes, W. E. Piers, and R. McDonald, J. Am. Chem. Soc. 124, 2132 (2002).


6. b-DIKETIMINATE-SUPPORTED TITANIUM ANDVANADIUM DICHLORIDE COMPLEXES

Submitted by DEBASHIS ADHIKARI� and DANIEL J. MINDIOLA�

Checked by KEVIN R. D. JOHNSON,� PAUL G. HAYES,�

FRANCISCO J. ZUNO-CRUZ,z and GLORIA SANCHEZ CABRERAz

General Procedures

All manipulations unless otherwise mentioned were performed under a nitro-

gen atmosphere using standard Schlenk line or glovebox techniques. THFwas dried

over Na/Ph2CO and distilled into an evacuated vacuum flask equipped with a gas

adapter and under a positive flow of N2 or Ar. The THF-filled flask was transferred

into the glovebox and stored over metallic Na (thin films). Anhydrous toluene and

pentanewere purchased fromAldrich in a sure-sealed reservoir (18 L) and dried by

passing through two columns of activated alumina and a Cu Q-5 column under a

pressure of N2. Before use, a 5 mL aliquot of each solvent was tested, qualitatively,

with a drop of Na/benzophenone ketyl radical in a THF solution (1–2 drops in 3–5

mL of solvent must give a blue to purple solution).1 Celite was dried under reduced

pressure at 180�C for 24 h. TiCl3(THF)3 was purchased from Strem and also

prepared according to the literature procedure.2 Solution magnetization measure-

ments were determined by the method of Evans.3,4 C6D6 was degassed and dried

over CaH2 and then vacuum transferred to 4A�molecular sieves. LMe,iPr2H and the

salt [LMe,iPr2Li]x (LMe,iPr2¼ [ArNC(Me)]2CH�, Ar¼ 2,6-iPr2C6H3) were synthe-

sized using a slightly modified protocol (described herein).5 [LtBu,iPr2Li]x (LtBu,

iPr2¼ [ArNC(tBu)]2CH�, Ar¼ 2,6-iPr2C6H3) was synthesized using the method

described herein for [LMe,iPr2Li]x.6

A. SYNTHESIS OF (LMe,iPr2)TiCl2(THF)

LiLMe;iPr2 þTiCl3ðTHFÞ3 !ðLMe;iPr2ÞTiCl2ðTHFÞþ 2 THFþLiCl

*Department of Chemistry and Molecular Structure Center, Indiana University,

Bloomington, IN 47405.�Department of Chemistry and Biochemistry, University of Lethbridge, Lethbridge, Alberta, Canada,

T1K 3M4.zCentro de InvestigacionesQu�ımicasUniversidadAutonoma del Estado deHidalgo, Pachuca, Estado de

Hidalgo, 42184. Mexico.

6. b-Diketiminate-Supported Titanium and Vanadium Dichloride Complexes 25

Procedure

Into a 350- or 500-mL thick-walled round-bottomed pressure vessel (Fig. 1)

equipped with a large stir bar are loaded 100mL of THF, TiCl3(THF)3 (5.00 g,

0.014mol), and [LMe,iPr2Li]x (5.94 g, 0.014mol). The vessel is sealed inside the

glovebox with a Teflon pin. After the mixing, the slurry becomes a green colored

solution. The reaction mixture is transferred out of the glovebox and heated to

reflux (80�C) for 12 h, during which time the solution color turns to deep green.

After this time, the solution is brought into the glovebox, transferred to a 300-mL

filter flask, and evaporated under reduced pressure. Thegreenmass is extractedwith

200mL toluene, and the extract is filtered throughCelite, which is thenwashedwith

toluene several times until the washed solution is nearly clear. The green filtrate is

then reduced in volume until solid begins to form on the sides of the flask. The

concentrated solution is capped with a large rubber stopper and stored at�35�C for

24 h to obtain deep green crystals and solid (LMe,iPr2)TiCl2(THF). To expedite

drying of the materials, the crystals and solids are washed with 25mL pentane and

then dried under vacuum. The combined yield is 6.19 g (0.010mol, 68%).

Anal. Calcd. for C33H49N2OCl2Ti: C, 65.13; H, 8.12; N, 4.60. Found: C, 65.10; H,

8.19;N, 4.60. 1H NMR(23�C,399.8MHz,C6D6):d 4.94 (Dn1/2¼ 73Hz), 3.50 (Dn1/2¼ 92Hz), 2.29 (Dn1/2¼ 47Hz), 1.67 (Dn1/2¼ 93Hz). meff¼ 2.05(12)mB (C6D6,

298K, Evans’method). UV–vis (toluene (e inM�1 cm�1)): 427 (1359), 542 (368) nm.

IR (Et2O,CaF2): 3088 (s), 3071 (s), 3029 (s), 3022 (m), 2963 (m), 1962 (m), 1962 (m),

1814 (m), 1560 (m), 1476 (s), 1464 (w), 1034 (s) cm�1. mp decomp. >200�C.

Properties

Complex (LMe,iPr2)TiCl2(THF) (deep green) is a close analogue of Budzelaar’s

nonsolvento complex (LMe,iPr2)TiCl2 (deep red-brown).6 Budzelaar reported that

THF can be removed by repeated distillation of toluene solutions at 1 bar.6

Although (LMe,iPr2)TiCl2(THF) can be stored indefinitely under an inert atmo-

sphere, it is recommended that samples be stored at �35�C in a well-sealed vial

since traces of O2, moisture, or other oxidants (e.g., CCl4) readily promote

decomposition. Both the solvent-free and THF complexes have similar solubi-

lities, being soluble in toluene, benzene, and THF, and insoluble in pentane and

hexane. The complex is partially soluble in Et2O. The complex gradually

decomposes in CH2Cl2. Decomposition to unidentified products also occurs when

either complex is exposed to air, moisture, or halogenated solvents such as CCl4.

Related Complexes

Complex (LMe,iPr2)TiCl2(THF) can be alkylated to give the dimethyl derivative,

(LMe,iPr2)TiMe2. When combined with B(C6F5)3, the complex forms a highly

active catalyst for the polymerization of propene and 1-hexene.6 Atactic

polymers can be generated from the polymerization reactions.6 THF coordi-


nation to (LMe,iPr2)TiCl2 does not seem to impede transmetallation reactions.

Likewise, THF can be readily displaced when the alkyl substituent is sterically

encumbering. For example, treatment of (LMe,iPr2)TiCl2(THF) with 2 equiv of

LiCH2tBu, LiCH2SiMe3, and LiNHAr (Ar¼ 2,6-iPr2C6H3) affords the four-

coordinate Ti(III) products, (LMe,iPr2)Ti(CH2tBu)2,

7 (LMe,iPr2)Ti(CH2SiMe3)2,8

and (LMe,iPr2)Ti(NHAr)2,9 respectively. Treatment of (LMe,iPr2)TiCl2(THF) with

1 equiv of NaN(SiMe3)2 provides (LMe,iPr2)TiCl[N(SiMe3)2] and free THF.10

B. SYNTHESIS OF (LtBu,iPr2)TiCl2

LiLtBu;iPr2 þTiCl3ðTHFÞ3 !ðLtBu;iPr2ÞTiCl2 þ 3 THFþLiCl

Procedure

In a 350- or 500-mL thick-walled glass round-bottomed pressure vessel

(CHEMGLASS) in the glovebox, TiCl3(THF)3 (1.3 g, 0.004mol) is transferred

into 30mL of toluene, and the suspension cooled to �35�C. In a conical flask,

[LtBu,iPr2Li]x (1.785 g, 0.004mol) is taken up with 30mL of toluene. The toluene

solution of [LtBu,iPr2Li]x is transferred by a pipette to the suspension of

TiCl3(THF)3 in toluene. During the addition of the salt, the blue color of the

TiCl3(THF)3 suspension gradually changes to greenish brown. Upon completing

the addition, the thick-walled reactionvessel (Fig. 1) is closedwith a Teflon-coated

cap. The reaction vessel is brought outside the glovebox and heated at 110�C for 3

days with vigorous stirring. Within 2 h of initial heating, the color of the solution

changes to intense green. After completion of the reaction, the reaction vessel is

brought back into the glovebox, the solution is filtered through aCelite bed, and the

volume of the filtrate is reduced to�20mLuntil greenmicrocrystals begin to form.

After allowing the solution to warm up to the box temperature to redissolve the

crystals, 25mL of hexane is added and the solution is cooled to�35�C for 24 h. At

this time, intense green microcrystals of (LtBu,iPr2)TiCl2 are separated after

filtering the solution through a medium porosity frit, and the solids are washed

with 10mL of hexane to afford 1.27 g of product (0.002mol, 58% yield).* The

filtrate from the first crystallization appears reddish in color. Reducing the volume

of the latter solution to �5mL and subsequent cooling to �35�C over 12–16 h

yields red crystals of (LtBu,iPr2)Ti¼NAr(Cl) (335mg, 0.0004mol, 12.5% yield).11

Anal. Calcd. for C35H53N2Cl2Ti: C, 67.73; H, 8.61; N, 4.51. Found: C, 66.19; H,

8.63; N, 4.40. 1H NMR (23�C, C6D6): d 8.50 (Dn1/2¼ 25Hz), 5.06 (Dn1/2¼ 48

Hz), 1.99 (Dn1/2¼ 127Hz). meff¼ 1.98(9)mB (C6D6, 298K, Evans’ method). UV–

* Sometimes it is necessary to physically separate the red crystals of (LtBu,iPr2)Ti¼NAr(Cl) from the

intensely green microcrystals of (LtBu,iPr2)TiCl2. To obtain reproducible recrystallization results, it is

highly recommended to have a homogeneous solution prior to cooling.

6. b-Diketiminate-Supported Titanium and Vanadium Dichloride 27

vis (toluene, 25�C): 344 nm (3780M�1 cm�1). IR (Nujol, CaF2): 1363 (s), 1258

(m), 1212 (w), 1180 (w), 939 (w). mp 146(3)�C (the color changes from green to

reddish during the melting process).

Properties

Complex (LtBu,iPr2)TiCl2 (intense green) is indefinitely stable at�35�C and in the

absence of oxidants or protic media. This complex is soluble in toluene, benzene,

THF, and Et2O, but insoluble in pentane and hexane. Unlike (LtBu,iPr2)TiCl2(THF),

(LtBu,iPr2)TiCl2 appears to be stable in CH2Cl2 over several hours at room

temperature, but decomposition ensues after extended times.

Related Compounds

Complex (LtBu,iPr2)TiCl2 can be alkylated to the dimethyl derivative, (LtBu,iPr2)

TiMe2, a precursor to the Ti(IV) complex (LtBu,iPr2)TiMe2(OTf) by AgOTf oxida-

tion.12 The latter complex is a convenient synthon to the phosphinidene, (LtBu,iPr2)

Ti¼P[Trip](Me),13 via the treatment with LiPH[Trip] (Trip¼ 2,4,6-iPr3C6H2).

Complex (LtBu,iPr2)TiCl2 can also be alkylated with 2 equiv of LiCH2tBu to afford

(LtBu,iPr2)Ti(CH2tBu)2,

12 a precursor to the four-coordinate alkylidene complex

(LtBu,iPr2)Ti¼CHtBu(OTf).12 An alternative synthesis of (LtBu,iPr2)TiCl2 without

formation of the imido impurity can be achieved usingTiCl3 instead ofTiCl3(THF)3in toluene.12 The low yield of (LtBu,iPr2)TiCl2 (�23%), however, coupled with the

expense in using TiCl3 makes this process unattractive.

C. SYNTHESIS OF (LMe,iPr2)VCl2

LiLtBu;iPr2 þVCl3ðTHFÞ3 !ðLMe;iPr2ÞVCl2ðTHFÞþ 2 THFþLiCl

ðLtBu;iPr2ÞVCl2ðTHFÞ! ðLtBu;iPr2ÞVCl2 þTHF

Procedure

The procedure for (LMe,iPr2)VCl2 is a slight modification of the literature

method.6 VCl3(THF)314 (3.00 g, 0.008mol) is slurried in 40mL of THF and

[LMe,iPr2Li]x (3.41 g, 0.008mol) is dissolved in 30mLofTHF. Inside the glovebox,

both solutions are loaded in a 350- or 500-mL heavy wall glass round-bottomed

pressure vessel (Fig.1, vide supra, CHEMGLASS), which is securely sealed with a

Teflon cap. After mixing, the color of the solution gradually changes to red-brown.

Themixture is transferred out of the glovebox and refluxedwith stirring at 90�C for

30min, upon which the solution rapidly turns to deep brown-red. The solution is

cooled to room temperature, and then the flask is brought into the glovebox and

transferred to a Schlenk flask. The volatiles are removed under reduced pressure

inside the glovebox to yield a red-brown solid. The flask is sealed with a glass


stopper, and then evacuated and brought out of the glovebox. The flask is then

heated at 100�C for 45min under dynamic vacuum on a Schlenk line. During the

heating/vacuum process, the complex loses THF to afford a deep green solid. The

flask is transferred into theglovebox, and the deep greenmass iswashedwith 25mL

of hexane and then extractedwith 200mLof toluene. The toluene solution is filtered

through a bed of Celite, rinsing the residue with 10mL portions of toluene until the

filtrate is almost colorless (approximately three portions). The volume of the deep

green filtrate is reduced to�50mL until a solid begins forming on the sides of the

flask.The solution is cappedwith a rubber stopper and cooled to�35�C for 2 days to

obtain bright green crystals of (LMe,iPr2)VCl2. After filtration, the green crystals are

collected and dried under reduced pressure. The filtrate is then concentrated

(�25mL) and stored at �35�C for 1 day to afford a second batch of product,

which is dried under vacuum. The combined yield is 3.29 g (0.006mol, 76% yield).

1H NMR (23�C, C6D6): d 5.91 (Dn1/2¼ 123Hz), 3.64 (Dn1/2¼ 561Hz), 2.66

(Dn1/2¼ 194Hz).meff¼ 2.90(1)mB (C6D6, 298K,Evans’method).UV–vis (toluene

(e inM�1 cm�1)): 789 (260), 586 (287), 416 (2100), 319 (7973) nm. IR (Nujol, KBr

plates) 1534 (m), 1340 (s), 1320 (s), 804 (m), 757 (w) cm�1. mp decomp. >200�C.6

Properties

Complex LMe,iPr2VCl2 is a deep greenmaterial soluble in toluene, Et2O, benzene,

and THF. It has properties similar to LMe,iPr2TiCl2(THF), being insoluble in

hexane and pentane. The complex gradually decomposes in CH2Cl2. Complex

LMe,iPr2VCl2 is readily oxidized by O2 and reacts rapidly with water to afford

intractable products.

Related Compounds

Complex LMe,iPr2VCl2 can be readily alkylated with 2 equiv of LiMe, LinBu, and

LiCH2tBu to afford the corresponding bis-alkyl complexes LMe,iPr2V(R)2 (R¼

Me,6n Bu,6 CH2tBu15). Complex LMe,iPr2V(Me)2 is not as active catalyst as the

titanium analogue for the polymerization of propene and 1-hexene when activated

with B(C6F5)3.6 However, the alkyl derivative LMe,iPr2V(CH2

tBu)2 is an excellent

precursor to both vanadium(IV) alkylidene species15 andV(V) alkylidynes such as

(LMe,iPr2)V:CtBu(OTf)16 and [(LMe,iPr2)V:CtBu(THF)][BPh4].16 The latter

complexes are prepared by a stepwise one-electron oxidation, followed by

alkylation with LiCH2SiMe3, and then another one-electron oxidation with AgX

(X¼OTf or BPh4).16 Complex (LMe,iPr2)VCl2 is also a convenient precursor to

terminal and neutral vanadium nitride complexes.17

Acknowledgments

Theauthors thank IndianaUniversity,Bloomington, theCamille andHenryDreyfus

Foundation (New Faculty and Teacher–Scholar Awards to D.J.M.), the Alfred P.

6. b-Diketiminate-Supported Titanium and Vanadium Dichloride 29

Sloan Foundation (fellowship toD.J.M.), and theU.S.National Science Foundation

(CHE-0348941, PECASE Award to D.J.M.) for support to this research.

References


15, 1518 (1996).

2. N. A. Jones, S. T. Liddle, C. Wilson, and P. L. Arnold, Organometallics 26, 755 (2007).

3. S. K. Sur, J. Magn. Reson. 82, 169 (1989).

4. D. F. Evans, J. Chem. Soc. 2003 (1959).




7. F. Basuli, B. C. Bailey, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola, J. Am. Chem. Soc. 125,

6052 (2003).

8. F. Basuli, D. Adhikari, J. C. Huffman, and D. J. Mindiola, J. Organomet. Chem. 692, 3115 (2007).

9. F. Basuli, B. C. Bailey, J. C. Huffman, and D. J. Mindiola, Chem. Commun. 1554 (2003).

10. B. C. Bailey, F. Basuli, J. C. Huffman, and D. J. Mindiola, Organometallics 25, 2725 (2006).

11. F. Basuli, R. L. Clark, B. C. Bailey, D. Brown, J. C. Huffman, and D. J. Mindiola,Chem. Commun.

2250 (2005).

12. F. Basuli, B. C. Bailey, L. A. Watson, J. Tomaszewski, J. C. Huffman, and D. J. Mindiola,


13. G. Zhao, F. Basuli, U. J. Kilgore, H. Fan, H. Aneetha, J. C. Huffman, G. Wu, and D. J. Mindiola,

J. Am. Chem. Soc. 128, 13575 (2006).


15. F. Basuli, U. J. Kilgore, X. Hu, K. Meyer, M. Pink, J. C. Huffman, and D. J. Mindiola, Angew.

Chem., Int. Ed. 43, 3156 (2004).

16. F. Basuli, B. C. Bailey, D. Brown, J. Tomaszewski, J. C. Huffman, M.-H. Baik, and D. J. Mindiola,

J. Am. Chem. Soc. 126, 10506 (2004).

17. B. L. Tran, M. Pink, X. Gao, H. Park, and D. J. Mindiola, J. Am. Chem. Soc. 132, 1458 (2010).

7. b-DIKETIMINATE-SUPPORTED VANADIUM ANDCHROMIUM CHLORIDE COMPLEXES

Submitted by CHULEEPORN PUTTNUAL,� LEONARD A. MacADAMS,�

and KLAUS H. THEOPOLD�

Checked by YOSRA M. BADIEI� and TIMOTHY H. WARREN�

General Procedures

Allmanipulations of compounds were carried out using standard Schlenk, vacuum

line, and glovebox techniques. Pentane, diethyl ether, tetrahydrofuran, and toluene

*Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716.�Department of Chemistry, Georgetown University, Washington, DC 20057-1227.


were distilled from purple Na benzophenone ketyl solutions. C6D6 was predried

with sodium and stored under vacuum over 4A�molecular sieves. NMR spectra

were referenced to the residual protons of the solvent (C6D5H¼ 7.15 ppm,

CDHCl2¼ 5.32 ppm). Molar magnetic susceptibilities were corrected for diamag-

netism using Pascal constants.

Butyllithium was purchased as a 1.6M solution in hexane from Aldrich. VCl3(anhydrous) and CrCl3 (anhydrous) were purchased fromStrem. VCl3(THF)3

1 and

CrCl3(THF)32 were prepared according to the literature procedures. HLMe,Me2 was

prepared according to Budzelaar’s method (see Section 2A).3

A. SYNTHESIS OF LMe,Me2VCl2

HLMe;Me2 þBuLi!LiLMe;Me2 þBuH

LiLMe;Me2 þVCl3ðTHFÞ3 !LMe;Me2VCl2ðTHFÞþLiClþ 2 THF

Procedure

A solution of 10.0 g (32.6mmol) of HLMe,Me2 in 100mL of diethyl ether is

prepared in a 250-mL Schlenk flask. The solution is cooled to �30�C and then

treated with 20.42mL (32.6mmol) of 1.6M n-butyllithium in hexane. The

mixture is allowed to warm to room temperature and the yellow solution thus

obtained is added to a 500-mL flask containing a red slurry of 12.18 g

(32.6mmol) of VCl3(THF)3 in 200mL of THF. The resulting dark red-brown

solution is stirred overnight at room temperature giving a dark green solution.

The solution is evaporated to dryness; the residue is triturated three times with

20mL of diethyl ether to give a green solid, discarding the ether. The residue is

then extracted three times with toluene totaling ca. 200mL, and the combined

extract is filtered through Celite, rinsing with ca. 10mL of toluene. The

resultant solution is concentrated to approximately one-third of its original

volume and left to crystallize at �30�C to afford red-brown crystals. Yield:

10.50 g (75%).

Anal. Calcd. for C21H25N2Cl2V: C, 59.03%; H, 5.90%; N, 6.49%; Cl, 16.59%.

Found: C, 59.06%;H, 5.85%;N, 6.42%;Cl, 16.33%. 1H NMR (CD2Cl2): d 8.1, 7.5(vb, 22H), �2.5 (b, 3H). IR (KBr): 3015 (w), 2918 (m), 1534 (s), 1467 (m), 1376

(m), 1323 (s), 1234 (m), 1170 (w), 1094 (w), 1020 (w), 866 (w), 772 (s), 416

(m) cm�1. EI-MS m/z (%): 426.0 (100) [Mþ ], 391.1 (8.3)[Mþ � Cl]. UV–vis

(toluene): lmax (e in M�1 cm�1) 415 (1773), 561 (409), 758 nm (460). meff¼ 3.1

(1)mB (294K). mp 268–270�C.

7. b-Diketiminate-Supported Vanadium and Chromium Chloride Complexes 31

Properties

LMe,Me2VCl2 is soluble in THF, toluene, and dichloromethane but essentially

insoluble in ether and pentane. In the b-diketiminato complexes LVCl2, the nature

of the N-aryl substituents determines the affinity of the complex for THF. For

instance, the parent N-phenyl-substituted b-diketiminate is isolated as a bis(THF)

solvate LMe,Me2VCl2(THF)2,4 whereas LMe,Me2VCl2, L

Me,Me3VCl2,3 and LMe,

iPr2VCl23 may be isolated THF-free. As outlined in the entry for LMe,iPr2VCl2

(described herein), b-diketiminato vanadium dihalide complexes have been

explored as precatalysts for a-olefin polymerization and may be alkylated to give

dialkyls LVR2.

B. SYNTHESIS OF LMe,Me2CrCl2(THF)2

HLMe;Me2 þBuLi!LiLMe;Me2 þBuH

LiLMe;Me2 þCrCl3ðTHFÞ3 !LMe;Me2CrCl2ðTHFÞþLiClþ 2 THF

Procedure

HLMe,Me2 (1.0 g, 3.27mmol) is dissolved in 50mL of THF and the solution was

cooled to �30�C. n-Butyllithium (2.0mL of 1.6M in hexanes, 3.27mmol) is

slowly added to this solution, and this mixture is stirred for another 30min and

allowed to warm to room temperature. The resultant solution of LiLMe,Me2 is then

slowly added over 3 h at room temperature to a slurry of CrCl3(THF)3 (1.224 g,

3.27mmol) in 150mL of THF. The color of the solution changes from purple to

red-brown. After stirring the solution at room temperature overnight, the THF is

removed and the solid is extracted with three 30-mL portions of toluene. The

solution is then filtered through Celite, rinsing with ca. 20mL toluene. The toluene

is then removed in vacuo and the solid is dissolved in ca. 40mLTHF and refiltered

through Celite. The resulting THF solution is concentrated to 20mL in vacuo and

allowed to crystallize overnight at �30�C. A dark red microcrystalline powder is

isolated by filtration. After washing with ca. 5mL cold THF and drying under

vacuum, 1.45 g (76%) of the product is isolated.

Anal. Calcd. for C29H41N2O2CrCl2: C, 60.84%; H, 7.22%; N, 4.89%. Found: C,

60.71%; H, 7.03%; N, 5.38%. 1H NMR (C6D6): d 40.7 (vb, 6H), 13.3 (vb, 4H), 9.4(vb, 4H), 3.8 (b, 8H), 1.4 (b, 8H), �4.2 (vb, 2H) ppm. IR (KBr): 3050 (w), 3014

(m), 2965 (s), 2925 (s), 2869 (s), 1520 (vs), 1459 (vs), 1448 (vs), 1377 (vs), 1259

(m), 1242 (m), 1177 (s), 1096 (m), 1015 (m), 1005 (m), 879 (s), 850 (s), 762

(s) cm�1. UV–vis (Et2O): lmax (e in M�1 cm�1) 656 (224), 506 (815), 476 (945),


407 (5300). meff¼ 4.0(1)mB (294K). mp 208–209�C. Mass spectrumm/z (%): 427

(4.14) [Mþ � 2THF], 392 (17.3) [Mþ � Cl, 2THF], 356 (17.6) [Mþ � 2Cl,

2THF].

Properties

LMe,Me2CrCl2(THF)2 is soluble in THF and partially soluble in toluene, benzene,

and ether. The solution is red-brown in THF, toluene, and benzene, but changes to a

yellow color in ether.

Related Compounds

b-Diketiminato chromium halide and alkyl complexes have been explored as

precatalysts for alkene polymerization.4–7 For instance, LMe,Me2CrCl2(THF)2reacts with alkyllithium reagents to give LMe,Me2CrMe2(THF) and LMe,Me2Cr

(CH2SiMe3)2.7 These dialkyls may be converted to alkyl cations such as [LMe,

iPr2Cr(CH2SiMe3)(OEt2)]þ that serves as a living ethylene polymerization cata-

lyst.7 In addition, hydrogenation of LMe,Me2Cr(CH2SiMe3)2 produces the stable

alkyl hydride complex [LMe,Me2Cr]2(m-CH2SiMe3)(m-H).8 The bulkier LMe,iPr2

ligand has been used to prepare the highly reactive synthons to the two-coordinate

LMe,iPr2Cr fragment [LMe,iPr2Cr]2(m-h2:h2-N2)9 and [LMe,iPr2Cr]2(m-h6:h6-tolu-

ene),10 which participate in a variety of interesting reactions such as oxidation by

O2 to give the d1 dioxo complex LMe,iPr2Cr(O)2.

References


2. W. Herwig and H. Zeiss, J. Org. Chem. 23, 1404 (1958).


4. W.-K. Kim, M. J. Fevola, L. M. Liable-Sands, A. L. Rheingold, and K. H. Theopold,


5. V. C.Gibson, C. Newton, C. Redshaw,G. A. Solan, A. J. P.White, andD. J.Williams,Eur. J. Inorg.

Chem. 1895 (2001).

6. L. A. MacAdams, W.-K. Kim, L. M. Liable-Sands, I. A. Guzei, A. L. Rheingold, and K. H.

Theopold, Organometallics 21, 952 (2002).

7. L. A. MacAdams, G. P. Buffone, C. D. Incarvito, A. L. Rheingold, and K. H. Theopold, J. Am.

Chem. Soc. 127, 1082 (2005).

8. L. A. MacAdams, G. P. Buffone, D. C. Incarvito, H. A. Golen, A. L. Rheingold, and K. H.

Theopold, Chem. Commun. 1164 (2003).

9. W. H. Monillas, G. P. A. Yap, L. A.MacAdams, and K. H. Theopold, J. Am. Chem. Soc. 129, 8090

(2007).

10. Y.-C. Tsai, P.-Y. Wang, S.-A. Chen, and J.-M. Chen, J. Am. Chem. Soc. 129, 8066 (2007).

7. b-Diketiminate-Supported Vanadium and Chromium Chloride Complexes 33

8. b-DIKETIMINATE-SUPPORTED MANGANESEAND ZINC COMPLEXES

Submitted by HERBERT W. ROESKY�

Checked by MATTHEW S. VARONKA� and TIMOTHY H. WARREN�

A two-step procedure is employed based on the literature procedure for LMe,

iPr2MnI(THF), which first generates the potassium salt KLMe,iPr2 prior to its

reaction with MnI2.1 The preparation of the potassium salt of the b-diketimine

HLMe,iPr2 was first reported by Mair and coworkers from HLMe,iPr2 and

KN(SiMe3)2 in relatively low yield (27%).2 Winter and coworkers have reported

a related THF adduct from KH.3 Here, the same reagents in diethyl ether give

a base-free potassium salt that was used to introduce LMe,iPr2 into manganese and

zinc complexes.

General Procedures

All reactions were performed using standard Schlenk and drybox techniques. All

the solvents except dichloromethane (P4O10) were distilled from sodium under dry

nitrogen. 12MHCl,MnI2, ZnI2, andBuLi in hexanewere purchased fromAldrich.

A. LMe,iPr2MnI(THF)

HLMe;iPr2 þKH!KLMe;iPr2 þH2

KLMe;iPr2 þMnI2 þTHF!LMe;iPr2MnIðTHFÞþKI

& Caution. Air-free procedures are required for use of potassium hydride,

which can explosively generate hydrogen gas upon uncontrolled hydrolysis.

Hydrogen gas is generated in the procedure and should not be performed in

a sealed flask.

Step 1: A suspension of KH (0.18 g, 4.5mmol) and HLMe,iPr2 (1.67 g, 4.00mmol)

in diethyl ether (50mL) is stirred at room temperature for 3 days. After filtration,

the light yellow filtrate is concentrated to ca. 10mL and stored at�26�C for 24 h to

afford crystalline solid. Yield: 1.59 g (87%).

*Institut f€ur Anorganische Chemie, Universit€at Gottingen, D-37077 Gottingen, Germany.�Department of Chemistry, Georgetown University, Washington, DC 20057-1227.


1H NMR (C6D6): d 7.08 (d, J¼ 8.0Hz, 4H, ArH), 6.96 (t, J¼ 8.0Hz, 2H, ArH),

4.74 (s, 1H,CH), 3.29 (sept, J¼ 7.2Hz, 4H,CH(CH3)2), 3.29 (sept, J¼ 7.2Hz, 4H,

CH(CH3)2), 1.81 (s, 6H, CH3), 1.19 (d, J¼ 6.8Hz, 12H, CH(CH3)2), 1.00 (d,

J¼ 6.8Hz, 12H, CH(CH3)2).

Step 2: A solution of KLMe,iPr2 (0.91 g, 2.0mmol) in THF (10mL) is added to

a suspension ofMnI2 (0.62 g, 2.0mmol) in THF (35mL) at�78�C. Themixture is

allowed to warm to room temperature and stirred for 14 h. The precipitate is

removed by filtration. The yellow filtrate is concentrated to ca. 5mL and stored at

�26�C for 24 h to give yellow crystals. Yield: 1.17 g (87%).*

Anal. Calcd. for C33H49IMnN2O (670.84): C, 59.03; H, 7.30; N, 4.17. Found: C,

58.95; H, 7.24; N, 4.16. EI-MS: m/z (%) 599 (100) [LMnI]þ . UV–vis (THF, nm(cm�1M�1)) 439 (93), 461 (64). mp 379–381�C. IR (KBr, Nujol mull, cm�1):

1624 (w), 1552 (w), 1520 (m), 1314 (m), 1262 (m), 1174 (w), 1100 (w), 1024 (m),

935 (w), 870 (w), 852 (w), 794 (m), 757 (w), 721 (w), 600 (vw), 524 (w), 468 (vw).

Properties

LMe,iPr2MnI(THF) is soluble in THF and toluene and sparingly soluble in Et2O and

n-pentane. The bound THF ligand may be readily removed by refluxing in toluene

(see below) and may be displaced by other Lewis bases such as a N-heterocyclic

carbene ligand.1

B. THE THF-FREE DIMER (LMe,iPr2MnI)2

LMe;iPr2MnIðTHFÞ!LMe;iPr2MnIþTHF

A solution of LMe,iPr2MnI(THF) (1.34 g, 2mmol) in toluene (40mL) is refluxed for

0.5 h. All volatiles are removed in vacuo and bright yellow microcrystals are

obtained. Yield: 1.15 g (96%).

Anal. Calcd. for C58H82I2Mn2N4 (1197.68): C, 58.11; H, 6.84; N, 4.67. Found: C,

58.34; H, 6.92; N, 4.85. EI-MS: m/z 599 (100) [LMnI]þ . IR (KBr, Nujol mull,

cm�1): 1657 (w), 1625 (w), 1552 (w), 1262 (m), 1097 (m), 1023 (m), 875 (w), 800

(m), 722 (w), 659 (w), 536 (w), 468 (w) cm�1. mp 271–273�C (dec).

Properties and Related Compounds

The product is soluble in toluene and insoluble in Et2O and pentane. This dimeric b-diketiminato manganese iodide complex as well as its chloride-bridged relative

* The checkers obtained yellow crystals from one crystallization with a yield of 53%.

8. b-Diketiminate-Supported Manganese and Zinc Complexes 35

(LMe,iPr2MnCl)24 can be alkylated with MeLi and arylated with PhLi to give the

dinuclear (LMe,iPr2Mn)2(m-Me)2 or the three-coordinate LMe,iPr2MnPh.4,5. A related

trinuclear species LMe,iPr2Mn(m-Cl)2Mn(m-Cl)2MnLMe,iPr2 undergoes related reac-

tion with allylmagnesium chloride to yield the four-coordinate LMe,iPr2Mn

(CH2CH¼CH2)(THF) and with phenylethynyl lithium to give (LMe,iPr2Mn)2(m-CCPh)2.

6 Reduction of (LMe,iPr2MnI)2 yields the highly reactive ferromagnetically

coupled dimer (LMe,iPr2Mn)2 with a Mn–Mn distance of 2.721(1)A�.7,8 This novel

MnI–MnI dimer reacts with dioxygen to form the bis(m-oxo) species (LMe,

iPr2Mn)2(m-O)2.7

C. LMe,iPr2ZnCl2Li(OEt2)2

HLMe;iPr2 þBuLiþEt2O!LiLMe;iPr2ðEt2OÞþBuH

LiLMe;iPr2ðEt2OÞþZnCl2 þEt2O!LMe;iPr2ZnCl2LiðEt2OÞþLiCl

& Caution. Butyllithium is pyrophoric in air and should be handled exclu-

sively under dry nitrogen or argon.

This two-stepprocedure uses the ether adduct of the lithiumsaltLMe,iPr2Li(OEt2)9,10

in the reaction with ZnCl2 to give the ‘‘ate’’ complex LMe,iPr2ZnCl2Li(OEt2)2.12

Step 1: HLMe,iPr2 (8.00 g, 19.1mmol) is dissolved in rapidly stirred Et2O (70mL),

and the resulting solution is treated with 12.0mL of a 1.6M n-BuLi solution in

hexane. Upon completion of the addition, the solution is allowed to warm to room

temperature and stirred for 12 h. The solution is concentrated to approximately

20mL under reduced pressure until the product precipitates, which redissolves

with mild heating. Cooling for 24 h at ca. �20�C affords LMe,iPr2Li(OEt2) as

colorless crystals. mp 138–139�C. Yields range between 75% and 90%.

1H NMR (CDCl3): d 7.02 (m, 6H, ArH), 4.62 (s, 1H, CH), 3.13 (sept, J¼ 6.8Hz,

4H, CH(CH3)2), 2.92 (quad, J¼ 6.8Hz, 4H, ether-CH2), 1.72 (s, 6H, CH3), 1.21

(d, J¼ 7.2Hz, 12H, CH(CH3)2), 1.07 (d, J¼ 7.2Hz, 12H, CH(CH3)2), 0.61

(t, J¼ 6.8Hz, 6H, ether-CH3).7Li NMR (C6D6): d 1.61.

Step 2: To a suspension of ZnCl2 (395mg, 2.90mmol) in Et2O (10mL) is slowly

added a solution of LMe,iPr2LiOEt2 (1.44 g. 2.90mmol) in Et2O (10mL) at�35�C.Themixture is allowed towarm to room temperature and then stirred for additional

3 h and then filtered. The solution is concentrated to 10mL and cooled overnight at

�35�C to yield colorless crystals. Yield: 1.36 g (67%).�

* The checkers note that closely related procedures have been reported to give the halide-freemonomer

LMe,iPr2ZnCl, though two attempts at checking gave only the LiCl adduct LMe,iPr2ZnCl2Li(OEt2)2 in

comparable yields to that described above.


Anal. Calcd. for C37H61Cl2LiN2O2Zn (709.15): C, 62.67; H, 8.67; N, 3.95. Found:

C, 62.46; H, 8.81; N, 4.19. 1H NMR (CDCl3): d 7.17 (m, 6H, ArH), 5.10 (s, 1H,

CH), 3.47 (quad, J¼ 7.2Hz, 8H, ether-CH2), 2.98 (sept, J¼ 6.8Hz, 4H, CH

(CH3)2), 1.81 (s, 6H, CH3), 1.25 (d, J¼ 6.8Hz, 12H, CH(CH3)2), 1.20 (t, J¼ 7.2

Hz, 12H, ether-CH3), 1.16 (d, J¼ 6.8Hz, 12H, CH(CH3)2);13C NMR (C6D6): d

170.1, 142.1, 141.5, 126.3, 123.6, 95.3, 65.8, 28.2, 24.2, 23.6, 23.2, 15.2.

Properties

LMe,iPr2Li(OEt2) is readily soluble in ether, THF, and hydrocarbons as well as

halogenated solvents such as CH2Cl2. LMe,iPr2ZnCl2Li(OEt2)2 is soluble in THF,

ether, and aromatic solvents, sparingly soluble inCH2Cl2, and essentially insoluble

in pentane. The Et2O coordinated to Li is somewhat labile. Titration of the

solid with other solvents such as CDCl3 results in a gradual loss of Et2O. This

b-diketiminate has been reported to be isolated as the three-coordinate complex

LMe,iPr2ZnCl via careful crystallization.11,12

Related Compounds

Both LMe,iPr2ZnCl and LMe,iPr2ZnCl2Li(OEt2)2 serve as platforms for subsequent

modification. Three-coordinate alkyl complexes LMe,iPr2Zn-R may be formed by

alkylation with alkyllithium reagents.Monoethyl complexesmay also be prepared

byuseofZnEt2withthefree ligandHL.13,14ReactionofLMe,Me2ZnMewithMe3SnF

gives thefluoride-bridgeddimer (LMe,Me2Zn)2(m-F)2,which canbe converted to thehydride-bridged dimer (LMe,Me2Zn)2(m-H)2 upon reaction with Et3SiH.

15 The

lithium halide-bridged adducts LZnX2Li(OEt2) are also synthetically useful in the

preparation of thiolate-bridged dimers (LMe,Me2Zn)2(m-SR)2.16 b-Diketiminato

zinc complexes have been investigated as catalysts for epoxide/CO2 copolymeri-

zation13,14,17–19 and ring-opening lactide polymerization.20–23 The related LMe,

iPr2ZnI2Li(OEt2)2 can be reduced by potassium metal to give the unusual ZnI–ZnI

dimer (LMe,iPr2Zn)2 with a Zn�Zn bond distance of 2.3586(7)A�.24

References

1. J. Chai, H. Zhu, K. Most, H. W. Roesky, D. Vidovic, H.-G. Schmidt, and M. Noltemeyer, Eur. J.

Inorg. Chem. 4332 (2003).

2. W. Clegg, E. K. Cope, A. J. Edwards, and F. S. Mair, Inorg. Chem. 37, 2317 (1998).

3. H. M. El-Kaderi, M. J. Heeg, and C. H. Winter, Polyhedron 25, 224 (2006).

4. J. Chai, H. Zhu, H. W. Roesky, C. He, H.-G. Schmidt, and M. Noltemeyer, Organometallics 23,

3284 (2004).

5. J. Chai, H. Zhu, H. Fan, H. W. Roesky, and J. Magull, Organometallics 23, 1177 (2004).

6. J. Chai, H. Zhu, H. W. Roesky, Z. Yang, V. Jancik, R. Herbst-Irmer, H.-G. Schmidt, and M.

Noltemeyer, Organometallics 23, 5003 (2004).

7. J. Chai, H. Zhu, A. C. St€uckl, H.W. Roesky, J. Magull, A. Bencini, A. Caneschi, and D. Gatteschi,

J. Am. Chem. Soc. 127, 9201 (2005).

8. b-Diketiminate-Supported Manganese and Zinc Complexes 37

8. L. Sorace, C. Golze, D. Gatteschi, A. Bencini, H. W. Roesky, J. Chai, and A. C. St€uckl, Inorg.Chem. 45, 395 (2006).


J. Chem. Soc., Dalton Trans. 3465 (2001).

10. Y. Ding, H.W. Roesky,M. Noltemeyer, H.-G. Schmidt, and P. P. Power,Organometallics 20, 1190

(2001).

11. J. Prust, A. Stasch,W.Zheng,H.W.Roesky, E.Alexopoulos, I. Uson,D.Bohler, andT. Schuchardt,


12. J. Prust, H. Hohmeister, A. Stasch, H. W. Roesky, J. Magull, E. Alexopoulos, I. Uson, H. G.

Schmidt, and M. Noltemeyer, Eur. J. Inorg. Chem. 2156 (2002).

13. M. Cheng, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 120, 11018 (1998).

14. M. Cheng, D. R. Moore, J. J. Reczek, B. M. Chamberlain, E. B. Lobkovsky, and G. W. Coates,

J. Am. Chem. Soc. 123, 8738 (2001).

15. H. Hao, C. Cui, H. W. Roesky, G. Bai, H.-G. Schmidt, and M. Noltemeyer, Chem. Commun. 1118

(2001).

16. M. S. Varonka and T. H. Warren, Inorg. Chim. Acta 360, 317 (2007).

17. S.D.Allen,D.R.Moore,E.B. Lobkovsky, andG.W.Coates, J. Am.Chem. Soc.124, 14284 (2002).

18. D. R. Moore, M. Cheng, E. B. Lobkovsky, and G. W. Coates, Angew. Chem., Int. Ed. 41, 2599

(2002).

19. C.M.Byrne, S.D.Allen, E.B. Lobkovsky, andG.W.Coates, J. Am.Chem. Soc.126, 11404 (2004).

20. M. Cheng, A. B. Attygalle, E. B. Lobkovsky, and G. W. Coates, J. Am. Chem. Soc. 121, 11583

(1999).

21. B.M.Chamberlain,M.Cheng,D.R.Moore,T.M.Ovitt, E.B. Lobkovsky, andG.W.Coates, J. Am.

Chem. Soc. 123, 3229 (2001).

22. L.R.Rieth,D.R.Moore, E.B. Lobkovsky, andG.W.Coates, J. Am.Chem. Soc.124, 15239 (2002).

23. A. P. Dove, V. C. Gibson, E. L. Marshall, A. J. P. White, and D. J. Williams, Dalton Trans. 570

(2004).

24. Y. Wang, B. Quillian, P. Wei, H. Wang, X.-J. Yang, Y. Xie, R. B. King, P. v. R. Schleyer, H. F.

SchaefferIII, and G. H. Robinson, J. Am. Chem. Soc. 127, 11944 (2005).

9. IRON 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYLCHLORIDE (LMe,iPr2FeCl)

Submitted by BRYAN D. STUBBERT� and PATRICK L. HOLLAND�

Checked by DEBASHIS ADHIKARI� and DANIEL J. MINDIOLA�

General Techniques

All manipulations were performed under a nitrogen atmosphere by standard

Schlenk techniques or in a glovebox maintained at or below 1 ppm of O2 and


47405.


H2O. Glassware was dried at 150�C overnight. Pentane and toluene were purified

by passing through activated alumina and Q-5 columns from Glass Contour Co.

Deuterated THF was first dried over CaH2, then over Na/benzophenone, and then

vacuum transferred into a storage container. Before use, an aliquot of each solvent

was tested with a drop of sodium benzophenone ketyl in THF solution. Celite was

dried overnight at 200�C under vacuum. The iron starting material FeCl2(THF)1.5was synthesized by the method of Kern,1 by heating anhydrous FeCl2

2 to

reflux overnight in THF and subsequently removing volatile materials in vacuo.*

[LMe,iPr2Li]x was prepared using the method described herein.

FeCl2ðTHFÞ1:5 þ ½LMe;iPr2Li�x !LMe;iPr2Feðm-ClÞ2FeLMe;iPr2 þLiCl

Procedure

In a glovebox, a 100-mL thick-walled flaskwith a resealable Teflonvalve (Fig. 1) is

charged with a magnetic stir bar and [LMe,iPr2Li]x (2.38 g, 5.60mmol). Toluene

(40mL) is added to dissolve the solid, forming a pale yellow solution, and while

stirring at 25�C, solid FeCl2(THF)1.5 (1.32 g, 5.72mmol) is added to the solution in

several portions. An immediate color change from pale yellow to light red is

observed during the FeCl2(THF)1.5 addition. The flask is then sealed and moved

from the glovebox to the Schlenk line where it is heated in an oil bath, gradually

raised from25to100�C.After18 h, the red-orangesuspension isallowed tocoolandis evaporated to dryness. The oil bath is then heated to 40�C, and the orange solid is

Figure 1. Reaction flask used in this procedure.

* The checkers prepared FeCl2(THF)1.5 by Sohxlet extraction of anhydrous FeCl2 with THF over the

course of 2 weeks.

9. Iron 2,4-BIS-(2,6-Diisopropylphenylimido)Pently Chloride (LMe,iPr2FeCl) 39

dried in vacuo for an additional 30–60min to ensure complete removal of THF.The

flask is then returned to the glovebox, and the solids are washed with pentane

(3� 10mL) to remove unreacted LiLMe,iPr. The orange powder obtained after

drying thismaterial in vacuo, [LMe,iPrFeCl]2�2LiCl, is normally recovered in95%

yield and is commonly used in later syntheseswithout further purification (because

later steps typically involvepentane extractions, theLiCl isfilteredoff at that stage).

Note: Contact of [LMe,iPrFeCl]2�2LiClwith THF or Et2O results in the formation of

the etherate complexes LMe,iPrFeCl2Li(THF)2 and LMe,iPrFeCl2Li(Et2O)2, which

may not be suitable for some later syntheses. The etherate complexes can be

desolvated, regenerating [LMe,iPrFeCl]2�2LiCl, by dissolving the yellow solids in

toluene and heating at 100�C for 12 h and evacuating to dryness.

The by-product LiCl can be removed by Soxhlet extraction. The insoluble

orange powder obtained above is slurried in pentane (3� 20mL) and collected by

gravity filtration in a glass thimble consisting of a coarse glass frit with a 0.5-cm

pad of predried Celite. The thimble containing the washed orange solid is then

placed in the Soxhlet extractor fitted with a 200-mL round-bottomed flask

containing a large magnetic stir bar and toluene (150mL) on the lower end and

a condenser with a resealable Teflon valve. (Note: It is beneficial to measure

the antechamber and assembled Soxhlet extraction apparatus prior to loading in the

glovebox, because the assembled apparatus may be quite long. If the assembled

apparatus is too long, the condenser can be attached to the flask outside the box

with a vigorous flow of N2). Under a N2 atmosphere on the Schlenk line, the

apparatus is heated in a 140�C oil bath. Most of the LiCl-free material is extracted

into hot toluene in 3–4 h; however, completely colorless extracts are not observed

until >12 h. After 24 h, the red suspension is evacuated to dryness, leaving a solidorange residue. In the glovebox, the residue is washed with pentane (3� 10mL)

and dried in vacuo, affording LiCl-free [LMe,iPrFeCl]2 in 82% yield (2.34 g,

2.30mmol). Purity is determined by 1H NMR spectroscopy.

1H NMR (THF-d8): d 17.6 (4H), 4.9 (12H), 3.3 (4H), �6.8 (12H), �38.3 (2H),

�67.9 (6H), �78.9 (1H).

Properties

[LMe,iPr2FeCl]2 is insoluble in alkane solvents, poorly soluble in Et2O and toluene,

and soluble in THF. It reacts slowly with CH2Cl2. Additional characterization in

noncoordinating solvents is limited by low solubility. It is sensitive to air and

moisture.

Related Compounds

This compound is a precursor to a wide variety of three- and four-coordinate

iron(II) complexes, including alkyl, aryl, hydride, sulfido, amido, and fluoride


complexes.3Abstraction of chloridewith borane4 gives cationic iron(II) complexes

withweak coordination of solvent or counterion. Reduction to an iron(I) dinitrogen

complex provides a pathway to iron(I) alkyne, alkene, carbonyl, isocyanide, arene,

and phosphine complexes, as well as a reactive iron(III) imido complex.3

Acknowledgments

This workwas supported by theNational Science Foundation (CHE-0112658) and

the Alfred P. Sloan Foundation (Research Fellowship).

References

1. R. J. Kern, J. Inorg. Nucl. Chem. 24, 1105 (1962).

2. G. Winter, Inorg. Synth. 14, 101 (1973).

3. P. L. Holland, Acc. Chem. Res. 41, 905 (2008).

4. T. J. J. Sciarone, A. Meetsma, B. Hessen, and J. H. Teuben, Chem. Commun. 1580 (2002).

10. IRON 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)HEPTYL CHLORIDE

(LtBu,iPr2FeCl)

Submitted by KAREN P. CHIANG� and PATRICK L. HOLLAND�


General Techniques



H2O. Glassware was dried at 150�C overnight. NMR spectra are referenced to

residual C6D5H at 7.16 ppm. Pentane and toluenewere purified by passing through

activated alumina and Q-5 columns from Glass Contour Co. Deuterated benzene

was first dried over CaH2, then over Na/benzophenone, and then vacuum trans-

ferred into a storage container. Before use, an aliquot of each solvent was tested

with a drop of sodium benzophenone ketyl in THF solution. Celite was dried

overnight at 200�C under vacuum. The iron starting material FeCl2(THF)1.5 was

synthesized by the method of Kern,1 by heating a THF slurry of anhydrous FeCl22


47405.

10. Iron 2,2,6,6-Tetramethyl-3,5-BIS-(2,6-Diisopropylphenylimido)Heptyl 41

at reflux overnight and subsequently removing volatile materials in vacuo.*

KLtBu;iPr2 þ FeCl2ðTHFÞ1:5 !LtBu;iPr2FeCl

Procedure

Solid KLtBu,iPr2 (0.50 g, 0.919mmol), FeCl2(THF)1.5 (0.2022 g, 0.919mmol), and

toluene (25mL) are added to a 150-mL Schlenk flask (see Fig. 1 in Section 9). The

chargedflask is removed from theglovebox, and the reactionmixture is heated in an

oil bath at 100�C for 18 h during which time it turns very dark red in color. The

solution is then cooled to room temperature, returned to the glovebox, and filtered

throughCelite.Thefiltrateisconcentratedto8mL,whereuponsomeredsolidbegins

to form.The sample iswarmed to ca. 40�C to redissolve the solid, and slowly cooled

to�35�C overnight to afford dark red crystals. The supernatant is decanted and the

red solid is washed with 2mL of pentane to remove trace LtBu,iPr2H, leaving LtBu,

iPr2FeCl (0.5306 g, 97%).Theoverall purity is best gaugedbyUV–vis spectroscopy.

UV–vis (toluene): 559 nm (626M�1 cm�1). 1H NMR (C6D6, 500MHz): d 104(s, 1H, a-H), 42 (s, 18H, tBu), 2.6 (s, 4H,m-aryl),�27 (s, 12H, iPr methyl),�108

(s, 4H, iPr methine),�111 (s, 12H, iPr methyl),�115 (s, 2H, p-aryl). Trace water

results in a small amount of LtBu,iPrH, which is observed as white solid and appears

in the 1H NMR spectrum at 1–2 ppm.

Properties

LtBu,iPrFeCl is very soluble in THF and toluene, somewhat soluble in diethyl ether,

and poorly soluble in pentane. It decomposes in CH2Cl2 in a few hours. It is

extremely sensitive to moisture and air. Coordinating solvents such as THF and

acetonitrile form yellow 1 : 1 adducts.

Related Compounds

This compound is a precursor to a wide variety of three- and four-coordinate iron

(II) complexes, including alkyl, aryl, hydride, oxo, hydroxo, amido, and fluoride

complexes.3,4 Reduction to an iron(I) dinitrogen complex provides a pathway to

iron(I) complexes.4

Acknowledgments



* The checkers prepared FeCl2(THF)1.5 through a Soxhlet extraction of anhydrous FeCl2with THFover

2 weeks.


References


2. G. Winter, Inorg. Synth. 14, 101 (1973).

3. V. C. Gibson, E. L. Marshall, D. Navarro-Llobet, A. J. P. White, and D. J. Williams, J. Chem. Soc.,


4. P. L. Holland, Acc. Chem. Res. 41, 905 (2008).

11. COBALT 2,2,6,6-TETRAMETHYL-3,5-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)HEPTYL CHLORIDE

(LtBu,iPr2CoCl)

Submitted by KEYING DING,� THOMAS R. DUGAN,�



The following reactionwas originally conducted in THF solution using LiLtBu,iPr2,

in which case the product is LtBu,iPr2Co(m-Cl)2Li(ether)2, which is four-coordinateat cobalt and hasmixed coordination of Et2O and THF at the lithium ion.1 By using

TlLtBu,iPr2 instead as the diketiminate source, the authors obtained the three-

coordinate LtBu,iPr2CoCl. Here, the lithium salt is used but in hot toluene, the LiCl

precipitates, and the three-coordinate monomer is obtained. This method elim-

inates the need for using the thallium salt.

General Procedures

Manipulations were performed under a nitrogen atmosphere by standard Schlenk

techniques or in a glovebox maintained at or below 1 ppm of O2 and H2O.

Glassware was dried at 150�C overnight. NMR spectra are referenced to residual

C6D5H at 7.16 ppm. Pentane and toluene were purified by passing through

activated alumina and Q-5 columns from Glass Contour Co. Deuterated benzene

was first dried over CaH2, then over Na/benzophenone, and then vacuum trans-

ferred into a storage container. Before use, an aliquot of each solvent was tested

with a drop of sodium benzophenone ketyl in THF solution. Celite was dried

overnight at 200�Cunder vacuum. The cobalt startingmaterial CoCl2(THF)1.5 was

synthesized by themethod ofKern,2 by heating anhydrous CoCl2 (Sigma) to reflux

overnight in THF and subsequently removing volatile materials in vacuo.


47405.

11. Cobalt 2,2,6,6-Tetramethyl-3,5-Bis-(2,6-Diisopropylphenylimido) 43

LtBu;iPr2LiðTHFÞþCoCl2ðTHFÞ1:5 !LtBu;iPr2CoClþLiCl

Procedure

In the glovebox, blue CoCl2(THF)1.51 (705mg, 2.96mmol) is added to a 500-mL

resealable flask (see Fig. 1 in Section 9) containing a pale yellow solution of LtBu,

iPr2Li(THF) (1.72 g, 2.96mmol) in toluene (100mL) and a stir bar, causing a slow

color change to blue-brown. The flask is sealed, taken out of the glovebox, and

heated in an oil bath, which is gradually heated to 100�C.After stirring for 18 h, theflask is returned to the glovebox, and the brown mixture is filtered through 1 cm of

Celite.* The filtrate is concentrated to 40mL and cooled at�35�C for 1 day to give

brown-purple crystals. The supernatant solution is removed and the crystals are

dried under vacuum to give 1.23 g of a brown-purple solid. Reducing the volume of

the supernatant solution to 18mL, adding 10mL of pentane, and cooling to�35�Cyields 0.25 g of additional crystals. The combined solids are washed with pentane

to remove traces of LtBu,iPr2Li(THF) and LtBu,iPrH. Combined yield: 84%.

1H NMR (400MHz, C6D6): d 59.9 (4H, m-aryl), 27.2 (18H, tBu), �2.7 (12H, iPr

methyl), �45.4 (2H, p-aryl), �56.5 (4H, iPr methine), �83.0 (12H, iPr methyl),

�89.3 (1H, a-H).

Properties

Purity is evaluated using 1H NMRspectroscopy. Solid samples of LtBu,iPr2CoCl are

brown-purple in color. LtBu,iPr2CoCl is soluble in tetrahydrofuran, CH2Cl2, and

toluene, somewhat soluble in diethyl ether, and poorly soluble in pentane. The

compound is extremely sensitive to moisture and air. LtBu,iPr2CoCl has been used

as a precursor to a three-coordinate cobalt(II) methyl complex.1

* In more recent work after submission and independent checking, we have seen that some batches of

CoCl2(THF)1.5 give incomplete conversion to LtBu,iPrCoCl (evident from significant amounts of light

blue material in the crude product). If this is a problem, a variant can be used as follows. A mixture of

CoCl2 (749mg, 5.77mmol, Strem) and THF (200mL) is heated to reflux overnight under N2 to give a

blue solution, and concentrated to 100mL under vacuum. A pale yellow solution of LtBu,iPrLi(THF)

(2.90 g, 5.71mmol) in THF (70mL) is added, and the greenmixture is heated at 70 �C for 4 h. The olive-

green mixture is stirred overnight at room temperature. Volatile materials are removed under reduced

pressure, giving a brown residue consisting primarily of LtBu,iPr2Co(m-Cl)2Li(THF)2. Toluene (125mL)

is added, and the mixture is heated at 100 �C overnight (this step dissociates THF and precipitates the

LiCl). After cooling to room temperature, volatile materials are again removed to give a dark purple

residue. The solid is dried under dynamic vacuum at 100 �C for 3 hours to remove all traces of THF. The

resulting solid is extracted with toluene (150mL), and the mixture is filtered through a pad of Celite to

remove a gray solid. Volatile materials are removed from the purple filtrate to give a semi-crystalline

purple solid. This solid is washed with cold pentane (60mL, precooled to�40 �C) and collected to give1.898 g (55.8% yield) of LtBu,iPrCoCl as a fine purple powder.


Acknowledgments



References

1. P. L. Holland, T. R. Cundari, L. L. Perez, N. A. Eckert, and R. J. Lachicotte, J. Am. Chem. Soc. 124,

14416 (2002).


12. b-DIKETIMINATE-SUPPORTED NICKEL(II) ANDNICKEL(I) COMPLEXES OF LME,ME3 (LME,ME3¼2,4-BIS-

(MESITYLIMIDO)PENTYL)

Submitted by MARIE M. MELZER,� ELZBIETA KOGUT,�

MATTHEW S. VARONKA,� STEFAN WIESE,� and TIMOTHY H. WARREN�

Checked by SARA S. ROCKS� and PATRICK L. HOLLAND�

General Procedures

All experiments were carried out in a dry nitrogen atmosphere using a glovebox

and/or standard Schlenk techniques. Diethyl ether and tetrahydrofuran (THF)were

first sparged with nitrogen and then dried by passing through activated alumina

columns.1 Pentane was first washed with concentrated HNO3/H2SO4 to remove

olefins, stored over CaCl2, sparged with nitrogen, and then dried by passing

through activated alumina columns.1 Dry toluene was stored over activated 4A�

molecular sieves. Deuterated solvents were sparged with nitrogen, dried over

activated 4A�molecular sieves, and stored under nitrogen.

Thallous acetate and 2,4-lutidine were purchased from Acros. Anhydrous

nickel(II) iodidewas purchased from Strem. These reagents were used as received.

A. LMe,Me3NiI(2,4-LUTIDINE)

TlLMe;Me3 þNiI2 þ 2; 4-Me2C5H3N!LMe;Me3NiIð2; 4-Me2C5H3NÞþTlI


12. b-Diketiminate-Supported Nickel(II) and Nickel(I) 45

Procedure

This synthesis is based on a reported procedure.2 A sample of TlLMe,Me3 (3.00 g,

5.58mmol) in 100mLTHF is added to a stirring solution of anhydrousNiI2 (1.74 g,

5.58mmol) in 60mL THF containing 3 equiv of 2,4-lutidine (1.95mL,

16.74mmol), and the resulting heterogeneous solution retains the dark green/black

color of the NiI2. The slurry is stirred overnight. The yellow precipitate of TlI is

removed by filtering through Celite, and the filtrate is concentrated to 50mL and

cooledat�35�Covernight.Themother liquor is removed, and the residue iswashed

with a few milliliters of cold pentane to yield 1.922 g of green/black crystals. The

volume of themother liquor is reduced to 15mL and cooled again to yield a second

cropofcrystals (0.698 g)withacombinedyieldof75%.�Thecrystals canbecrushed

into a fine powder and dried in vacuo to give a THF-free sample.

Anal. Calcd. forC30H38N3INi: C, 57.55;H, 6.07;N, 6.71. Found: C, 57.82;H, 6.04;

N, 6.65. 1H NMR (C6D6, 400MHz, 25�C): d 93.5 (s, 1, 2,4-lut-ArH), 47.5 (s, 6, Ar-p-Me), 34.8 (s, 12, Ar-o-Me2), 32.7 (s, 4, m-Ar-H), �4.2 (br s, 3, 2,4-lut-Me),

�11.3 (br s, 3, 2,4-lut-Me),�46.6 (s, 6, backbone-Me),�118.1 (s, 1, 2,4-lut-ArH).

The backbone-H and one 2,4-lut-ArH cannot be observed in the 1H NMR

spectrum. meff¼ 2.38 B.M. (C6D6 solution). UV–vis (CH2Cl2 (M�1 cm�1)): 527

(562) and 676 (507) nm.

Properties

LMe,Me3NiI(2,4-lutidine) is very soluble in CH2Cl2 andTHF, soluble in toluene, and

muchless soluble inpentaneordiethylether. In theabsenceofaneutraldonor ligand,

b-diketiminato(II) nickel halide species have a strong tendency to dimerize through

bridging halogen groups. For instance, the tetrahedral bridged dimers (LMe,Me2Ni)2(m-Cl)23 and (LMe,iPr2Ni)2(m-Cl)24 have been structurally characterized.

Related Compounds

b-Diketiminato monohalide-lutidine species have been used in the synthesis of

monoalkyl complexes with Grignard reagents to give [(b-diketiminate)Ni(R)(2,4-

lutidine)] (R¼CH2CH3 and CH2CH2CH3).3 These square planar alkyl complexes

dissociate 2,4-lutidine to give the crystallographically characterized b-agosticcomplexes with the formula LMe,Me2NiR, which are models for intermediates in

Ni-catalyzed polymerization of alkenes.5

B. LMe,Me3Ni(2,4-LUTIDINE)

TlLMe;Me3 þNiI2 þ 2; 4-Me2C5H3N!LMe;Me3NiIð2; 4-Me2C5H3NÞþTlI

LMe;Me3NiIð2; 4-Me2C5H3NÞþNa!LMe;Me3Nið2; 4-Me2C5H3NÞþNaI


Procedure

This one-pot procedure is based on a published synthesis that employed NiCl2.6 A

solution ofTlLMe,Me3 (2.50 g, 4.65mmol) in 20mLTHF is added to a suspension of

NiI2 (1.46 g, 4.65mmol) and 2,4-lutidine (0.50 g, 4.65mmol) in ca. 20mL THF.

The reaction is stirred at room temperature overnight and then filtered through

Celite to yield a dark green solution.* A 0.5% w/w Na/Hg amalgam (21.4 g of

amalgam¼ 0.107 g Na, 4.65mmol Na) is added to the solution and stirred

vigorously for 3 h. The resulting red solution is decanted away from the remaining

amalgam and filtered through Celite. The volatiles are removed over 3 h in vacuo

and the red solid is taken up in 40mL of Et2O. The solution is again filtered through

Celite to remove any remaining NaI and then concentrated in vacuo to a volume of

about 10mL. The solution is cooled to�35�C overnight to give deep red crystals.

A second crop of crystals is isolated to yield a total of 1.29 g (57%) of product after

drying.

UV–vis (Et2O with added lutidine, nm (M�1 cm�1)): 396 (5200) and 488

(3300).meff¼ 2.00B.M. (C6D6with ca. 10 equiv added 2,4-lutidine). EPR (toluene

with ca. 10 equiv added lutidine, 77K, frozen glass): g¼ 2.437, 2.131, 2.068.

Properties

LMe,Me3Ni(2,4-lutidine) is very soluble in aliphatic and aromatic hydrocarbons as

well as diethyl ether and THF. 2,4-Lutidine is added during the characterization

owing to the lability of this ligand. The nickel(I) compound is extremely reactive

toward halogenated solvents as well as oxygen and water. For instance, blue-green

LMe,Me3NiCl(2,4-lutidine) forms upon exposure to CH2Cl2 and a green hydroxo

species (LNi)2(m-OH)2 forms upon exposure to dioxygen.7

Related Compounds

Nickel(I) b-diketiminates LNi(2,4-lutidine) react with nitric oxide to give

stable three-coordinate nitrosyls LNi(NO) (L¼LMe,Me2 and LMe,Me3).8 Depend-

ing on their steric bulk, these b-diketiminate complexes react with CO to give

either dimeric (LMe,Me3Ni)2(m-CO)26 or T-shaped three-coordinate LMe,iPr2Ni

(CO)9 derivatives. Addition of adamantyl azide (N3Ad) to LNi(2,4-lutidine) gives

the dinickel nitrene (LMe,Me2Ni)2(m-NAd) as well as the terminal LMe,Me3-

Ni¼NAd, which undergoes nitrene group transfer to nucleophiles such as CNBut

.6

A related b-diketiminato nickel(I) complex (LMe,iPr2

Ni)2(m-toluene)10 also reacts

* The checkers filtered their product through Celite twice to remove TlI.

12. b-Diketiminate-Supported Nickel(II) and Nickel(I) 47

with organoazides to give reactive nickel nitrene intermediates11 as well as allows

for the isolation of a nickel(II) superoxo complex LMe,iPr2Ni(h2-O2).12

Acknowledgments


and PRF-AC awards to T.H.W.), and the U.S. National Science Foundation


this research.

References


15, 1518 (1996).

2. M. M. Melzer, S. Jarchow-Choy, E. Kogut, and T. H. Warren, Inorg. Chem. 47, 10187 (2008).

3. H. L. Wiencko, E. Kogut, and T. H. Warren, Inorg. Chim. Acta 345, 199 (2003).

4. N. A. Eckert, E. M. Bones, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 42, 1720 (2003).

5. E. Kogut, A. Zeller, T. H. Warren, and T. Strassner, J. Am. Chem. Soc. 126, 11984 (2004).

6. E.Kogut,H. L.Wiencko, L. Zhang,D. E.Cordeau, andT.H.Warren, J. Am.Chem. Soc.127, 11248

(2005).

7. Y. Li, L. Jiang, L. Wang, H. Gao, F. Zhu, and Q. Wu, Appl. Organomet. Chem. 20, 181 (2006).

8. S. C. Puiu and T. H. Warren, Organometallics 22, 3974 (2003).

9. N. A. Eckert, A. Dinescu, T. R. Cundari, and P. L. Holland, Inorg. Chem. 44, 7702 (2005).

10. G. Bai, P. Wei and D. W. Stephan, Organometallics 24, 5901 (2005).

11. G. Bai and D. W. Stephan, Angew. Chem., Int. Ed. 46, 1856 (2007).

12. S.Yao,E.Bill, C.Milsmann,K.Wieghardt, andM.Driess,Angew.Chem., Int. Ed. 47, 7110 (2008).

13. NICKEL 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL CHLORIDE DIMER, [LMe,iPr2Ni(m-Cl)]2

Submitted by THOMAS R. DUGAN� and PATRICK L. HOLLAND�

Checked by STEFAN WIESE� and TIMOTHY H. WARREN�

General Procedures



H2O. Glassware was dried at 150 �C overnight. NMR spectra are referenced to

residual CDHCl2 at 5.31 ppm. UV–vis spectra were measured using screw-cap

*Department of Chemistry, University of Rochester, Rochester, NY 14627.�Department of Chemistry, Georgetown University, Washington, DC 20057-1227.


cuvettes. Pentane, diethyl ether, and toluene were purified by passing through

activated alumina and Q-5 columns from Glass Contour Co. Deuterated dichlor-

omethane was first dried over CaH2, and then vacuum transferred into a storage

container. Celite was dried overnight at 200�C under vacuum. NiCl2(THF)x is

prepared by refluxing anhydrous NiCl2 (Strem),*,1 in dry tetrahydrofuran under

nitrogen for 24 h.2 The amount of THF coordinated toNi varies from 0.1 to 0.7, and

the stoichiometry of this starting material is obtained through the gravimetric

determination of Ni2þ content with dimethylglyoxime.3

½LMe;iPr2Li�x þNiCl2ðTHFÞ0:4 !LMe;iPr2Niðm-ClÞ2NiLMe;iPr2 þLiCl

Procedure

TanNiCl2(THF)0.4 (335mg, 2.11mmol) and [LMe,iPr2Li]x (888mg, 2.09mmol) are

placed ina100-mLresealableflask(seeFig.1 inSection9), and toluene (�30mL) is

added toproduce a tan colored slurry.Theflask is closed, and the reactionmixture is

heated and stirred at 100�C. After 24 h, the dark blue reaction mixture is cooled to

room temperature, and the solvent is removed under reduced pressure. Under a

nitrogen atmosphere, CH2Cl2 (30mL) is added to the residue, and the mixture is

filtered through 3 cmofCelite. The dark blue solution is concentrated to 18mL and

cooled to�45�C,whichyields thefirstcropofbluecrystals (254mg).Asecondcrop

of crystals (228mg) is obtained by reducing the volume of the supernatant to

6mLand cooling to�45�C.The solids arewashedwith pentane to remove traces of

LMe,iPr2H and LiLMe,iPr2. Combined yield: 482mg (45%).�

1H NMR (CD2Cl2, 500MHz, 25�C): d 58 (4H, CH(CH3)2 or m-Ar), 36 (4H, CH

(CH3)2 or m-Ar), 9.7 (12H, CH(CH3)2), 8.5 (12H, CH(CH3)2), �27 (2H, p-Ar),

�90 (6H, CH3), �282 (1H, backbone-H). UV–vis (CH2Cl2, e in M�1 cm�1): 575

(680), 765 (2800) nm. UV–vis (toluene, e in M�1 cm�1): 580 (1200), 740

(2800) nm.

Properties

Solid samples of [LMe,iPr2NiCl]2 are dark blue, and the purity can be tested by1H NMR spectroscopy in CD2Cl2. [L

Me,iPr2NiCl]2 is very soluble in CH2Cl2,

* Although commercial material was used here without special precautions, it is uncertain that

commercial ‘‘anhydrous’’ NiCl2 is completely free of water. Methods have been reported for removing

trace moisture from NiCl2 using anhydrous HCl: see Ref. 1.� The checkers observed a dark green solution after heating, and the greenCH2Cl2 solution yielded blue

crystals in a yield of 40%. These crystals had spectroscopic properties identical to those described

above. The reaction failed with some sources of nickel(II) chloride.�

13. Nickel 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride Dimer 49

soluble in toluene, and slightly soluble in pentane and diethyl ether. It reacts with

tetrahydrofuran to give a purple solution of the adduct LMe,iPr2Ni(Cl)(THF), with

UV–vis (THF, e in M�1 cm�1): 520 (1300), 670 (830) nm.2

Related Compounds

[LMe,iPr2NiCl]2 has been used as a precursor to a nickel(II) amido complex, and to

an unusual T-shaped nickel(I)-carbonyl complex.4 The analogous bromide com-

plex has been used as an ethylene polymerization catalyst,5 and as a source of

nickel(I) for group-transfer and bond activation reactions (described inmore detail

in Section 12).

Acknowledgments



References

1. (a) D. I. Ryabchikov and V. M. Shul’man, Zh. Prikl. Khim. 7, 1162 (1934). (b) M. Nehme and S. J.

Teichner,Bull. Soc. Chim. Fr. 2, 389 (1960). (c) L. E. Topol and S. J. Yosim, Synth. Inorg.Met.-Org.

Chem. 3, 47 (1973).

2. N. A. Eckert, E. M. Bones, R. J. Lachicotte, and P. L. Holland, Inorg. Chem. 42, 1720 (2003).

3. A. I. Vogel, Textbook of Quantitative Inorganic Chemistry, 3rd ed., Wiley, New York, 1961,

pp. 479–481.

4. N. A. Eckert, A. Dinescu, T. R. Cundari, and P. L. Holland, Inorg. Chem. 44, 7702 (2005).

5. J. Zhang, Z. Ke, F. Bao, J. Long, H. Gao, F. Zhu, and Q. Wu, J. Mol. Catal. A 249, 31 (2006).

14. BIS[COPPER 2,4-BIS-(2,4,6-TRIMETHYLPHENYLIMIDO)PENTYL] TOLUENE, (LMe,Me3Cu)2(m-h

2:h2-C7H8)

Submitted by YOSRA M. BADIEI� and TIMOTHY H. WARREN�

Checked by KAREN P. CHIANG� and PATRICK L. HOLLAND�

Following Sadighi’s use of copper(I) tert-butoxide in the synthesis of a fluorinated

b-diketiminato copper(I) complex,1 a two-step procedure is employed beginning



with a recently reported preparation for copper(I) tert-butoxide,2 which is then

combined with HLMe,Me3 to give [LMe,Me3Cu]2(m-benzene).3 Copper(I) tert-

butoxide is first prepared by a modification of the original procedure, which

employed LiOBut and anhydrous CuCl. This preparation gave the tetrameric

[CuO-tert-Bu]4 when crystallized from hexane or benzene.4 Additionally, an

octameric structure [CuO-tert-Bu]8 has been observed in the reaction of mesi-

tylcopper(I) with tert-butanol after crystallization from toluene.5

General Procedures

Experimentswere carried out in a dry nitrogen atmosphere using a glovebox and/or

standard Schlenk techniques. Diethyl ether and tetrahydrofuran (THF) were first

sparged with nitrogen and then dried by passing through activated alumina

columns.6 Pentane was first washed with conc. HNO3/H2SO4 to remove olefins,

stored over CaCl2, sparged with nitrogen, and then dried by passing through

activated alumina columns.6 Dry toluene was purchased from Aldrich and was

stored over activated 4A�molecular sieves. All deuterated solvents were sparged

with nitrogen, dried over activated 4A�molecular sieves, and stored under nitrogen.

Potassium tert-butoxide was purchased from Acros. Anhydrous copper(I) iodide

was purchased from Strem.

A. COPPER tert-BUTOXIDE

KO-tert-BuþCuI!CuO-tert-BuþKI

Procedure

A chilled (�35�C) solution of commercial potassium tert-butoxide (1.95 g,

17.4mmol) in 20mL THF is added to a suspension of anhydrous copper(I)

iodide (3.00 g, 15.79mmol) in 25mL of THF. The mixture is stirred overnight

at room temperature. The resulting solution is then filtered through Celite to

remove the precipitated KI followed by removal of all volatiles from the

filtrate in vacuo to give a brown-yellow residue. Addition of ca. 5mL of cold

pentane allows the isolation of a pale yellow solid from this residue by

filtration and dried in vacuo to afford 1.69 g (78%) of pale yellow copper(I)

tert-butoxide.

1H NMR (benzene-d6): d 1.31 (s, tBu). 13C{1H} NMR (benzene d6): d 72.6 C

(CH3), 35.8 (CH3).

14. Bis[Copper 2,4-Bis-(2,4,6-Trimethylphenylimido)Pentyl] Toluene 51

B. BIS[COPPER 2,4-BIS-(2,4,6-TRIMETHYLPHENYLIMIDO)

PENTYL] TOLUENE

2CuO-tert-Buþ 2 HLMe;Me3 þC6H5Me!½LMe;Me3Cu�2ðC6H5MeÞþ 2 tert-BuOH

Procedure

To a stirring solution of copper(I) tert-butoxide (1.250 g, 9.150mmol) in 20mL

toluene is added a solution of HLMe,Me3 (2.550 g, 7.620mmol) in 20mL of toluene.

After stirring for 3 h, the dark brown solution is filtered through Celite, and the

volatilematerials are removed in vacuo to give a yellowbrown, slightly oily residue.

This residue is triturated with a small amount of pentane to reveal a yellow solid,

which is then recrystallized by extraction into pentane (ca. 5–10mL) containing a

small amount of toluene (1–2mL) followed by chilling to�35�C. Filtration affords2.85 g (85%) of the dinuclear product as a yellow solid in two crops.

1H NMR (benzene-d6): major species: d 6.92 (br s, 4, Ar-H), 4.79 (s, 1, backbone-CH), 2.27 (s, 6, Ar-p-CH3), 2.03 (s, 12, Ar-p-CH3), 1.67 (s, 6, backbone-CH3).13C{1H} NMR (benzene d6): 162.7, 148.3, 131.8, 130.3, 128.9, 94.5 (backbone-

CH), 23.2, 21.1, 18.8, 18.7. Minor species: d 6.81 (s, 8, Ar-H), 4.76 (s, 2,

backbone C-H), 2.24 (s, 12, Ar-p-CH3), 1.89 (s, 24, Ar-o-CH3), 1.58 (s, 12,

backbone-CH3).

Properties

Theb-diketiminato copper(I) complex is a pale yellow solid that is freely soluble in

benzene, toluene, chlorobenzene, THF, and acetonitrile while partially soluble in

diethyl ether and pentane. In solution, the toluene ligand dissociates. When

dissolved in benzene, for example, the NMR spectrum exhibits signals for both

LMe,Me3Cu(benzene) (major species) and [LMe,Me3Cu]2(benzene) (minor species).

The copper(I) complex reacts slowly with chloroform and dichloromethane,

resulting in a gradual darkening of the solution to purple.

Related Compounds

Reaction with oxygen leads to formation of brown (LMe,Me3Cu)2(m-OH)2, pre-sumably through the intermediacy of a dicopper(III) bis(m-oxo) species

(LMe,Me3Cu)2(m-O)2.7–9 More hindered b-diketiminato copper(I) complexes

such as LtBu,iPr2Cu(MeCN) react with dioxygen to give the crystallographically

characterized Cu(III) side-on peroxo complex LtBu,iPr2Cu(h2-O2).10 Employing

the diazoalkane N¼N¼CPh2, [(LMe,Me3)Cu]2(m-benzene) may be used for the


synthesis of dicopper and terminal carbenes [(LMe,Me3)Cu]2(m-CPh2)2 and (LMe,

Me3)Cu¼CPh2.11 Similarly, this copper(I) complex reacts with the organoazide

N¼N¼NAr (Ar¼ 3,5-Me2C6H3) to give the discrete dicopper nitrene [(LMe,Me3)

Cu]2(m-NAr), which undergoes nitrene group transfer to nucleophiles such as

CNBut.12 Related Cu(I) b-diketiminates have been used for catalytic nitrene group

transfer to alkenes with PhI¼NTs to afford aziridines.13 Moreover, the related

[(LMe,Cl2)Cu]2(m-benzene) may be prepared similarly fromHLMe,Cl2 and copper(I)

tert-butoxide and serves as an active C-H amination catalyst with N3Ad, formally

inserting the NAd moiety into C-H bonds.2

1H NMR spectra in benzene-d6 indicate a mixture of dinuclear {LMe,Me3Cu}2(m-benzene) and mononuclear LMe,Me3Cu(benzene) along with free toluene

(d 7.13–7.02 (m, 5, toluene-Ar), 2.10 (s, 3, toluene-CH3)).2Keq¼ [{LMe,Me3Cu}

(benzene)]2/[{LMe,Me3Cu}2(m-benzene)] was about 0.5M at 25�C with the mono-

nuclear species predominating under typical NMR concentrations (0.01–0.1M).

Acknowledgments


and PRF-AC awards to T.H.W.), and the U.S. National Science Foundation


this research.

References

1. D. S. Laitar, C. J. N. Mathison, W. M. Davis, and J. P. Sadighi, Inorg. Chem. 42, 7354 (2003).

2. Y. M. Badiei, A. Dinescu, X. Dai, R. M. Palomino, F. W. Heinemann, T. R. Cundari, and T. H.

Warren, Angew. Chem., Int. Ed. 47, 9961 (2008).

3. Y. M. Badiei and T. H. Warren, J. Organomet. Chem. 690, 5989 (2005).

4. T. Greiser and E. Weiss, Chem. Ber. 109, 3142 (1976).

5. M. Hakansson, C. Lopes, and S. Jagner, Inorg. Chim. Acta 304, 178 (2000).


15, 1518 (1996).

7. X. Dai and T. H. Warren, Chem. Commun. 1998 (2001).

8. D. J. E. Spencer, N.W. Aboelella, A. M. Reynolds, P. L. Holland, andW. B. Tolman, J. Am. Chem.

Soc. 124, 2108 (2002).

9. D. J. E. Spencer, A. M. Reynolds, P. L. Holland, B. A. Jazdzewski, C. Duboc-Toia, L. Le Pape,

S. Yokota, Y. Tachi, S. Itoh, and W. B. Tolman, Inorg. Chem. 41, 6307 (2002).

10. N.W. Aboelella, E. A. Lewis, A. M. Reynolds,W.W. Brennessel, C. J. Cramer, andW. B. Tolman,

J. Am. Chem. Soc. 124, 10660 (2002).

11. X. Dai and T. H. Warren, J. Am. Chem. Soc. 126, 10085 (2004).

12. Y. M. Badiei, A. Krishnaswamy, M. M. Melzer, and T. H. Warren, J. Am. Chem. Soc. 128, 15056

(2006).

13. L. D. Amisial, X. Dai, R. A. Kinney, A. Krishnaswamy, and T. H. Warren, Inorg. Chem. 43, 6537

(2004).

14. Bis[Copper 2,4-Bis-(2,4,6-Trimethylphenylimido)Pentyl] Toluene 53

15. COPPER 2,4-BIS-(2,6-DIISOPROPYLPHENYLIMIDO)PENTYL CHLORIDE (LMe,iPr2CuCl)

Submitted by PATRICK L. HOLLAND�

Checked by MARIE M. MELZER� and TIMOTHY H. WARREN�

This compound was the first example of a three-coordinate complex of copper(II)

outside a protein environment, and it is a precursor to other three-coordinate

copper(II) complexes.1 The chloride ligand in this complex has been substituted

with thiolate and phenolate ligands to give mimics of type 1 copper sites1,2 and of

reduced galactose oxidase,3 respectively. Itoh and Tolman have examined the

influence of diketiminate substitution pattern on the copper(II) chemistry.4

General Procedures



H2O. Glassware was dried at 150�C overnight. UV–vis spectra were measured

using screw-cap cuvettes. Pentane and dichloromethane were purified by passing

through activated alumina and Q-5 columns. Celite was dried overnight at 200�Cunder vacuum.AnhydrousCuCl2was purchased fromAldrich and converted to the

THF adduct by the method of Kern.5

LMe;iPr2LiþCuCl2ðTHFÞ0:8 !LMe;iPr2CuClþLiCl

Procedure

Orange CuCl2(THF)0.8 (158mg, 0.822mmol) is added to a scintillation vial

containing a pale yellow solution of [LMe,iPr2Li]x (see Section 3, 351mg,

0.827mmol) in tetrahydrofuran (7mL), causing an immediate color change to

red-brown.z After stirring the reaction solution for 1.5 h, the solvent is evaporatedunder reduced pressure. The residue is extracted with CH2Cl2 (15mL), and the

mixture is filtered through 1 cm of Celite. The volume of the filtrate is reduced to

5mL, and 2mL of pentane is added before cooling to �40�C to give one crop of

*Department of Chemistry, University of Rochester, Rochester, NY 14627.�Department of Chemistry, Georgetown University, Washington, DC 20057-1227.z When the checkers added LiLMe,iPr2 to a solution of CuCl2(THF)0.8, it turned dark green.


crystals (101mg). Adding 7mL of pentane to the filtrate and cooling yields

a second crop of solid (155mg), and reducing the volume of supernatant to 3mL

and cooling yields a third crop of solid (96mg). The solids arewashedwith pentane

to remove traces of LMe,iPr2H and LMe,iPr2Li. The combined yield is 352mg

(82.9%). The purity is verified by UV–vis spectroscopy.

UV–vis (0.3–0.4mM solutions in CH2Cl2, e in M�1 cm�1): 507 (4100), 835 nm

(650).

Properties

Solid samples of LMe,iPr2CuCl are purple-brown in color. It can also be character-

ized by its EPR spectrum at 77 K (g|| 2.20, A|| 130� 10�4 cm�1, g? 2.05, A?8� 10�4 cm�1). LMe,iPrCuCl is highly soluble in CH2Cl2 and tetrahydrofuran,

somewhat soluble in toluene, poorly soluble in MeCN, and insoluble in diethyl

ether and pentane.

Acknowledgments

The author gratefully acknowledges the support of William Tolman and the

National Institutes of Health (F32GM018991) during the timewhen this synthesis

was developed.

References

1. P. L. Holland and W. B. Tolman, J. Am. Chem. Soc. 121, 7270 (1999).

2. (a) P. L. Holland and W. B. Tolman, J. Am. Chem. Soc. 122, 6331 (2000). (b) D. W. Randall, S. D.

George, P. L. Holland, B. Hedman, K. O. Hodgson,W. B. Tolman, and E. I. Solomon, J. Am. Chem.

Soc. 122, 11632 (2000). (c) A. Chowdhury, L. A. Peteanu, P. L. Holland, andW. B. Tolman, J. Phys.

Chem. B 106, 3007 (2002). (d) W. Z. Lee and W. B. Tolman, Inorg. Chem. 41, 5656 (2002).

3. (a) B. A. Jazdzewski, P. L. Holland, M. Pink, V. G. YoungJr., D. J. E. Spencer, and W. B. Tolman,

Inorg. Chem. 40, 6097 (2001). (b) B. A. Jazdzewski, A.M. Reynolds, P. L. Holland, V. G. Young, S.

Kaderli, A. D. Zuberb€uhler, and W. B. Tolman, J. Biol. Inorg. Chem. 8, 381 (2003).

4. (a) C. Shimokawa, S. Yokota, Y. Tachi, N. Nishiwaki, M. Ariga, and S. Itoh, Inorg. Chem. 42, 8395

(2003). (b) D. J. E. Spencer, A.M. Reynolds, P. L. Holland, B. A. Jazdzewski, C. Duboc-Toia, L. Le

Pape, S. Yokota, Y. Tachi, S. Itoh, and W. B. Tolman, Inorg. Chem. 41, 6307 (2002).


15. Copper 2,4-Bis-(2,6-Diisopropylphenylimido)Pentyl Chloride 55

Chapter Two

BORON CLUSTER COMPOUNDS

16. SALTS OF DODECAMETHYLCARBA-closo-DODECABORATE(�) ANION, CB11Me12

�, ANDTHE RADICAL DODECAMETHYLCARBA-closo-

DODECABORANYL, CB11Me12.

Submitted by JOSHUA R. CLAYTON,* BENJAMIN T. KING,*

ILYA ZHAROV,* MATTHEW G. FETE,* VICTORIA VOLKIS,*

CHRISTOS DOUVRIS,* MICHAL VALASEK,� and JOSEF MICHL*�

Checked by KARL MATOSz

The chemistry of the deltahedral carba-closo-dodecaborate(�) anion1 (CB11H12�)

has been reviewed.2,3 It has a highly dispersed charge and no exposed lone pairs,

aromatic rings, or multiple bonds, but the boron hydrogens have a distinctly

hydridic character and can serve as ligands. Its halogenated derivatives are among

the most weakly nucleophilic anions known,4 as is the explosive pertrifluoro-

methylated analogue.5 The permethylated CB11Me12� is also only weakly nucle-

ophilic,6 and its salts are remarkably lipophilic.7 Solutions of the lithium salt in

nonpolar solvents have high Lewis acidity. They catalyze pericyclic reactions,8

and, in the presence of traces of sulfolane, radical polymerization of alkenes.9–11

The anion can be oxidized to the stable neutral free radical, CB11Me12., a


*Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309.�Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610

Prague 6, Czech Republic.zBASF Corporation, Evans City, PA 16033.

56

one-electron oxidant with a redox potential �1.15Vabove ferrocene (in acetoni-

trile and in liquid SO2).12,13

The reported6 synthesis of the dodecamethylcarba-closo-dodecaborate(�)

anion (CB11Me12�) involved the use of the expensive sterically hindered base,

2,6-di-tert-butylpyridine, in the second step. An optimized second step reported

here utilizes calcium hydride as the only base. The overall procedure starting with

CB11H12� provides a 84% yield of 99% pure Cs[CB11Me12]. Procedures for the

conversion of the cesium salt to [Me4N][CB11Me12] and Li[CB11Me12] are also

described. Oxidation of the cesium salt to CB11Me12.is straightforward and

proceeds in 76% isolated yield.

A. CESIUM 1-METHYLCARBA-closo-DODECABORATE(�),

Cs[1-Me-CB11H11]

½Me3NH�½CB11H12� þ 2 n-C4H9Li!Li½LiCB11H11� þMe3Nþ 2 n-C4H10

Li½LiCB11H11� þMeI!Cs½1-Me-CB11H11� þLiI

Procedure*

Commercial� trimethylammonium carba-closo-dodecaborate(�), [Me3NH]

[CB11H12], which can also be prepared in the laboratory from decaborane14 or

sodium borohydride,15 is methylated on carbon in 94% yield using an improved

version of a published16 alkylation procedure. [Me3NH][CB11H12] (7.0 g,

34.5mmol) is placed in a 300-mL Schlenk flask and dried under vacuum at 100�Cfor 60min. The flask is charged with argon and THF (150mL, freshly distilled

fromNa/benzophenone) is added. A 1.6M solution of n-BuLi in hexanes (1 equiv,

21.6mL, 34.5mmol) is added dropwise over 1 h at 0�C. The solution is allowed towarm to room temperature and is stirred for an additional 1 h. The volume of the

mixture is then reduced slowly to �50mL by removing the argon flow and

connecting the flask to a vacuum line (NMe3 and almost half of the THF are

removed). The flask is filled again with argon, charged with an additional 100mL

of fresh THF, and cooled to �78�C using a dry ice/acetone bath. At this

temperature, a 1.6M solution of n-BuLi in hexanes (3 equiv, 64.7mL, 103.5mmol)

is added dropwise and the mixture is allowed to reach room temperature with

stirring. It is then stirred at room temperature for 3 h. Methyl iodide (4 equiv,

8.6mL, 138mmol) is added and the mixture is stirred for 3 h. Water (25mL) is

* If themethylation is performedonCs[CB11H12]13 instead of the commercialMe3NH[CB11H12], using

1.5 equiv of n-butyllithium and 2 equiv of methyl iodide, it proceeds to completion and a second step is

not required.� Katchem, Ltd., El. Kr�asnohorsk�e 6, 11000 Praha 1, Czech Republic.

16. Salts of Dodecamethylcarba-closo-Dodecaborate(�) Anion 57

added and the reactionmixture evaporated to dryness. The residue is extractedwith

diethyl ether (3� 100mL) and the combined extracts are washed with a 20%

solution of CsCl (3� 50mL). The combined CsCl wash is extracted with diethyl

ether (3� 50mL). The combined organic phase is evaporated to dryness and the

crude solid recrystallized from a minimum amount of water (10–20mL) with

filtration at 70–80�C followed by cooling to room temperature. It provides 9.31 g

(94%) of 97% pure Cs[1-Me-CB11H11], containing 3% Cs[CB11H12]. If desired,

thematerial can then be dried andmethylated again under the same conditions, and

worked up in the samemanner to provide at least 99% pure Cs[1-Me-CB11H11], in

which Cs[CB11H12] is undetectable by 1H NMR and ESI-MS.

Anal. (for Ph4P[1-Me-CB11H11]) Calcd. for C26B11H34P: C, 62.91; H, 6.90. Found

C, 63.20; H, 6.84. NMR spectrum of the Ph4Pþ salt in acetone-d6:

1H{11B} NMR:

d 7.92 [t, 4H, PPh4þ ], 7.76 [m, 8H, PPh4

þ ], 7.60 [m, 8H,PPh4þ ], 1.74 [s, 5H], 1.54

[s, 5H], 1.50 [s, 3H, CH3 (1)], 1.46 [s, 1H, H (12)]; 11B{1H}NMR: d�11.09 [s, 1B,

B(12)],�12.83 [s, 10B, B(2–11)]; 13C{1H}NMR: d 135.63 [d, PPh4þ ], 131.37 [d,

PPh4þ ], 118.82 [d, PPh4

þ ], 27.68 [s, CH3 (1)]. ESI-MS (m/e): 157. IR (Csþ salt,

KBr pellet) 487, 728, 938, 1039, 1194, 1311, 1383, 1458, 2544, 2875, 2938 cm�1.

B. CESIUM, TETRAMETHYLAMMONIUM, and LITHIUM

DODECAMETHYLCARBA-closo-DODECABORATES(�),

Cs[CB11Me12], [NMe4][CB11Me12], and Li[CB11Me12]

2 Cs½1-Me-CB11H11� þ 22MeOTfþ 11 CaH2 ! 2 Cs½CB11Me12�

þ 11 CaðOTfÞ2 þ 22 H2

Procedure

& Caution.Methyl triflate is highly toxic.Handlewith extreme care in awell

ventilated hood.

Calcium hydride (8.4 g, 200mmol) is added to Cs[1-Me-CB11H11] (1.45 g,

5mmol) dissolved in 19mL of sulfolane (24 g, 200mmol) in a 250-mL three-

necked round-bottomed flask, and the system is placed under argon. Themixture is

stirred. The reaction temperature should be held constant at 25�C to avoid

fluctuations in reaction time and formation of by-products (triflyloxy derivatives).

To this mixture is added freshly distilled methyl triflate (11.3mL, 16.4 g,

100mmol) with a syringe pump over a period of 20 h. Stirring is continued until

the reaction mixture solidifies (2–3 days). A solution of 5.5mL of methyl triflate

(8 g, 48.7mmol) in 10mL of sulfolane is added to the reaction mixture in one

58 Boron Cluster Compounds

portion and stirring is continued. After a further 2 days of stirring, the reaction is

normally complete, depending on reagent quality. A small aliquot is taken out and

checked by ESI-MS. The solidified reaction mixture is diluted with 300mL of dry

methylene chloride and CaH2 is removed by vacuum filtration. The filtrate is

neutralized slowly with a few milliliters of 27% ammonium hydroxide solution

and the organic phase is evaporated. The remaining solution is extracted with

diethyl ether (3� 150mL).

Cs[CB11Me12]. The combined organic layer is washed with 20% aqueous CsCl

(3� 50mL). The combinedCsCl wash is extractedwith diethyl ether (3� 50mL).

The combined ether solution is evaporated and the residual sulfolane is removed by

heating the sample under reduced pressure (<0.05mmHg) at 150�C.* The resultingsolid is recrystallized from hotwater (�100mL), filtering at 70–80�C, rinsingwithadditional 100mL of boiling water, and cooling to room temperature to provide Cs

[CB11Me12] (2.0 g, 90% yield, 99% purity).� This slightly yellowish material is of

adequate purity for most purposes. An additional recrystallization yields a snow-

white product.

Anal. (for Ph4P[CB11Me12]) Calcd. for C37B11H56P: C, 68.29; H, 8.68. Found C,

68.15; H, 8.74. For the Ph4Pþ salt, 1H{11B} NMR (acetone-d6): d 7.92 [t, 4H,

PPh4þ ], 7.76 [m, 8H, PPh4

þ ], 7.60 [m, 8H, PPh4þ ], 0.802 [s, 3H, CH3 (1)],

�0.330 [s, 15H, CH3 (2–6)], �0.400 [s, 15H, CH3 (7–11)], �0.505 [s, 3H, CH3

(12)]; 11B{1H}NMR (acetone-d6): d�0.60 [s, 1B, B(12)],�8.67 [s, 5B, B(7-11)],

�10.70 [s, 5B, B(2–6)]; 13C{1H} (acetone-d6): d 135.63 [d, PPh4þ ], 131.37

[d, PPh4þ ], 118.82 [d, PPh4

þ ],�3 [vb, CH3 (2–12)], 13.31 [s, CH3 (1)]. ESI-MS

(m/e): 311. IR (Csþ salt, KBr pellet): 916, 1052, 1152, 1313, 1438, 2830, 2900,

2935 cm�1.

NMe4[CB11Me12]. A solution of Cs[CB11Me12] (2 g) in ether (250mL) is

extracted with a 20% aqueous solution of NMe4Cl (3 � 100mL). Combined

aqueous fractions are washed with ether (3� 50mL), dried with activated molec-

ular sieves, filtered, and rinsed with dry ether (3� 20mL). The filtrate is evapo-

rated, and the resulting powder is washed with warm (40–50�C) hexane under

vigorous stirring (3� 100mL). The residue is dried under reduced pressure at

* If the sulfolane distills too slowly, an alternative workup can be used. The oily residue after the

evaporation of methylene chloride is poured onto excess crushed ice, and after 30min, the mixture is

extracted with Et2O (3� 60mL). The organic layer is washedwith 20%CsCl (3� 60mL) and the CsCl

wash is extracted with Et2O. The combined ether extracts are dried with Cs2CO3, filtered, and

evaporated. The resulting solid is recrystallized from water (hot filtration) and the residual sulfolane

evaporated.� The primary impurity is residual sulfolane, which can be removed by conversion of the salt into the

HMe3Nþ derivative using an equimolar amount of [NHMe3]Cl in 3:2 H2O–Et2O (�60mL), followed

by evaporation of the ether. An aqueous suspension of [NHMe3][CB11Me12] can be converted back to

the Csþ salt by neutralizing with NaOH in 3:2 H2O–Et2O followed by addition of aqueous CsCl.


room temperature (8 h), then at 50–60�C (8–10 h), and finally at 160�C (overnight)

affording off-white NMe4[CB11Me12] (1.74 g, 90% yield).

Properties

1H NMR (acetone-d6): d 3.43 [s, 12H, CH3 ([NMe4]þ )], 0.82 [s, 3H, CH3 (1)],

�0.310 [s, 15H, CH3 (2–6)],�0.41 [s, 15H, CH3 (7–11)],�0.53 [s, 3H, CH3 (12)];11B{1H} NMR (acetone-d6): d �1.12 [s, 1B, B(12)], �8.88 [s, 5B, B(7–11)],

�11.12 [s, 5B, B(2–6)]. ESI-MS (m/e): 311.

Li[CB11Me12]. A 1-cm diameter column is filled with Amberlyst 36 (cross-

linked polystyrene sulfonic acid) cation-exchange resin (acid form) (15 g, Al-

drich), previously washed with methanol to remove yellow color (3� 100mL).

Through this column is eluted (5�) a solution of Cs[CB11Me12] (1 g) in methanol

(100mL). The column is washed with methanol (�200mL) until the eluate

contains no boron by 11B{1H} NMR. The combined methanol fractions are

concentrated to �10mL using a rotary evaporator. A 10% aqueous solution of

LiOH (100mL) is added and the solution is evaporated to dryness under reduced

pressure. The resulting solid is extracted with ether (3� 50mL). The combined

ether fractions are reduced to 100mL on a rotary evaporator, washed with water

(3� 30mL), and dried with activated molecular sieves. The sieves are filtered off

and washed with dry ether (3� 20mL). The combined ether extracts are stirred

with LiH (2 g) for 24 h under argon atmosphere at room temperature to remove any

residual LiOH, filtered, and evaporated under reduced pressure to afford a

yellowish oil. To obtain a white product, the oil is dissolved in acetonitrile

(�200mL) and this solution is stirred overnight with activated charcoal

(5–10% by weight). This step also helps to remove any residual sulfolane. The

charcoal is filtered off using a paper filter and then a 0.45-mm Teflon filter and

washed with acetonitrile (2� 50mL). Combined filtrates are evaporated and the

product is dried in a Kugelrohr apparatus under reduced pressure at room

temperature (8 h), then at 50–60�C (8–10 h), and finally at 180�C (overnight).

The flask is cooled to room temperature under reduced pressure, the highly

hygroscopic white powder of Li[CB11Me12] (0.69 g, 87% yield) is removed under

argon, and sealed. The solid is characterized by NMR spectroscopy (Table 1).

Properties

We recommend that CB11Me12� be isolated as its cesium salt, which has favorable

solubility properties, is easy to store, and is well suited for the oxidation to the

radical. Conversion into the tetramethylammonium salt NMe4[CB11Me12] is

useful if all traces of sulfolane are to be absent. Li[CB11Me12] containing traces

of sulfolane is often beneficial when it is to be used as a catalyst in a low-polarity


solvent. For more efficient combustion in elemental analysis and for spectroscopic

characterization, small amounts of anions are converted into tetraphenylpho-

sphonium salts by precipitation with (PPh4)Cl in methanol.13,17

C. DODECAMETHYLCARBA-closo-DODECABORANYL RADICAL,

CB11Me12.

2 Cs½CB11Me12� þ PbO2 þ 4 CF3CO2H! 2 CB11Me12.

þ 2 ðCF3CO2Þ2Pbþ 2 CF3CO2Csþ 2 H2O

Procedure

The preparation of CB11Me12.is carried out in an apparatus shown in Fig. 1 under

an atmosphere of argon using solvents from which all reducing impurities have

been carefully removed (boiling with KMnO4 and distillation). Amixture of PbO2

(10 g, 41.8mmol) and Cs[CB11Me12] (1.0 g, 2.25mmol) is treated with degassed

acetonitrile (40mL) and degassed pentane (40mL), followed by degassed tri-

fluoroacetic acid (10mL, 59.3mmol). This mixture is stirred for 3min. The deep

blue pentane phase is collected through a Teflon cannula. Extraction with pentane

(40mL portions) is repeated until the blue color of CB11Me12.is no longer evident

(�5�). The pentane solution is extracted with degassed acetonitrile (30mL) and

pentane is removed with a stream of argon, providing 0.53 g (76% yield) of black

crystalline CB11Me12..

Table 1. NMR spectroscopic properties of Li[CB11Me12]

NMR chemical shift

(dppm) Acetone-d6 Benzene-d6 Toluene-d8

1,1,2,2-Tetra-

chloroethane-d2

11B{1H} B2–6 �10.8 �9.7 �9.0 �11.5

B7–11 �8.5 �8.2 �9.0 �9.5

B12 �0.5 �5.4 �3.0 �1.9

1H{11B} B2–6-Me �0.5 �0.5 �0.25 �1.45

B7–11-Me �0.4 �0.08 0.05 �1.38

B12-Me �0.3 0.2 0.25 �1.25

C1-Me 0.8 1.07 1.2 �0.12


Anal. Calcd. for C13B11H36: C, 50.15; H, 11.65. Found: C, 49.96; H, 11.58. ESI-

MS (m/e): 311. EPR (pentane): g 2.0037(3). IR (KBr pellet): 916, 1052, 1152,

1313, 1438, 2830, 2900, 2935 cm�1.

Properties

The radical is soluble in nonpolar organic solvents (pentane) and the solutions

exhibit no NMR signals. The radical is somewhat sensitive to air and moisture and

is best stored under argon in a refrigerator. Under these conditions, it is stable for

many months.

Acknowledgment

This work was supported by the NSF (CHE 0446688 and 0848477).

References

1. W. H. Knoth, J. Am. Chem. Soc. 89, 1274 (1967).

2. S. Korbe, P. J. Schreiber, and J. Michl, Chem Rev. 106, 5208 (2006).

3. J. Michl, Pure Appl. Chem. 80, 429 (2008).

Figure 1. Apparatus for oxidation of CB11Me12� to CB11Me12

..


4. (a) S. H. Strauss, Chem. Rev. 93, 927 (1993). (b) C. A. Reed, Acc. Chem. Res. 31, 133 (1998).

(c) I. Krossing and I. Raabe, Angew. Chem., Int. Ed. 43, 2066 (2004).

5. B. T. King and J. Michl, J. Am. Chem. Soc. 122, 10255 (2000).

6. (a) B. T. King, Z. Janousek, B. Gruner, M. Trammell, B. C. Noll, and J. Michl, J. Am. Chem. Soc.

118, 3313 (1996). (b) J. Michl, B. T. King and Z. Janousek,U.S. Patent 5,731,470, (1998).

7. L. Posp�ısil, B. T. King, and J. Michl, Electrochim. Acta 44, 103 (1998).

8. S. Moss, B. T. King, A. de Meijere, S. I. Kozhushkov, P. E. Eaton, and J. Michl,Org. Lett. 3, 2375

(2001).

9. K. Vyakaranam, J. B. Barbour and J. Michl, J. Am. Chem. Soc. 128, 5610 (2006).

10. V. Volkis, H. Mei, R. K. Shoemaker, and J. Michl, J. Am. Chem. Soc. 131, 3132 (2009).

11. J. Michl, K. Vyakaranam, and S. Korbe,U.S. Patent 2009/0069520 A1, (2009).

12. B. T. King, B. C. Noll, A. J. McKinley, and J. Michl, J. Am. Chem. Soc. 118, 10902 (1996).

13. B. T. King, S. Korbe, P. J. Schreiber, J. Clayton, A. Nemcov�a, Z. Havlas, K. Vyakaranam,

M. G. Fete, I. Zharov, J. Ceremuga, and J. Michl, J. Am. Chem. Soc. 129, 12960 (2007).

14. J. Plesek, T. Jel�ınek, E. Drd�akov�a, S. He�rm�anek, and B. St�ıbr,Collect. Czech. Chem. Commun. 49,

1559 (1984).

15. (a) G. B. Dunks and K. P. Ordonez, Inorg. Chem. 17, 1514 (1978). (b) A. Franken, B. T. King,

J. Rudolf, P. Rao, B. C. Noll, and J. Michl, Collect. Czech. Chem. Commun. 66, 1238 (2001).

16. T. Jelinek, P. Baldwin, E. R. Scheidt, and C. A. Reed, Inorg. Chem. 32, 1982 (1993).

17. L. Eriksson, K. Vyakaranam, J. Ludv�ık, and J. Michl, J. Org. Chem. 72, 2351 (2007).

17. CESIUM DODECAHYDROXY-closo-DODECABORATE,Cs2[B12(OH)12]

Submitted by MARK W. LEE, JR.,* ALEXANDER V. SAFRONOV,*

SATISH S. JALISATGI,* and M. FREDERICK HAWTHORNE*

Checked by AMARTYA CHAKRABARTI,�z and NARAYAN HOSMANEz

The dodecahydro-closo-dodecaborate ion [B12H12]2� exhibits extraordinary

kinetic stability owing to extensive delocalization of its 26 cage-bonding elec-

trons.1,2 Illustrative of its stability is the anion’s inertness toward strongly acidic

(3N HCl) or basic (1N NaOH) aqueous solutions at elevated temperatures for

extended times.3In vacuo, alkali metal salts of [B12H12]2� are stable at tempera-

tures above 800�C for extended periods of time.3 Despite this extraordinary kinetic

stability, an extensive array of exopolyhedral substitution reactions has been

described.4 As a three-dimensional aromatic species, closo-dodecaborate under-

goes substitution reactions akin to aromatic substitution in organic chemistry. The

*International Institute of Nano andMolecular Medicine, University ofMissouri, Columbia, MO 65211.�Department of Chemistry & Biochemistry, Northern Illinois University, DeKalb, IL 60115-2862.zDepartment of Chemistry, Southern Methodist University, Dallas, TX 75275.

17. Cesium Dodecahydroxy-closo-Dodecaborate, Cs2[B12(OH)12] 63

reactions of [B12H12]2� are typically limited, however, to the formation of mono-

and bis-substituted derivatives.

All 12 B-H vertices have been replaced by halides,5 methyl groups,6 and

hydroxyl substituents,7 forming the [B12X12]2�, [B12Me12]

2�, and [B12(OH)12]2�

species, respectively. In [B12(OH)12]2�, the 12 hydroxyl groups form a reactive

sheath upon which 12-fold ether and ester derivatives may be constructed.8,9 This

unique class of molecules, which are nearly spherical in nature and with diameters

of 1–5 nm, has previously been given the designation of ‘‘closomers.’’10While the

only known synthetic route toward the perhydroxylation of [B12H12]2� is de-

scribed here, substitution of up to four B-H vertices has been accomplished.11–14

Closomers having 12 ether substituents undergo reversible oxidations through two

one-electron reactions, producing stable paramagnetic intensely permanganate-

red radical and intensely yellow neutral species.8,15

& Caution. Hydrogen peroxide must not come in contact with organic

material or solvents, due to the possibility of fire or explosion. Extreme care must

be taken to ensure the identity of the cesium dodecahydro-closo-dodecaborate

reagent. The exposure of other polyhedral borane or carborane species to the

reaction conditions described herein could result in spontaneous explosion. All

reactionswere conducted inwell-ventilated hoods using additional polycarbonate

blast shields. The product, Cs[B12(OH)12], must not be brought to dryness in the

presence of peroxide solutions as the solid peroxide has been observed to be a

shock-sensitive explosive.

General Comments

Commercially available Cs2B12H12�MeOH, obtained from BASF, was recrystal-

lized from a fivefold mass amount of boiling, distilled water to remove methanol.

Upon cooling in ice, a solid forms. Distilled water is used throughout these

procedures, as the sodium salt of the product is quite insoluble inwater. The cesium

salt is chosen here owing to the moderate solubility of the product salt in water

(4.68 g/L at 25�C). The colorless crystals obtained were dried under vacuum for

48 h at 50�C and contained <2.5wt% ofMeOH (based on 1H NMR spectroscopy).

Aqueous solution of 30wt% hydrogen peroxide was obtained from Fisher

Scientific. Cs2B12H12 characterization: IR (Nujol) n 2915, 2472, 1461, 1377,

1070, 715 cm�1. 1H NMR (500MHz, D2O) d 0.88 to 1.62 (m). 11B NMR

(160MHz, H2O, external standard BF3�etherate) d �15.04 (s).

Cs2½B12H12� þ 12H2O2 !Cs2½B12ðOHÞ12� þ 12H2O


Procedure

In a 250-mL three-necked round-bottomed flask equipped with thermometer,

reflux condenser, magnetic stir bar, and glass stopper are placed 15.00 g

(36.8mmol) of dry recrystallized Cs2B12H12 and 50mL of 30% hydrogen perox-

ide. The reactionmixture is heated to 90�Cwith vigorous stirring, and an additional

60mL of hydrogen peroxide is added to the hot reactionmixture in 10-mLportions

at approximately 2-h intervals. The reaction is allowed to cool to below 50�Cbefore each addition. The temperature of the reaction mixture is increased to

105�C and maintained at that temperature over a several day period with constant

stirring. Reaction progress is monitored by 11B NMR spectroscopy every 2 days.

During the course of the reaction, an additional 40mL of 30% hydrogen peroxide

is added to the reaction mixture in 10-mL portions. The reaction mixture is cooled

to room temperature before each addition. In total, 150mL of 30% hydrogen

peroxide is added. After 12 days (see General Comments), the reaction mixture,

which contains some white precipitated product, was allowed to cool to room

temperature and was then placed in a refrigerator and maintained at 4�C for 12 h.

The white precipitate formed is vacuum filtered and washed with cold, distilled

water. The precipitate is dried in a desiccator under vacuum (over P4O10) for 4 days

to give Cs2[B12(OH)12] as a white solid. Yield: 19.05 g (86%).*

HRMS (ESI) Calcd for B12H12O12: (M)�2 (100% peak) 167.597. Found: 167.596

(6 ppm). IR (Nujol): n 3352, 2842, 1461, 1377, 1133, 721 cm�1. 11B NMR (H2O,

external standard BF3�H2O): d �17.9.

Properties

The compound Cs2B12(OH)12 is a white solid that upon prolonged exposure to

air turns slightly yellow in color. Its properties and NMR spectra do not

change, however. Recrystallization from a minimum quantity of boiling,

distilled water, which requires approximately 25mL/g, returns the compound’s

white appearance.

Thewater solubility of the alkalimetal salts of [B12(OH)12]2� increaseswith the

increasing radius of the metal cation.7 Although the water solubility of the cesium

salt is onlymoderate at room temperature (4.7 g/L), it is sufficient to allow efficient

ion exchange to the tetrabutylammonium (TBA) salt using exchange resin at

elevated temperatures.8 The TBA salt of dodecahydroxydodecaborate is quite

soluble in polar organic solvents, such as acetonitrile. The TBA salt is also highly

water soluble and hydroscopic, much more so than the cesium salt.

* Ten percent additional product can often be obtained from the filtrate after decomposing the hydrogen

peroxide (e.g., using Pd/C).

17. Cesium Dodecahydroxy-closo-Dodecaborate, Cs2[B12(OH)12] 65

References

1. (a) A. R. Pitochelli and M. F. Hawthorne, J. Am. Chem. Soc. 82, 3228 (1960). (b) J. A. Wunderlich

and W. N. Lipscomb, J. Am. Chem. Soc. 82, 4427 (1960). (c) H. C. Longuet-Higgins and M. de V.

Roberts, Proc. R. Soc. Lond. Ser. A 230, 110 (1955).

2. (a) R. Hoffmann and W. N. Lipscomb, J. Chem. Phys. 38, 2179 (1962). (b) M. F. Hawthorne,

Advances in Boron Chemistry, Special Publication No. 201, Royal Society of Chemistry, London,

1997, Vol. 82, p. 261.

3. E. L. Muetterties, J. H. Balthis, Y. T. Chia, W. H. Knoth, and H. C. Miller, Inorg. Chem. 3, 444

(1964).

4. I. B. Sivaev, V. I. Bregadze, and S. Sjoberg, Collect. Czech. Chem. Commun. 67, 679 (2002).

5. W.Knoth, H.Miller, J. Sauer, J. Balthis, Y. Chia, andE. L.Muetterties, Inorg. Chem. 3, 159 (1964).

6. T. Peymann, C. Knobler, and M. F. Hawthorne, J. Am. Chem. Soc. 121, 5601 (1999).

7. T. Peymann, C. Knobler, S. Khan, and M. F. Hawthorne, J. Am. Chem. Soc. 123, 2182 (2001).

8. (a) T. Peymann, C. Knobler, S. Khan, and M. F. Hawthorne, Angew. Chem., Int. Ed. 140, 1664

(2001). (b) O. Farha, R. Julius, M. W. Lee, R. Huertas, C. Knobler, and M. F. Hawthorne, J. Am.

Chem. Soc. 127, 18243 (2005).

9. T. Li, S. Jalisatgi, M. Bayer, A. Maderna, S. Khan, and M. F. Hawthorne, J. Am. Chem. Soc. 127,

17832 (2005).

10. (a) A. Maderna, C. Knobler, and M. F. Hawthorne, Angew. Chem., Int. Ed. 113, 1709 (2001).

(b)M. F. Hawthorne,Pure Appl. Chem. 75, 1157 (2003). (c) T. Peymann, C. Knobler, S. Khan, and

M. F. Hawthorne, Angew. Chem., Int. Ed. 113, 1713 (2001).

11. W. Knoth, J. Sauer, D. England,W. Hertler, and E.Muetterties, J. Am. Chem. Soc. 86, 3973 (1964).

12. A. Antsyshkina, et al., Russ. J. Inorg. Chem. 46, 1323 (2001).

13. A. Semioshkin and B. Brellochs, 8th International Meeting on Boron Chemistry (IMEBORON),

Knoxville, TN (1993).

14. T. Peymann, C. Knobler, and M. F. Hawthorne, Inorg. Chem. 39, 1163 (2000).

15. M. W. Lee, O. Farha, C. Hansch, and M. F. Hawthorne, Angew. Chem., Int. Ed. 46, 3018 (2007).


Chapter Three

COORDINATION COMPOUNDS

18. PENTAAQUANITROSYLCHROMIUM SULFATE

Submitted by ANDERS DØSSING* and ANNE METTE FREY*

Checked by ROSS D. PUTMAN� and THOMAS B. RAUCHFUSS�

The pentaaquanitrosylchromium complex [Cr(OH2)5(NO)]2þ was first prepared

by Ardon by the reaction between aqueous chromium(II) perchlorate and nitric

oxide and isolated as a sulfate salt after an ion-exchange chromatography

purification.1 Later, Ardon prepared the complex more conveniently by the

reduction of CrO3 with NH3OHþ , followed by column chromatography with

0.5M sulfuric acid as the eluent.2 The chromatographicworkup is inconvenient for

the preparation of [Cr(OH2)5(NO)]SO4 at large scale. The synthesis described here

takes advantage of the fact that acetonitrile complexes are useful as synthetic

precursors. The compound [Cr(NCCH3)5(NO)](BF4)2 can be easily synthesized in

a high yield by themethod of Taylor3 from the commercially available compounds

hexacarbonylchromium and nitrosonium tetrafluoroborate. Hydrolysis of the

cation [Cr(NCCH3)5(NO)]2þ in dilute sulfuric acid quantitatively affords

[Cr(OH2)5(NO)]2þ , and a solution with a high concentration of the latter complex

can thus readily be obtained from which the sulfate salt can be isolated.


*Department of Chemistry, University of Copenhagen, DK-2100 Copenhagen Ø, Denmark.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

67

Materials and General Procedures

The reactions are conducted using standard Schlenk techniques. Exposure to light

should be minimized owing to the photolability of the nitrosyl complexes.

& Caution. Cr(CO)6 and CO are toxic by inhalation and nitrosonium

tetrafluoroborate is corrosive and moisture sensitive and should be stored under

nitrogen in a freezer.

A. PENTAAQUANITROSYLCHROMIUM SULFATE

CrðCOÞ6þ2 NOBF4þ5 CH3CN!½CrðNCCH3Þ5ðNOÞ�ðBF4Þ2þ6 COþNO

½CrðNCCH3Þ5ðNOÞ�ðBF4Þ2þ5 H2OþH2SO4!½CrðOH2Þ5ðNOÞ�SO4

þ5 CH3CNþ2 HBF4

Procedure

A 100-mL Schlenk flask is charged with NOBF4 (1.22 g, 10.4mmol), Cr(CO)6(0.55 g, 2.50mmol), acetonitrile (20mL), and amagnetic stirring bar. The reaction

mixture is stirred for 2 h during which time the solution becomes yellow-brown.*

The reaction mixture is filtered in order to remove a small amount of unreacted

Cr(CO)6. Diethyl ether (100mL) is added to the filtrate dropwisewith stirring, and

a yellow-brown precipitate of [Cr(NCCH3)5(NO)](BF4)2 is formed. The mother

liquor is decanted away and to the precipitate a mixture of 2M H2SO4 (2mL,

4.0mmol) and acetone (20mL) is added. Themixture is stirred for 3 hduringwhich

time the color changes from yellow-brown through green to red-brown. During the

last hour, a red-brown precipitate forms. Filtration followed by several washings

with acetone and drying in a nitrogen flow yields [Cr(OH2)5(NO)]SO4 (67–82%

based on chromium) in the range of 0.45–0.55 g. Storage of the filtrate at 5�Covernight gives a small crop of X-ray quality crystals of [Cr(OH2)5NO]SO4�H2O

(see below).

Anal.Calcd. for H10NCrO10S: H, 3.76; N, 5.22; Cr, 19.39. Found: H, 3.73; N, 5.05;

Cr, 19.31. Electronic spectrum in 10�3M HClO4 (l (nm), e (M�1 cm�1)) at 25�C:(561, 27.7), (449, 115), (325, 88.6). IR (KBr): 3115s, 1733s (nNO), 1654m, 1076s,

988m, 881m, 602s cm�1. The crystals of [Cr(OH2)5NO]SO4�H2O obtained from

* The checkers found that the reaction flask should be wrapped in aluminum foil to minimize

photochemical side reactions.

68 Coordination Compounds

the filtrate are orthorhombic, space group Pnma (No. 62), with a¼ 21.9990(4) A�,

b¼ 6.6690(5)A�, c¼ 6.8960(16)A

�, V¼ 1011.7(2) A

� 3, Z¼ 4 at 122K.5

Properties and Notes

[Cr(OH2)5(NO)]SO4 is easily soluble in water and methanol but insoluble

in acetone. Irradiation of an aqueous solution of [Cr(OH2)5(NO)]2þ

produces nitric oxide and [Cr(OH2)6]2þ .4 The back-reaction is, however, so fast

(k¼ 2.5� 108M�1 s�1) that no net photochemistry is observed in deaerated

solutions. In an aerated solution, photodecomposition occurs through trapping

of [Cr(OH2)6]2þ with dioxygen giving the superoxo complex that reacts further,

yielding various Cr(III) species.4 On the other hand, [Cr(OH2)5(NO)]2þ is stable

in aerated solutions kept in the dark. In the solid state, [Cr(OH2)5(NO)]SO4

decomposes thermally and photochemically and should therefore be stored in a

freezer. As a result of the release of NO upon light exposure, the nitrogen content

found in the elemental analysis of [Cr(OH2)5(NO)]SO4 is often found to be lower

than that calculated. Exposure to light should accordingly be minimized in the

handling of the solid.

The fluoroborate salt can be purified by extracting the crude product into

acetonitrile (20mL) and diluting the filtrate with diethyl ether (100mL) with

stirring. After two to three such recrystallizations, 0.5–0.6 g (43–52%) of curry-

yellow powder of [Cr(NCCH3)5(NO)](BF4)2 is obtained.

Anal.Calcd. for C10H15N6B2CrF8O: C, 26.06; H, 3.28; N, 18.23; Cr, 11.28. Found:

C, 25.95;H, 3.10;N, 17.73;Cr, 11.37. Electronic spectrum in acetonitrile (l (nm), e(M�1 cm�1)) at 25�C: (749, 33.0), (436, 242), (313, 306).5 By usingNOPF6 insteadof NOBF4, the product [Cr(NCCH3)5(NO)](PF6)2 can be isolated in higher yield

(80–90%). However, due to the low solubility of this product in the H2SO4/acetone

mixture, this product cannot be used in the further synthesis of [Cr(OH2)5(NO)]

SO4.

References

1. M. Ardon and J. I. Herman, J. Chem. Soc. 507 (1962).

2. M. Ardon and S. Cohen, Inorg. Chem. 32, 3241 (1993).

3. S. Clamp,N. G. Connelly, G. E. Taylor, and T. S. Louttit, J. Chem. Soc., Dalton Trans. 2162 (1980).

4. A. Nemes, O. Pestovsky, and A. Bakac, J. Am. Chem. Soc. 124, 421 (2002).

5. A. Døssing and A. M. Frey, Inorg. Chim. Acta 359, 1681 (2006).

18. Pentaaquanitrosylchromium Sulfate 69

19. THE TETRADENTATE BISPIDINE LIGAND DIMETHYL-(3,7-DIMETHYL-9-OXO-2,4-BIS(2-PYRIDYL)-3,7-

DIAZABICYCLO[3.3.1]NONANE)-1,5-DICARBOXYLATEAND ITS COPPER(II) COMPLEX

Submitted by PETER COMBA,* MAIK JAKOB,* and MARION KERSCHER*

Checked by MARIA E. CARROLL� and THOMAS B. RAUCHFUSS�

The first bispidines were prepared byMannich1,2 and the first bispidine complexes

were described around 50 years ago. The first complexes of the ligand reported

here were prepared 40 years ago.3,4 The importance of the bispidine ligands in

transition metal coordination chemistry derives from the facts that (i) molecular

properties depend on molecular structures, (ii) structures of transition metal

complexes may be enforced by rigid multidentate ligands, and (iii) tetra-, pen-

ta-, and hexadentate bispidine ligands are as diazaadamantane derivatives ex-

tremely rigid ligands that enforce unique coordination geometries (see Fig. 1 for the

structure of the tetradentate ligand described here, L¼ 3,7-dimethyl-9-oxo-2,4-bis

(2-pyridyl-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate dimethylester).5,6 The

piperidonepLmaybeobtainedinhighyield inaprocedurefirstdescribedbyMannich

andMohs (see Fig. 2).2 Variation of the aldehyde and amine component has led to a

number of piperidone derivatives.6 The bispidone L is also obtained in good yield

from pL as also first described by Mannich and Mohs (see Fig. 2),2 and a variety of

other ligands with different donor sets and denticity have been described.6

For copper(II) in particular, the tetradentate bispidone L has a high degree of

preorganization and complementarity and therefore leads to very stable complexes

with a range of interesting properties, in particular also due to the unique square

pyramidal structure with an in-plane monodentate coligand.6

A. PIPERIDONE (pL)

Procedure

Methylamine (Fluka, 40% aq. solution, 1.5mL, 17.31mmol, d¼ 0.897) and

pyridine-2-aldehyde (Fluka, 3.31mL, 34.62mmol, d¼ 1.121) in MeOH (25mL)

are cooled to 0�C in a 50-mL flask. To this yellow solution, dimethyl-1,3-

acetonedicarboxylate (Aldrich, 2.5mL, 17.31mmol, d¼ 1.206 g/mL) is added

within 5min while stirring. The brownish solution is stirred for another 15min at

*Universit€at Heidelberg, Anorganisch-Chemisches Institut, D-69120, Heidelberg, Germany.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL61801.


0�C, then 45min under ambient atmosphere, and finally overnight at ambient

temperature. Crystallization starts after approximately 1.5 h. After cooling on an

ice bath, the solid is collected on a filter, washed withMeOH (15mL), and dried in

high vacuum. More of the piperidone pL is obtained by partial evaporation of the

filtrate (rotary evaporator, 15mL). The total yield of colorless crystals of amixture

of keto and enol form of the piperidone pL is 5.42 g (14.14mmol, 82%).

Anal. Calcd. for C20H21N3O5: C, 62.65; H, 5.52; N, 10.96. Found: C, 62.56; H,

5.50; N, 10.96. Decomp. 118�C. 1H NMR (CDCl3, keto form): d¼ 1.71 (s, 3H, N-

CH3); 3.60 (s, 6H, O-CH3); 4.42 (d, 3J ¼ 11.2 Hz, 2H, N-CH-CH-); 4.65 (d,3J ¼ 11.2 Hz, 2H, N-CH-CH-); 7.15, 7.48, 7.65, 8.51 (m, 2H every,Har).

13C NMR

Figure 1. Structures of the tetradentate bispidone ligand L (left) and diamond (right).

Figure 2. Synthesis of the bispidone copper(II) complex.

19. The Tetradentate Bispidine Ligand Dimethyl 71

(CDCl3, keto form): d¼ 33.30 (1C, N-CH3); 51.83 (2C, O-CH3); 56.94 (2C,

-CH-CO); 69.77 (2C, -CH-N); 122.81, 124.31, 136,35, 148.79, 157,18 (10C, Car);

168.32 (2C, -COOCH3); 200.45 (1C, C¼O).

B. BISPIDONE 3,7-DIMETHYL-9-OXO-2,4-BIS(2-PYRIDYL-3,7-DIAZABICYCLO[3.3.1]NONANE-1,5-DICARBOXYLATE

DIMETHYLESTER (L)

Procedure

The piperidone pL (4.5 g, 11.74mmol), suspended in THF (30mL) in a 100-mL

one-necked flask, is heated to 50�C before the amine component (methylamine,

Fluka, 40% aq. solution, 1.26mL, 14.09mmol) and then the aldehyde (formalde-

hyde, Riedel de-H€aen, 37% aq. solution, 1.94mL, 28.18mmol) are added under

stirring. The resulting solution is heated to reflux (80�C) for 1 h under rigorous

stirring and then left to cool. Afterward, the solvent is completely removed on a

rotary evaporator, and the resulting solid is recrystallized from MeOH (10mL,

crystals start to form after approximately 90min). Themixture is then treated in an

ultrasonic bath for 2min and then left in the refrigerator (4�C) overnight. The solidis collected on a filter, washed with cold MeOH (5mL), and dried in high vacuum.

The filtrate is evaporated (rotary evaporator) to 50% of its original volume (5mL)

to producemore of the ligandL. This is also recrystallized and its purity checked by

NMR spectroscopy. Yield: 3.46 g (7.89mmol, 67%).

Anal. Calcd. for C23H28N4O5: C, 63.00; H, 5.98; N, 12.78. Found: C, 62.89; H,

5.96; N, 12.63. Decomp. 162�C (brown color 152�C). 1H NMR (CDCl3): d¼ 1.99

(s, 3H, N-CH3); 2.21 (s, 3H, N-CH3); 2.47 (d,2J ¼ 12.3 Hz, 2H, -CHaxHeq-); 2.93

(d, 2J ¼ 12.3Hz, 2H, -CHaxHeq-); 3.79 (s, 6H, O-CH3); 4.70 (s, 2H, N-CH-); 7.18

(m, 2H,Har); 7.75 (td,3J ¼ 7.7Hz, 4J ¼ 1.7Hz, 2H,Har); 8.05 (d,

3J ¼ 7.9Hz, 2H,

Har); 8.46 (d,3J ¼ 4.8Hz, 2H, Har).

13C NMR (CDCl3): d¼ 43.19, 44.41 (2C, N-

CH3); 52.40 (2C, O-CH3); 60.75 (2C, N-CH2-); 62.16 (2C, N-CH-); 73.78 (2C, -C-

CO); 122.90, 123.46, 136.30, 149.16, 158.97 (10C, Car); 168.49 (2C, -COOCH3);

203.54 (1C,C¼O). IR (cm�1): 620, 750, 764, 787, 957, 969, 987, 996, 1038, 1082,

1092, 1161, 1168, 1253, 1268, 1289, 1364, 1434, 1471, 1570, 1590, 1715, 1729,

1756, 2715, 2795, 2848, 2895, 2952, 2980, 3003, 3070, 3433 (broad).

C. COPPER(II) BISPIDONE CHLORIDE (CuLCl)

Procedure

The copper(II) complex [Cu(L)Cl]Cl� 2H2O is obtained in over 70% yield. To

a suspension of L (0.5 g, 1.14mmol) in MeOH (5mL) is added under stirring


a solution of CuCl2� 2H2O (0.194 g, 1.14mmol) in 2mL of MeOH. The imme-

diate appearance of an intense blue color indicates complexation. After stirring the

solution for 2 h at ambient conditions, crystallization is initiated by ether diffusion

into the solution of the complex. After 7–14 days, the blue crystals of the bispidine

copper(II) complex are collected on a filter, washed with little coldMeOH (2mL),

and dried in high vacuum. Yield: 0.5 g (0.82mmol, 72.0%).

Anal. Calcd. forC23H32Cl2CuN4O7:C, 45.36;H, 4.97;N, 9.20. Found:C, 45.04;H,

5.02; N, 9.09. IR (cm�1): 515, 649, 744, 759, 782, 827, 935, 960, 1014, 1028, 1046,

1065, 1106, 1165, 1206, 1256, 1267, 1377, 1434, 1449, 1473, 1573, 1607, 1631,

1730, 2957, 3071, 3108, 3427 (broad).

Properties

The piperidone pL and bispidone L are air-stable, colorless crystalline compounds.

As for bispidones in general, the IR spectrum of L has characteristic Bohlmann

bands (2795 and 2848 cm�1), which disappear upon complexation. The blue

crystalline copper(II) complex [Cu(L)(Cl)]þ is stable in air. In the UV–vis

spectrum (aqueous solution), it shows a d–d transition at lmax¼ 656 nm

(15244 cm�1) with e656¼ 90 cm�1M�1. The spin Hamiltonian parameters (ob-

tained by simulation of a measured frozen solution EPR spectrum [116K, DMF/

CH3OH¼ 2:1]) are gz¼ 2.224, gx¼ gy¼ 2.05; Az¼ 175� 10�4 cm�1, Ay¼ 22

� 10�4 cm�1, Ax¼ 18� 10�4 cm�1. The redox potential of the corresponding

CH3CN complex [Cu(L)(NCCH3)]2þ , measured by cyclic voltammetry (CV) in

CH3CN solution, is�510mV vs. Fc/Fcþ . The structure (X-ray diffraction, ligandL hydrolyzed at C9) has been published (CCDC-113633).7

References

1. C. Mannich and F. Veit, Chem. Ber. 68, 506 (1935).

2. C. Mannich and P. Mohs, Chem. Ber. B63, 608 (1930).

3. H. Stetter and R. Merten, Chem. Ber. 90, 868 (1957).

4. R. Haller, Arch. Pharm. 302, 113 (1969).

5. P. Comba and W. Schiek, Coord. Chem. Rev. 238-239, 21 (2003).

6. P. Comba, M. Kerscher and W. Schiek, Prog. Inorg. Chem. 55, 613 (2007).

7. H. Borzel, P. Comba,C.Katsichtis,W.Kiefer, A. Lienke,V.Nagel andH. Pritzkow,Chem.Eur. J. 5,

1716 (1999).

19. The Tetradentate Bispidine Ligand Dimethyl 73

20. TRIS(2-PICOLINYL)METHANE AND ITS COPPER(I)COMPLEX

Submitted by YUUJI KAJITA,* YOSHIMITSU TACHI,* YUTAKA HITOMI*

TOMOYUKI NAKAGAWA,* YOSHIHISA KISHIMA,* and

MASAHITO KODERA*

Checked by CHRISTOPHER S. LETKO� and THOMAS B. RAUCHFUSS�

Many different kinds of tridentate facial capping ligands based on nitrogen

heterocycles have been developed to afford biologically relevant and functional

metal complexes.1–4 Prominent examples include tris(pyridyl), tris(pyrazolyl),

and tris(imidazolyl) tripodal ligands. These ligands often feature various bridge-

head groups, such as CH, COH, N, P, PO, As, B, Sn(n-Bu), and Pb, that may be

useful for introducing structural perturbations to the metal complexes.5 Moreover,

sterically hindered tripodal ligands stabilize monometallic complexes with open

coordination sites essential for functions. Bulky ligands often stabilize complexes

that usefully mimic metalloenzyme active sites.6 Herein, we present syntheses of

a sterically hindered tripodal ligand tris(2-picolinyl)methane and its Cu(I) com-

plexes.7 The procedures include improvements of our original methods.7

General Comments

Standard inert atmosphere techniques are required.

A. BIS(2-PICOLINYL)METHANE

2; 6-Me2C5H3N þ BuLi!C5H3N-2-CH2Li-6-Me þ BuH

C5H3N-2-CH2Li-6-Me þ C5H3N-2-Br-6-Me ! ð6-C5H3N-2-MeÞ2CH2 þ LiBr

Procedure

A 500-mL three-necked round-bottomed flask is fitted with a rubber septum,

a reflux condenser, and a three-way N2 inlet/outlet. The flask is charged with

a magnetic stirring bar, THF (100mL), and 2,6-lutidine (10.7 g, 0.1mol). To this

solution is added n-BuLi (125mL, 0.21mol, 1.69M in hexane) at �78�C. Thesolution iswarmed to room temperature and stirred for 3 h. The resultant solution is

cooled to �78�C, and a solution of anhydrous ZnCl2 (30 g, 0.22mol) in dry THF

*Department of Molecular Chemistry and Biochemistry, Doshisha University, Kyotanabe, Kyoto

610-0321, Japan.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.


(100mL) is added. To the mixture are added Pd(dppf)Cl28 (0.73 g, 0.001mol) and

2-bromo-6-picoline* (18.9 g, 0.11mol) at �78�C. The mixture is heated to reflux

with vigorous stirring for 15 h. After the resultant mixture is cooled to room

temperature, THF is removed by distillation. The residue is suspended in CHCl3(100mL). To this suspension is added an aqueous solution (10mL) of NaOH

(4.4 g, 0.11mol) followed by an aqueous solution (50mL) of Na2S�9H2O (26.4 g,

0.11mol). The mixture is stirred for 1 h to give a white precipitate. The precipitate

is removed by filtration and washed with CHCl3 (200mL). The filtrate and

washings are combined, and the CHCl3 layer is separated with a separatory funnel.

The aqueous layer is extracted with CHCl3 (3� 80mL). The CHCl3 layers are

combined and dried over anhydrousNa2SO4 and concentrated by rotary evaporator.

The oily residue is purified by vacuum distillation. Bis(2-picolinyl)methane is

isolated at 80–120�C/0.1Torr. The oil is crystallized to afford yellow solid at room

temperature. Yield: 13.3–14.5 g (67–73%), mp 45�C.

Properties

1H NMR (CDCl3): d 7.47 (t, 2H, py-4), 6.99 (d, 4H, py-3, 5), 4.29 (s, 2H,

methylene), and 2.55 (s, 6H, methyl).

B. TRIS(2-PICOLINYL)METHANE

ð6-C5H3N-2-MeÞ2CH2 þ BuLi ! ð6-C5H3N-2-MeÞ2CHLi þ BuH

ð6-C5H3N-2-MeÞ2CHLi þ C5H3N-2-Br-6-Me!ð6-C5H3N-2-MeÞ3CH þ LiBr

Procedure

A300-mL three-necked round-bottomed flask is equippedwith amagnetic stirring

bar, a rubber septum, a reflux condenser, and a three-way stopcock for N2 inlet/

outlet. The flask is charged with THF (100mL) and bis(2-picolinyl)methane

(9.91 g, 0.05mol). The solution is cooled to�78�C and is then treatedwith n-BuLi

(33.5mL, 0.055mol of a 1.69M solution in hexane). The solution is warmed to

room temperature and stirred for 3 h. To the solution are added Pd(PPh3)4 (0.58 g,

0.0005mol) and 2-bromo-6-picoline (9.46 g, 0.055mol) at�78�C. The mixture is

heated to refluxwith vigorous stirring for 15 h.After the resultantmixture is cooled

to room temperature, THF is removed by distillation. To the residue are addedH2O

(100mL) and CHCl3 (200mL), and the CHCl3 layer is collected. The aqueous

* The checkers prepared 2-bromo-6-picoline from inexpensive 2-amino-6-picoline: R. Adams and S.

Miyano, J. Am. Chem. Soc. 76, 3168–3171 (1954).

20. Tris(2-Picolinyl)Methane and Its Cu(I) Complex 75

layer is further extracted with CHCl3 (3� 80mL). The CHCl3 extracts are

combined and dried over anhydrous Na2SO4 and concentrated by rotary evapora-

tor. Upon addition of Et2O to the residue, tris(2-picolinyl)methane is precipitated

as a white solid.� The solid is collected by filtration and washed by Et2O several

times. Yield: 8.22–9.50 g (57–66%).

1H NMR (CDCl3): d 7.47 (t, 3H, py-4), 7.04 (d, 3H, py-3), 6.99 (t, 3H, py-5), 5.90(s, 1H, methine), and 2.50 (s, 9H, methyl).

Properties

The ligand HL is air stable. HL reacts with methanol solution of CuBr2 in air to

afford HOL, bis(2-picolinyl)ketone (bpk), and MeOL.7a With catalytic amount of

CuBr2, the bridgehead oxidation is quantitative. Under anaerobic conditions, HL

and CuBr2 react to give CuBr2(HL) quantitatively.

C. COPPER(I) (TRIS(2-PICOLINYL)METHANE)ACETONITRILE

HEXAFLUOROPHOSPHATE

ð6-C5H3N-2-MeÞ3CH þ ½CuðMeCNÞ4�PF6 !½Cuð6-C5H3N-2-MeÞ3CHÞ�ðMeCNÞ�PF6 þ 3 MeCN

Procedure

A 50-mL Schlenk tube equipped with a magnetic stirring bar and a three-way

N2 inlet/outlet is charged with MeCN (10mL) and degassed by a few cycles of

evacuation and refilling with N2. To this solution are added tris(2-picolinyl)

methane (28.9mg, 0.1mmol) and [Cu(MeCN)4]PF6 (41.0mg, 0.11mmol).9 The

solution is stirred for 1 h at room temperature. Upon addition of Et2O (20mL) to

the reaction mixture, a pale yellow solid precipitates. The pale yellow solid is

collected by filtration and washed well with Et2O. Yield: 33.0–35.4mg (84–90%).

The copper(I) complex is recrystallized by dissolving in about 5mL of MeCN

followed by diffusion of Et2O vapor.

1H NMR (CD3CN): d 7.76 (t, 3H, py-4), 7.57 (d, 3H, py-3), 7.28 (d, 3H, py-5), 5.94(s, 1H, methine), and 2.73 (s, 9H, methyl).

�The checkers evaporated the CHCl3 extracts to dryness, dissolved the crude product in a minimum of

CHCl3, and precipitated the product by the addition of hexane.


Properties

The copper complex is insoluble in nonpolar solvents but soluble in dichloro-

methane, MeCN, and some organic solvents. The Cu(I) complex is air stable.

References

1. (a) L. F. Szczepura, L. M. Witham, and K. J. Takeuchi, Coord. Chem. Rev. 174, 5 (1998).

(b) D. L. White and J. W. Faller, Inorg. Chem. 21, 3119 (1982).

2. (a) P. L. Dedert, T. Sorrell, T. J. Marks, and J. A. Ibers, Inorg. Chem. 21, 3506 (1982). (b) T. Sorrell

and A. S. Borovik, J. Am. Chem. Soc. 109, 4255 (1987).

3. (a) W. E. Lynch, D. M. Kurts Jr., S. Wang, and R. A. Scott, J. Am. Chem. Soc. 116, 11030 (1994).

4. (a) T. Sorrell, W. E. Allen, and P. S. White, Inorg. Chem. 34, 952 (1995). (b) W. E. Allenand

T. Sorrell, Inorg. Chem. 36, 1732 (1997).

5. (a) R. K. Boggess and D. A. Zatko, Inorg. Chem. 15, 626 (1976). (b) D. J. Szalda and F. R. Keene,

Inorg. Chem. 25, 2795 (1986). (c) F. R.Keene,D. J. Szalda, andT.A.Wilson, Inorg.Chem. 26, 2211

(1987). (d) T.A.Hafeli andF.R.Keene,Aust. J. Chem.41, 1379 (1988). (e) F.R.Keene,M.R. Snow,

P. J. Stephenson, and E. R. T. Tiekink, Inorg. Chem. 27, 2040 (1988). (f) F. R. Keeneand

P. J. Stephenson, Inorg. Chem. Acta 187, 217 (1991). (g) T. Astley, P. J. Ellis, H. C. Freeman,

M. A. Hitchman, F. R. Keene, and E. R. T. Tiekink, J. Chem. Soc., Dalton Trans. 595 (1995).

(h) T. Astley,M. A. Hitchman, F. R. Keene, and E. R. T. Tiekink, J. Chem. Soc., Dalton Trans. 1845

(1996).

6. N. Kitajima and Y. Morooka, Chem. Rev. 94, 737 (1994).

7. (a) M. Kodera, Y. Tachi, T. Kita, H. Kobushi, Y. Sumi, K. Kano, M. Shiro, M. Koikawa, T. Tokii,

M. Ohba, and H. Okawa, Inorg. Chem. 39, 226 (2000). (b) M. Kodera, Y. Kajita, Y. Tachi,and K.

Kano, Inorg. Chem. 42, 1193 (2003).

8. T. Hayashi,M. Konishi, Y. Kobori, M. Kumada, T. Higuchi, and K. Hirotsu, J. Am. Chem. Soc. 106,

158 (1984).

9. G. J. Kubas, Inorg. Synth. 28, 68–70 (1990).

20. Tris(2-Picolinyl)Methane and Its Cu(I) Complex 77

Chapter Four

CARBENE LIGANDS AND COMPLEXES

21. 1,3-DIALKYL-IMIDAZOLE-2-YLIDENES

Submitted by THOMAS SCHAUB* and UDO RADIUS�

Checked by ALEXANDRIA BRUCKS,z MARY P. CHOULES,z

MATTHEW T. OLSEN,z and THOMAS B. RAUCHFUSSz

During the past decade, there has been considerable interest in N-heterocyclic

carbenes (NHC) as spectator ligands in organometallic chemistry, particularly as

alternatives to phosphine ligands in the field of homogeneous catalysis.1 A number

of studies have suggested that nucleophilic carbenes have ligating properties

similar to electron-rich trialkylphosphines, and the strong s-donor properties ofthese ligands often result in more stable catalysts compared to analogous phos-

phine systems.1,2 1,3-Dialkyl-substituted NHCs are better s-donating ligands

compared to their widely used aryl-substituted counterparts and trialkylpho-

sphines, so they can be used to obtain metal complexes featuring a high metal

basicity.3We describe here the two-step synthesis of theN-alkyl-substituted NHCs

1,3-dimethyl-imidazole-2-ylidene (Me2Im), di-n-propyl-imidazole-2-ylidene

(nPr2Im), diisopropyl-imidazole-2-ylidene (iPr2Im), and the mixed substituted

1-methyl-3-isopropyl-imidazole-2-ylidene (MeiPrIm) (see Fig. 1). In the first step,

the corresponding imidazolium salts are prepared either by condensation of

glyoxal, paraformaldehyde, alkylamine, and HCl (iPr2ImHCl, nPr2ImHCl)3b,4 or

by reaction of 1-methylimidazole with the alkyl iodide (Me2ImHI, MeiPrImHI).


*BASF SE, 67056 Ludwigshafen, Germany.�Institut f€ur Anorganische Chemie der Universit€at W€urzburg, 97074 W€urzburg, Germany.zDepartment of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

78

In the second step, these imidazolium salts are deprotonated with NaH either at

room temperature in THF using KOtBu as a phase-transfer catalyst (iPr2Im,nPr2Im) or at �78�C in liquid NH3 (Me2Im, MeiPrIm) to yield the stable NHCs.

A. 1,3-DI-n-PROPYL-IMIDAZOLIUM CHLORIDE (nPr2ImHCl)

and 1,3-DIISOPROPYL-IMIDAZOLIUM CHLORIDE (iPr2ImHCl)

ðCHOÞ2 þ 2RNH2 þHClþ 1=nðCH2OÞn !R2ImHClþ 3H2OðR ¼ iPr; nPrÞ

Procedure

In a 1-L three-necked round-bottomed flask fitted with a reflux condenser and a

dropping funnel, the primary amine (iPrNH2: 61.8mL, 0.72mol; nPrNH2:

59.4mL, 0.72mol) is added dropwise with stirring over a period of 90min to a

suspension of paraformaldehyde (21.6 g, 0.71mol) in 120mL toluene. Using a

water bath, the temperature of the reaction mixture is strictly kept under 40�Cduring addition. The reaction mixture is stirred for additional 10min and then

cooled to 0�C. Another equivalent of the amine (iPrNH2: 61.8mL, 0.72mol;nPrNH2: 59.4mL, 0.72mol) is then added dropwise over a period of 90min

followed by slow, dropwise hydrolysis using 6N HCl (120mL, 0.72mol), also

over a period of 90min. After hydrolysis, the solution is warmed to room

temperature and glyoxal (82.8mL, 0.72mol; 40% in H2O) is added dropwise (it

is advantageous to use a fresh glyoxal solution). The mixture is then stirred

overnight to give a brown emulsion.All volatilematerials are removed in vacuo at a

rotation evaporator (water bath temperature: 90�C; 10mbar vacuum). The result-

ing brown, sticky residue is then transferredwhile hot into a 1-L one-necked round-

bottomed Schlenk flask and vigorously dried in vacuo (2 � 10�3mbar) at 150�Cfor 6 h. The brown, compact product is crushed in a glovebox to yield 113.0 g

(83%; for both nPr2ImHCl and iPr2ImHCl) of a brown hygroscopic solid.

Properties

The products are very hygroscopic and should be stored under an inert atmosphere

to prevent hydrolysis before deprotonation in the second step. 1H NMR (D2O):nPr2ImHCl: d 0.82 (t, 6H, 3JHH ¼ 7.4Hz, CH3), 1.80 (sext, 4H, 3JHH ¼ 7.2Hz,

R1 = R2 = Me (Me2Im)R1 R2

CN N

R1 = Me, R2 = iPr (MeiPrIm)

R1 = R2 = nPr (nPr2Im)R1 = R2 = iPr (iPr2Im)

Figure 1. 1,3-Dialkyl-substituded imidazole-2-ylidenes.

A. 1,3-DI-n-Propyl-Imidazolium Chloride (nPr2ImHCl) 79

NCH2CH2), 4.08 (t, 4H,3JHH ¼ 7.0, NCH2), 7.41 (s, 2H, NCHCHN), 8.71 (s, 1H,

NCHN); iPr2ImHCl: d 1.43 (d, 12H, CH3), 4.52 (m, 2 H, iPr-CH), 7.47 (s, 2H,

NCHCHN), 8.76 (s, 1H, NCHN); 13C{1H} NMR (D2O):nPr2ImHCl: d 9.8 (CH3),

22.8 (NCH2CH2), 51.1 (NCH2), 122.3 (NCCN), 135.2 (NCN);iPr2ImHCl: d 22.1

(CH3), 53.0 (iPr-CH), 120.5 (NCCN), 132.5 (NCN).

B. 1,3-DIMETHYL-IMIDAZOLIUM IODIDE (Me2ImHI) AND

1-METHYL-3-ISOPROPYL-IMIDAZOLIUM IODIDE (MeiPrImHI)

MeImþRI!MeðRÞImHIðR ¼ Me; iPrÞ

Procedure

The entire procedure is performed in an anhydrous atmosphere because of the

hygroscopic nature of the reaction products. Methylimidazole (20.8 g, 0.253mol)

and the alkyl iodide (iodomethane: 35.9 g, 0.253mol; 2-iodopropane: 43.0 g,

0.253mol) are dissolved in a 250-mL two-necked round-bottomed Schlenk flask

equipped with a reflux condenser in 100mL toluene. The reaction mixture is

vigorously stirred overnight under reflux. During this time, a white solid forms,

which is filtered off after cooling to room temperature, washed twice with 40mL

hexane, and dried in vacuo to yield 56.0 g (99%, Me2ImHI) or 57.7 g (90%,

MeiPrImHI) of the product in the form of a white powder.

1H NMR:Me2ImHI (D2O): d 3.85 (s, 6H, CH3), 7.38 (s, 2 H, CHCH), 8.62 (s, 1H,

NCHN);MeiPrImHI (CDCl3): d 1.61 (d, 6H, 3JHH ¼ 6.7Hz, iPr-CH3), 4.10 (s, 3H,

N-CH3), 4.81 (sept, 1H,3JHH ¼ 6.7Hz, iPr-CH), 7.60 (m, 2H, NCHCHN), 9.95 (s,

1H, NCHN); 13C NMR: Me2ImHI (D2O): d 36.0 (CH3), 123.5 (CHCH), 136.6

(NCN); MeiPrImHI (CDCl3): d 23.3 (iPr-CH3), 37.1 (N-CH3), 53.5 (iPr-CH),

120.5 (NCCN), 125.3 (NCCN), 135.5 (NCN).

Properties

The products are very hygroscopic and should be stored under an inert atmosphere

to prevent hydrolysis before deprotonation in the second step.

C. 1,3-DI-n-PROPYL-IMIDAZOL-2-YLIDENE (nPr2Im)

AND 1,3-DIISOPROPYL-IMIDAZOL-2-YLIDENE (iPr2Im)

R2ImHClþNaH cat:KOtBu��! R2ImþNaClþH2 ðR ¼ nPr; iPrÞ

80 Carbene Ligands and Complexes

& Caution. The alkyl-substituted NHCs are highly reactive compounds

and not yet toxicologically tested. They should be handled with great care and any

contact with skin should be avoided. Generally, reactions of alkyl-substituted

NHCs in pure halogenated solvents or solvent mixtures containing halogenated

solvents should be avoided. Especially NMR samples of these NHCs should never

be recorded in CDCl3 because of their very exothermic reaction with chloroform.

The NHC’s can be gently decomposed to nonreactive compounds by the addition

of (wet) acetone. NaH reacts violently with water; it can be safely decomposed by

the addition of 2-propanol under a stream of nitrogen.

Procedure

THF (600mL) is added at room temperature to a mixture of imidazolium salt

(113.0 g, 0.60mol; nPr2ImHCl or iPr2ImHCl), sodium hydride (15.7 g, 0.65mol),

and potassium tert-butoxide (3.30 g, 29.4mmol) in a 1-L one-necked round-

bottomed Schlenk flask equipped with a pressure outlet (due to the evolution of H2

during the reaction). Themixture is stirred overnight to give a dark suspension. All

volatiles are removed in vacuo into a liquid nitrogen cooled trap to leave a brown,

sticky residue as the crude product in the flask. The Schlenk flask is then connected

under a stream of nitrogen with a joint to a 150-mL Schlenk tube and a liquid

nitrogen cooled trap is installed between the apparatus and the vacuum pump. The

experimental setup is shown in Fig. 2. The whole apparatus is then evacuated for

10min and the Schlenk tube is cooled afterward with liquid nitrogen. The

temperature of the oil bath is raised to 150�180�C, and the parts of the flask

not covered by the oil bath aswell as the joint are kept at high temperature bymeans

of a heat gun (600�C), mainly to prevent the condensation of the carbene outside

Figure 2. Apparatus for the flash distillation of the NHCs.

21. 1,3-Dialkyl-Imidazole-2-Ylidenes 81

the Schlenk tube. The distillation is usually finished in 1–2 h and dynamic vacuum

is used throughout this process, which also removes last traces of tBuOH and THF

from the product. Afterward, the oil bath is removed and the apparatus is flushed

with nitrogen. The Schlenk tube with the colorless to yellow carbenes (iPr2Im:

crystalline at �40�C; nPr2Im: liquid at �40�C) is closed and should be stored at

�40�C because of the thermal lability of the NHCs. Yields: nPr2Im 82.2 g (90%);iPr2Im 73.0 g (80%). The residue in the 1-L Schlenk flask is mainly NaCl.

1H NMR (C6D6):nPr2Im: d 0.72 (t, 6H, 3JHH ¼ 7.8Hz, CH3), 1.63 (sext, 4H,

3JHH ¼ 7.6Hz, CH2CH3), 3.80 (t, 4H, 3JHH ¼ 7.1Hz, NCH2), 6.8 (s, 2H,

NCHCHN); iPr2Im: d 1.27 (d, 12H, CH3), 4.40 (m, 2H, iPr-CH), 6.63 (s, 2H,

NCHCHN); 13C{1H} NMR (C6D6):nPr2Im: d 11.7 (CH3), 26.1 (NCH2CH2), 53.7

(NCH2), 119.7 (NCCN), 214.9 (NCN);iPr2Im: d 24.3 (CH3), 52.1 (

iPr-CH), 115.7

(NCCN), 211.9 (NCN).

Properties

nPr2Im and iPr2Im are very moisture sensitive, thermally labile, and decompose at

room temperature after a few days with the formation of black oils. However, these

carbenes can be stored under an inert atmosphere at �40�C for months without

recognizable decomposition. For further reactions, the carbenes can be used as

liquids at room temperature (density at 20�C approximately 1 g/cm3), but they

should be restored at �40�C immediately after use. These carbenes are highly

soluble in THF, diethylether, toluene, and benzene, and are moderately soluble in

hexane and pentane. They are strong bases and decompose in solvents with acidic

C�H bonds such as acetone or acetonitrile. With halogenated solvents such as

chloroform, they decompose exothermically.

D. 1,3-DIMETHYL-IMIDAZOL-2-YLIDENE (Me2Im) AND

1-METHYL-3-ISOPROPYL-IMIDAZOL-2-YLIDENE (MeiPrIm)

MeRImHIþNaH!MeRImþNaIþH2ðR ¼ Me; iPrÞ& Caution. Ammonia is toxic and corrosive. All manipulation should be

conducted in an efficient fume hood, and gloves and goggles should be worn. For

the carbenes and NaH, see part C.

Procedure

At�78�C (2-propanol/dry ice cooling bath), NH3 (ca. 200mL) is condensed into a

500-mL one-necked round-bottomed Schlenk flask equipped with an pressure

outlet (evolution of H2 and NH3), which is charged with a mixture of the


imidazolium iodide (Me2ImHI: 32.0 g, 0.143mol; MeiPrImHI: 36.2 g, 0.143mol)

and NaH (3.43 g, 0.143mol). The resulting solution is stirred for 1 h at this

temperature and the cooling bath is removed afterward. Ammonia is removed

by stirring the mixture overnight and last traces of the solvent are eliminated by

evacuation at room temperature. The resulting brownish crude reaction product is

distilled as described in part C using the apparatus shown in Fig. 2 to giveMe2Im as

a yellow to red liquid (which solidifies at�40�C) (11.9 g, 77%) and MeiPrIm as a

red liquid (15.8 g, 79%).

1H NMR (C6D6):Me2Im: d 3.43 (s, 6H, CH3), 6.70 (s, 2H,NCHCHN);MeiPrIm: d1.26 (d, 6H, 3JHH ¼ 6.7Hz, iPr-CH3), 3.44 (s, 3H, N-CH3), 4.36 (sept, 1H,3JHH ¼ 6.7Hz, iPr-CH), 6.59 (d, 1H, 3JHH ¼ 1.6Hz, NCHCHN), 6.71 (d, 1H,3JHH ¼ 1.6Hz, NCHCHN); 13C{1H} NMR (C6D6): Me2Im: d 37.4 (CH3), 120.2

(NCCN), 214.6 (NCN); MeiPrIm: d 25.0 (iPr-CH3), 38.4 (N-CH3), 52.7 (iPr-CH),

117.4 (NCCN), 120.8 (NCCN), 214.4 (NCN).

Properties

In terms of the principal properties (solubility, storage, reactivity), these deriva-

tives resemble the carbenes in part C.

References

1. See, for example, (a) A. J. Arduengo, Acc. Chem. Res. 32, 913 (1999). (b) W. A. Herrmann,

Angew. Chem. 108, 1342 (2002); Angew. Chem., Int. Ed. 41, 1290 (2002). (c) N. M. Scott and S. P.

Nolan, Eur. J. Inorg. Chem. 1815 (2005). (d) For a special issue on NHC chemistry, see: R. H.

Crabtree,Coord. Chem. Rev. 251 (5/6) 595 (2007). (e) F. E. Hahn andM. C. Jahnke, Angew. Chem.

120, 3166 (2008); Angew. Chem., Int. Ed. 47, 3122 (2008).

2. (a) R. H. Crabtree, J. Organomet. Chem. 690, 5451 (2005). (b) N. Marion, O. Navarro, J. Mei,

E. D. Stevens, N. M. Scott, and S. P. Nolan, J. Am. Chem. Soc. 128, 4101 (2006). (c) U. Radius and

F. M. Bickelhaupt,Organometallics 27, 3410 (2008). (d) U. Radius and F. M. Bickelhaupt, Coord.

Chem. Rev. 253, 678 (2009).

3. (a) T. Schaub and U. Radius, Chem. Eur. J. 11, 5024 (2005). (b) T. Schaub, M. Backes, and U.

Radius,Organometallics 25, 4196 (2006) and references cited. (c) T. Schaub, P. Fischer, A. Steffen,

T. Braun, U. Radius, and A. Mix, J. Am. Chem. Soc. 130, 9304 (2008).

4. M.Niehues, G.Kehr, G. Erker, B.Wibbeling, R. Frohlich, O. Blacque, andH.Berke, J. Organomet.

Chem. 663, 192 (2002).

21. 1,3-Dialkyl-Imidazole-2-Ylidenes 83

22. A CHELATING RHODIUM N-HETEROCYCLICCARBENE COMPLEX BY TRANSMETALLATION

FROM A SILVER–NHC INTERMEDIATE

Submitted by CHIN HIN LEUNG,* ANTHONY R. CHIANESE,*

BENJAMIN R. GARRETT,� CHRISTOPHER S. LETKO,� and

ROBERT H. CRABTREE*

Checked by JOSHUA DAY,� and THOMAS B. RAUCHFUSS�

First introduced by Lin andWang,1 the route to metal complexes ofN-heterocyclic

carbenes (NHCs) using NHC–silver intermediates as transmetallation agents

avoids generating the highly air- and moisture-sensitive free carbene with base.

It thus requires less stringent operating conditions and tolerates a wider range of

functionality than the traditional use of strong base. Recent studies by Lin2 and

others3 show how silver–NHC complexes, usually generated from Ag2O and an

imidazolium salt, can subsequently transfer the NHC to other metals, such as

Rh. Ag2O is the silver source of choice, and recent work4 attributes this to the

higher basicity of Ag2O compared to other common sources of Ag. Many

variations of Lin’s method have since been introduced.5–7 For example, Youngs

was the first to use water as a solvent for the formation of a silver–NHC complex.6

Slaughter was only able to obtain a stable, characterizable Ag–bis-NHC cation by

replacing the initial Br� counterion with BF4�. The product acted as an effective

transmetallation agent.7

A. METHYLENEBIS(N-(t-BUTYL)IMIDAZOLIUM) BROMIDEz

Step 1: ðCHOÞ2 þNH3 þCH2Oþ t-BuNH2 ! t-BuC3H3N2 þ 3H2O

Step 2: 2t-BuC3H3N2 þCH2Br2 !½CH2ðt-BuC3H3N2Þ2�Br2

Procedure

1. 1-(t-Butyl)imidazole.8 A 500-mL three-necked round-bottomed flask containing

a Teflon-coated stir bar is fitted with a 125-mL addition funnel on one of the side necks.

*Department of Chemistry, Yale University, New Haven, CT 06520-8107.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.zWe thank Professor Peter Hofmann (Ruprecht-Karls-Universitaet Heidelberg) for advice on this

procedure.


The flask is charged with 15.39 g (480mmol) of paraformaldehyde. The flask is cooled to

about �5�C using an ice–salt bath. t-BuNH2 (50.7mL, 35.14 g, 480mmol) diluted with

an equal volume of water is loaded into the addition funnel. The aqueous t-BuNH2

solution is added to the paraformaldehyde dropwise and with stirring over the course of

15min. The addition funnel is then loaded with a 40% aqueous solution of glyoxal

(54.88mL, 69.7 g, 480mmol). The glyoxal is added to the t-BuNH2–CH2O solution.

Simultaneously, NH4HCO3 (37.98 g, 480mmol, pulverized with a mortar and pestle) is

added in small portions through one of the necks. The additions of NH4HCO3 and glyoxal

should be timed so that their additions are complete after 15min. The NH4HCO3 is not

readily soluble in the cold glyoxal-t-BuNH2–paraformaldehyde mixture even with

vigorous stirring, so the clumps of NH4HCO3 are broken up with a spatula. The

temperature of the reaction is not critical. After the addition is complete, the ice bath

is removed, and the pale yellow slurry is stirred for a further 12 h at room temperature.

During this time, the remaining NH4HCO3 dissolves. The resulting red-brown mixture is

poured into a 500-mL separatory funnel and extractedwith five 50-mLportions of EtOAc.

Most of the ethyl acetate is removed from the combined extracts using a rotary evaporator,

and the remaining product is vacuum distilled at 60�C (1mmHg) to afford a pale yellow

liquid. Yield: �14.5 g (�25%).

1H NMR (CDCl3): d 7.62 (s, 1H, 2H), 7.05 (s, 1H, 5H), 7.05 (s, 1H, 4H), 1.56 (s,

9H, CH3).

2. Methylene(bis(N-t-butyl)imidazolium) dibromide.A 50-mL round-bottomed flask

is equippedwith a reflux condenser and a Teflon-coated stir bar and is chargedwith 16mL

of toluene, 2.50 g (20.1mmol) of t-butyl imidazole, and 4.35 g (25.0mmol) of dibro-

momethane. The colorless solution is boiled to distill off ca. 1mL. The solution is cooled

to room temperature, 1.4 g (8.0mmol) of dibromomethane is added, and the flask is fitted

with an efficient condenser. The resulting solution is heated at reflux for 24 h. Upon

cooling to room temperature an off-white precipitate is formed, which is collected by

filtration, washed with 20mL of toluene, and dried at high vacuum for 24 h. The yield is

2.18 g (64%).9

1H NMR (DMSO-d6): d 9.72 (s, 2H,CH(imid), 8.22 (s, 2H,CH(imid)), 8.16 (s, 2H,

CH(imid)), 6.63 (s, 2H, CH2(linker)), 1.61 (s, 18H, C(CH3)3).

B. {METHYLENEBIS(N-(t-BUTYL)IMIDAZOL-2-YLIDENE)}

(1,5-CYCLOOCTADIENE)RHODIUM(I)

HEXAFLUOROPHOSPHATE

Step 1: ½CH2ðt-BuC3H3N2Þ2�Br2 þ 0:5Ag2OþKPF6 þ 0:5H2O!½AgfCH2

ðt-BuC3H2N2Þ2g�PF6 þH2OþKBr

Procedure

1. Generation of Ag–carbene complex. A suspension of methylenebis(N-(t-butyl)

imidazolium) dibromide (200mg, 0.47mmol) and Ag2O (460mg, 1.9mmol) in deio-

nized water (10mL) is stirred vigorously in the dark at 0�C for 30min. The dark

suspension is warmed to room temperature and excess Ag2O is removed by filtration

through a pad of Celite. The colorless filtrate is treated with a solution of KPF6(1.25mmol, 230mg) in H2O (5mL). An off-white precipitate immediately forms, but

the suspension is allowed to stand at 0�C for 30min to complete the precipitation.

The resulting off-white precipitate is collected on filter paper and dried under vacuum for

ca. 0.5 h.*

2. Transmetallation to a Rh(I) precursor. The off-white silver–carbene species

(ca. 200mg) is suspended in degassed CH2Cl2 (15mL). The mixture is heated to reflux

under an inert atmosphere to give a light yellow solution. This solution is treated with [Rh

(cod)Cl]2 (0.24mmol, 117mg), added as a solid. Immediate precipitation of a fine white

powder is observed. The mixture is heated at reflux for 30min before being allowed to

cool to room temperature. The crude brown-yellow mixture is filtered in air through ca.

2 cm of Celite and the filtrate is reduced in volume to ca. 1mL under reduced pressure.

Addition of 30mL Et2O to the concentrated yellow-orange CH2Cl2 solution affords a

yellow precipitate. The yellow solid is isolated via filtration and redissolved in ca. 1mL

CH2Cl2. The product is reprecipitated by addition of 30mL Et2O. The yellow precipitate

is isolated via filtration and dried under vacuum to afford a yellow powder. Yield: 65mg

(22% based on Rh).

Anal. Calcd. for C23H36F6N4PRh (MW 616.43): C, 44.81; H, 5.89; N, 9.09.

Found: C, 44.61; H, 5.99; N, 9.02. ESI-MS (MeOH, 20V, m/z): 471.7 (Mþ ),

* Washing the collected solid with diethyl ether or pentane seems to lead to rapid decomposition, as

indicated bydarkening of color and significant formation ofmetallic silver upon redissolving inCH2Cl2.


363.7 (Mþ -cod). 1H NMR (CD2Cl2): d 7.32, 6.92 (d, 3JH�H ¼ 2.2Hz, 4H, CH

(imid)); 6.86, 6.07 (AB system, 2JH�H ¼ 12.7Hz, 2H, CH2(linker)); 4.50, 4.43 (m,

4H, CH(cod)); 2.42–1.96 (m, 8H, CH2(cod)); 1.57 (s, 18H, CH3).13C{1H} NMR

(CD2Cl2): d 180.4 (d, 1JRh�C ¼ 51.8 Hz, C(carbene)); 121.9, 119.2 (s, CH(imid));

90.5 (d, 1JRh�C ¼ 9.5Hz, CH(cod)); 85.2 (d, 1JRh�C ¼ 7.4Hz, CH(cod)); 65.5 (s,

CH2(linker)); 58.4 (s, C(CH3)3); 32.2 (s, CH3); 30.9 (s, CH2(cod)).

Properties

The chelate character of the complex was determined by X-ray crystallography.9

The ESI-MS and analytical data are also consistent with this structure. The

conformation of the chelating NHC renders the two protons on the CH2 linker

nonequivalent by NMR spectroscopy.

The bis-NHC–Ag(I) transmetallation agent generated in this reaction is unsta-

ble and significant decomposition occurs within hours. On the other hand, the

resulting bis-NHC–Rh(I) complex is stable in air for months. The stability of

metal–NHCs in general can be highly dependent on the N-substituents and on the

identity of the metal. For example, a related bis-NHC–Rh(I) (where N-substituent

is n-butyl instead of t-butyl) decomposes in solution within a few minutes when

exposed to air.10 Unlike the unstable bis-NHC–Ag(I) transmetallation agent

presented here, many Ag(I) complexes of NHCs have been successfully

characterized.11

References

1. H. M. J. Wang, C. Y. L. Chen, and I. J. B. Lin, Organometallics 18, 1216–1223 (1999).

2. I. J. B. Lin and C. S. Vasam, Coord. Chem. Rev. 251, 642–670 (2007).

3. (a) J. C. Garrison and W. J. Youngs, Chem. Rev. 105, 3978–4008 (2005). (b) P. L. Arnold,

Heteroatom Chem. 13, 534–539 (2002). (c) I. J. B. Lin and C. S. Vasam, Comments Inorg. Chem.

25, 75–129 (2004).

4. J. M. Hayes, M. Viciano, E. Peris, G. Ujaque, and A. Lledos, Organometallics, 26, 6170–6183

(2007).

5. For recent applications of the silver transmetallation method, see: (a) F. W. Li, S. Q. Bai, and

T. S. A. Hor, Organometallics 27, 672–677 (2008). (b) G. Dyson, J. C. Frison, S. Simonovic,

A. C. Whitwood, and R. E. Douthwaite, Organometallics 27, 281–288 (2008). (c) F. Tewes,

A. Schlecker, K. Harms, and F. Glorius, J. Organomet. Chem. 692, 4593–4602 (2007).

6. J. C. Garrison, R. S. Simons, C. A. Tessier, andW. J. Youngs, J. Organomet. Chem. 673, 1–4 (2003).

7. Y. A. Wanniarachchi, M. A. Khan, and L. M. Slaughter, Organometallics 23, 5881–5884 (2004).

8. A. J. Arduengo, III, F. P. Gentry, Jr., P. K. Taverkere, and H. E. Simmons, III,(E. I. Du Pont de

Nemours & Co., USA). U.S. Patent 6,177,575, 2001, 7 pp.

9. K. D. Wells, M. J. Ferguson, R. McDonald, and M. Cowie, Organometallics 27, 691–703 (2008).

10. C. H. Leung, C. D. Incarvito, and R. H. Crabtree, Organometallics 25, 6099–6107 (2006).

11. A. R. Chianese, X. Li, M. C. Janzen, J. W. Faller, and R. H. Crabtree, Organometallics 22,

1663–1667 (2003).

22. A Chelating Rhodium N-Heterocyclic Carbene Complex 87

23. RHODIUM AND IRIDIUM N-HETEROCYCLIC CARBENECOMPLEXES FROM IMIDAZOLIUM CARBOXYLATES

Submitted by ADELINA M. VOUTCHKOVA* and ROBERT H. CRABTREE*

Checked by ROSS D. PUTMAN,� KATHLEEN H. KELLEY,� and

THOMAS B. RAUCHFUSS�

Transition metal N-heterocyclic carbene (NHC) complexes are increasingly used

as homogeneous catalysts.1 Current synthetic routes to NHC complexes still lack

generality2 and new selective routes are desirable. Themost common route to these

complexes involves transmetallation from a silver–NHC complex, which in turn is

formed by the action of Ag2O on an imidazolium salt.3 While very general, this

method can give unexpected products.4 We have found that N,N0-disubstitutedimidazolium carboxylates, readily synthesized, isolable, air- and water-stable

reagents, provide a new facile synthetic route to Rh, Ir, Ru, Pt, and Pd NHC

complexes.5 We have optimized simple procedures involving dimethylcarbonate

for the preparation of the requiredN-alkyl,N0-methyl imidazolium carboxylates. In

addition, by a more general previously reported procedure,6N,N0-disubstitutedimidazoliumcarboxylates canbeaccessed fromthe imidazoliumsalt directly,which

lifts the limitation toN-alkyl,N0-methyl NHCs. Altering the reaction conditions for

NHCtransfer can selectivelygiveeithermono-orbis-NHCsorbis- and tris-NHCs.5b

A. N,N0-DIMETHYLIMIDAZOLIUM-2-CARBOXYLATE

Procedure

A screw-top pressure tube (Fischer) is charged with dimethyl carbonate (3.0mL,

35.6mmol), 1-methylimidazole (2mL, 25.1mmol), and a stir bar. It is sealed and

heated for 30 h at 90�C.After approximately 2 h, the initially clear solution became

cloudy and a white precipitate was apparent, and after 24 h there was a copious

amount of white solid in a brown supernatant liquid. The solid is filtered and

*Department of Chemistry, Yale University, New Haven, CT 06520-8107.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.


washed thoroughly with methylene chloride (3� 15mL), acetone (3� 15mL),

and diethyl ether (2� 10mL). Thewhite solid proved to be the title compoundwith

less than 3% of the 4-carboxylate isomer. The solid was isolated with a total yield

of 2.91 g (82%).

1H NMR (D2O): d 3.82 (s, 6H,N-CH3), 7.26 (s, 2H, H-4, and H-5).13C{1H}NMR

(D2O): d 36.58, 121.89, 139.25, 157.56.7

Properties

The carboxylate showed no appreciable solubility in methylene chloride or ethyl

acetate, but was partially soluble in acetonitrile and DMSO and very soluble in

water and methanol. If the reaction is carried out above 100�C, the ratio of 4-

carboxylate to 2-carboxylate is greatly increased. The mixed 2- and 4-isomeric

material can still be used directly for transfer to a transition metal because only the

2-isomer undergoes transfer. This product can also be made by an analogous

procedure using microwave heating in 55% yield.

B. CHLORO(1,5-CYCLOOCTADIENE)(1,3-

DIMETHYLIMIDAZOLIUM-2-YLIDENE) RHODIUM(I)

½RhClðcodÞ�2 þ 2Me2ImCO2 ! 2 RhðcodÞðMe2ImÞClþ 2 CO2

Procedure

This known compound was prepared from a mixture of [Rh(cod)Cl]2 (500mg,

1.01mmol) and N,N0-dimethylimidazolium-2-carboxylate (340mg, 2.39mmol)

stirred in acetonitrile (7mL) for 40min at room temperature (alternatively, this

compound can be prepared by heating the same mixture to 75�C for 15min). The

reaction mixture is evaporated in vacuo, and the residue washed well with diethyl

ether. The yellow solid so obtained is analytically pure (638mg, 93%), but the

complex can also be recrystallized from dichloromethane–diethyl ether by slow

diffusion.

1H NMR (CDCl3): d 6.72 (s, 2H, NCH), 4.94 (m, 2H, cod CH), 4.02 (s, 6H, CH3),

3.22 (m, 2H, cod CH), 2.34 (m, 4H, cod CH2), 1.88 (m, 4H, cod CH2).13C{1H}

NMR (CDCl3): d 182.84 (d, 1JRh�C ¼ 50.9 Hz, NCN), 122.04 (NCH), 98.72 (d,1JRh�C ¼ 6.9Hz, cod CH), 67.84 (d, 1JRh�C ¼ 14.6 Hz, cod CH), 37.81 (CH3),

33.13 (d, 1JRh�C ¼ 1.0Hz, cod CH2), 29.05 (cod CH2).2a,5a

Properties

The compound is air stable and soluble in chloroform, methylene chloride,

methanol, and acetonitrile.

23. Rhodium and Iridium N-Heterocyclic Carbene Complexes 89

C. (h4-1,5-CYCLOOCTADIENE)(BIS-1,3-DIMETHYLIMIDAZOLE-

2-YLIDENE)IRIDIUM(I) HEXAFLUOROPHOSPHATE

½IrClðcodÞ�2 þ 4Me2ImCO2 þ 2 KPF6 ! 2 ½IrðcodÞðMe2ImÞ2�PF6þ 4 CO2 þ 2 KCl

A mixture of [Ir(cod)(Cl)]2 (40mg, 59mmol), N,N’-dimethylimidazolium-2-car-

boxylate (41mg, 288mmol), and sodium acetate (0.100 g) is suspended in aceto-

nitrile (4mL) in a 10-mLSchlenkflask. The reactionmixture is stirred for 10min at

room temperature and then heated in oil bath (75�C, 2 h), during which time it

turned bright orange. The reaction is then allowed to cool to room temperature, and

the solution is filtered to remove excess imidazolium carboxylate and sodium

acetate, after which the filtrate is concentrated to dryness in vacuo. The solid is

dissolved in 2mL methylene chloride and loaded onto a silica column prepared

with 4:1 hexane/ethyl acetate. Unreacted [IrCl(cod)]2 is eluted with 4:1 hexane/

ethyl acetate. The mobile phase is changed to a saturated solution of KPF6 in

acetone (0.7 g KPF6 in 200mL acetone), which mobilizes the product as an orange

band.* The orange fraction is evaporated to dryness in vacuo and the residue is

extracted into methylene chloride (20mL), which dissolves the product but not the

excess KPF6. The resulting suspension is filtered, and the filtrate is evaporated to

dryness in vacuo. The product is recrystallized by dissolving in aminimumvolume

(1mL) of methylene chloride followed by the slow addition of approximately

20mL of diethyl ether. The product is isolated as orange prisms (64mg, 85%).

Anal. Calcd. for C18H30F6IrN4P: C, 33.91%; H, 4.43%; N, 8.79%. Found: C,

34.06%; H, 4.53%; N, 8.84%. 1H NMR (CDCl3): d 7.10 (s, 4H, NCH), 3.89

(s, 12H, CH3), 3.72 (br m, 4H, cod CH), 2.10 (br m, 4H, cod CH2), 1.89 (br m, 4H,

cod CH2).13C{1H} NMR (CDCl3): d 178.88 (s, NCN), 124.70 (s, NCH), 77.22,

39.22 (s, cod), 35.87 (s, NCH3).31P NMR (CDCl3): d �143.12 (PF6).

5b

Properties

This complex can also be prepared in good yield by an analogous procedure using

[Ir(cod)(py)2]PF6 or [Ir(cod)(PPh3)2]PF6 with 2 equiv of N,N0-dimethylimidazo-

lium-2-carboxylate (no sodium acetate) in yields of �80%. The compound is

soluble in chloroform, methylene chloride, acetone, methanol, and acetonitrile.

* The checkers conducted the reaction on a 2� scale. Instead of the chromatography step, the crude

[Ir(cod)(Me2Im-H)]þ salt was treated with 10� excess of KPF6 in 10mL of acetone for a fewminutes.

This solutionwas evaporated, and the residuewas extracted into a fewmilliliters of CH2Cl2. Dilution of

this extract with 3� volume of Et2O gave the product.


References

1. (a) W. A. Herrmann and C. Kocher, Angew. Chem., Int. Ed. Engl. 36, 2163–2187 (1997).

(b) D. Bourissou, O. Guerret, F. P. Gabbai, and G. Bertrand, Chem. Rev. 100, 39–91 (2000).

(c) E. Peris and R. H. Crabtree, Coord. Chem. Rev. 248, 2239–2246 (2004).

2. (a) W. A. Herrmann, C. Kocher, L. J. Goossen, and G. R. J. Artus, Chem. Eur. J. 2, 1627–1636

(1996). (b) K. Ofele, J. Organomet. Chem. 12, P42–P43 (1968). (c) D. S.McGuinness, K. J. Cavell,

B. W. Skelton, and A. H. White, Organometallics 18, 1596–1605 (1999). (d) S. Gr€undemann, M.

Albrecht, A. Kovacevic, J. W. Faller, and R. H. Crabtree, J. Chem. Soc., Dalton Trans. 2163–2167

(2002).

3. (a) H. M. J. Wang, and I. J. B. Lin, Organometallics 17, 972–975 (1998). (b) I. J. B. Lin and

C. S. Vasam, Comments Inorg. Chem. 25, 75–129 (2004).

4. (a) J. A. Mata, A. R. Chianese, J. R. Miecznikowski, M. Poyatos, E. Peris, J. W. Faller, and

R. H. Crabtree, Organometallics 23, 1253–1263 (2004). (b) C. H. Leung, C. D. Incarvito, and

R. H. Crabtree, Organometallics 25, 6099–6107 (2006).

5. (a) A.M.Voutchkova, L. N. Appelhans, A. R. Chianese, and R. H. Crabtree, J. Am. Chem. Soc. 127,

17624–17625 (2005). (b) A. M. Voutchkova, M. Feliz, E. Clot, O. Eisenstein, C. Incarvito, and

R. H. Crabtree, J. Am. Chem. Soc. 129, 12834–12846 (2007).

6. A. Tudose, A. Demonceau, and L. Delaude, J. Organomet. Chem. 691, 5356–5365 (2006).

7. J. D. Holbrey,W.M. Reichert, I. Tkatchenko, E. Bouajila, O.Walter, I. Tommasi, and R. D. Rogers,

Chem. Commun. 28–29 (2003).

23. Rhodium and Iridium N-Heterocyclic Carbene Complexes 91

Chapter Five

FUNCTIONAL LIGANDS AND COMPLEXES

24. N-tert-BUTYL ortho-AMINOPHENOL,ortho-IMINOQUINONE, AND A ZIRCONIUM(IV)

BIS(AMINOPHENOLATE) COMPLEX

Submitted by KAREN J. BLACKMORE,* ANDY I. NGUYEN,*

and ALAN F. HEYDUK*

Checked by MARK E. RINGENBERG� and THOMAS B. RAUCHFUSS�

Redox-active and noninnocent ligands continue to attract attention for the inter-

esting electronic properties they impart to transition metal complexes. More

recently, ‘‘designer’’ ligands that go beyond catechol, ortho-phenylenediamine,

and ortho-aminophenol have been prepared in order to elicit further electronic and

steric control at the chelated metal ion. One such derivative, 2,4-di-tert-butyl-6-

(tert-butylamino)phenol, has been used to support new complexes of the group IV

metals, which previously had received little attention with noninnocent ligand

platforms. Most important, it has been demonstrated recently that zirconium(IV)

complexes of the 2,4-di-tert-butyl-6-(tert-butylamido)phenolate ligand are capa-

ble of undergoing two-electron reactions analogous to the oxidative addition and

reductive elimination reactions of electron-rich, late transitionmetals.1,2 Synthesis

of the 2,4-di-tert-butyl-6-(tert-butylamino)phenol is described below. Compared

toN-aryl derivatives,3 2,4-di-tert-butyl-6-(tert-butylamino)phenol is substantially

more air sensitive and benefits from a reductive workup to increase reaction yield.

For synthetic flexibility, it is often beneficial to have access to the quinone form


*Department of Chemistry, University of California, Irvine, CA 92697.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

92

of the ligand, so a synthesis of two-electron oxidized 2,4-di-tert-butyl-6-(tert-

butylimino)quinone, which is isolated as a mixture of E and Z isomers, is also

presented. Finally, the installation of the dianionic form of the ligand, 2,4-di-tert-

butyl-6-(tert-butylamido)phenolate, on zirconium(IV) is provided as one route

to metallation.

A. 2,4-DI-tert-BUTYL-6-(tert-BUTYLAMINO)PHENOL

Procedure

A solution is prepared from 3,5-di-tert-butylcatechol (10 g, 45mmol, 1 equiv)

in 60mL of acetonitrile in a 250-mL round-bottomed flask. To the solution are

added activated, 1–2mm beads, 3A�sieves (20mL), and tert-butyl amine (6mL,

56mmol, 1.25 equiv). The solution is heated to gentle reflux for 4 h. An efficient

condenser is required to minimize the loss of tert-butyl amine. The solution

changed from yellow to dark blue-green.

The reaction mixture is gravity filtered through a plug of glass wool in a glass

funnel. The sieves are rinsed with three 50-mL portions of diethyl ether. The

combined organic phases are added to a 500-mL separatory funnel containing

150mL of 1M aqueous sodium dithionite (Na2S2O4). The solution is shaken until

it turned dark yellow, and then allowed to separate without opening the funnel to

air. The water layer is removed and the organic layer is transferred to a 500-mL

round-bottomed flask. The solvent is quickly removed using a rotary evaporator,

and the residue is stored under active vacuum overnight. Small amounts of

oxidation will give the product a pink hue.

The crude product is transferred to a nitrogen-filled glovebox for final purifi-

cation. The solid residue is loaded into a 60-mL coarse sintered glass frit and

washed with stirring with acetonitrile (40mL). The washing step is repeated

with half the volume of acetonitrile to afford the product as a white solid in 63%

yield (7.93 g).

1H NMR (C6D6): d 0.90 (s, 9H,N-C(CH3)3), 1.35 (s, 9H,Ar-C(CH3)3), 1.63 (s, 9H,

Ar-C(CH3)3), 1.77 (s, 1H,NH), 6.85 (d, 1H,Ar-H,3JHH ¼ 3.00), 7.38 (d, 1H,Ar-H,

24. N-tert-Butyl ortho-Aminophenol, ortho-Iminoquinone 93

3JHH ¼ 3.00), 8.01 (s, 1H, OH). 13C NMR (C6D6): d 29.16 (N-C(CH3)3), 29.66

(Ar-C(CH3)3), 31.81 (Ar-C(CH3)3), 34.15 (Ar-C(CH3)3), 35.01 (Ar-C(CH3)3),

52.94 (N-C(CH3)3), 121.09 (Ar-C), 123.53 (Ar-C), 129.65 (Ar-C), 134.04 (Ar-C),

139.79 (Ar-C), 151.56 (Ar-C). mp 104–106�C.

Properties

The scale has been increased up to 50 g of starting catechol with linear scaling of

the other reagents and solvents. The yield increases 5–10% on a larger scale. The

presence of oxidized products is readily determined by observation of their dark

colors mixed with the colorless product.

B. 2,4-DI-tert-BUTYL-6-(tert-BUTYLIMINO)QUINONE

ðtBuÞ2C6H2ðOHÞðNH-t-BuÞþ 2 BuLi!ðtBuÞ2C6H2ðOLiÞðNLi-t-BuÞþ 2 BuH

ðtBuÞ2C6H2ðOLiÞðNLi-t-BuÞþPhICl2!ðtBuÞ2C6H2ðOÞðN-t-BuÞþ2LiClþPhI

Procedure

In a nitrogen-filled glovebox, 2,4-di-tert-butyl-6-(tert-butylamino)phenol (5.0 g,

18mmol, 1 equiv) is dissolved in 100mL of dry, degassed diethyl ether in a

250-mL flask. The solution is frozen in a liquid nitrogen cold well. Upon thawing,

n-BuLi solution (2.5M in hexanes, 14.5mL, 2 equiv) is added by micropipette.

After the solution saturates at ambient temperature for 1 h, it is frozen again. Upon

melting, freshly prepared PhICl2 (5.0 g, 18mmol, 1 equiv) is added as a yellow

solid.4 The solution immediately turns dark blue and is allowed to warm with

stirring to 26�C. After 12 h, additional PhICl2 is added in small batches (every

5min) until the solution became orange with a yellow precipitate. The solution is

filtered through a coarse glass frit. The yellow solid is washed with 50mL of cold

pentane and dried under reduced pressure.

Continuing to exclude all air and water, the residue is loaded into a Soxhlet

extractor. All joints are fitted with Teflon sleeves. The residue is extracted with

pentane (150mL) for 2 days or until the residue becomes white and the solution is

reddish brown. The volatiles are removed from the solution to afford the product as

a brown solid in 66% yield (3.2 g). mp 80–82�C.

1HNMR (C6D6): d 6.77 (d, 1H, J¼ 2.3 Hz), 6.49 (d, 1H, J¼ 2.3 Hz), 1.35 (s, 9H),

1.24 (s, 9H), 0.90 (s, 9H). 13C NMR (C6D6, 25�C): d 186.86 (CO), 184.58 (CO),

94 Functional Ligands and Complexes

158.18 (aryl C), 156.84 (aryl C), 150.76 (aryl C), 149.38 (aryl C), 148.91

(aryl C), 147.62 (aryl C), 133.07 (aryl C), 132.10 (aryl C), 115.65 (aryl C),

59.54 (C(CH3)), 57.90 (C(CH3)), 35.50 (C(CH3)), 35.17 (C(CH3)), 35.00

(C(CH3)), 34.35 (C(CH3)), 31.45 (C(CH3)), 30.43 (C(CH3)), 29.81 (C(CH3)),

29.60 (C(CH3)), 28.55 (C(CH3)), 28.46 (C(CH3)). Z-isomer: 1H NMR (C6D6):

d 6.75 (d, 0.2H, J¼ 2.3 Hz), 6.43 (d, 0.2H, J¼ 2.3 Hz), 1.23 (s, 2H), 0.89

(s, 2H).

Properties

Both E and Z imine isomers (5:1 ratio) are obtained and can be identified by their1H NMR spectra. They do not interconvert in room-temperature solution.

C. ZrIV(ap)2(THF)2

Procedure

In a nitrogen-filled glovebox, 2,4-di-tert-butyl-6-(tert-butylamino)phenol

(1.00 g, 3.6mmol, 1 equiv) is dissolved in 35mL of diethyl ether in a 100-mL

round-bottomed flask. The solution is frozen in a liquid nitrogen cold well. The

frozen solution is removed from the cold well and thawed. Using a micropipette,

n-BuLi solution (2.71M in hexanes, 2.67mL, 2 equiv) is added to the cold

solution. The reaction mixture is allowed to warm to room temperature over 2 h.

The reaction mixture is then refrozen. Immediately upon thawing, ZrCl4(THF)2(0.679 g, 1.79mmol, 0.5 equiv) is added to the cold solution,5 which is allowed to

warm to 26�C and stirred for 2 h while a white precipitate formed. Pentane

(35mL) is added and the precipitate is removed by suction filtration. The

precipitate is washed with a small aliquot of pentane, the organic phases are

combined, and the solvent is removed under reduced pressure. The residue is

washed with cold pentane (10mL, –35�C) to give the product as a bright yellowsolid that is dried under reduced pressure. Yield: 0.94 g (68%). X-ray quality

crystals are obtained by cooling saturated pentane solutions of the product

to �35�C.

24. N-tert-Butyl ortho-Aminophenol, ortho-Iminoquinone 95

Anal. Calcd. for C44H74N2O4Zr: C, 67.21; H, 9.49; N, 3.56. Found: C, 66.93: H,

9.21; N, 3.57. 1H NMR (C6D6): d 1.14 (m, 8H, THF), 1.45 (s, 18H, C(CH3)3), 1.67

(s, 18H, C(CH3)3), 1.70 (s, 18H, C(CH3)3), 3.79 (m, 4H, THF), 4.11 (m, 4H, THF),

6.96 (d, 2H, Ar-H, 3JHH ¼ 1.5), 7.00 (d, 1H, Ar-H, 3JHH ¼ 1.5). 13C NMR (C6D6):

d 25.0 (THF), 30.4 (C(CH3)3), 30.7 (C(CH3)3), 32.4 (C(CH3)3), 34.8 (C(CH3)3),

34.9 (C(CH3)3), 54.2 (C(CH3)3), 73.1 (THF), 110.9 (Ar-C), 111.1 (Ar-C), 132.3

(Ar-C), 139.4 (Ar-C), 148.9 (Ar-C), 152.5 (Ar-C). IR (KBr): 486, 539, 558, 584,

636, 661, 673, 735, 784, 831, 851, 879, 899, 915, 964, 1036, 1121, 1164, 1201,

1237, 1264, 1302, 1361, 1388, 1415, 1483, 1559, 1598, 2869, 2906, 2960,

3256 cm�1.

References

1. K. J. Blackmore, J. W. Ziller, and A. F. Heyduk, Inorg. Chem. 16, 5559 (2005).

2. M. R. Haneline and A. F. Heyduk, J. Am. Chem. Soc. 26, 8410 (2006).

3. P. Chaudhuri, C. N. Verani, E. Bill, E. Bothe, T. Weyherm€uller, and K Wieghardt, J. Am. Chem.

Soc. 123, 2213 (2001).

4. H. J. Lucas and E. R. Kennedy, Org. Synth. 3, 482 (1955).


25. SYNTHESIS OF THE WATER-SOLUBLE BIDENTATE(P, N) LIGAND PTN(Me) (PTN(Me) ¼ 7-PHOSPHA-3-METHYL-

1,3,5-TRIAZABICYCLO[3.3.1]NONANE)

Submitted by MARIA CAPORALI,* LUCA GONSALVI,* FABRIZIO ZANOBINI,*

and MAURIZIO PERUZZINI*


Among the many advances in homogeneous catalysis, a significant one has dealt

with the replacement of simple bidentate phosphines and diamines with mixed

donor ligands including phosphino-ethers, phosphino-thioethers, and aminopho-

sphines.1 Furthermore, traditional catalytic processes are being replaced with

novel water-based protocols, often centered on the use of hydrosoluble ancillary

ligands, which can facilitate catalyst recyclability and product separation.2,3

Among neutral water-soluble bidentate aminophosphines, the bowl-shaped alkyl

or aryl P-substituted 7-phospha-3-methyl-1,3,5-triazabicyclo[3.3.1]nonanes, abbre-

viated as PTN(R), were originally synthesized by Schmidbaur et al.4 Rhodium

*Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organometallici (ICCOM-

CNR), 50019, Sesto Fiorentino, Italy.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.


complexes of some of these ligands (R¼Me, Ph) have recently been used for

catalytic olefin hydroformylation under biphasic conditions.5 Other examples of

coordination chemistry of PTN(R) includeAu andMo complexes exhibiting either

mono- or bidentate coordination modes,6 that is, [k1-P-AuCl{PTN(R)}] (R¼Me,

Ph), [k1-P-AuCl{PTN(Me)}2], [k2-P,N-AuMe2{PTN(Me)}][AuCl4], and k2-P,N-[Mo(CO)4{PTN(R)}] (R¼Me, Ph), as well as some palladium PTN(Me)

complexes.7

The previously described synthesis uses the commercially available tetrakis

(hydroxymethyl)phosphonium chloride that is at first dried, and then converted

into P(CH2OH)3 by treatment with either sodium hydroxide8 or triethylamine,9

the latter method requiring long and laborious workup. In our labs, this procedure

has been improved by conducting the reaction in ethanol instead of water, thus

affording a crystalline product in high yields instead of the oily product as

previously reported. The following step is the quaternization of the phosphine

with alkyl or aryl iodide, and then cage closing by reaction of the phosphonium salt

with paraformaldehyde and ammonium acetate. Finally, using Na/NH3 the result-

ing P-R(PTA)I intermediate undergoes reductive P-C cleavage at low temperature

to give the final desired ligand PTN(R). In this contribution, a detailed procedure

for the preparation of the methyl derivative, PTN(Me), is provided. Similar

synthetic protocols can be used to prepare other bidentate PTN(R) ligands with

yields strongly depending on the nature of the alkyl or aryl substituent of the

quaternized phosphorus atom.

Materials and General Procedures

All experiments have been performed under a dry nitrogen atmosphere by standard

Schlenk techniques. Solvents have been purified by distillation over suitable

drying agents and degassed prior to use. All other reagents (technical grade) have

been purchased from commercial sources and used as received. 1H and 31P NMR

chemical shifts are referenced with respect to external TMS and aqueous 85%

H3PO4, respectively.

A. DEHYDRATION OF TETRAKIS(HYDROXYMETHYL)

PHOSPHONIUM CHLORIDE, THPC, [P(CH2OH)4]Cl

Procedure

In a 100-mL round-bottomed flask, 23.75 g of the commercially available tetrakis

(hydroxymethyl)phosphonium chloride (80% solution in water; 0.1mol of salt)*

* THPC utilized was obtained from Aldrich as 80% solution in water [124-64-1].

25. Synthesis of the Water-Soluble Bidentate (P, N) Ligand PTN(Me) (PTN(Me) 97

is evaporated under vacuum at 60�C until an oily residue is obtained and the initial

weight is reduced of ca. 20%. The residue is then dried under vacuum at 60�C until

the weight becomes constant. The crude product is finally recrystallized from 2-

propanol (ca. 2.5mL of 2-propanol per gram of crude product) warming gently the

suspension in order to dissolve the solid. The saturated solution is allowed to cool

to 0�C and maintained at this temperature overnight. The white crystalline

precipitate is isolated by filtration under inert atmosphere and washed with several

aliquots of cold 2-propanol and n-pentane in turn to afford 18.92 g (0.099mol) of

the pure product, which is vacuum dried. The hygroscopic solid is stored under

nitrogen.

B. TRIS(HYDROXYMETHYL)PHOSPHINE, P(CH2OH)3

½PðCH2OHÞ4�ClþNaOH! PðCH2OHÞ3 þH2OþNaClþCH2O

Procedure

An oven-dried 500-mL two-necked round-bottomed flask equipped with a mag-

netic stirrer is charged with 19.00 g (0.1mol) of dry THPC. Absolute ethanol

(100mL) is added via syringe. A solution of NaOH (0.1M in EtOH), freshly

prepared by dissolving 4.00 g (0.1mol) of NaOH in 150mL of ethanol, is then

added in small aliquots over 5min; immediately a fine white precipitate starts to

separate from the solution. The stirred reaction mixture is maintained at room

temperature for ca. 90min and then the solid is collected by filtration under

nitrogen on a frit. The clear solution was stripped under vacuum keeping the flask

in a water bath at 50�C. The oily residue is dissolved in methanol (8mL of MeOH

per 10 g of oily residue), and this solution is diluted with diethyl ether (10mL),

which precipitates the product. The flask is cooled to �20�C to maximize

precipitation of white flakes of crystalline tris(hydroxymethyl)phosphine, which

is filtered under nitrogen, washed with cold diethyl ether, and then dried under

vacuum. Yield: 9.90 g (80%).*

Anal. Calcd. for C3H9O3P (MW¼ 124.07): C, 29.04%; H, 7.31%. Found: C,

29.19%; H, 7.55%.

NMR spectral data are in agreement with those reported in the literature.10

1H NMR (D2O, 20�C): d 3.91 (d, 2JHP ¼ 5.3 Hz, CH2, 6H);

13C{1H} NMR

(D2O, 20�C): d 56.1 (d, 1JPC ¼ 10.2 Hz); 31P{1H} NMR (D2O, 20�C):d �24.5 (s).

* The checkers isolated tris(hydroxymethyl)phosphine as a colorless oil, which was used without

further purification.


C. TRIS(HYDROXYMETHYL)METHYL PHOSPHONIUM IODIDE,

[PCH3(CH2OH)3]I

Procedure

Method I. As for part A described above, 19.00 g (0.0997mol) of dry THPC is

suspended in 100mL of absolute ethanol. A 0.1M solution of NaOH, prepared

by dissolving 4.00 g (0.1mol) of NaOH in 150mL of absolute ethanol, is added

in small aliquots over 5min, inducing an immediate precipitation of a fine white

precipitate of sodium chloride. The stirred reaction mixture is maintained at

room temperature for 90min before the solid is separated by filtration under

nitrogen. To the filtrate, containing tris(hydroxymethyl)phosphine, 28.00 g

(0.197mol; 2 equiv) of methyl iodide is added dropwise over the course of

20min maintaining the reaction temperature at about 10�C. After the addition of

methyl iodide is complete, the stirred mixture is maintained at room temperature

overnight. The solvent is then evaporated under vacuum leaving a colorless oil

that can be used for the next reaction step without further purification. Yield:

26.10 g (98%).

½PðCH2OHÞ4�Cl��!1ÞNaOH2ÞMeI

½MePðCH2OHÞ3�IþH2OþNaClþCH2O

Method II. Tris(hydroxymethyl)phosphine, 19.00 g (0.0997mol, 1 equiv) pre-

pared according to method B, is placed in a 250-mL two-necked round-bottomed

flask containing amagnetic stir bar togetherwith absolute ethanol (150mL). To the

solution, 28.00 g (0.197mol, 2 equiv) of methyl iodide is added dropwise keeping

the reaction vessel at 10�C since the reaction is slightly exothermic. Themixture is

maintained at room temperature overnight under vigorous stirring. Evaporation of

the solvent under vacuum gives the pure phosphonium iodide as a colorless oil.

Yield: 26.20 g (99%).

PðCH2OHÞ3 þMeI!½MePðCH2OHÞ3�I

Anal. Calcd. for C4H12O3IP (MW¼ 266.01): C, 18.06%; H, 4.55%. Found: C,

18.20%; H, 4.49%. 1H NMR (CD3OD, 20�C): d 1.90 (d, 2JHP ¼ 14.3Hz, PCH3,

3H), 4.58 (d, 2JHP ¼ 2.2Hz, PCH2, 6H);13C{1H} NMR (D2O, 20

�C): d 1.30

(d, 1JPC ¼ 50.4Hz, PCH3), 50.90 (d, 1JPC ¼ 56.2Hz, PCH2);31P{1H} NMR

(CD3OD, 20�C): d 28.29 (s).

25 Synthesis of the Water-Soluble Bidentate (P, N) Ligand PTN(Me) (PTN(Me) 99

D. 7-METHYL-1,3,5-TRIAZA-7-PHOSPHONIAADAMANTANE

IODIDE

½MePðCH2OHÞ3�Iþ3CH2Oþ3NH4OAc!½MePðCH2Þ6N3�Iþ6H2Oþ3 AcOH

Procedure

In an oven-dried 500-mL two-necked round-bottomed flask equipped with a

magnetic stirrer and a reflux condenser, 26.20 g (0.0985mol) of [MeP(CH2OH)3]

I is dissolved in 120mL of degassed methanol under a nitrogen stream. To the

vigorously stirred solution, 22.77 g (0.295mol, 3 equiv) of ammonium acetate

and 8.87 g (0.295mol, 3 equiv of monomer) of paraformaldehyde* are added.

The mixture is refluxed until the solids are completely dissolved (ca. 4 h). The

reaction mixture is then allowed to cool to room temperature before being stored

overnight at 0�C. The white crystalline precipitate is filtered under nitrogen andwashed with cold methanol (2� 10mL) and diethyl ether (1� 20mL). Yield:

14.14 g (48%).

Anal. Calcd. for C7H15N3IP (MW¼ 299.09): C, 40.49%; H, 7.28%; N,

14.05%. Found: C, 40.62%; H, 7.40%; N, 13.96%. NMR spectral data are in

agreement with those reported in the literature.11 1H NMR (D2O, 20�C): d 1.84

(d, CH3,2JPH ¼ 16.1 Hz), 4.37 (s, NCH2N, 3H), 4.42 (s, NCH2N, 3H),

4.53 (d, 2JPH ¼ 13.4 Hz, PCH2N, 6H); 13C{1H} NMR (D2O, 20�C): d3.60 (d, 1JCP ¼ 32.2Hz, PCH3), 47.0 (d, 1JPC ¼ 37.4 Hz, PCH2N), 70.65

(d, 3JCP ¼ 9.6Hz, NCH2N);31P{1H} NMR (D2O, 20

�C): d �39.0 (s).

E. 7-PHOSPHA-3-METHYL-1,3,5-TRIAZABICYCLO[3.3.1]NONANE,

PTN(Me)

* Paraformaldehyde, (CH2O)n, was obtained fromAldrich as a 95%pure powder [30525-89-4] and used

without further purification.


Procedure

An oven-dried 250-mL round-bottomed Schlenk flask is equipped with a gas inlet

connected to a cylinder containing gaseous ammonia.* About 120mL of ammonia

is condensed into the flask, which was cooled to �78�C using an ethanol slush

bath.� 15.00 g (50.00mmol) of solid 7-methyl-1,3,5-triaza-7-phosphoniaadaman-

tane iodide is added to the flask, and the suspension is kept at �60�C under

vigorous stirring. At this point, 1.32 g of sodium (60.0mmol, 1.2 equiv) is added in

small portions (ca. 50mg each). The sodium turns the mixture blue, but this color

quickly fades to colorless before another portion of sodium is added. When the

light blue color persists for more than twomin, the reaction is considered to be

complete and addition of sodium is stopped (ca. 50min). At this point, the reaction

mixture is allowed to warm to room temperature under a nitrogen stream, the

ammonia evaporates and the white solid residue is transferred to a sublimation

apparatus. The crude product is then purified by sublimation, heating the flask at

80�Cunder a vacuumof 1 Torr.White crystals of PTN(Me) are collected and stored

under nitrogen. Yield: 3.1 g (36%). The nonvolatile residue in the sublimation

apparatus consisted of PTA (ca. 20%) and its oxide O¼PTA (75%).

Anal. Calcd. for C7H16N3P (MW¼ 173.20): C, 48.54%; H, 9.31%; N, 24.26%.

Found: C, 48.63%;H, 9.42%;N, 24.28%.NMRspectral data are in agreementwith

those reported in the literature.6 1H NMR (C6D6, 20�C): d 0.80 (d, 2JPH ¼ 5.3Hz,

PCH3, 3H), 1.85 (s, NCH3, 3H), 3.25 (dd, 2JHH 14.3 Hz, 2JPH ¼ 8.2Hz, PCH2N,

2H), 3.39 (d, 2JHH ¼ 10.1Hz, NCH2N, 2H), 3.64 (dd, 2JHH ¼ 14.3 Hz, 3JPH¼ 25.9Hz, PCH2N, 2H), 3.72 (d, 2JHH ¼ 10.1Hz, NCH2N, 2H), 3.89

(AB system, 2JHH ¼ 13.1 Hz, NCH2Nbridge, 2H);13C{1H} NMR (C6D6, 20

�C):d 10.22 (d, 1JCP ¼ 21.1Hz, PCH3), 38.14 (s, NCH3), 56.90 (d, 1JPC ¼ 26.0Hz,

PCH2N), 71.30 (d, 3JCP ¼ 8.9Hz, NCH2N), 77.22 (d, 3JCP ¼ 2.6Hz, NCH2N);31P{1H} NMR (C6D6, 20

�C): d �92.2 (s). mp 81–82�C.

Properties

PTN(Me) is a white microcrystalline material, which is air stable in the solid state.

The corresponding oxide cannot be obtained by classical P-phosphine oxidation

with hydrogen peroxide, while the sulfide and selenide derivatives are easily and

quantitatively prepared by reaction with the appropriate chalcogen element.6 PTN

(Me) is soluble in nonpolar and polar solvents includingwater. At 20�C, PTN(Me),

1.18 g dissolves in 1mL of water (6.81� 10�2M).

* The checkers dispensed liquid ammonia from an inverted cylinder of ammonia without the use of

cryogens.

25 Synthesis of the Water-Soluble Bidentate (P, N) Ligand PTN(Me) (PTN(Me) 101

References

1. C. S. Slone, D. A. Weinberger, and C. A. Mirkin, Prog. Inorg. Chem. 48, 233 (1999).

2. For a review on water-soluble phosphine complexes and their application in homogeneous

catalysis, see: N. Pinault and D. W. Bruce, Coord. Chem. Rev. 241, 1 (2003).

3. The synthesis of many hydrosoluble phosphines was reported in M.Darensbourg, ed., Inorganic

Syntheses, John Wiley & Sons, New York, 1998, Vol. 32, pp. 1–43.

4. B. Assmann, K. Angermaier, and H. Schmidbaur, J. Chem. Soc., Chem. Commun. 941 (1994).

5. A. D. Phillips, S. Bolano, S. S. Bosquain, J.-C. Daran, R. Malacea, M. Peruzzini, R. Poli, and L.

Gonsalvi, Organometallics 25, 2189 (2006).

6. B. Assmann, K. Angermaier, M. Paul, H. Riede, and H. Schmidbaur, Chem. Ber. 128, 891

(1995).

7. M. Caporali, C. Bianchini, S. Bolano, S. S. Bosquain, L. Gonsalvi, W. Oberhauser, A. Rossin, and

M. Peruzzini, Inorg. Chim. Acta 361, 3017 (2008).

8. M. Grayson, J. Am. Chem. Soc. 79, 85 (1963).

9. J.W. Ellis, K. N.Harrison, P. A. T.Hoye, A.G. Orpen, P. G. Pringle, andM.B. Smith, Inorg. Chem.

31, 3026 (1992).

10. D. L. Dubois and A. Miedaner, J. Am. Chem. Soc. 109, 113 (1987).

11. E. Fluck, J.-E. Forster, J. Weidlein, and E. H€adicke, Z. Naturforsch. 32B, 499 (1977).

26. SYNTHESIS OF METAL-ORGANIC FRAMEWORKS:MOF-5 AND MOF-177

Submitted by DAVID J. TRANCHEMONTAGNE,* LISA DUDEK,*

and OMAR M. YAGHI*

Checked by SERGIO S. ROSNEL� and JOHN ARNOLD�

Metal-organic frameworks (MOFs) represent a new class of porous crystalline

materials for which it is possible to designmaterials constructed from rigid organic

molecules as struts and shape-directing metal clusters as joints to achieve pre-

determined structures.1 Using this type of chemistry, called reticular chemistry,

one can choose different organic links to synthesize functionalized materials with

the same underlying topology.2 More important, one can design a wide variety of

new materials by combining the rich knowledge of metal cluster chemistry with

that of organic synthesis, opening endless possibilities for applications.3 Here, we

present syntheses of two important MOFs: MOF-51 (a) and MOF-1774 (b)

(representative units of the extended materials are shown: C, O, and Zn in light

gray, dark gray, and black, respectively).

*Department of Chemistry and Biochemistry, University of California, Los Angeles,

CA 90095-1569.�Department of Chemistry, University of California, Berkeley, CA 94720-1460.


In 1999, MOF-5 was discovered using base diffusion techniques that were

later generalized for use in varied MOF synthesis: triethylamine is diffused into

a solution of the organic link and metal salt, often producing crystals suitable for

single-crystal analysis.1 However, most MOF syntheses are now performed

by solvothermal methods: a mixture of organic link and metal salt is heated in

a solvent system containing formamide in a closed vessel. These conditions

allow the slow formation of amines in the reaction, producing high-quality

crystals. However, as with the base diffusion techniques, they have the disad-

vantage of being relatively slow (days to weeks). Furthermore, solvothermal

conditions require reaction ovens and are unsuitable for thermally sensitive

starting materials.

Recently, we discovered that the methods used to synthesize MOFs can

significantly impact their properties, specifically porosity.5 As a result, we have

begun exploring new synthesis strategies for the production of highly crystalline

MOFs. One such strategy is to choose a metal salt with a mildly basic anion,

allowing for facile reactions that occur at room temperaturewithout the addition of

extra base. These newer reactions have the advantages of allowing more open

glassware, not requiring ovens, and proceeding more quickly (minutes to hours).

They tend to yield microcrystalline powders rather than single crystals.

A. MOF-5: Zn4O(TEREPHTHALATE)3 (Solvothermal)

Procedure

Zinc nitrate tetrahydrate (13.82 g, 52.98mmol, EMD) and terephthalic acid

(3.06 g, 12.24mmol, Aldrich) are dissolved in 350mL of N,N-diethylformamide

26. Synthesis of Metal-Organic Frameworks: MOF-5 and MOF-177 103

(DEF) in a 500-mL jar following vigorous shaking and sonication. The jar is sealed

tightly and heated in an isothermal oven at 100�C for 2 days. Upon removal from

the oven, themother liquor is decantedwhile still warm, and the crystals are shaken

with fresh DEF, which is again decanted. Twice more additional DEF is added to

the jar and decanted. The synthesis is complete, and the purity of the crystalline

phase can be assessed using powder X-ray diffraction (PXRD). MOF-5 can be

stored for a few weeks at this stage in fresh DEF or N,N-dimethylformamide

(DMF).

Prior to use for gas storage or separation, the material is activated, clearing the

pores of solvent molecules and other guests. This is achieved by first exchanging

the guests in the pores with a volatile solvent, and then heating in vacuo to remove

the solvent. The crystals are rinsed (shaken and decanted) with pentene-stabilized

chloroform three times and left to soak overnight in fresh chloroform (also

pentene stabilized). The rinse/soak cycle is repeated once a day over two

additional days, and as the third chloroform soak is decanted, the crystals are

brought under vacuum in a 500-mL round-bottomed Schlenk flask. The crystals

are kept damp during the transfer so as not to allow adsorption of water from air.

The MOF is evacuated to �10mTorr and slowly heated to 120�C in vacuo for

24 h, yielding 3.75 g (40% based on terephthalic acid). Evacuation of the pores

confers air sensitivity to many MOFs; after placing MOF-5 under vacuum, it is

only handled under nitrogen, argon, or vacuum to maintain the maximum

accessible surface area.�

Properties

The identity and crystalline purity of the bulk material are determined by PXRD:

[d, A�(I, %)]: 12.919 (100), 9.136 (22), 7.797 (0.7), 6.458 (11.5), 5.927 (1.5), 5.772

(6.3), 5.273 (0.2), 4.968 (1.3), 4.566 (0.8), 4.366 (2.8), 4.308 (1.1), 4.084 (0.1),

3.941 (2.5), 3.895 (0.7), 3.727 (0.1), 3.619 (1.8), 3.582 (0.2), 3.450 (0.5), 3.363

(4.2), 3.156 (1), 3.134 (0.2), 3.045 (0.5), 2.984 (2.7), 2.834 (2.3), 2.709 (0.6), 2.596

(2.3), 2.582 (0.8), 2.532 (1), 2.498 (1.2), 2.485 (0.7), 2.409 (1.2), 2.396 (0.2), 2.359

(0.2), 2.329 (0.4), 2.284 (0.2), 2.258 (1.4), 2.215 (0.3), 2.191 (0.6), 2.153 (0.9),

2.123 (2), 2.095 (1.3), 2.074 (0.7), 2.042 (0.6), 2.017 (1.2), 1.993 (0.3), 1.975 (0.5),

1.947 (0.1), 1.930 (0.1), 1.890 (0.3), 1.846 (0.3). Solvent exchange in the pores is

confirmed by thermogravimetric analysis (TGA), and full evacuation is confirmed

either by TGA (when the only weight loss is decomposition at 420�C) or, more

rigorously, by gas adsorption (N2, 77K, Langmuir surface area of 4170m2/g).*

* The checkers conducted the procedure using zinc nitrate hexahydrate and at 1/5 scale (3.15 g Zn

(NO3)2�6H2O and 0.612 g terephthalic acid in 70mL DEF). After exchanging solvents and evacuating

at 120�C, 0.76 g of pure highly crystalline MOF-5 was obtained.


B. MOF-5: Zn4O(TEREPHTHALATE)3 (Room Temperature)

Procedure

For room-temperature reaction conditions without the addition of extra base, an

appropriate metal salt (often the acetate) is chosen to drive the reaction and

concentrated solutions are used. Terephthalic acid (254mg, 1.53mmol, Aldrich) is

dissolved in 20mL of DMF in a 50-mL Erlenmeyer flask, and zinc acetate

dihydrate (718mg, 3.27mmol, Alfa Aesar) is dissolved in a separate container

in 20mL of DMF via vigorous shaking and sonication. The zinc salt solution is

added dropwise to the terephthalic acid solution flask over 15min while stirring

with a Teflon-coated magnetic stirring bar. A white precipitate is formed almost

immediately, and the solution is stirred for 45min. Powder X-ray diffraction is

used to confirmphase pureMOF-5. This procedure has successfully been scaled up

to 3.37 g.

The crystalline precipitate is filtered using aNylonmembrane filter with 0.2mmdiameter pore size, immersed in 40mL DMF, and filtered again in the same

manner. For this procedure, exchanging solvents constitutes filtering the precipi-

tate from the current solvent and immersing in fresh solvent. The DMF is

exchanged for 40mL pentene-stabilized chloroform, which is again exchanged

with fresh chloroform (40mL) and left to soak for 2 days. It is again important to

use pentene-stabilized chloroform, as ethanol-stabilized chloroform will degrade

the framework. The mixture is exchanged with fresh chloroform and allowed to

soak over 2 days thrice more (for a total soak of 8 days). The chloroform is filtered,

without letting the MOF dry, and the product is quickly transferred to a 100-mL

round-bottomed Schlenk flask evacuated to�10mTorr and slowly heated to 120�Cin vacuo for 24 h, yielding 274mg (70%based on terephthalic acid). The product is

kept damp with solvent until under vacuum to obtain the best surface area. The

flask is then slowly heated to 120�C in vacuo for 6 h. After activation, the product is

air sensitive and is only handled under nitrogen, argon, or vacuum.*

Properties

The identity and crystalline purity of the bulk material are determined by PXRD,

with the same diffraction pattern as the solvothermal reaction above. Solvent

exchange in the pores is confirmed by thermogravimetric analysis and full

evacuation is confirmed either by TGA (again, no weight loss until 420�C) or,more rigorously, by gas adsorption (N2, 77K, Langmuir surface area of 3909m2/g).

* The checkers filtered the immediate white precipitate using filter paper (Whatman #1) via cannula.

After solvent exchange and evacuation at 120�C, they obtained 110mg of crystalline MOF-5.


C. MOF-177: Zn4O(1,3,5-BENZENETRIBENZOATE)2 (Room

Temperature)

Procedure

1,3,5-Benzenetribenzoic acid is synthesized through acetylation and subse-

quent oxidation of 1,3,5-triphenylbenzene, which is carried out in a fume hood.

1,3,5-Triphenylbenzene (10 g, 32.6mmol, Aldrich) is dissolved in 200mL

dichloromethane, while 33 g of aluminum trichloride is dissolved separately

in 180mL of acetyl chloride in a 1-L round-bottomed flask that is placed in an

ice water bath. The 1,3,5-triphenylbenzene solution is transferred to a dropping

funnel and added dropwise to the cold acetyl chloride solution while stirring

with a Teflon-coated magnetic stir bar, and the solution quickly turns deep red.

The ice bath is removed and the reaction is stirred for 2 h longer at room

temperature. The suspension is quenched by slowly pouring the contents of the

round-bottomed flask into a 2-L Erlenmeyer flask containing 1800mL of ice

(the reaction quenches vigorously, and this step is done with care). A Teflon-

coated stir bar is added, and the mixture is stirred overnight to form a yellow

slurry. Then the slurry is extracted with 3� 200mL of dichloromethane. The

dichloromethane fractions are collected and back-extracted with 2� 200mL of

0.3M NaOH. The dichloromethane solution is dried over MgSO4 and filtered,

and the solvent is removed on a rotary evaporator. The resulting white solid is

stirred in 1 L of boiling ethanol for 0.5 h and is then removed from the hot

ethanol by filtration. The ethanol purification is repeated once more, and the

resulting product is dried in air overnight to obtain 11 g of acetylated precursor.

The precursor is then suspended in 500mL 1,4-dioxane in a 1-L round-

bottomed flask. Separately, 35 g of NaOH is dissolved in 240mL of distilled

water in a 500-mL round-bottomed flask and cooled in the freezer for 1 h, after

which 16mL of bromine is added dropwise while stirring with a Teflon-coated

magnetic stir bar to yield a deep yellow solution. This yellow solution is then

added slowly to the dioxane solution with stirring, generating a white, turbid

suspension. The suspension is heated to 60�C and allowed to stir for 2 h, after

which it is cooled to room temperature. Sodium thiosulfate (100mL, 1.6M

aqueous) is added, and the solution is stirred for 10min. Concentrated HCl

(50mL) is added with stirring, and the resulting white suspension is filtered and

washed with 150mL of water and then dried, yielding 13.1 g (92%). mp

318–322�C (dec, literature: 315–318 and 325–326�C6). IR: 1692 (vs), 1610

(vs), 1425 (s), 1390 (s), 1314 (s), 1287 (s), 1244 (s) 1183 (s), 1116 (m), 1017

(m), 852 (m), 770 (s); 1H NMR (DMSO-d6, 400MHz): d 8.06 (m); 13C NMR

(DMSO-d6, 100MHz): d 125.59, 127.44, 129.95, 130.05, 140.77, 143.87,

167.19.


Benzenetribenzoic acid (0.626 g, 1.43mmol, above) and zinc acetate dihy-

drate (2.51 g, 11.4mmol, Alfa Aesar) are stirred with a Teflon-coated magnetic

stir bar in 50mL of DEF in a 125-mL Erlenmeyer flask for 3 h. The product,

which is shown to be phase pure MOF-177 by PXRD, is filtered using Nylon

filters with 0.2 mm diameter pores over a specialty large-pore glass frit for use

with fine Nylon filters. We note here that PXRD should be obtained of as-

synthesized material prior to solvent exchange and still damp with mother

liquor; solvent-exchanged, dried material may become amorphous, but typically

maintains porosity. After filtration, the product is mixed with 10mL of DEF and

filtered again in the same manner. It is then mixed with 40mL of chloroform

(pentene stabilized) and allowed to sit overnight. It is filtered again, mixed with

40mL of fresh chloroform, and allowed to sit for 3 days. It is filtered, mixed with

fresh chloroform, and allowed to sit overnight once more. The product is filtered

and transferred into a 100-mL round-bottomed Schlenk flask and evacuated to

�10mTorr overnight. The flask is then heated slowly to 120�C in vacuo for 12 h,

yielding 0.490 g (30% based on benzenetribenzoic acid). After activation, the

material is air sensitive and should be handled under nitrogen, argon, or

vacuum.*

Properties

The identity and crystalline purity of the bulk material are determined by PXRD:

[d, A�(I, %)]: 21.854 (3.3), 16.007 (54.7), 14.952 (49.6), 14.117 (100), 12.087

(7.2), 11.626 (23.1), 11.219 (22.5), 10.940 (14.5), 10.715 (6.4), 9.512 (6.7),

9.244 (12), 8.470 (11), 7.859 (11.9), 7.737 (7.8), 7.484 (2.6), 7.132 (2.4), 6.937

(3.4), 6.796 (3), 6.622 (3.2), 6.332 (4.9), 5.903 (4.4), 5.816 (4.6), 5.613 (2.6),

5.362 (2.2), 4.971 (1.7), 4.641 (1.8). Solvent exchange in the pores is confirmed

by TGA, and full evacuation is confirmed by either TGA (no weight loss until

340 �C) or, more rigorously, by gas adsorption (N2, 77K, Langmuir surface area of

5250m2/g).

References

1. H. Li, M. Eddaoudi, M. O’Keeffe, and O. M. Yaghi, Nature 402, 276 (1999).

2. M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O’Keeffe, and O. M. Yaghi, Science 295,

469 (2002).

* The checkers used 0.223 g of 1,3,5-benzenetribenzoic acid, 0.894 g of zinc acetate dihydrate, and

17mL of DEF placed in a capped 25mL vial. Trials with uncapped containers failed. Thewhite product

obtained was worked up using Schlenk techniques.


3. O. M. Yaghi, M. O’Keeffe, N. Ockwig, H. K. Chae, M. Eddaoudi, and J. Kim, Nature 423, 705

(2003).

4. H. Chae, D. Y. Siberio-P�erez, J. Kim, Y. Go, M. Eddaoudi, A. Matzger, M. O’Keeffe, and O. M.

Yaghi, Nature 427, 523 (2004).

5. S. S. Kaye, A. Dailly, O. M. Yaghi, and J. R. Long, J. Am. Chem. Soc. 129, 14176 (2007).

6. E.Weber, M. Hecker, E. Koepp,W. Orlia, M. Czugler, and I. Csoregh, J. Chem. Soc., Perkin Trans.

2, 1251 (1988);W. J. Svirbely and H. E. Weisberg, J. Am. Chem. Soc. 81, 257 (1959).


Chapter Six

ORGANOMETALLIC REAGENTS

27. TRICARBONYL 1,3,5-TRIMETHYL-1,3,5-TRIAZACYCLOHEXANE COMPLEXES OF CHROMIUM(0),MOLYBDENUM(0), AND TUNGSTEN(0) [M(CO)3(Me3TACH)

(M ¼ Cr, Mo, W)]

Submitted by NICOLE L. ARMANASCO,� MURRAY V. BAKER,�

ALISON G. BARNES,� DAVID H. BROWN,� VALERIE J. HESLER,� andMICHAEL R. NORTH�

Checked by DAMON LEE, MICHAEL J. PAROLINE, and

THOMAS B. RAUCHFUSS�

1,3,5-Triazacyclohexanes (R3TACH) typically serve as tripodal ligands. The first

reported complexes of a group VI metal (Cr, Mo, W) tricarbonyl with a R3TACH

were the chromium andmolybdenum complexes fac-M(CO)3(R3TACH) (M¼Cr,

Mo; R ¼ Me, Et, Cy), prepared from the metal hexacarbonyls M(CO)6 (M ¼ Cr,

Mo) in refluxing dibutyl ether, and in one case from Mo(CO)3(py)3 (py ¼pyridine), although no yield was specified.1 The complexes fac-Mo(CO)3(R3TACH) (R ¼ Me, Pri, Bn) were isolated in excellent yields (89–95%) by the

reaction of Mo(CO)3(h6-cycloheptatriene) with the corresponding triazacyclo-

hexane.2 The applicability of this method to the synthesis of chromium or tungsten

analogues has not been reported; however, the reported yield of W(CO)3(h6-

cycloheptatriene) fromW(CO)6 is low. Since these reports, fac-M(CO)3(R3TACH)


*Chemistry M313, School of Biomedical, Biomolecular and Chemical Sciences, The University of

Western Australia, Crawley, WA 6009, Australia .�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

109

(M¼ Cr, Mo,W) complexes have been prepared fromM(CO)6 (M¼ Cr, Mo, W),

M(CO)3(CH3CN)3 (M ¼ Cr, W), and M(CO)3(CH3CH2CN)3 (M ¼ Cr, Mo).3–7

In the case of the nitrile precursors, complete formation of the tris(nitrile)

complexes M(CO)3(RCN)3 (R ¼ Me, Et) is not required and the reaction of

R3TACH with M(CO)6�n(RCN)n (n ¼ 2 or 3) will afford the TACH complex

fac-M(CO)3(R3TACH).

Of synthetic utility are the complexes of 1,3,5-trimethyl-1,3,5-triazacyclo-

hexane (Me3TACH), fac-M(CO)3(Me3TACH) (M ¼ Cr, Mo, W). 1,3,5-Triaza-

cyclohexanes (TACH) are the smallest members of the triazacycloalkane family.

The small ring size results in significant strain in triazacyclohexane complexes.

In the case of fac-M(CO)3(Me3TACH) (M ¼ Cr, Mo, W), the Me3TACH ligands

are labile, and these complexes can serve as convenient sources of the fac-

M(CO)3 fragment without the need for thermal or photochemical activation. For

example, treatment of fac-M(CO)3(Me3TACH) (M ¼ Cr, Mo, W) with phos-

phines at room temperature affords tris(phosphine) complexes rapidly, exclu-

sively with a fac-M(CO)3 fragment, though sterically hindered phosphines and

phosphines with additional donor groups can afford different products.3–5,8–10

Dissolution of fac-Cr(CO)3(Me3TACH) in pyridine rapidly affords fac-

Cr(CO)3(py)3 while treatment with 1 equiv of fac-Cr(CO)3(Me3TACH) with tris

(3,5-dimethylpyrazol-1-yl)methane [(3,5-Me2pz)3CH] affords fac-Cr(CO)3[(3,5-

Me2pz)3CH].4 Dissolution of the tungsten and molybdenum complexes

fac-M(CO)3(Me3TACH) (M¼Mo, W) in acetonitrile at room temperature affords

exclusively fac-M(CO)3(CH3CN)3 (M ¼Mo, W), which can be readily isolated

in analytically pure forms.5 In contrast, when prepared by the standard method

(heating themetal hexacarbonyl in acetonitrile at reflux for an extended period of

time), the tris(nitrile) complexes fac-M(CO)3(CH3CN)3 can be contaminated

with bis(nitrile) complexes M(CO)4(CH3CN)2. The tungsten complex fac-

W(CO)3(Me3TACH) can react with alkynes to afford W(CO)(h2-RC�CR)3.5

The molybdenum and tungsten complexes are more labile than the chromium

analogue.

Starting Materials

Technical grade metal hexacarbonyls (96–98%) are suitable. While 1,3,5-

trimethyl-1,3,5-triazacyclohexane (1,3,5-trimethylhexahydro-1,3,5-triazine) is

commercially available, it is also conveniently prepared from aqueous methyl-

amine and aqueous formaldehyde solution or paraformaldehyde following the

method of Graymore and purified by distillation (60–61�C at 12mmHg).11

& Caution. The metal hexacarbonyls (volatile solids) and CO gas

are toxic. All operations should be performed in a well-ventilated fume

hood.

110 Organometallic Reagents

A. TRICARBONYL(1,3,5-TRIMETHYL-1,3,5-

TRIAZACYCLOHEXANE)CHROMIUM(0), fac-Cr(CO)3(Me3TACH)

CrðCOÞ6 þMe3TACH!CrðCOÞ3ðMe3TACHÞþ 3CO

Procedure

1,3,5-Trimethyl-1,3,5-triazacyclohexane (2.1 g, 16mmol) is added to xylenes

(40mL) in a 50-mL Schlenk flask equipped with a magnetic stirrer bar. The

solution is degassed by at least three freeze–pump–thaw cycles. Chromium

hexacarbonyl (1.6 g, 7.3mmol) is quickly added to the solution under a stream

of nitrogen. A Liebig condenser, the top of which is connected to a nitrogen

supply and a bubbler (to allow escape of CO), is fitted to the Schlenk flask. The

flask is heated so that the solvent refluxes vigorously until Cr(CO)6 no longer

sublimes from the reaction mixture (ca. 24 h). In all three preparations, the metal

hexacarbonyl tends to sublime into the condenser. Typically, if the reaction

temperature is initially raised slowly and then, once the reaction mixture is at

reflux, it is allowed to reflux vigorously, the solvent washes the sublimed material

back into the reaction mixture. As the reaction proceeds, the amount of sublimed

material decreases. Alternatively, the reaction flask can be removed from the heat,

and then under a blanket of nitrogen, a long spatula can be used to dislodge the

sublimed material back into the reaction mixture. It may be necessary to repeat

this process a number of times. Similar methods (swirling the reaction flask to

dislodge sublimed material, allowing solvent to wash down the metal hexacar-

bonyl, scraping the metal hexacarbonyl off the condenser wall, and/or slow heat

ramping) have been suggested by other researchers working with group VI

hexacarbonyls.12–14

As the reaction proceeds, an orange precipitate forms. While the mixture is

warm, the precipitate is collected under nitrogen, most conveniently using a small

Schlenk filter with a porosity-3 glass frit. The product is transferred to an inert

atmosphere glovebox. The orange crystalline solid is washed with hexane (2 �20mL), ethyl acetate (2 � 20mL), and hexane (2 � 20mL), and is then dried

in vacuo to afford Cr(CO)3(Me3TACH). Yield: 1.6 g (80%).

Anal. Calcd. for C9H15N3O3Cr: C, 40.76; H, 5.70; N, 15.84. Found: C, 40.59;

H, 5.55; N, 15.74. mp >240�C (decomp.). IR (Nujol) 1907, 1760 (br) (CO). Mass

spectrum: m/z 266.0601 (M þ H) (requires 266.0597). 1H NMR (acetone-d6):

d 2.49 (9H, s, 3�NCH3), 4.02 (3H, apparent d, splitting 8.3Hz, 3�NCHHN) and

4.66 (3H, apparent d, splitting 8.3Hz, 3 � NCHHN); 13C NMR (acetone-d6):

d 42.4 (CH3), 83.2 (NCH2N), and 237.5 (CO).

27. Tricarbonyl 1,3,5-Trimethyl-1,3,5-Triazacyclohexane 111

Properties

Tricarbonyl(1,3,5-trimethyl-1,3,5-triazacyclohexane)chromium(0) is an orange

crystalline, air-sensitive solid. On exposure to air, solid samples show visible

signs of decomposition within 30min. NMR solvents must be rigorously

degassed. Under an inert atmosphere, the complex is stable indefinitely in the

solid state. The complex is insoluble in nonpolar solvents but slightly soluble in

polar solvents (<0.4mg/mL in THF and ca. 19mg/mL in DMSO). Unlike the

molybdenum and tungsten analogues, Cr(CO)3(Me3TACH) does not undergo

solvolysis in DMSO.1H NMR spectroscopy is a diagnostic tool for the analysis of products. Signals

for the methylene protons of the conformationally rigid triazacyclohexane ring

appear as two apparent doublets (an AA0A00XX0X00 spin system), one for the three

axial protons and one for the three equatorial protons. In the 1H NMR spectrum

of free Me3TACH, the methylene protons appear as a very broad singlet, a

consequence of the fluxional nature of the free TACH ring system.15

B. TRICARBONYL(1,3,5-TRIMETHYL-1,3,5-TRIAZA-

CYCLOHEXANE)MOLYBDENUM(0), fac-Mo(CO)3(Me3TACH)

MoðCOÞ6 þMe3TACH!MoðCOÞ3ðMe3TACHÞþ 3CO

Procedure

The synthesis is similar to that for the chromium complex, using 1,3,5-trimethyl-

1,3,5-triazacyclohexane (2.1 g, 16mmol), molybdenum hexacarbonyl (1.86 g,

7.0mmol), and xylenes (30mL, mixture of isomers). The mixture is heated so

that the solvent refluxes vigorously for 3 h. The product is obtained as a yellow

powder (1.9 g, 88%).

Anal. Calcd. for C9H15N3O3Mo: C, 34.9; H, 4.9; N, 13.6. Found: C, 34.9; H, 5.1; N,

13.7. mp >200�C (decomp.). IR (KBr): 1900, 1785 (sh), 1750 (CO). 1H NMR

(acetone-d6): d 2.51 (9H, s, 3�NCH3), 4.08 (3H, apparent d, splitting 8.8 Hz, 3�NCHHN), and 4.70 (3H, apparent d, splitting 8.8 Hz, 3 � NCHHN). 13C NMR

(acetone-d6): d 42.4 (CH3), 83.3 (NCH2N), and 232.55 (CO).

Properties

Tricarbonyl(1,3,5-trimethyl-1,3,5-triazacyclohexane)molybdenum(0) is a yellow

air-sensitive compound. Exposure of the solid to air produces a dark brown solid

and Mo(CO)6. Under an inert atmosphere, the complex is stable indefinitely in the

solid state. The complex is insoluble in nonpolar solvents but sparingly soluble in


polar solvents such as acetone. Dissolution of the complex in DMSO rapidly

affords the solvolysis product Mo(CO)3(DMSO)3. The1H NMR spectrum can be

analyzed as described above for the Cr complex.

C. TRICARBONYL(1,3,5-TRIMETHYL-1,3,5-

TRIAZACYCLOHEXANE)TUNGSTEN(0), fac-W(CO)3(Me3TACH)

WðCOÞ6 þMe3TACH!WðCOÞ3ðMe3TACHÞþ 3CO

Procedure

The tungsten complex was prepared in 73% yield in a manner similar to the

chromium and molybdenum complexes.

Anal. Calcd. for C9H15N3O3W: C, 27.2; H, 3.8; N, 10.6. Found: C, 26.8; H, 3.8; N,

10.8.mp>190�C (decomp.). 1H NMR(acetone-d6): d 2.61 (9H, s, 3�NCH3), 4.91

(3H, apparent d, splitting 8.5Hz, with unresolved fine structure, 3�NCHHN), and

5.06 (3H, apparent d, splitting 8.5 Hz, with unresolved fine structure, 3 �NCHHN). 13C NMR (acetone-d6): d 42.9 (CH3), 83.5 (NCH2N), and 226.0 (CO).

IR (KBr): 1895, 1772 (sh), 1740 (CO).

Properties

W(CO)3(Me3TACH) is a yellow-tan air-sensitive compound. It also forms at lower

temperatures by the reaction ofMe3TACHwithW(CO)3(RCN)3 (R¼Me or Et) in

THF, and in these cases, the isolated complex is bright yellow. Spectroscopic

analysis indicates no appreciable differences between the products prepared by the

different methods. Exposure of the solid to air produces a dark brown solid and

W(CO)6. Under an inert atmosphere, the complex is stable indefinitely in the solid

state. The complex is insoluble in nonpolar solvents and only sparingly soluble in

polar solvents (ca. 0.05mg/mL in acetone). Dissolution of the complex in DMSO

rapidly affords the solvolysis product W(CO)3(DMSO)3. The1H NMR spectrum

can be analyzed as described above for the Cr complex.

References

1. A. L€uttringhaus and W. Kullick, Tetrahedron Lett. (10), 13 (1959).

2. H. Schumann, Z. Naturforsch. B 50, 1038 (1995).

3. N. L. Armanasco,M.V. Baker,M. R. North, B.W. Skelton, andA. H.White, J. Chem. Soc., Dalton

Trans. 1145 (1998).

4. N. L. Armanasco,M.V. Baker,M. R. North, B.W. Skelton, andA. H.White, J. Chem. Soc., Dalton

Trans. 1363 (1997).

27. Tricarbonyl 1,3,5-Trimethyl-1,3,5-Triazacyclohexane 113

5. M. V. Baker and M. R. North, J. Organomet. Chem. 565, 225 (1998).

6. M.V.Baker,D.H.Brown,B.W. Skelton, andA.H.White, J.Chem. Soc., Dalton Trans. 763 (2000).

7. M. V. Baker, D. H. Brown, B. W. Skelton, and A. H. White, J. Chem. Soc., Dalton Trans. 1483

(1999).

8. W.-Y. Yeh, S.-M. Peng, and G.-H. Lee, J. Organomet. Chem. 671, 145 (2003).

9. W.-Y. Yeh, C.-S. Lin, S.-M. Peng, and G.-H. Lee, Organometallics 23, 917 (2004).

10. N. Kuhn, M. Gohner, and M. Steimann, Z. Naturforsch. 56b, 95 (2001).

11. J. Graymore, J. Chem. Soc. 134, 1490 (1931).

12. K. R. Birdwhistell, Inorg. Synth. 29, 141 (1992).

13. A. R. Manning, P. Hackett, R. Birdwhistell, and P. Soye, Inorg. Synth. 28, 148 (1990).

14. G. J. Kubas and L. S. Van der Sluys, Inorg. Synth. 28, 29 (1990).

15. C. H. Bushweller, M. Z. Lourandos, and J. A. Brunelle, J. Am. Chem. Soc. 96, 1591 (1974).

28. MANGANESE TRICARBONYL TRANSFER(MTT) AGENTS

Submitted by SANG BOK KIM,� SIMON LOTZ,�

SHOUHENG SUN,� YOUNG KEUN CHUNG,z ROBERT D. PIKE,§ and

DWIGHT A. SWEIGART�

Checked by MARIA E. CARROLL,# DIDIER MORVAN,#

and THOMAS B. RAUCHFUSS#

The complexes [Mn(h6-arene)(CO)3]þ are isoelectronicwith [Cr(h6-arene)(CO)3]

and, as is the case with the chromium complexes, can be synthesized with a wide

variety of arenes.1 Functionalized arene ligands are of particular importance

because [Mn(arene)(CO)3]þ undergoes high-yield regio- and stereoselective attack

by a wide range of nucleophiles.2 A number of methods are available to make

p-arene tricarbonyl complexes of manganese(I), and the one selected is often

determined by the nature of the arene ring to be coordinated, which can have

substituents that are electron donating, electron withdrawing, or sterically

demanding.3 Condensed polyaromatic hydrocarbons such as naphthalene and

heterocyclic fused ring systems such as indole, benzofuran, and benzothiophene

can also p-bond in a h6-manner to manganese(I) tricarbonyl. Analogously, the

heteroaromatic five-membered thiophene ring can p-bond in a h5-fashion and

thereby donate six electrons.

*Department of Chemistry, Brown University, Providence, RI 02912.�Department of Chemistry, University of Pretoria, Pretoria 0002, South Africa .zDepartment of Chemistry, Seoul National University, Seoul 151-742, Korea .§Department of Chemistry, College of William and Mary, Williamsburg, VA 23187.#Department of Chemistry, University of Illinois at Urbana-Champaign,

Urbana, IL 61801.


Most methods to prepare [Mn(arene)(CO)3]þ make use of the abstraction of

the halogen from [Mn(CO)5X] (X ¼ halogen) by Lewis acids such as AlCl3(referred to as the Fischer–Hafner method)4 or by precipitation of silver(I) halide

(referred to as the silver method).5 The [Mn(CO)5]þ species can also be

generated via other indirect methods, most notably using dimanganese dec-

acarbonyl and trifluoroacetic anhydride in acidic medium.6 Coordination of the

arene rings is often achieved under harsh thermal conditions by refluxing in

appropriate solvents, with concomitant substitution for several carbonyl ligands.

The very popular silver method involves using silver(I) salts with weakly

coordinating anions such as perchlorate,7 triflate,8 or tetrafluoroborate9 and is

the method of choice for arenes with high sensitivity to acid. The silver method

uses milder reaction conditions in comparison to the Fischer–Hafner or tri-

fluoroacetic anhydride (TFA) procedures. The advantages and scope of these

different methods have been discussed by Pike and coworkers.3 It should be

noted that the synthesis of [Mn(arene)(CO)3]þ complexes starting from

[Mn(CO)5X] is often problematic when the arene contains electron-withdrawing

substituents. However, in recent significant work, it has been shown that access

to such electron-deficient systems is possible via the palladium-catalyzed

substitution for chloride in (h5-chlorocyclohexadienyl)Mn(CO)3, followed by

hydride abstraction.10

A synthetic strategy conceptually different from the ones that start with

Mn(CO)5X involves the initial generation of an intermediate arene manganese

tricarbonyl complex that has an arene ring sufficiently labile that it can be easily

replaced by reaction with a second arene. This method can also be seen as

transferring a Mn(CO)3þ fragment from one arene ligand to another (Eq. 1).

Studies of the stability of p-arene manganese tricarbonyl complexes with polycy-

clic condensed arenes (‘‘polyarenes’’) indicated that these compounds were

ideally suited to act as Mn(CO)3þ transfer reagents (MTT reagents).11 It was

observed that the polyarene complexes undergo ring slippage processes much

more readily than do the monocyclic analogues, which has been ascribed to a

smaller loss in resonance energy that accompanies the h6 ! h4 transformation in

the polyarene cases. Facile ring slippage is the requirement for the reaction shown

in Eq. 1 to be useful, and a series of [Mn(h6-polyarene)(CO)3]þ complexes have

been tested for their ability to effectively transfer the Mn(CO)3þ fragment in this

manner. A key feature of the synthesis of [Mn(arene)(CO)3]þ viaMTT reagents is

the very mild conditions—simply warming the reactants in dichloromethane

solvent (see below). The MTT reagents of choice contain a readily displaceable

naphthalene or acenaphthene ligand (Fig. 1). Both have been used with success

and both are quite stable thermally as solids or in solution in the absence of

nucleophilic reagents. The MTT method for the synthesis of [Mn(arene)(CO)3]þ

complexes often translates into an improved yield or a cleaner reaction product in

comparison to that afforded by other synthetic methods.11

28. Manganese Tricarbonyl Transfer (MTT) Agents 115

½Mnðarene0ÞðCOÞ3�þ þ arene!½MnðareneÞðCOÞ3�þ þ arene0

ðarene0 ¼ labile arene ligandÞ ð1Þ

Herein, an example is given of how the MTT method can be used to coordinate

Mn(CO)3þ to a p-molecule. Figure 2 gives examples of such p-systems. Thus,Mn

(CO)3þ can be coordinated to redox-active hydroquinones,12 sterically encum-

bered aromatics, and the curved (convex) face of centropolyindanes.13 Coordina-

tion tometal complexes containing a free arene or thiophene ring affords binuclear

systems useful in construction of nonlinear optical materials.14 It has been shown

that chiral metallocenes can react with MTT reagents by the transfer of a

cyclopentadienyl ring to generate planar chiral (cyclopentadienyl)Mn(CO)3 com-

plexes with high stereoselectivity.15 Alternatively, MTT reagents can transfer the

Mn(CO)3þ unit to metallocenes without Cp ring cleavage, resulting in novel

Figure 2. Examples of molecules that react with MTT reagents by p-coordination of the

Mn(CO)3þ unit.

Figure 1. Mn(h6-polyarene)(CO)3þ complexes that function as excellent MTT reagents.


bimetallic multidecker systems capped by the manganese tricarbonyl fragment.15

For each of the representative compounds shown below, the MTT method affords

products that can be obtained only in lower yields or cannot be obtained at all by

the other synthetic methods for the coordination of Mn(CO)3þ .

A. ACENAPHTHENE(TRICARBONYL)MANGANESE(I)*

MnðCOÞ5BrþAgBF4 !MnðCOÞ5BF4 þAgBr

MnðCOÞ5BF4 þC12H10 !½MnðC12H10ÞðCOÞ3�BF4 þ 2CO

Procedure

Under an atmosphere of nitrogen, a 250-mL two-necked flask is charged with Mn

(CO)5Br16 (1.10 g, 4.0mmol) along with a Teflon-coated stirring bar. Dichlor-

omethane (50mL, Fisher HPLC Grade D143-1) is added, and the solution stirred

until all the [Mn(CO)5Br] dissolves. The flask is covered with aluminum foil to

exclude light, and silver tetrafluoroborate is added (0.82 g, 4.2mmol). After

stirring the solution for 20min, a solution of acenaphthene (0.93 g, 6.0mmol)

in 10mL dichloromethane is added. The reaction mixture is refluxed for 3–4 h.

After being cooled to room temperature, the reaction mixture is filtered through a

Celite plug into a flask containing 250mL diethyl ether while stirring vigorously.

The Celite removes AgBr together with some undissolved product. The residue on

the Celite is washed with small portions (3 � 10mL) of dichloromethane, which

are collected separately, concentrated, and added dropwise to the stirred ether

solution. The product separates as a fine yellow solid. The yellow powder is

filtered off, washed with diethyl ether, and dried in vacuo. Although normally

quite pure at this stage, the solid can be further purified by redissolving in a

minimum of dichloromethane and treating as before by adding the solution in a

dropwise manner to a stirred solution of diethyl ether (250mL). Yield: 1.32 g

(3.48mmol, 87%).

Anal. Calcd (%): C, 47.37; H, 2.63. IR (CH2Cl2): 2072, 2012 cm�1. Found (%): C,

47.23; H, 2.72. 1H NMR (CD2Cl2): d 8.07 (m, H6), 7.90–7.75 (m, H5,7), 7.17 (d, J

¼ 7Hz, H4), 6.75 (m, H3), 6.58 (d, J ¼ 6Hz, H2), 3.90–3.60 (m, H9,10).

* Checkers obtainedyields about 30% lower than reported probablybecause of incomplete precipitation

of the products from the dichloromethane reaction solution. After the addition of the arene, the reaction

of Mn(CO)5Br with AgBF4 was monitored by IR spectroscopy. In some reactions, it was found that

additional AgBF4 (up to 20%) was required to completely convert all Mn(CO)5Br.


Properties

Acenaphthene(tricarbonyl)manganese(I) tetrafluoroborate11 is a light yellow solid

(mp 130�C decomp.) and is best kept under inert atmosphere to avoid contact with

moisture, with which it reacts to liberate the coordinated acenaphthene. Similarly,

it reacts rapidly with nucleophilic solvents such as acetonitrile and DMSO but is

highly soluble and stable in CH2Cl2. It is insoluble in ether and aromatic or

aliphatic hydrocarbons. The acenaphthene complex [Mn(h6-C12H10)(CO)3]BF4 is

the MTT reagent of choice in terms of cost, ease of synthesis, and shelf life.

B. NAPHTHALENE(TRICARBONYL)MANGANESE(I)

MnðCOÞ5BrþAgBF4 !MnðCOÞ5BF4 þAgBr

MnðCOÞ5BF4 þC10H8 !½MnðC10H8ÞðCOÞ3�BF4 þ 2CO

Procedure

The complex was prepared from Mn(CO)5Br16 (1.10 g, 4.0mmol), silver tetra-

fluoroborate (0.82 g, 4.2mmol), and naphthalene (0.77 g, 6.0mmol) by a proce-

dure analogous to that employed for the acenaphthene analogue. The product, a

pale yellow solid, was again isolated by filtration, washed with ether, and dried in

vacuo. Yield: 1.22 g (3.44mmol, 86%).

Anal. Calcd (%): C, 44.11; H, 2.28. Found (%): C, 43.87; H, 2.30. IR (CH2Cl2):

2077, 2022 cm�1. 1H NMR (CD2Cl2): d 8.06 (s, H5–8), 7.50–7.35 (m, H1,4),

6.80–6.65 (m, H2,3).

Properties

Naphthalene(tricarbonyl)manganese(I) tetrafluoroborate11 is a pale yellow solid

(mp 108�C decomp.). It is best kept under inert atmosphere due to its moisture

sensitivity. It dissolves readily in CH2Cl2 but is insoluble in ether and aromatic or

aliphatic hydrocarbons. As a MTT reagent, the naphthalene complex undergoes

arene substitution faster than theacenaphthene(tricarbonyl)manganese(I) analogue.

C. SYNTHESIS OF h6-N,N-DIMETHYLANILINE(TRICARBONYL)-MANGANESE(I) TETRAFLUOROBORATE,

[Mn(h6-C6H5NMe2)(CO)3]BF4

½MnðC12H10ÞðCOÞ3�BF4þC6H5NMe2!½MnðC6H5NMe2ÞðCOÞ3�F4þC12H10


Procedure

& Caution. The procedure involves heating a dichloromethane solution to

70�C, thus generating up to several atmospheres pressure. For this reason, the

experimental apparatus should be placed behind an appropriate protective shield.

A 30-mL pressure tube was flame dried under nitrogen and charged with [Mn(h6-

C12H10)(CO)3]BF4 (0.21 g, 0.55mmol) and N,N-dimethylaniline (1.40mL,

1.10mmol) dissolved in 20mL dichloromethane. N,N-Dimethylaniline was dried

prior to use with 4A�molecular sieves. The tube was sealed, heated in a silicon oil

bath at 75�C for 3 h, and then cooled to room temperature. After evaporation to ca.

5mL, this solution was added slowly to 100mL of diethyl ether through a plug of

Celite. The light yellow solid was filtered off and washed three times with 10mL

aliquots of diethyl ether. The isolated yield of [Mn(h6-C6H5NMe2)(CO)3]BF4 was

0.18 g (0.52mmol, 94%).

Anal. Calcd (%): C, 38.08; H, 3.20; N, 4.04. Found (%): C, 39.04; H, 3.17; N, 4.30.

IR (CH2Cl2): 2066, 2000 cm�1. 1H NMR (acetone-d6): d 6.92 (t, H3,5), 6.09 (t,

H4), 5.87 (d, H2,6), 3.35 (s, Me).

Properties

N,N-Dimethylaniline(tricarbonyl)manganese(I) tetrafluoroborate is a yellow solid

(mp 168�C with decomp.). It dissolves readily in CH2Cl2 but is insoluble in ether,

aromatic, and aliphatic hydrocarbons.

References

1. D. A. Sweigart, J. A. Reingold, and S. U. Son, Manganese compounds containing CO ligands, in

Comprehensive Organometallic Chemistry, 3rd ed., R. H. Crabtree and D. M. P. Mingos, eds.,

Elsevier, Oxford, 2006, Vol. 5, Chapter 10, pp. 761–814.

2. (a) L. A. P. Kane-Maguire, E. D. Honig, and D. A. Sweigart, Chem. Rev. 84, 525 (1984).

(b) R. D. Pike, D. A. Sweigart, Coord. Chem. Rev. 187, 183 (1999). (c) D. A. Sweigart, T. J.

Alavosus, Y. K. Chung,W. A.Halpin, E. D. Honig, and J. C.Williams,Metal carbonyl cationswith

cyclic p-hydrocarbon ligands, in Organometallic Synthesis, R. B. Kingand J. J. Eisch, eds.,

Academic Press, New York, 1988, Vol. 4, p. 108.

3. J. D. Jackson, S. J. Villa, D. S. Bacon, R. D. Pike, and G. B. Carpenter, Organometallics 13, 3972

(1994).

4. (a) G. Winkhaus, L. Pratt, and G. Wilkinson, J. Chem. Soc. 3807 (1961). (b) P. L. Pauson and

J. A. Segal, J. Chem. Soc., Dalton Trans. 1677 (1975). (c) L. A. P. Kane-Maguire and D. A.

Sweigart, Inorg. Chem. 18, 700 (1979).

5. (a) R. Mews, Angew. Chem., Int. Ed. Engl., 14, 640 (1975). (b) F. L. Wimmer, M. R. Snow, and

Aust. J. Chem. 31, 267 (1978). (c) R. Uson, V. Riera, J. Gimano, M. Laguna, M. P. Gamasa,

J. Chem. Soc., Dalton Trans. 966 (1974). (d) F. A. Cotton, D. J. Darensbourg, and W. S.

Kolthammer, Inorg. Chem. 20, 1267 (1981).


6. (a) M. I. Rybinskaya, V. S. Kaganovich, and A. R. Kydinov, Izv. Akad. Nauk. SSR Ser. A Khim.

885 (1984). (b) A. J. Pearson and H. Shin, Tetrahedron 48, 7527 (1992).

7. (a) K. K. Basin, W. G. Balkeen, and P. L. Pauson, J. Organomet. Chem. 204, C25 (1981).

(b) Y.-A. Lee, Y. K. Chung, Y. Kim, and J. H. Jeong,Organometallics 9, 2851 (1990). (c) E. Jeong

and Y. K. Chung, J. Organomet. Chem., 434, 225 (1992). (d) S. S. Lee, J-S. Lee, and Y. K. Chung,

Organometallics 12, 4640 (1993). (e) S. C. Chaffee, J. C. Sutton, C. S. Babbitt, J. T. Maeyer,

K. A. Guy, and R. D. Pike, Organometallics 17, 5568 (1998).

8. S. P. Schmidt, J. Nitschke, and W. C. Trogler, Inorg. Synth. 26, 113 (1989).

9. W. J. Ryan, P. E. Peterson, Y. Cao, P. G. Willard, D. A. Sweigart, C. D. Baer, C. F. Thompson,

Y. K. Chung, and T.-M. Chung, Inorg. Chim. Acta 211, 1 (1993).

10. A. Auffrant, D. Prim, F. Rose-Munch, E. Rose, S. Schouteeten, and J. Vaissermann,


11. (a) S. Sun, L. K. Yeung, D. A. Sweigart, T.-Y. Lee, Y. K. Chung, S. R. Switzer, and R. D. Pike,

Organometallics 14, 2613 (1995). (b) M. Oh, J. A. Reingold, G. B. Carpenter, and D. A. Sweigart,

Coord. Chem. Rev. 248, 561 (2004).

12. S. Sun, G. B. Carpenter, and D.A. Sweigart, J. Organomet. Chem. 512, 257 (1996).

13. C. A. Dullaghan, G. B. Carpenter, D. A. Sweigart, D. Kuck, C. Fusco, and R. Curci,


14. (a) I. S. Lee, H. Seo, and Y. K. Chung, Organometallics 18 1091 (1999). (b) S. S. Lee, T.-Y. Lee,

J. E. Lee, I.-S. Lee, Y.K. Chung, and M.S. Lah, Organometallics 15, 3664 (1996).

15. (a) E. J. Watson, K. L. Virkaitis, H. Li, A. J. Nowak, J. S. D’Acchioli, K. Yu, G. B. Carpenter,

Y. K. Chung, and D. A. Sweigart,Chem. Commun. 457 (2001). (b) S. U. Son, K. H. Park, S. J. Lee,

Y. K. Chung, and D. A. Sweigart, Chem. Commun. 1290 (2001).

16. M. H. Quick and R. J. Angelici, Inorg. Synth. 19, 160 (1979).

29. BIS(1,5-CYCLOOCTADIENE)NICKEL(0)

Submitted by J. WOLFRAM WIELANDT� and DAVID RUCKERBAUER�

Checked by T. ZELL§ and U. RADIUS§

Bis(1,5-cyclooctadiene)nickel(0) is useful for the synthesis of a variety of novel

nickel complexes1–5 since the 1,5-cyclooctadiene ligands are easily displaced

by other stronger electron-donating ligands.6 The compound has been prepared

by reduction of nickel(II) salts with manganese powder7 or by sodium8 in the

presence of 1,5-cyclooctadiene. Moreover, triethylaluminum has become a com-

mon reducing agent, but butadiene is required as the protective atmosphere.9

A butadiene-free preparation procedure has been reported that uses diisobutyla-

luminum hydride (DIBAH) to reduce technical grade (90%) Ni3(acac)6.10 Here,

di(n-butyl)magnesium is used as an alternative,4 since it is cheap and much less

dangerous than triethylaluminum. Also, no butadiene atmosphere is required.

*Institute of Chemistry, Inorganic Department, Karl-Franzens-University, 8010 Graz, Austria.§Institut fur Anorganische Chemie der Julius-Maximilians-Universitat Wurzburg, Am Hubland,

D-97074 Wurzburg, Germany.


Di(n-butyl)magnesium can be purchased as a 1.0M solution in n-heptane.

Alternatively, the preparative method given below can be applied, which follows

the general synthetic pathway for dialkyl magnesium compounds outlined

by Kamienski.11 The preparation involves the treatment of an ethereal solution

of (n-butyl)magnesium bromide with n-butyl lithium solution in hexanes. Other

methods of preparation include treatment of (n-butyl)magnesium halide solutions

withMe(OCH2CH2)nOMe,12 1,4-dioxane,13 and THF,14 or reaction ofmagnesium

hydride with 1-butene under pressure in an autoclave.15

& Caution. Di(n-butyl)magnesium reacts violently with water, and in the

dry state it ignites spontaneously upon exposure to air. Nickel and its compounds

are regarded as carcinogens. It also can cause allergic reactions, asthma, and

chronic bronchitis. Uptake of large quantities of nickel may lead to lung

embolism, respiratory failure, and heart disorders. Therefore, all manipulations

should be performed with care in a well-ventilated hood.

Materials

1,5-Cyclooctadiene (Aldrich Chemicals) was distilled from sodium and stored

under argon. n-Butyl bromide and 1.6M n-butyl lithium solution were purchased

from Aldrich and used as received. Solvents used in the syntheses were dried with

appropriate drying agents16 and freshly distilled under inert gas before use. All

procedures are performed in an anhydrous, oxygen-free atmosphere using standard

techniques for bench-top inert atmosphere reactions.17,18

A. HEXAKIS(ACETYLACETONATO)TRINICKEL(II)

NiðNO3Þ2 �6H2Oþ2NaC5H7O2!NiðC5H8O2Þ2 �2H2Oþ4H2Oþ2NaNO3

3NiðC5H8O2Þ2 �2H2O!Ni3ðC5H8O2Þ6þ6H2O

Procedure

Under air, Ni(NO3)2�6H2O (29.8 g, 0.1mol) and 2,4-pentanedione (20.5 g,

0.205mol) are dissolved in water (40mL) and treated with a 0.2M aqueous

solution of NaOH (40mL). Immediately, a turquoise precipitate is formed. After

the addition is complete, the mixture is heated to reflux for 30min, cooled to

ambient temperature, and filtered. The filter cake iswashedwithwater (50mL) and

dried under air for 2 h; yield: 26.9 g (92%) of light turquoise bis(2,4-pentadionato)

nickel(II) dihydrate. In a 500-mL round-bottomed flask attached to a Dean–Stark

apparatus, a suspension of bis(2,4-pentadionato)nickel(II) dihydrate (26.9 g,

29. Bis(1,5-Cyclooctadiene)Nickel(0) 121

0.092mol) in toluene (150mL) is carefully heated to reflux under air. (Note: An oil

bath should be applied as heating source, not a heatingmantle. Themixture tends to

foam, and when heating is performed too rapidly, some of the solid material spills

over into the water collector.)9 The mixture is heated under reflux for 48 h until no

morewater is separated. A dark green slurry is formed, which is allowed to cool to

ambient temperature under inert gas. The insoluble parts are removed by filtration

with exclusion of air. The filter cake is extracted with dry toluene (20mL). All

filtrates are combined and are taken to dryness under vacuum. The oily residue is

rinsed with ether (30mL) in order to remove traces of grease. Solvent is decanted

from the green solid, which is dried under vacuum. Yield: 17.0 g (0.066mol).

B. DI(n-BUTYL)MAGNESIUM

n-C4H9BrþMg! n-C4H9MgBr

n-C4H9MgBrþ n-C4H9Li!ðn-C4H9Þ2MgþLiBr

Procedure

A500-mL three-necked round-bottomed flask is equippedwith a reflux condenser,

topped by a gas outlet, and two pressure-equalizing dropping funnels (one with

100mL volume and the other with 250mL volume). Before the second dropping

funnel is attached, dry magnesium turnings (6.1 g, 0.25mol) and a few crystals of

iodine are added to the flask. The apparatus is flushed with nitrogen for a few

minutes, and then the small dropping funnel is charged with n-butyl bromide

(34.26 g, 0.25mol) and the large one is filled with dry diethyl ether (100mL). The

magnesium turnings are heated without solvent with a heating gun until violet

fume has filled the whole apparatus. Then, approximately 5% of the volume of

n-butyl bromide is added to the hot magnesium turnings, followed by dropwise

addition of the solvent. As soon as the Grignard reaction starts, the bromide and

the solvent are added in a dropwise manner to keep the mixture refluxing gently.

(Note: The bromide should be added cautiously. An efficient reflux condenser is

recommended.)Upon complete addition, the dark graymixture is kept under reflux

for another 30min using a water bath.

Into the second reaction apparatus consisting of a 1-L three-necked round-

bottomed flask equipped with a reflux condenser, a gas inlet, and a pressure-

equalizing 250-mL addition funnel, the Grignard solution is transferred under

argon via cannula in order to separate it from unreacted magnesium. (Note: By

weighing the amount of unreacted Mg, the amount of n-butyl lithium solution

required can be accurately determined. Usually, the conversion is 90–95%.) The

dropping funnel is now charged with 1.6M n-butyl lithium solution in hexanes


(138mL, 0.220mol) and added dropwise under cooling with an ice bath. The

resulting gray suspension is heated at reflux for 30min, cooled to ambient

temperature, and filtered under nitrogen using a Schlenk frit attached to a 1-L

Schlenk flask. (Note: It is recommended that the inorganic salts be allowed to settle

prior to filtration, and the filtration process itself should be performed without

pressure to prevent LiBr from passing through the filter�.) The nearly colorless

clear filtrate is collected and used in the next step. (Note: An excess of reducing

agent does not affect the preparation described in step B.) To isolate the dibutyl

magnesium, the filtrate is evaporated to dryness under vacuum and the resulting

white solid is further dried at 10�2mbar at 60�C for 15 h to give 33.1 g (95%). This

solid contains small amounts of lithium bromide.

C. BIS(1,5-CYCLOOCTADIENE)NICKEL(0)

Ni3ðC5H7O2Þ6 þ 6 ðn-C4H9Þ2Mgþ 6C8H12 ! 3 ðC8H12Þ2Niþ 6 ðn-C4H9ÞMgðC5H7O2Þþ 3C8H18

Procedure

A 1-L three-necked round-bottomed flask is equipped with a 100-mL pressure-

equalizing dropping funnel and two gas outlets, one attached to a gas bubbler and

the other to an inert gas source. The flask is charged with Ni3(C5H7O2)6 (9.79 g,

0.038mol), 1,5-cyclooctadiene (15.22 g, 0.1408mol ofNi), andTHF (55mL). The

dropping funnel is charged with di(n-butyl)magnesium (0.075mol) obtained by

one of the following three methods:

(i) A commercial solution in n-heptane.

(ii) The diethyl ether/hexane filtrate from part B above.

(iii) A solution of di(n-butyl)magnesium (10.39 g, 0.075mol) in THF

(100mL). (Note: Solid di(n-butyl)magnesium dissolves slowly in THF

to give a slightly milky solution.)

The reaction flask is cooled to �100�C using an EtOH/N2 bath, and the MgBu2solution is slowly added dropwise, maintaining the reaction temperature below

�80�C. The addition requires approximately 2 h. The color of the reaction mixture

turns gradually from green to brownish-yellow over a period of several hours. Upon

completeaddition,thereactionmixtureisallowedtoreachambient temperatureandis

*The checkers removed insoluble material via filtration through a pad of dry Celite. The resulting

solutionwas used for the synthesis ofNi(cod)2 and transferred into the dropping funnel. The di(n-butyl)

magnesium solution in diethyl ether/hexane could not be stored > �40 ˚C.

29. Bis(1,5-Cyclooctadiene)Nickel(0) 123

stirredovernight.Thereactionmixture isevaporatedundervacuum,and thebrownish

residue is cautiously treated with MeOH (100mL)�. The resulting dark yellow

suspension is stirred for 10min and then allowed to settle, and the brown solution

is decanted or removed by cannula, leaving a fine yellow solid. (Note: Filtration

through Celite is possible in principle, but the frit is easily clogged.) The MeOH

washing step is repeated until the decanted solution is very pale. Finally, the yellow

material is extractedonceeachwithEtOH(50mL)andn-pentane(50mL)and is then

driedundervacuum(withprotectionfromlight)yielding9.1 g(0.033mol,87%)ofNi

(1,5-C8H12)2. This material is usually pure enough for further transformations�.

The product can be purified by recrystallization. Solid Ni(cod)2 (1–2 g) is

placed on top of a 1-cm layer of Celite on a Schlenk frit that is attached to a

250-mL Schlenk flask. Toluene (50mL) is added carefully, and the mixture is

carefully stirred with a plastic spatula while keeping the Celite settled. (Note:

Metal spatulas catalyze decomposition of the compound.) The dark yellowmixture

is carefully filtered to give a clear yellow filtrate. The procedure is repeated until

the extracts are almost colorless. The resulting filtrate is concentrated under

reduced pressure until incipient crystallization. The flask is filled with argon, and

the golden yellow solution is slowly treated with ether (50mL). (Note: If at this

stage some brown flakymaterial is formed, the mixture should be carefully filtered

once more.) The mixture is stored overnight at �30�C affording golden yellow

crystals that are isolated by removing the supernatant. A second crop can be

obtained by concentrating the mother liquor under vacuum to a few milliliters,

adding ether (20mL), and storing the mixture overnight at�30�C. The combined

recovery efficiency is usually 60–80%.

Anal. Calcd. for C16H24Ni: C, 69.9; H, 8.8%. Found: C, 69.6; H 8.9%. 1H NMR10

(C6D6): d 2.06 (s, 8H,CH2); 4.29 (s, bd, 4H,CH). The checkers found d 2.08 (s, 8H,CH2); 4.30 (s, 4H, CH).

Properties

The solid complex decomposes after several minutes in air; solutions decompose

in air more rapidly. It is moderately soluble in benzene and THF, but heating these

solutions above 60�C leads to decomposition. The solid decomposes at

135–140�C. It is nearly insoluble in diethyl ether and saturated hydrocarbons.

The complex is decomposed catalytically by halocarbons,19 and even upon storage

under inert gas for a prolonged time, it can decompose turning dark slowly.

*The checkers found that the methanolysis of the reaction mixture is a crucial step in the synthesis. The

MeOH used should be rigorously dried and the reaction mixture should be cooled using a iPrOH/CO2

cooling bath (�78 ˚C). It is important to proceed with the preparation since the reaction mixture

decomposes over MeOH after days. For storage, we advice to remove all volatiles in vaccuo.�The checkers obtained 80–85% yield of tan solid that was pure by 1H NMR spectroscopy.


References

1. A. J. Arduengo, III, S. F. Gamper, J. C. Calabrese, and F. Davidson, J. Am. Chem. Soc. 116, 4391

(1994).

2. R. M. Ceder, J. Granell, G. Muller, M. Font-Bard�ıa, and X. Solans, Organometallics 14, 5544

(1995).

3. S. Ogoshi, K. Tonomori, M. Oka, and H. Kurosawa, J. Am. Chem. Soc. 128, 7077 (2006).

4. M. J. Tenorio, M. C. Puerta, I. Salcedo, and P. Valerga, J. Chem. Soc., Dalton Trans. 653 (2001).

5. M. Stol, D. J.M. Snelders,M.D.Godbode,R.W.A.Havenith,D.Haddleton,G.Clarkson,M.Lutz,

A. L. Spek, G. P. M. van Klink, and G. van Koten, Organometallics 26, 3985 (2007).

6. S. D. Ittel, Inorg. Synth. 28, 98 (1990).

7. F. Guerini and G. Salerno, J. Organomet. Chem. 114, 339 (1976).

8. (a) H. M. Colquhoun, D. J. Thompson, and M. W. Twigg, New Pathways for Organic Synthesis,

Plenum Press, London, 1984, p. 389. (b) T. R. Belderra�ın, D. A. Knight, D. J. Irvine, M. Paneque,

M. L. Poveda, and E. Carmona, J. Chem. Soc., Dalton Trans. 1491 (1992).

9. R. A. Schunn, S. D. Ittel, and M. A. Cushing, Inorg. Synth. 28, 94 (1990).

10. D. J. Krysan and P. B. Mackenzie, J. Org. Chem. 55, 4229 (1990).

11. C. W. Kamienski and J. F. Eastham, J. Organomet. Chem. 8, 542 (1967).

12. Y. Saheki, K. Sasada, N. Satoh, N. Kawaichi, and K. Negoro, Chem. Lett. 2299 (1987).

13. W. Strohmeier and F. Seifert, Chem. Ber. 94, 2356 (1961).

14. K. L€uhder, D. Nehls, and K. Majeda, J. Prakt. Chem. 325, 1027 (1983).

15. B. Bogdanovi�c, P. Bons, S. Konstantinovi�c, M. Schwickardi, and U. Westeppe, Chem. Ber. 126,

1371 (1993).

16. W. L. F. Armarego and D. D. Perrin, Purification of Laboratory Chemicals, 4th ed., Butterworth/

Heinemann, Oxford, 1996.

17. D. F. Shriver and M. A. Drezdon, The Manipulation of Air-Sensitive Compounds, Wiley,

Chichester, 1986.

18. R. B. King, in Organometallic Syntheses, J. J. Eischand R. B. King, eds., Academic Press, Inc.,

New York, 1965, Vol. 1.

19. C. A. Tolman, D. W. Reutter, and W. C. Seidel, J. Organomet. Chem. 117, C30 (1976).

30. SODIUM (h5-CYCLOPENTADIENYL)TRIS(DIMETHYLPHOSPHITO-P)COBALTATE(III),

Na[(C5H5)Co{P(O)(OMe)2}3]

Submitted by WOLFGANG KL€AUI� and PETER C. KUNZ�

Checked by SABINE N. SEIDEL� and JOHN A. GLADYSZz

The chemistry of cobaltocene is dominated by its tendency to act as an

electron-rich radical that can undergo one-electron oxidation, ring addition,

*Lehrstuhl I: Bioanorganische Chemie und Katalyse, Heinrich-Heine-Universit€at D€usseldorf, 40225

D€usseldorf, Germany .�Lehrst€uhle f€ur Anorganische Chemie, 91058 Erlangen, Germany .zDepartment of Chemistry, Texas A&M University, College Station, TX .

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)Cobaltate(III) 125

and ring substitution reactions. Secondary phosphites HP(O)(OR)2 react with

cobaltocene in a complex manner that includes both oxidation and ring substi-

tution to produce mixed-valence trinuclear cobalt complexes of the type [Co

((C5H5)Co{P(O)(OR)2}3)2]. This reaction is synthetically valuable since it gives

ready access to the anionic complexes [(C5H5)Co{P(O)(OR)2}3]�, a versatile

class of tripodal oxygen ligands. An important feature of these ligands is their

inertness and their high tendency to form complexes with main-group and

transition metals. In addition, they can stabilize a large variety of organometallic

fragments.1,2

A. [Co((C5H5)Co{P(O)(OMe)2}3)2], Co(LOMe)2

3CoCp2þ6HPðOÞðOMeÞ2!½CoððC5H5ÞCofPðOÞðOMeÞ2g3Þ2�þ4HCpþH2

Procedure

Freshly sublimed cobaltocene (25 g, 0.13mol) and 44mL (0.48mol) of dimethyl

phosphite, HP(O)(OMe)2, are added under a nitrogen atmosphere to a 250-mL

round-bottomed Schlenk flask equipped with a magnetic stirring bar. A reflux

condenser equippedwith a pressure relief valve is attached to the Schlenk flask and

the apparatus is purged with dry nitrogen. The reflux condenser need not to be

connected towater cooling; it is used as a splash guard. The oil bath temperature is

set to 100–120�C. After about 1 h, cyclopentadiene that is formed in the reaction

starts refluxing and orange crystals form. After several hours, the brown color of

cobaltocene disappears, but the solution is still dark. The heating is switched off

and the apparatus kept in the oil bath that slowly cools overnight. The air-stable

product forms as large orange crystals that are filtered off, washedwith ethanol and

pentane, and dried in vacuo. The yield is 40 g (42mmol, 94%).

Properties

[Co((C5H5)Co{P(O)(OMe)2}3)2] is thermally stable up to 300�C, paramagnetic,

and soluble in chlorinated solvents and in strong acids.3 The infrared spectrum

(KBr wafer) has medium to strong absorptions at 2980, 2840, 1425, 1175, 1125,

1035, 1005, 835, and 585 cm�1.

B. Na[(C5H5)Co{P(O)(OMe)2}3], NaLOMe

2 ½CoððC5H5ÞCofPðOÞðOMeÞ2g 3Þ2� þ 12NaCNþ 0:5O2 þH2O!4Na½ðC5H5ÞCofPðOÞðOMeÞ2g3� þ 2Na3½CoðCNÞ6� þ 2NaOH


Procedure4

Co(LOMe)2 (40 g, 42mmol) is suspended in 350mL of methanol in a 1-L three-

necked round-bottomed flask equipped with a thermometer and a gas inlet with a

porous frit. The suspension is cooled to �10 to �5�C in an acetone/ice bath.

A vigorous stream of pressurized air is bubbled through the suspension. Sodium

cyanide (14 g, 0.29mol) is then added slowly to the suspension in small portions

over the course of 1 h. The reaction mixture is stirred for one more hour, and then

the solvent is removed using a rotary evaporator and the residue dried in vacuo.

The resulting yellow solid is transferred to a Soxhlet apparatus and the sodium

salt of the tripodal oxygen ligand, NaLOMe, is separated from the sodium salts

Na3[Co(CN)6] and NaCN by extraction with dichloromethane. The extraction

requires several days. Rotary evaporation of the extract followed by drying

in vacuo leaves NaLOMe as bright yellow powder. The yield is 36–38 g

(76–80mmol, 91–96%). The product is pure enough for most purposes. If

necessary, it can be dissolved in twice distilled water, and the solution filtered

through amembrane followed by evaporation at room temperature. Single crystals

of a coordination polymer of NaLOMe have been obtained by slow diffusion of

pentane into a solution of NaLOMe in dry dichloromethane.5

31P{1H} NMR (CDCl3): d 111 (s). 1H NMR (CDCl3): 3.6 (virt. q, 18H,3JHCOP ¼ 11 Hz, OCH3), 5.1 (q, 5H,

3JHCCoP ¼ 0:5 Hz, C5H5). IR (KBr): medium

to strong absorptions at 2835, 1430, 1170, 1080, 835, 750, 580 cm�1.

Properties

The tripodal oxygen ligandNaLOMe is very soluble inwater andmethanol, but only

very slightly soluble in acetone, diethyl ether, and pentane. Freshly precipitated

NaLOMe is soluble in CH2Cl2, but recrystallized solid is not.

The sodium salt of the corresponding ligand [LOEt]�, [(C5H5)Co{P(O)

(OEt)2}3]�, prepared analogously from cobaltocene and HP(O)(OEt)2, crystal-

30. Sodium (h5-Cyclopentadienyl)Tris(Dimethylphosphito-P)Cobaltate(III) 127

lizes from water as 3NaLOEt�4H2O.6 It is much more soluble in organic solvents,

even in pentane, as well as in water. For sterically demanding ligands such as

[LOPh]�, other synthetic routes are available.7 Tripodal oxygen ligands of the type

[(C5R05)M{P(O)(OMe)2}3]

� with M ¼ Rh or Ir and R0 ¼ H, CH3 are accessible

via Michaelis–Arbuzov reactions of Rh(III) and Ir(III) complexes with

trimethylphosphite.8,9

References

1. W. Kl€aui, Angew. Chem. 102, 661–670 (1990); Angew. Chem., Int. Ed. Engl. 29, 627–637 (1990).

2. W.-H. Leung, Q.-F. Zhang, and X.-Y. Yi, Coord. Chem. Rev. 251, 2266–2279 (2007).

3. W. Kl€aui, H. Neukomm, H. Werner, and G. Huttner, Chem. Ber. 110, 2283–2289 (1977).

4. W. Kl€aui, B. Lenders, B. Hessner, and K. Evertz, Organometallics 7, 1357–1363 (1988).

5. W. Kl€aui, D. Matt, F. Balegroune, and D. Grandjean, Acta Crystallogr. C 47, 1614–1617 (1991).

6. W. Kl€aui, A. M€uller, W. Eberspach, R. Boese, and I. Goldberg, J. Am. Chem. Soc. 109, 164–169

(1987).

7. W. Kl€aui, H.-O. Asbahr, G. Schramm, and U. Englert, Chem. Ber. 130, 1223–1229 (1997).

8. W. Kl€aui, H. Otto, W. Eberspach, and E. Buchholz, Chem. Ber. 115, 1922–1933 (1982)

9. M. Scotti, M. Valderrama, P. Campos, and W. Kl€aui, Inorg. Chim. Acta 207, 141–145 (1993).


Chapter Seven

BIO-INSPIRED IRON AND NICKELCOMPLEXES

31. IRON–CYANOCARBONYL COMPLEXES[PPN][Fe(CO)4(CN)] AND [PPN][FeBr(CO)3(CN)2]

Submitted by CHIEN-HONG CHEN* and WEN-FENG LIAW�

Checked by C. MATTHEW WHALEYz and THOMAS B. RAUCHFUSSz

The iron motif of the active-site structures of [NiFe]-hydrogenases isolated from

D. gigas, D. vulgaris, D. fructosovorans, and D. desulfuricans ATCC27774 has

been established as a square pyramidal [Fe(CN)2(CO)(Scys)2] in the reduced state

based on the single-crystal X-ray diffraction and infrared spectroscopy.1–4 The

structural information inspired the bioinorganic/bioorganometallic chemists to

synthesize the model complexes that closely mimic the features of the Ni-A, Ni-B,

Ni-R, and Ni-SIa states of the catalytic cycle of [NiFe]-hydrogenases. Synthetic

approaches to iron–thiolate cyanocarbonyl complexes, to our best knowledge,

involve (i) substitution of the carbon monoxide (CO) with cyanide (CN�) from

iron–thiolate carbonyl complexes, (ii) reaction of iron salt, cyanide salt, and thiolate

under carbon monoxide atmosphere, and (iii) purge of carbon monoxide through the

solution of iron–thiolate–cyano complexes. Based on these synthetic methods, a few

mononuclear iron–thiolate cyanocarbonyl compounds [Fe(CN)2(CO)(S2C6H4-S,S)]2�,5

[(PS3)Fe(CN)(CO)]2� (PS3H3¼ tris(2-phenylthiol)phosphine),6 and [(S3)Fe(CN)2(CO)]2�


*School of Applied Chemistry, Chung Shan Medical University, Taichung, Taiwan.�Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan.zDepartment of Chemistry, University of Illinois at Urbana-Champaign,

Urbana, IL 61801.

129

(S3 ¼ bis(2-mercaptophenyl)sulfide(2�))7 have been reported by Rauchfuss et al.,

Koch et al., and Sellmann et al., respectively.

In addition to the above synthetic strategies, complex [FeIIBr(CO)3(CN)2]�,

obtained from oxidative addition of BrCN to [Fe(CO)4(CN)]� (as shown

below), serves as a useful precursor to synthesize a series of iron(II)–thiolate

cyanocarbonyl complexes [Fe(CN)2(CO)2(S2CR-S,S)]�, [Fe(CN)2(CO)(S2CR-S,

S)]� (R ¼ OEt, NEt2),8cis,cis-[Fe(CO)2(CN)2(CS3-S,S)]

2�, cis-[Fe(CO)2(CN)(S(CH2)2 S(CH2)2S-S,S,S)]

�,9 and [Fe(CO)2(CN)2(pdt)K]� (pdt ¼ 1,3-

propanedithiolate).10

A. BIS(TRIPHENYLPHOSPHORANYLIDENE)AMMONIUM

TETRACARBONYLCYANOFERRATE(0), [PPN][Fe(CO)4(CN)]

FeðCOÞ5 þNaNðSiMe3Þ2 !Na½FeðCNÞðCOÞ4� þOðSiMe3Þ2Na½FeðCNÞðCOÞ4� þ ½PPN�Cl! PPN½FeðCNÞðCOÞ4� þNaCl

& Caution. Fe(CO)5is extremely toxic on account of the high volatility.

All work must be carried out in a well-ventilated fume hood.

Procedure

A 1M THF solution of NaN(SiMe3)2 (5mL) is added dropwise by syringe to the

solution containing Fe(CO)5 (5mmol, 0.65mL) in THF (15mL). The resulting red

solution is stirred for 8 h under N2 atmosphere at room temperature and then

transferred to another 50-mL Schlenk flask loaded with [PPN]Cl (5mmol, 2.87 g)

by cannula under a positive pressure of N2. After stirring for another 8 h at room

temperature, the reaction mixture is filtered through Celite to remove NaCl. The

filtrate is concentrated to 5mL under vacuum, and diethyl ether (40mL) is added

to precipitate the white solid. The white solid is washed with diethyl ether

(15mL) twice and recrystallized by dissolution in THF (10mL) followed by the

addition of hexanes (�30mL) to give the white solid PPN[Fe(CO)4(CN)].11,12

Yield: 0.255 g (68%).

IR (THF): 2112 (vw), 2033 (w), 1924(s) cm�1.

Properties

The white microcrystalline [PPN][Fe(CO)4(CN)] is moderately air sensitive and

should be handled under an inert atmosphere. Complex PPN[Fe(CO)4(CN)]

is readily soluble in THF, acetonitrile, and dichloromethane.

130 Bio-Inspired Iron and Nickel Complexes

B. BIS(TRIPHENYLPHOSPHORANYLIDENE)AMMONIUM

BROMOTRICARBONYLCYANOFERRATE(II),[PPN][FeIIBr(CO)3(CN)2]

PPN½FeðCNÞðCOÞ4� þBrCN! PPN½FeBrðCNÞ2ðCOÞ3� þCO

& Caution. Cyanogen bromide (BrCN) (5Macetonitrile solution or solid)

is corrosive, volatile (fumes in air), and toxic. Use safety gloves and goggles, avoid

inhalations of vapors, and conduct all operations in a well-ventilated hood far

from ignition sources.

Procedure

In a 50-mL Schlenk flask is prepared a stirred solution of PPN[Fe(CO)4(CN)]

(0.5mmol, 0.365 g) in THF (8mL) sealed with a rubber septum. This solution

is treated dropwise with 120 mL of a 5M solution of BrCN (0.6mmol) in MeCN.

The oxidative reaction is immediately indicated by evolution of CO gas. At this

time, a needle is quickly inserted into the rubber septum to release the CO gas.

After 30min of stirring at room temperature, the reaction mixture is filtered

through Celite and hexane (25mL) is added to precipitate the light yellow solid.

Recrystallization by dissolution in THF (10mL) followed by the addition of

diethyl ether (50mL) gives the light yellow solid [PPN][FeBr(CO)3(CN)2]. Yield:

0.277 g (68%).

Anal. Calcd. for C41H30BrFeN3O3P2: C, 60.77; H, 3.73; N, 5.19. Found: C, 60.88;

H, 4.03; N, 4.96. IR (THF): 2139 (vw), 2127 (vw) 2099 (m), 2056 (s), 2035

(m) cm�1. UV–vis (THF, e in cm�1M�1): 325 (1990), 383 (658) nm.

Properties

The light yellow microcrystalline [PPN][FeBr(CO)3(CN)2] is moderately air

sensitive and reacts slowly with air to yield an impure light yellow solid. Complex

[PPN][FeBr(CO)3(CN)2] is readily soluble in organic solvents, such as tetrahy-

drofuran, acetonitrile, and dichloromethane. Although THF solution of complex

[PPN][FeBr(CO)3(CN)2] ismoderately air sensitive at room temperature, it should

be handled under an inert atmosphere.

References

1. (a) A. Volbeda, M.-H. Charon, C. Piras, E. C. Hatchikian, M. Frey, and J. C. Fontecilla-Camps,

Nature 373, 580 (1995). (b) E. Garcin, X. Vernede, E. C. Hatchikian, A. Volbeda,M. Frey, and J. C.

31. Iron–Cyanocarbonyl Complexes[PPN][Fe(CO)4(CN)] and [PPN][FeBr(CO)3(CN)2] 131

Fontecilla-Camps, Structure (London) 7, 557 (1999). (c) R. Happe, W. Rosenboom, A. J. Pierik,

S. P. J. Albracht, and K. A. Bagley, Nature 385, 126 (1997). (d) A. Volbeda, E. Garcin, C. Piras,

A. L. de Lacey, V. M. Fernandez, E. C. Hatchikian, M. Frey, and J. C. Fontecilla-Camps, J. Am.

Chem. Soc. 118, 12989 (1996). (e) A. Volbeda, L. Martin, C. Cavazza, M. Matho, B. W. Faber,

W. Roseboom, S. P. J. Albracht, E. Garcin, M. Rousset, and J. C. Fontecilla-Camps, J. Biol. Inorg.

Chem. 10, 239 (2005).

2. (a) Y. Higuchi, H. Ogata, K. Miki, N. Yasuoka, and T. Yagi, Structure (London) 7, 549 (1999).

(b) Y. Higuchi, T. Yagi, and N. Yasuoka, Structure (London) 5, 1671 (1997). (c) H. Ogata,

Y. Mizoguchi, N. Mizuno, K.Miki, S.-I. Adachi, N. Yasuoka, T. Yagi, O. Yamauchi, S. Hirota, and

Y. Higuchi, J. Am. Chem. Soc. 124, 11628 (2002). (d) S. Foerster, M. Stein, M. Brecht, H. Ogata,

Y. Higuchi, andW. Lubitz, J. Am. Chem. Soc. 125, 83 (2003). (e) H. Ogata, S. Hirota, A. Nakahara,

H. Komori, N. Shibata, T. Kato, K. Kano, and Y. Higuchi, Structure (Cambridge, MA) 13, 1635

(2005).

3. M.Rousset,Y.Montet, B.Guigliarelli, N. Forget,M.Asso, P. Bertrand, J. C. Fontecilla-Camps, and

E. C. Hatchikian, Proc. Natl. Acad. Sci. USA. 95, 11625 (1998).

4. P. M. Matias, C. M. Soares, L. M. Saraiva, R. Coelho, J. Morais, J. Le Gall, and M. A. Carrondo,

J. Biol. Inorg. Chem. 6, 63 (2001).

5. T. B. Rauchfuss, S. M. Contakes, S. C. Hsu, M. A. Reynolds, and S. R. Wilson, J. Am. Chem. Soc.

123, 6933 (2001).

6. H.-F. Hsu, S. A. Koch, C. V. Popescu, and E. M€unck, J. Am. Chem. Soc. 119, 8371 (1997).

7. D. Sellmann, F. Geipel, and F. W. Heinemann, Chem. Eur. J. 8, 958 (2002).

8. W.-F. Liaw, J.-H. Lee, H.-B. Gau, C.-H. Chen, S.-J. Jung, C.-H. Hung, W.-Y. Chen, C.-H. Hu, and

G.-H. Lee, J. Am. Chem. Soc. 124, 1680 (2002).

9. C.-H. Chen, Y.-S. Chang, C.-Y. Yang, T.-N. Chen, C.-M. Lee, and W.-F. Liaw, Dalton Trans. 137

(2004).

10. Z. Li, Y. Ohki, and K. Tatsumi, J. Am. Chem. Soc. 127, 8950 (2005).

11. J. K. Ruff, Inorg. Chem. 8, 86 (1969).

12. S. A. Goldfield and K. N. Raymond, Inorg. Chem. 13, 770 (1974).

32. NICKEL COMPLEXES OF BIS(DIETHYLPHOSPHINOMETHYL)METHYLAMINE

Submitted by DANIEL L. DUBOIS* and MARY RAKOWSKI DUBOIS*

Checked by MARK R. RINGENBERG� and THOMAS B. RAUCHFUSS�

Several types of phosphine ligands that incorporate an amine base have been

synthesized. As illustrated in the selected leading references, studies of the metal

complexes of these ligands have shown that in some cases the base can participate

in small-molecule activation and hydrogen bonding interactions.1–6 In one large

class of mixed phosphine–amine ligands, prepared by Mannich-type reactions, a

*Chemical and Materials Sciences Division, Pacific Northwest National Laboratory,

Richland, WA 99352�Department of Chemistry, University of Illinois at Urbana-Champaign,

Urbana, IL 61801


methylene group separates the two heteroatoms.7 A simple example of this ligand

type is a 1,3-diphosphine with a noncoordinating amine incorporated into the

chelate ring backbone, bis(diethylphosphinomethyl)methylamine (PNP). The

ligand is readily prepared in a high-yield, one-flask procedure over a period of

5–6 h by the reaction of diethylphosphine with aqueous formaldehyde, followed

by addition of methylamine. Complexes of this ligand with several metal ions

have been synthesized and studied.8 The pKa of the protonated pendant amine in

several PNP complexes has been determined to lie in the range of 9–11 in

acetonitrile, depending on the nature of the metal ion and other ligands. The nickel

PNPderivatives are of special interest because of the extensive thermodynamic data

available for these and related nickel diphosphines.9 In the Ni(II) derivative,

[Ni(PNP)2]2þ , the hydride acceptor ability of the metal ion is well matched with

the proton acceptor ability of the pendant base. As a result, the complex reacts

readily with hydrogen (1 atm) to form the heterolytic cleavage product

[HNi(PNHP)PNP]2þ .8a The pendant base in the PNP ligand has been found to

function as a very effective proton relay. Rapid intramolecularM–H/N–H exchange

and intermolecular proton/hydride exchange have been characterized. This contri-

bution describes the procedures for the syntheses of the PNP ligand, Ni(PNP)2, and

its protonation to form [HNi(PNP)2]PF6 and [Ni(PNP)2](BF4)2.

All reactions are performed under an inert atmosphere using standard Schlenk

techniques, and all solvents are dried and degassed by standard procedures before

use. Startingmaterials are reagent-grade commercially available compounds, with

the exception of [Ni(MeCN)6](BF4)2�0.5MeCN,which is prepared by a previously

reported procedure.10

A. BIS(DIETHYLPHOSPHINOMETHYL)METHYLAMINE

2Et2PHþ 2CH2Oþ ½MeNH3�ClþEt3N

!ðEt2PCH2Þ2NMeþ 2H2Oþ ½Et3NH�Cl

Procedure

& Caution. Diethylphosphine is a pyrophoric liquid that must be handled

under rigorously anaerobic conditions.

A 250-mL Schlenk flask is charged with diethylphosphine (2.27 g, 25.2mmol)

and degassed aqueous formaldehyde (37wt%, 1.95mL, 26mmol) in ethanol

(10mL), and the solution is stirred for 30min. A solution of hydrochloride salt

of methylamine (MeNH3Cl, 0.85 g, 12.65mmol) in an ethanol/water solution

(10mL, 3:1 ratio) is added by cannula or syringe to the phosphine solution. Finally,

triethylamine (2mL, 14mmol) is added to deprotonate the methylamine salt. The

32. Nickel Complexes of Bis(Diethylphosphinomethyl)Methylamine 133

mixture is stirred at room temperature for 3 h, and the solvent is then removed

in vacuo. The remaining solid is extractedwith diethyl ether (3� 25mL). Removal

of the solvent from the combined extracts results in isolation of the product as

a colorless liquid. Yield: 2.12 g (71%).

Anal. Calcd. for C11H27NP2: C, 56.15;H, 11.57;N, 5.95; P, 26.33. Found:C, 55.73;

H, 12.22;N, 5.78; P, 25.76. 1H NMR (CD3CN): d 2.62 (d,2JPH ¼ 2:1 Hz, PCH2N);

2.36 (s, NCH3); 1.37 (q,3JPH ¼ 7:8 Hz, PCH2CH3); 1.02 (d of tr,

3JPH ¼ 14:1 Hz,PCH2CH3).

31P NMR (vs. external H3PO4, CD3CN): d �30.99 (s).

Properties

The PNP ligand is an air-sensitive, clear high-boiling liquid that is soluble in most

organic solvents. It can be characterized by its 1H and 31P NMR spectra.

B. BIS(BIS(DIETHYLPHOSPHINOMETHYL)METHYLAMINE)

NICKEL(0), Ni(PNP)2

2 ðEt2PCH2Þ2NMeþNiðCODÞ2 !Ni½ðEt2PCH2Þ2NMe�2 þ 2COD

Procedure

Solid Ni(COD)2 (0.76 g, 2.76mmol) is added to a solution of PNP (2.30 g, 5.

52mmol) in tetrahydrofuran (60mL) that has been cooled to �80�C using a dry

ice/isopropanol bath. The resulting suspension is allowed to warm to room

temperature while stirring over a period of ca. 1 h. Solvent is removed from the

light yellow solution under vacuum to produce the product as a white solid. The

solid is washed with acetonitrile (10mL) and dried again under vacuum to give

an analytically pure product. Yield: 1.2 g (81%).

Anal. Calcd. for C22H54N2P4Ni: C, 49.93; H, 10.28; N, 5.29. Found: C, 49.15; H,

10.36; N, 4.96. 1H NMR (toluene-d8): d 2.42 (s, PCH2N); 2.22 (s, NCH3); 1.31 and

1.65 (m, PCH2CH3); 1.05 (m, PCH2CH3).31P NMR (vs. external H3PO4, toluene-

d8): d 6.60 (s).

Properties

Ni(PNP)2 is awhite, air-sensitive solid that is soluble in nonpolar organic solvents.

C. HYDRIDOBIS(PNP)NICKEL(II) HEXAFLUOROPHOSPHATE

NiððEt2PCH2Þ2NMeÞ2 þNH4PF6 !½HNiððEt2PCH2Þ2NMeÞ2�PF6 þNH3


Procedure

A solution of ammonium hexafluorophosphate (NH4PF6) (0.20g, 1.23mmol) in

absolute ethanol (10mL) is filtered, purged with nitrogen, and added to a solution

of Ni(PNP)2 (0.30g, 0.57mmol) in tetrahydrofuran (30mL) under nitrogen at room

temperature.The resultingyellowsolution is stirred for 0.5 h, and thevolume is reduced

to 10mL. Yellow needles form when this solution is placed in a freezer overnight.

These are collected by filtration and dried under vacuum. Yield: 0.20g (51%).

Anal. Calcd. for C22H55F6N2NiP5: C, 39.13; H, 8.21; N, 4.15. Found: C, 38.05; H,

8.14; N, 4.13. 1H NMR (CD3CN): d 2.70 (s, PCH2N); 2.38 (s, NCH3); 1.62 and

1.72 (m, PCH2CH3); 1.06 (m, PCH2CH3); �14.75 (pentet, 2JPH ¼ 6.3Hz, NiH).31P NMR (CD3CN): d 5.46 (s). IR (Nujol mull): 1933 cm�1 (nNi–H).

Properties

[HNi(PNP)2](PF6) is an air-sensitive yellow crystalline material. It is soluble in

polar organic solvents such as acetonitrile and acetone.

D. BIS(PNP)NICKEL(II) TETRAFLUOROBORATE

½NiðMeCNÞ6�ðBF4Þ2 þ 2 ðEt2PCH2Þ2NMe

!½NiððEt2PCH2Þ2NMeÞ2�ðBF4Þ2 þ 6MeCN

Procedure

Solid [Ni(MeCN)6](BF4)2�0.5MeCN (0.62 g, 1.25mmol) is added to a solution of

PNP (0.59 g, 2.50mmol) in acetonitrile (30mL). The resulting deep red solution is

stirred at room temperature for 1 h. Removal of the solvent under vacuum results in

a red powder, which is washed with hexanes (50mL) and dried in a vacuum. Yield:

0.74 g (74%).

Anal. Calcd. for C22H54N2B2F8NiP4: C, 37.59; H, 7.74; N, 3.99. Found: C, 36.92;

H, 7.69; N, 3.99. 1H NMR (CD3CN): d 2.87 (s, PCH2N); 2.44 (s, NCH3); 2.0 (m,

PCH2CH3); 1.21 (m, PCH2CH3).31P NMR (CD3CN): d 1.70 (s).

Properties

[Ni(PNP)2](BF4)2 is an air-sensitive red solid that is soluble in acetonitrile,

dichloromethane, and acetone. The product tends to undergo slow decomposition

in solution, and recrystallization was not effective. The cyclic voltammogram

32. Nickel Complexes of Bis(Diethylphosphinomethyl)Methylamine 135

using a glassy carbon electrode in acetonitrile with 0.2M Et4NBF4 shows

reversible one-electron reductions at �0.64 (NiII/I) and �1.24V (NiI/0) vs. the

ferrocenium/ferrocene couple. When a CD3CN solution of [Ni(PNP)2](BF4)2(25mg) in an NMR tube is purged with hydrogen at room temperature, a color

change from red to yellow is observed, and the formation of [HNi(PNHP)(PNP)]

(BF4)2 is observed byNMRspectroscopy to be completewithin 10min as shown in

the equation. The hydrogen addition product is characterized by 1H and 31P NMR

spectroscopies. 1H NMR (CD3CN): d 3.10 (br s, PCH2N); 2.78 (br s, NCH3); 1.82

and 1.72 (m PCH2CH3); 1.07 (m, PCH2CH3); �3.35 (br s, average of rapidly

exchanging Ni–H and N–H). 31P NMR (CD3CN): d 7.25 (s).

Acknowledgment

The Pacific Northwest National Laboratory is operated by Battelle for the U.S.

Department of Energy.

References

1. (a) L. Morello, M. J. Ferreira, B. O. Patrick, and M. D. Fryzuk, Inorg. Chem. 47, 1319 (2008).

(b) E. A. MacLachlan, F. M. Hess, B. O. Patrick, andM. D. Fryzuk, J. Am. Chem. Soc. 129, 10895

(2007).

2. (a) T. Li, I. Bergner, F. N. Haque, M. Zimmer-De Iuliis, D. Song, and R. H. Morris,

Organometallics 26, 5940 (2007). (b) T. Li, R. Churlaud, A. J. Lough, K. Abdur-Rashid, and

R. H. Morris, Organometallics 23, 6239 (2004).

3. M. Jimenez-Tenorio,M.D. Palacios,M.C. Puerta, and P.Valerga,Organometallics 24, 3088 (2005).

4. (a) A. Choualeb, A. J. Lough, and D. G. Gusev,Organometallics 26, 3509 (2007). (b) Z. E. Clarke,

P. T. Maragh, T. P. Dasgupta, D. G. Gusev, A. J. Lough, and K. Abdur-Rashid, Organometallics

25, 4113 (2006).

5. (a)B. J. Fullmer, J. Fan,M. Pink, andK.G.Caulton, Inorg.Chem.47, 1865 (2008). (b)M. Ingleson,

J. Fan, M. Pink, J. Tomaszewski, and K. G. Caulton, J. Am. Chem. Soc. 128, 1804 (2006).

6. (a) D. B. Grotjahn, Chem. Eur. J. 11, 7146 (2005). (b) D. B. Grotjahn, V. Miranda-Soto, E. J.

Kragulj, D. A. Lev, G. Erdogan, X. Zeng, and A. L. Cooksy, J. Am. Chem. Soc. 130, 20 (2008).

7. (a) K.Moedritzer and R. R. Irani, J. Org. Chem. 31, 1603–1607 (1966).(b) L. J.Matienzo and S. O.

Grim, in Inorganic Syntheses, F. Basolo, ed.,McGraw-Hill,NewYork, 1976,Vol. 16, pp. 198–199.

8. (a) C. J. Curtis, A. Miedaner, R. Ciancanelli, W. W. Ellis, B. C. Noll, M. Rakowski DuBois, and

D. L. DuBois, Inorg. Chem. 42, 216 (2003). (b) C. J. Curtis, A. Miedaner, J. W. Raebiger, and

D. L. DuBois, Orgnometallics 23, 511 (2004). (c) R. M. Henry, R. K. Shoemaker, R. H. Newell,

G.M. Jacobsen, D. L. DuBois, andM.Rakowski DuBois,Organometallics 24, 2481–2491 (2005).

(d)R.M.Henry, R.K. Shoemaker,D.L.DuBois, andM.RakowskiDuBois, J. Am.Chem. Soc.128,


3002 (2006). (e) G. M. Jacobsen, R. K. Shoemaker, M. Rakowski DuBois, and D. L. DuBois,

Organometallics 26, 4964 (2007). (f) G. M. Jacobsen, J. Yang, B. Twamley, A. D. Wilson,

M. Bullock, M. Rakowski DuBois, and D. L. DuBois, Energy Environ. Sci. 1, 167 (2008).

9. (a) D. E. Berning, B. C. Noll, and D. L. DuBois, J. Am. Chem. Soc. 121, 11432 (1999). (b) C. J.

Curtis, A. Miedaner, W.W. Ellis, and D. L. DuBois, J. Am. Chem. Soc. 124, 1918 (2002). (c) D. E.

Berning, A. Miedaner, C. J. Curtis, B. C. Noll, M. Rakowski DuBois, and D. L. DuBois,

Organometallics 20 1832 (2001).

10. (a) B. J. Hathaway, D. G. Holah, and A. E. Underhill, J. Chem. Soc. 2444 (1962).

33. MONOMERIC IRON(II) COMPLEXES HAVING TWOSTERICALLY HINDERED ARYLTHIOLATES

Submitted by YASUHIRO OHKI,* SHUN OHTA,* and KAZUYUKI TATSUMI*

Checked by LUKE M. DAVIS,� GREGORY S. GIROLAMI,�

AARON M. ROYER,� and THOMAS B. RAUCHFUSS�

Iron–thiolate complexes serve as starting materials for synthetic analogues of

iron–sulfur clusters in proteins. The chemistry of iron(II)–thiolate complexes

generally starts with iron halides (FeX2; X¼Cl, Br, I) and thiolate salts, and such a

reaction usually produces the tetrakis-thiolate complex, [Fe(SR)4]2� (R¼ alkyl or

aryl groups).1,2 Whereas [Fe(SR)4]2� have been extensively used in the prepara-

tion of ferredoxin models,1,2 bis-thiolate complexes of iron, [Fe(SAr)2]n (Ar ¼bulky aryl groups, n ¼ 1 or 2), recently appeared to serve as precursors for

iron–sulfur clusters relevant to the nitrogenase active sites.3 The metal centers in

[Fe(SAr)2]n are coordinatively and electronically unsaturated, and thus they also

serve as potential reaction sites. For instance, Henkel and coworkers have

demonstrated that the iron center in {Fe[SC6H3-2,6-(SiMe3)2]2}2 reacts with

CH3CN or OPEt3 to form {Fe[SC6H3-2,6-(SiMe3)2]2(CH3CN)}2 or Fe[SC6H3-

2,6-(SiMe3)2]2(OPEt3), respectively.4 Herein, we describe a facile synthetic

procedure for iron(II) bis-thiolate complexes having sterically hindered thiolate

groups. The preparation uses bis(trimethylsilylamido)iron(II), which is prepared

by a modification of the procedure of Andersen et al.5

General Considerations

Manipulations are carried out under a nitrogen atmosphere using standard Schlenk

techniques unless otherwise noted. Compounds from commercial suppliers are

used without further purification, but elemental sulfur is crystallized from hot

*Department of Chemistry, Graduate School of Science, and Research Center for Materials Science,

Nagoya University, Nagoya 464-8602, Japan�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801

33. Monomeric Iron(II) Complexes Having Two Sterically Hindered Arylthiolates 137

toluene. Anhydrous FeCl2 is gradually hydrolyzed and oxidized under air and thus

should be stored under an inert atmosphere. Solvents were distilled from so-

dium–benzophenone or purified by passing over columns of a supported copper

catalyst and activated alumina.6

A. BIS[BIS(TRIMETHYLSILYL)AMIDO]IRON(II)

FeCl2 þ 2LiNðSiMe3Þ2 ! Fe½NðSiMe3Þ2�2 þ 2LiCl

Procedure*

According to the procedure of Amonoo-Neizer et al.,7 lithium bis(trimethylsilyl)

amide is prepared from 1,1,1,3,3,3-hexamethyldisilazane (7.0mL, 32mmol) and

a hexane solution of n-butyllithium (1.56M, 21mL, 32mmol) in a 100-mL two-

necked round-bottomed flask with a stirring bar, a three-way stopcock, and

a glass stopper. (Caution: Butyllithium must be handled with care under an inert

atmosphere.) The resultant solution of lithium bis(trimethylsilyl)amide is evapo-

rated until dryness under reduced pressure. The flask with a white solid of LiN

(SiMe3)2 is cooled with an ice bath and 25mL of diethyl ether is carefully added

via syringe to dissolve the solid.� (Caution: Lithium bis(trimethylsilyl)amide

must be handled with care under an inert atmosphere.) The glass stopper is

removed from the flask under nitrogen flow, and FeCl2 (2.05 g, 16mmol) is

quickly added to the flask via funnel. As soon as the addition is completed, the

flask is closed with the glass stopper. The ice bath is removed, and the mixture is

allowed to warm to room temperature with stirring for 12 h. The color of reaction

mixture turns from dark brown to green during the course of the reaction.z Thesolvent is removed under reduced pressure to afford an oily green solid. The flask

is taken into a glovebox, and 20mL of hexane is added to the flask. The dark

green suspension is filtered, and then the dark green solution is transferred to the

left side of the H-shaped glassware shown in Fig. 1.§ A stirring bar is dropped into

* The checkers prefer the preparation of lithium bis(trimethylsilyl)amide by Bradley and Copperthwaite

(Inorg. Synth. 18, 112–120 (1978)). The checkers also found that commercial lithium bis(trimethylsilyl)-

amide solution in hexanes could be used with good results.� The checkers found that the solubility of lithium bis(trimethylsilyl)amide salt in diethyl ether was

limited, and a slurry rather than a solution resulted in this step.z The checkers found that the solution remained dark brown and did not turn green.§ To avoid repeated trips into the glovebox, the checkers instead added dry, deoxygenated hexane to the

reaction vessel through a rubber septum, and then transferred the green solution through a filter cannula

to a round-bottomed Schlenk flask. Several such extractions (in 20-mL portions) were necessary to

obtain a good yield of product. After the solvent was removed from the combined extracts, the product

was distilled from the oily residue under vacuum through a short elbow to a second Schlenk flask.


the green solution, and a glass stopper and a J. Young tap are attached to the

glassware, and then the glassware is taken out from the glovebox. The solvent is

removed under reduced pressure at room temperature, leaving a dark green oil.

After completion of the removal of hexane, the resultant green oil is distilled to

the other side of the glassware at 90–100�C under 0.01mmHg. The J. Young tap

is closed, and the glassware is taken into a glovebox to collect the product. The

product is initially a green oil that solidifies after a few hours at room tempera-

ture. Yield: 4.98 g (84%).

1H NMR (600MHz, C6D6, 0.33M, 299K): d 65.6 (CH3).

Properties

The iron–amide complex is an extremely air- and moisture-sensitive light green

solid and must be stored under a strictly inert atmosphere. Handling in a glovebox

Figure 1. Apparatus for distillation of Fe[N(SiMe3)2]2.


is recommended. It is very soluble in hexane and toluene, while THF binds to the

iron center to produce a three-coordinate THF adduct {(THF)Fe[N(SiMe3)2]2}.8

The product crystallizes as the dimer (mp 36–38�C), but the monomeric form is

dominant in solution at room temperature, as indicated by the 1H NMR spectrum

where a single SiMe3 signal is observed at d 65.6. The monomer–dimer

equilibrium constants have been evaluated by the temperature-dependent 1H

NMR spectra in toluene-d8.8 Other physicochemical properties have been

described.5,8,9

B. 2,6-DI(MESITYL)BENZENETHIOL

2; 4;6-Me3C6H2BrþMg! 2;4;6-Me3C6H2MgBr

1;3-Cl2C6H4 þBuLi! 1;3-Cl2C6H3-2-LiþBuH

1;3-Cl2C6H3-2-Liþ 2 2;4;6-Me3C6H2MgBr

! 1;3-ðmesitylÞ2C6H3Liþ 2MgBrCl

1;3-ðmesitylÞ2C6H3Liþ S! 1;3-ðmesitylÞ2C6H3SLi

1;3-ðmesitylÞ2C6H3SLiþHCl! 1;3-ðmesitylÞ2C6H3SHþLiCl

This compound is reported by Power and coworkers.10 The following method

using 1,3-dichlorobenzene as the precursor is a modification of the procedure of

Saednya and Hart.11 A 500-mL three-necked round-bottomed flask equipped with

a 250-mL pressure-equalized dropping funnel, water-cooled reflux condenser, and

a magnetic stirring bar is connected via a three-way stopcock to the Schlenk line.

After magnesium turnings (3.60 g, 145mmol) are charged into the flask, the entire

apparatus is evacuated and filled with nitrogen three times. Under nitrogen flow,

THF (20mL) is added to the flask, and 1-bromo-2,4,6-trimethylbenzene (22.5mL,

144mmol) and THF (200mL) are charged into the dropping funnel. A THF

solution of 1-bromo-2,4,6-trimethylbenzene is added dropwise to magnesium at

room temperature, and the solution is kept stirring overnight to generate a THF

solution of 2,4,6-Me3C6H2MgBr (A).

A 1000-mL three-necked round-bottomed flask with a stirring bar, a three-way

stopcock, a 200-mL pressure-equalized dropping funnel, and a reflux condenser is

evacuated and filled with nitrogen three times. Under nitrogen flow, 1,3-dichloro-

benzene (8.1mL,69.6mmol) andTHF (200mL)are added to theflaskand ahexane

solution ofn-butyllithium (1.57M, 44mL, 69.6mmol) is charged into the dropping

funnel. The flask is cooled below �78�C with methanol/liquid nitrogen bath, and

the n-butyllithium solution is added dropwise. After being stirred for 1 h below


�78�C, a half of the THF solution of 2,4,6-Me3C6H2MgBr (A) is transferred to the

dropping funnel via cannula under nitrogen, and A is added dropwise to the flask.

Another half of the THF solution ofA is successively added below�78�C, and themixture is stirred at this temperature for 1 h.With stirring, themixture is allowed to

warm to room temperature, and then it is refluxed for 1 h to form a dark brown

solution.After cooling to room temperature, theflask is cooledwith an ice bath, and

sulfur (11.4 g, 355mmol) is added in small portions under nitrogen to give an

orange-brown solution, which is warmed to room temperature and stirred for 3 h.

The flask is again cooled with an ice bath, and LiAlH4 (9.43 g, 236mmol) is added

portionwise. (Caution:Lithiumaluminumhydride shouldbehandledunderan inert

atmosphere.) The mixture is stirred at room temperature for 12 h. The following

procedure iscarriedoutunderair.Theflaskis takenintoawell-ventilatedfumehood,

and a tube is connected from the three-way stopcock to a solvent trap, which is also

connected via another tube to an Erlenmeyer flask containing a dilute aqueous

NaOH solution. A mixture of distilled water and THF (1:1 v/v, 50mL) is added

dropwise to the flask via pipette. (Caution: Residual LiAlH4 reacts vigorouslywith

water.) After completing the gas evolution, distilled water (200mL) is added, and

then conc. HCl (300mL) is carefully added with stirring. The reaction mixture is

filtered, and the resultant solution is concentratedwith rotary evaporator to remove

mostofTHF.Theproduct isextractedwithCH2Cl2(5�100mL)andseparatedfrom

the aqueous layer. After being dried over MgSO4, the solution is evaporated until

dryness.Thecompound is crystallized fromethyl acetate (150mL) togivecolorless

crystals. Yield: 11.0 g (45%).

1H NMR (CDCl3):10 d 7.22 (t, J ¼ 7.6Hz, 1H), 7.02 (d, J ¼ 7.6Hz, 2H), 6.97

(s, 4H), 3.01 (s, 1H), 2.33 (s, 6H), 2.01 (s, 12H). mp 211–214�C.

C. Fe[SC6H3-2,6-(MESITYL)2]2 (MESITYL ¼ C6H2-2,4,6-Me3)

Fe½NðSiMe3Þ2�2 þ 2HSC6H3-2; 6-ðmesitylÞ2! Fe½SC6H3-2; 6-ðmesitylÞ2�2 þ 2HNðSiMe3Þ2

Procedure

This compound is reported by Power and coworkers.10 In a glovebox, a toluene

(5mL) solution of Fe[N(SiMe3)2]2 (0.380 g, 1.01mmol) is charged into a Schlenk

tube. Also in the glovebox, HSC6H3-2,6-(mesityl)2 (0.700g, 2.76mmol) is dissolved

in toluene (5mL) and hexane (10mL), and this solution is added to the iron(II) bis-

amide solution using a pipette. The reaction proceeds smoothly with the formation

of a red suspension. The Schlenk tube is taken out from the glovebox, and then the


solution is stirred for 15min at room temperature. Themixture is heated at 70�C to

lead to a homogeneous solution, and then the Schlenk tube is left standing at room

temperature. Within 1 day, red crystals of product precipitate from the solution.

The Schlenk tube is taken into a glovebox, and the crystals are collected by

filtration. Yield: 0.370 g (49%).

1H NMR (600MHz,C6D6, 297K): d 49.8 (4H,m-C6H3), 42.2 (12H, p-mesityl), 7.0

(24H, o-mesityl), �22.4 (8H, m-mesityl), �24.8 (2H, p-C6H3). UV–vis (cyclo-

hexane, (e, M�1 cm�1)): 287 (sh, 2300) nm. mp 270–272�C.

Properties

The product is an extremely air- and moisture-sensitive red solid that can be stored

for months in the absence of air and moisture.10 It is soluble in

aromatic hydrocarbons. 1H NMR (toluene-d8) and infrared spectrum have been

described.10

Related Compounds

Using only 1 equiv of the thiol affords the monothiolate-monoamide {Fe[SC6H3-

2,6-(mesityl)2]{N(SiMe3)2}. 2,6-Di(xylyl)benzenethiol,�which was reported by

Luening and Baumgartner,12 gives analogous complex Fe[SC6H3-2,6-(xylyl)2]2,

which is less soluble than the mesityl derivative.131H NMR (600MHz, C6D6,

297K): d 49.2 (4H, m-C6H3 or p-xylyl), 6.7 (24H, –CH3), �22.2 (8H, m-xylyl),

�26.1 (2H þ 4H, p-C6H3 and m-C6H3 or p-xylyl). UV–vis (cyclohexane, lmax,

nm (e, M�1 cm�1)): 452 (300), 395 (300), 287 (sh, 750). meff (Evans method,

297K): 5.1 mB. Anal. Calcd. for C44H42FeS2: C, 76.50; H, 6.13; S, 9.28. Found: C,

76.57; H, 5.91; S, 9.41. mp 295–297�C.

References

1. R. H. Holm, Acc. Chem. Res. 10, 427–434 (1977).

2. P. V. Rao and R. H. Holm, Chem. Rev. 104, 527–560 (2004).

3. Y. Ohki, Y. Ikagawa, and K. Tatsumi, J. Am. Chem. Soc. 129, 10457–10465 (2007).

4. R. Hauptmann, R. Klib J. Schneider, and G. Henkel, Z. Anorg. Allg. Chem. 624, 1927–1936

(1998).

� 1H NMR (C6D6): d 7.10 (t, J¼ 7.4Hz, 2H), 7.04 (d, J¼ 7.4Hz, 4H), 6.96 (t, J¼ 7.6Hz, 1H), 6.81 (d,

J ¼ 7.6Hz, 2H), 3.06 (s, 1H), 2.08 (s, 12H). 1H NMR (CDCl3): d 7.25 (obscured CDCl3, 1H), 7.20

(t, J ¼ 7.6Hz, 2H), 7.14 (d, J ¼ 7.6Hz, 4H), 7.04 (d, J ¼ 7.6Hz, 2H), 2.96 (s, 1H), 2.05 (s, 12H). mp

114–116�C.


5. R. A. Andersen, K. Faegri Jr., J. C. Green, A. Haaland,M. F. Lappert,W.-P. Leung, and K. Rypdal,

Inorg. Chem. 27, 1782–1786 (1988)


15, 1518–1520 (1996).

7. E. H. Amonoo-Neizer, R. A. Shaw, D. O. Skovlin, and B. C. Smith, Inorg. Synth. 8, 19–22

(1966).

8. M. M. Olmstead, P. P. Power, and S. C. Shoner, Inorg. Chem. 30, 2547–2551 (1991).

9. D. J. Evans, D. L. Hughes, and J. Silver, Inorg. Chem. 36, 747–748 (1997).

10. J. J. Ellison, K. Ruhlandt-Senge, and P. P. Power, Angew. Chem., Int. Ed. Engl. 33, 1178–1180

(1994).

11. A. Saednya and H. Hart, Synthesis 1455–1458 (1996).

12. U. Luening and H. Baumgartner, Synlett 8, 571–572 (1993).

13. S. Ohta, Y. Ohki, Y. Ikagawa, R. Suizu, and K. Tatsumi, J. Organomet. Chem. 692, 4792–4799

(2007).

34. (1,3-PROPANEDITHIOLATO)-HEXACARBONYLDIIRONAND CYANIDE DERIVATIVES

Submitted by AMANDA E. MACK* and THOMAS B. RAUCHFUSS*

Checked by KOSHI OHNISHI,� YASUHIRO OHKI,� and

KAZUYUKI TATSUMI�

Dithiolatodiiron hexacarbonyl complexes were first reported by Reihlen and

then Hieber and are generally prepared from the reaction of thiols with iron

carbonyls.1 Fe2(S2CnH2n)(CO)6 derived from ethanedithiol (n ¼ 2) and 1,3-

propanedithiol (n ¼ 3) were prepared by Huttner and coworkers by the reaction

of Fe3(CO)12 with the respective dithiols.2 Lotz prepared the propanedithiolatex

from Fe(CO)5 and 1,3-dithiane (S2(CH2)3).3 Extensive work has been reported

for the related methanethiolates Fe2(SCH3)2(CO)6, which exist in solution as two

isomers, depending on the relative orientation of the methyl groups.4 The

ethanedithiolate is more amenable to analysis because it exists exclusively as

a single isomer of C2v symmetry. The propanedithiolate is structurally more

complex owing to the folded conformation of the Fe2S2C3 core.2 In solution, the

two conformers rapidly interconvert.

*Department of Chemistry, University of Illinois at Urbana-Champaign,

Urbana, IL 61801�Department of Chemistry, Graduate School of Science, Nagoya University,

Nagoya 464-8602, Japan

34. (1,3-Propanedithiolato)-Hexacarbonyldiiron and Cyanide Derivatives 143

The hexacarbonyls Fe2(S2CnH2n)(CO)6 readily undergo substitution by cya-

nide,5,6 phosphines,7 isocyanides,8N-heterocyclic carbenes,9 and other donor

ligands. With monodentate ligands, disubstitution proceeds efficiently to afford

derivatives Fe2(S2CnH2n)(CO)4L2 (L¼RNC,NHC) and, for cyanide, [Fe2(S2CnH2n)

(CO)4(CN)2]2�.10 Monosubstitution can be complicated by competitive disubstitu-

tion reactions, but this problemcan be circumvented by in situ generation of the labile

acetonitrile complex, which undergoes rapid monosubstitution as illustrated in a

procedure given below.10 In contrast to the parent hexacarbonyls, substituted

derivatives undergo many electrophilic reactions, including protonation to afford

hydrides. The hydrides are efficient catalysts for hydrogen evolution.11

& Caution. Dithiols are malodorous as well as irritants to the eyes

and skin.

A. (1,3-PROPANEDITHIOLATO)HEXACARBONYLDIIRON

2 Fe3ðCOÞ12 þ 6C3H6ðSHÞ2 ! 3 Fe2ðS2C3H6ÞðCOÞ6 þ 3H2 þ 6CO

Procedure

A 250-mL round-bottomed Schlenk flask containing a Teflon-covered magnetic

stirring bar is chargedwith benzene (20mL). The benzene is spargedwith nitrogen

for a few minutes and then 1,3 propanedithiol (0.79mL, 7.95mmol) and solid

Fe3(CO)12 (3.2 g, 6.36mmol) are added. The flask is fitted with a reflux condenser,

and the mixture is heated at vigorous reflux under nitrogen for 1.5–2 h. During the

reaction, the solution changes the color from green to red. The reaction solution

was allowed to cool to room temperature, and the contents were evaporated to an

oily red solid. The solid is dissolved in 5mL of hexane and chromatographed on

a 40 cm � 2 cm column, eluting with hexanes. The main band, which is red, is

collected and evaporated to dryness, leaving red-orange crystals. The yield is

2.26 g (92%).*

* The checkers used a 1.5-h reflux time to give a 69% yield


Anal. Calcd. for C9H6Fe2O6S2: C, 28.00; H, 1.55; N, 0.00. Found: C, 28.03;

H, 1.37; N, 0.12. IR (hexanes): 2076, 2035, 2006, 1993, 1982 cm�1. 1H NMR

(acetone-d6): d 2.26 (t, 4H), 1.86 (m, 2H).

Properties

The product is air stable for extended periods. It is soluble in a variety of organic

solvents. The product is best characterized by its infrared spectrum. The same

procedure can be used to prepare ethanedithiolate. IR (hexanes): 2077, 2037,

2007,1995, 1984 cm�1. 1H NMR (CDCl3): d 2.38 (s, 4H).

B. TETRAETHYLAMMONIUM (1,3-PROPANEDITHIOLATO)

TETRACARBONYLDIIRON DICYANIDE

Fe2ðS2C3H6ÞðCOÞ6þ2NEt4CN!ðNEt4Þ2½Fe2ðS2C3H6ÞðCNÞ2ðCOÞ4�þ2CO

Procedure

A 100-mL round-bottomed Schlenk flask containing a magnetic stirring bar is

charged with Fe2(S2C3H6)(CO)6 (0.56 g, 1.45mmol, 1 equiv) andMeCN (20mL).

The red-orange solution is treated with a solution of NEt4CN (0.45 g, 2.9mmol)

in 10mL acetonitrile and stirred for 1 h. The resulting dark red solution was

evaporated to dryness, and the remaining red solid was washed with 3 � 5mL

hexanes and dried in vacuum. The yield is 0.86 g (95%).

Anal. Calcd. for C24H46Fe2N4O4S2: C, 45.72; H, 7.35; N, 8.89; S, 10.17; Fe, 17.72.

Found: C, 45.97; H, 7.33; N, 8.98; S, 10.34; Fe, 17.59. 1H NMR (CD3CN): d 1.21(t, 24H, NCH2CH3), 1.67 (m, 2H, CH2CH2CH2), 1.85 (t, 4H, SCH2), 3.18 (q, 16H,

NCH2CH3). IR (MeCN): 2072, 2036, 1961, 1913, 1879 cm�1.

Properties

The compound is soluble in water, methanol, and acetonitrile. Both the solid and

especially its solutions are unstable in air. (NEt4)2[Fe2(S2C3H6)(CN)2(CO)4] is

unreactive toward other ligands, including cyanide. It has been characterized

crystallographically.5

The reaction of the ethanedithiolate Fe2(S2C2H4)(CO)6 with NEt4CN under the

same conditions afforded (NEt4)2[Fe2(S2C3H6)(CN)2(CO)4].1H NMR (CD3OD):

d 3.28 (q, 16H, NCH2CH3), 1.96 (s, 4H, SCH2), 1.21 (t, 24H, NCH2CH3).

IR (MeCN): 2078, 2029, 1961, 1917, 1880 cm�1.


C. TETRAETHYLAMMONIUM (1,3-PROPANEDITHIOLATO)

PENTACARBONYLDIIRON CYANIDE

Fe2ðS2C3H6ÞðCOÞ6 þMe3NOþMeCN

! Fe2ðS2C3H6ÞðCOÞ5ðMeCNÞþNMe3 þCO2

Fe2ðS2C3H6ÞðCOÞ5ðMeCNÞþNEt4CN

!NEt4½Fe2ðS2C3H6ÞðCNÞðCOÞ5� þMeCN

Procedure

A solution of 0.25 g (0.65mmol) of Fe2(S2C3H6)(CO)6 in 10mL of MeCN is

treated with a solution of 0.049 g (0.65mmol) of Me3NO in 10mL of MeCN. The

infrared spectrum of the resulting dark brown solution indicates formation of

the acetonitrile adduct [IR(MeCN): nCO ¼ 2050, 2040, 1990, 1962, 1932 cm�1].

The dark brown solution is then cooled to�40�C and is treated with a solution of

0.10 g (0.65mmol) of NEt4CN in 10mL of MeCN. The solution changes to dark

red within minutes. The cooling bath is removed and the reaction mixture is

allowed to warm to room temperature. The dark red solution is evaporated to

dryness under vacuum. The resulting red oil is extracted into 10mL of THF, and

this extract is filtered. The filtrate is reduced to approximately 1mL, and the

product is precipitated upon addition of 20mL of hexanes and washed with

additional hexanes to leave an oily residue. The crude red product is dried under

vacuum for 1 h, leaving a red solid. Yield: 0.29 g (87%).

Anal. Calcd. for C17H26Fe2N2O5S2: C, 39.71; H, 5.10; N, 5.45; S, 12.47. Found: C,

39.43; H, 5.06; N, 5.43; S, 12.47. IR (THF): nCN¼ 2091; nCO¼ 2030, 1975, 1955,

1941, 1914 cm�1. 1H NMR(CD3CN): d 3.16 (q, 8H,NCH2CH3), 2.18 and 1.77 (br,

6H, S(CH2)3S), 1.19 (t, 12H,NCH2CH3).

Properties

The compound is soluble in water, methanol, and acetonitrile. Both the solid and

especially its solutions are unstable in air. The product is most easily obtained as a

glassy solid, but single crystals can be obtained by recrystallization from

THF–hexanes. The salt has been characterized crystallographically.10 The aceto-

nitrile complex is stable for minutes in acetonitrile solution. It undergoes substi-

tution by a variety of ligands under mild conditions.10


References

1. (a) H. Reihlen, A. Gruhl, and G. v. Hessling, J. Liebigs Ann. Chem. 472, 268–287 (1929).

(b) W. Hieber and P. Spacu, Z. Anorg. Allg. Chem. 233, 852–864 (1937).

2. A. Winter, L. Zsolnai, and G. Huttner, Z. Naturforsch. 37b, 1430–1436 (1982).

3. S. Lotz, P. H. van Rooyan, and M. M. Dyk, Organometallics 6, 499–505 (1987).

4. (a) K. Fauvel, R. Mathieu, and R. Poilblanc, Inorg. Chem. 15, 976–978 (1976). (b) J. J. Bonnet,

R. Mathieu, R. Poilblanc, and J. A. Ibers, J. Am. Chem. Soc. 101, 7487–7496 (1979).

5. M. Schmidt, S. M. Contakes, and T. B. Rauchfuss, J. Am. Chem. Soc. 121, 9736–9737 (1999).

6. (a) E. J. Lyon, I. P. Georgakaki, J. H. Reibenspies, andM. Y. Darensbourg, Angew. Chem., Int. Ed.

38, 3178–3180 (1999). (b) A. Le Cloirec, S. C. Davies, D. J. Evans, D. L. Hughes, C. J. Pickett,

S. P. Best, and S. Borg, Chem Commun. 2285–2286 (1999).

7. P. Li, M. Wang, C. He, G. Li, X. Liu, C. Chen, B. Akermark, and L. Sun, Eur. J. Inorg. Chem.

2506–2513 (2005).

8. (a) J. L. Nehring and D. M. Heinekey, Inorg. Chem. 42, 4288–4292 (2003). (b) C. A. Boyke, T. B.

Rauchfuss, S. R. Wilson, M.-M. Rohmer, and M. B�enard, J. Am. Chem. Soc. 126, 15151–15160

(2004).

9. (a) J.-F. Capon, S. El Hassnaoui, F. Gloaguen, P. Schollhammer, and J. Talarmin,Organometallics

24, 2020–2022 (2005). (b) J. W. Tye, J. Lee, H. W. Wang, R. Mejia-Rodriguez, J. H. Reibenspies,

M. B. Hall, and M. Y. Darensbourg, Inorg. Chem. 44, 5550–5552 (2005).

10. F. Gloaguen, J. D. Lawrence, M. Schmidt, S. R. Wilson, and T. B. Rauchfuss, J. Am. Chem. Soc.

123, 12518–12527 (2001).

11. F. Gloaguen, J. D. Lawrence, and T. B. Rauchfuss, J. Am. Chem. Soc. 123, 9476–9477 (2001).


Chapter Eight

RUTHENIUM COMPLEXES

35. RUTHENIUM(II)-CHLORIDO COMPLEXES OFDIMETHYLSULFOXIDE

Submitted by IOANNIS BRATSOS* and ENZO ALESSIO*

Checked by MARK E. RINGENBERG� and THOMAS B. RAUCHFUSS�

The two ruthenium(II)-chlorido-dimethylsulfoxide (dmso) complexes cis- and

trans-[RuCl2(dmso)4], and in particular the cis isomer, have a rich chemistry

and are widely used as precursors in inorganic synthesis.1 Depending on the

conditions, both the dmso and the chlorido ligands can be selectively replaced

by mono- or polydentate ligands. The preparation of cis-[RuCl2(dmso)4] was

first reported in 1971 by James et al., by treatment of hydrated RuCl3 with H2 in

warm dimethylsulfoxide (DMSO).2 This procedure is however inconvenient for

routine syntheses. Two years later, Wilkinson and coworkers reported an

improved and simpler synthetic procedure for cis-[RuCl2(dmso)4], in which

hydrated RuCl3 was simply refluxed in DMSO for 5min and the product was

eventually precipitated by addition of acetone after concentration.3 In 1975, the

geometry of the complex was unambiguously established as cis by X-ray

crystallography.4 The complex can be more correctly formulated as cis,fac-

[RuCl2(dmso-S)3(dmso-O)], since three of the sulfoxide ligands are bound in


*Dipartimento di Scienze Chimiche, Universit�a di Trieste, 34127 Trieste, Italy.�Department of Chemistry, University of Illinois at Urbana-Champaign,

Urbana, IL 61801.

148

facial geometry through sulfur (dmso-S), while the fourth and most labile is

bound through oxygen (dmso-O).

Despite the wide use of cis-[RuCl2(dmso)4] as Ru(II) precursor, its apparently

simple and straightforward synthetic procedure can be problematic, possibly

because the reaction mechanism is largely unknown, the nature of hydrated

RuCl3 is uncertain and depends on the commercial source (even though it is

typically formulated as RuCl3�3H2O, it is actually a mixture of Ru(III) and

Ru(IV) species and the number of water molecules is variable), and the DMSO

solvent can contain variable amounts of impurities (in primis water and di-

methylsulfide). The influence of these factors in the successful synthesis remains,

to date, unclear but definitely they contribute to the variability of Wilkinson’s

procedure.

On the other hand, the synthetic procedures leading to the trans isomer (in

which all four sulfoxides are bound through sulfur) are uncontested. Our group

reported first, in 1988, the synthesis of trans-[RuCl2(dmso-S)4] by photochemi-

cal isomerization of the cis isomer in DMSO solution at room temperature

and established its structure by X-ray analysis.5 The same compound was

also obtained by electrochemical reduction of the Ru(III) intermediate hydro-

gen trans-bis(dimethylsulfoxide)tetrachloridoruthenate(III) ([(dmso)2H]trans-

[Ru(dmso-S)2Cl4]).6 In 1990, James and coworkers reported a third alternative

synthesis of trans-[RuCl2(dmso-S)4], by treatment of hydrated RuCl3 in DMSO

at 70�C.7 The last two preparations established that the trans complex is a

kinetic intermediate in the reduction of hydrated RuCl3 in DMSO to the

thermodynamically most stable cis isomer (trans to cis isomerization occurs

quantitatively in warm DMSO).

Ru

SCl

Me2S

Me2S

ClO

OO

O

SMe2

Ru

SCl

Cl

Me2S

SMe2

S

OO

O O

heat

hv

cis-[RuCl2(dmso)4] trans-[RuCl2(dmso-S)4]

RuCl3 xH2Oheat

DMSO

Me2 Me2

Me2

Herein, we present an improved, convenient, and highly reproducible

synthesis of cis-[RuCl2(dmso)4], as well as the routine synthesis of the trans

isomer, trans-[RuCl2(dmso-S)4]. The first procedure is a modified and im-

proved version of that given in the literature.3 It involves a preliminary, but

essential, step: the reflux of commercial hydrated RuCl3 in ethanol. This

procedure, compared to that originally established byWilkinson and coworkers,

besides being well reproducible, also avoids the tedious concentration of the hot

DMSO solution.

35. Ruthenium(II)-Chlorido Complexes of Dimethylsulfoxide 149

A. cis-DICHLORIDOTETRAKIS(DIMETHYLSULFOXIDE)

RUTHENIUM(II)

Procedure

A100-mL round-bottomed flask equippedwith a condenser and amagnetic stirring

bar is charged with RuCl3�xH2O (2.00 g, 7.65mmol assuming x¼ 3) partially

dissolved in ethanol (50mL). The stirred mixture is heated to reflux for 3 h, during

which time the starting material dissolves completely, and the color of the solution

changes from brown to deep green. Ethanol is removed with rotary evaporator

(filtration on paper should be performed prior to concentration if undissolved black

material is found at the bottomof the flask). The remaining dark green oily residue is

dissolved in DMSO (8mL) in a 100-mL round-bottomed flask. The flask is

connected to a condenser, and the mixture is placed in an oil bath preheated at

150�C and magnetically stirred for 2 h. Within the first minutes, the solution

becomesmore fluid and its color changes from green to bright orange (typical of Ru

(III)-chlorido-dmso intermediates). After 1 h, formation of the product as a yellow

solid is observed.After cooling to room temperature,moreproduct precipitates.The

formation of the bright yellow microcrystalline solid is completed by addition of

acetone (60mL). After allowing the slurry to stand at room temperature for 1 day,

the product is collected by filtration, thoroughly washed with acetone (3� 5mL),

and dried in vacuum. Yield: 2.77 g (5.72mmol, 75%).

1H NMR (D2O): d 3.46 (dmso-S), 3.44 (dmso-S), 3.32 (dmso-S), 2.80 (dmso-O).

IR (KBr, nSO): 1122, 1110, and 1095 (dmso-S), 921 cm�1 (dmso-O).

Properties

The product is light, air, and moisture stable for very long periods of time at room

temperature. It is well soluble in water, nitromethane, chloroform, and dichlor-

omethane, and partially soluble in methanol and DMSO. In aqueous solution, this

compound releases within minutes the O-bonded dmso. Thus, evenwhen recorded

immediately after dissolution, the 1H NMR spectrum in D2O displays, in addition

to the signals of the parent compound, three new intense singlets in the dmso-S

region (d¼ 3.49, 3.47, 3.39) for the aqua species cis,fac-[RuCl2(dmso-S)3(H2O)],

together with the resonance of free dmso (d¼ 2.71). The singlets of the parent

compound disappear withinminutes and the spectrum of the resulting aqua species

changes very slowly (hours) due to the dissociation of one chlorido ligand. Partial

hydrolysis also occurs in commercial CDCl3 and CD2Cl2 and the corresponding

NMR spectra are always the sum of those of the parent compound (equally intense

singlets at d¼ 3.50, 3.43, 3.33 for dmso-S, and at d¼ 2.73 for dmso-O) and of the

aqua species (equally intense singlets at d¼ 3.53, 3.47, 3.41 for dmso-S, and at

150 Ruthenium Complexes

d¼ 2.62 for free dmso). The extent of the hydrolysis depends on the concentration

of the complex and on the content of adventitious water. This feature is often

confusing, andwrongly suggests the presence of by-products in the original sample.

Solid-state IR spectroscopy is highly diagnostic for establishing the binding

mode of dmso through the frequency of the SO stretching mode: nSO for dmso-S is

higher (range 1080–1150 cm�1), and for dmso-O is lower (range 890–950 cm�1),

compared to that of the free ligand at 1055 cm�1. Thus, the IR spectrum of

cis-[RuCl2(dmso)4] (see above) presents strong SO stretching bands in both ranges

(however, in the solid state, their number and frequencies depend slightly upon

the conformations of the coordinated sulfoxides).5

B. trans-DICHLORIDOTETRAKIS(DIMETHYLSULFOXIDE)

RUTHENIUM(II)

Procedure

A 100-mL round-bottomed flask equipped with a condenser and a magnetic stirring

bar is charged with cis-[RuCl2(dmso)4] (2.50 g, 5.16mmol) suspended in DMSO

(40mL).Themixture is stirred andwarmed to 80�Cuntil complete dissolution of the

yellow solid (ca. 30min). The yellow solution is transferred into a water-cooled

photoreactor equipped with 125-W mercury lamp and is irradiated for 4 h. During

this time, the temperature is maintained at ca. 25�C. The same reaction can also be

performed under direct sunlight, but requires typically at least 6 h. The deep yellow

microcrystalline precipitate is filtered, washed with DMSO (2mL) and acetone

(3� 5mL), and vacuumdried at room temperature.Yield: 2.00 g (4.13mmol, 80%).

Properties

The compound is deep yellow solid, which is light, air, andmoisture stable for long

periods of time at room temperature. It is, like the cis isomer, soluble in water but

dissolution takes a fewminutes. It is also soluble in nitromethane, chloroform, and

dichloromethane, but considerably less soluble in DMSO. It is very labile in

aqueous solution. The 1H NMR spectrum in D2O displays two equally intense

singlets at d 3.35 (dmso-S) and 2.71 (free dmso). The downfield resonance is

assigned to the equivalent S-bonded sulfoxides in the diaqua species trans,cis,cis-

[RuCl2(dmso-S)2(H2O)2], which forms from the parent compound immediately

after dissolution upon release of two adjacent dimethylsulfoxide molecules. In

CDCl3, the1H NMR spectrum shows two singlets in 3:1 ratio at d 3.41 (dmso-S)

and 2.62 (free dmso), consistent with the dissociation of only one dmso-S

and formation of a symmetrical five-coordinate RuCl2(dmso-S)3 species. The

solid-state IR spectrum is simpler than that of the cis isomer and shows a single SO

stretching band at 1080 cm�1 for the four equivalent dmso-S ligands.

35. Ruthenium(II)-Chlorido Complexes of Dimethylsulfoxide 151

References

1. E. Alessio, Chem. Rev. 104, 4203 (2004).

2. B. R. James, E. Ochiai, and G.I. Rempel, Inorg. Nucl. Chem. Lett. 7, 781 (1971).

3. I. P. Evans, A. Spencer, and G. Wilkinson, J. Chem. Soc., Dalton Trans. 204 (1973).

4. A. Mercer and J. Trotter, J. Chem. Soc., Dalton Trans. 2480 (1975).

5. E. Alessio, G.Mestroni, G. Nardin,W.M.Attia,M. Calligaris, G. Sava, and S. Zorzet, Inorg. Chem.

27, 4099 (1988).

6. E.Alessio,G. Balducci,M.Calligaris, G.Costa,W.M.Attia, andG.Mestroni, Inorg. Chem. 30, 609

(1991).

7. J. S. Jaswal, S. J. Rettig, and B. R. James, Can. J. Chem. 68, 1808 (1990).

36. SYNTHESIS OF CHLORIDE-FREE RUTHENIUM(II)HEXAAQUA TOSYLATE, [Ru(H2O)6]tos2

Submitted by CELINE FELLAY* and GABOR LAURENCZY*

Checked by STEVEN M. BISCHOF� and ROY A. PERIANA�

The general starting material for the synthesis of water-soluble Ru compounds

is the commercially available RuCl3�xH2O, but many organometallic processes

and fundamental kinetic studies and its equilibrium behavior require halogen-free

Ru(II) complexes, such as [Ru(H2O)6]2þ.1 The complex [Ru(H2O)6]

2þ has only

water in the first coordination sphere, with weakly coordinating anions such as

p-toluenesulfonate (tos). Furthermore, [Ru(H2O)6]tos2 can be used as specific

‘‘source’’ to synthesize Ru catalysts where a high yield and a halogen-free

compound are needed. Here, we report the modified synthesis2 of the

[Ru(H2O)6]tos2 complex. The synthesis entails reduction of RuO4 with Pb, which

is chosen for its mild redox potential. Although an excess is used, most of the Pb

is removed/reused. The small amount of Pb2þ generated in this reaction is

precipitated as the very sparingly soluble PbSO4 (Ks¼ 1.82� 10�8M2). Thus,

the use of Pb does not present major disposal issue.

General Remarks

All manipulations are performed under argon atmosphere using standard Schlenk

techniques. All solutions are degassed with argon prior to use.

*Institut des Sciences et Ing�enierie Chimiques, Ecole Polytechnique F�ed�erale de Lausanne (EPFL),

CH-1015 Lausanne, Switzerland.�The Scripps Energy Laboratories, The Scripps Research Institute, Jupiter, FL 33458.


& Caution RuO4 is a toxic gas; therefore, the setup should be placed in

a well-ventilated fume hood.

Procedure

(a) Synthesis of RuO2.

3.0 g (ca. 12mmol) RuCl3�xH2O (Johnson Matthey, 40–43% ruthenium,

x� 2) is added to a solution of 24.6 g NaOH (0.6mol) dissolved in 123mL

H2O. The reaction mixture is then heated to 60�C for 30min and stirred

overnight at room temperature. The black product is collected by filtration,

washed with H2O until the filtrate is chloride free (negative AgNO3 test),

and dried in air. Yield: 2.1 g of the oxide containing some chloride and

water.

(b) Preparation of [Ru(H2O)6]tos2.

RuO2 ��!NaIO4

H2SO4

RuO4 ��!Pb

H2SiF6 ½RuðH2OÞ6�2 þ ��!ion exchange ½RuðH2OÞ6�ðtosÞ2

Prepare the following four solutions:

Solution A: 10.5 g (0.049mol) NaIO4 in H2O (85mL).

Solution B: 20 g Pb (ca. 0.1mol, approx. particle diameter is 0.5mm), previously

activated by stirring in 28mL 50% HNO3,* in a 1M solution of H2SiF6

(140mL).

Solution C: 3 g Pb (ca. 15mmol), previously activated in 4.3mL of 50% HNO3,

in 30mL H2SiF6 1M.

Solution D: ice-cold 50% H2SO4 solution (42mL).

The first three solutions are placed in the setup described in Fig. 1, except for

solution D. Solutions A and B are magnetically stirred, and A is placed in an ice

bath. Thewhole setup is degassed with argon during 1 h. The sulfuric acid solution

D is degassed separately. The dropping funnel is filled with this solution. The flow

of argon is maintained at a slow rate, a few bubbles per second. Then, the 2.1 g

RuO2 is added to A and dropwise addition of H2SO4 into A is started, while

maintaining the argon stream. The addition requires about 30min.

* Pb is stirred for 15min in HNO3 50%, filtered, washed with water until neutrality, and used

immediately.

36. Synthesis of Chloride-Free Ruthenium(II) Hexaaqua Tosylate 153

Once the addition of solutionD is complete, the ice bath is removed fromA, and the

reaction mixture is allowed to reach room temperature. Stirring is continued for 2

days under an argon stream and in the dark.

After 2 days, solutionA is black, indicating an incomplete reaction. B is dark red

indicative of product. ToflaskB is added Pb (5 g, ca. 15mmol), activated in 7mLof

50% HNO3. To flask A is added NaIO4 (1.26 g, 0.006mol). Flask A is then heated

at 40�C for 1 day.

Although solution A remains black, solution B is filtered under argon. H2SO4

2M (42mL, degassed with argon) is added to the filtrate to precipitate PbSO4, the

solution is stirred for 30min, decanted for 15min, and filtered.

A 30-mm diameter chromatography column is charged with a Dowex 50 Hþ

resin (40 g). The resin is first washed with degassed H2O. Then, the solution

containing [Ru(H2O)6]2þ is added dropwise using a dropping funnel. A purple

band is formed on top of the column. The column is then washed with H2O

(125mL), with a 0.1M tosylic acid (Htos) solution (300mL),* and thenwith 1.2M

Figure 1. Apparatus for generation and reduction of RuO4. The apparatus consists of a

500-mL three-necked flask (A), a 500-mL two-necked flask (B), a 250-mL bubbler (C), and

a 100-mL dropping funnel (D). Joints were sealed with parafilm, no grease was used, and

interconnections between flasks were made with plastic tubing. Before addition of the

solution, thewhole setup is placed under vacuum to check for leaks. The distance betweenA

and B should be as short as possible. The entire apparatus is protected from light (the fume

hood window was carefully covered by black paper).

* The checkers observed a reddish band when eluting with the dilute Htos solution. The band was

discarded.


Htos (300mL). The purple band is eluted with the 1.2MHtos solution. The band

is collected and concentrated under vacuum at 40�C until precipitation occurs

(ca. 120mL), which requires ca. 9 h. The solution is left overnight at 0�C to

allow for more complete precipitation. The solution is then filtered under argon,

and the pink fluffy needles are washed with degassed ethyl acetate (2� 20mL)

and then diethyl ether (2� 20mL) and dried in vacuo. The filtrate is concen-

trated at 40�C, and a second fraction is obtained and worked up. Yield (two

fractions): 3.3 g (50%, based on RuCl3�xH2O). The apparatus was cleaned as

usual, and the ruthenium deposit traces were eliminated by a 5% sodium

hypochlorite solution.

Anal. Calcd. for C14H26O12S2Ru: C, 30.5; H, 4.7. Found: C, 31.0; H, 4.8. UV–vis:

534 and 394 nm with the molar absorbances e¼ 12M�1 cm�1 and 15M�1 cm�1,

respectively (no traces could be detected of Ru3þ at 390 nm, e ¼ 30M�1 cm�1).

The concentrated aqueous solution gives a singlet signal in the 17O NMR spectrum

at�196 ppm from the reference water resonance at 0 ppm (no other signals could

be detected in the region from þ 50 to�200 ppm, no traces of [Ru(H2O)6]3þ were

detected at þ 35 ppm).3

Properties

[Ru(H2O)6](tos)2 is a pink solid with a high solubility in water. It is soluble

in dmso, but insoluble in diethyl ether. The resulting aqueous solution of

[Ru(H2O)6]2þ is readily oxidized to yellow [Ru(H2O)6]

3þ . [Ru(H2O)6](tos)2was successfully used for kinetic studies,4 synthesis,5 and catalysis.6

Acknowledgments

We thank the Swiss National Science Foundation and EPFL for financial support.

References

1. M. Loy and G. Laurenczy, Helv. Chim. Acta 88, 557 (2005).

2. (a) P. Bernhard, H. B. B€urgi, J. Hauser, H. Lehmann, and A. Ludi, Inorg. Chem. 21, 3936

(1982).

(b) P. Bernhard, M. Biner, and A. Ludi, Polyhedron 9, 1095 (1990).

3. N. Aebischer, G. Laurenczy, A. Ludi, and A. E. Merbach, Inorg. Chem. 32, 2810 (1993).

4. (a) P. V. Grundler, G. Laurenczy, and A. E. Merbach, Helv. Chim. Acta 84, 2854

(2001).

(b) G. Laurenczy, F. Joo, and L. N�adasdi, Inorg. Chem. 39, 5083 (2000).

5. (a) G. Laurenczy, L. Helm, A. Ludi, and A. E. Merbach, Inorg. Chim. Acta 189, 131 (1991).

(b) G. Laurenczy and A. E. Merbach, Chem. Commun. 187 (1993).

6. C. Fellay, P. J. Dyson, and G. Laurenczy, Angew. Chem., Int. Ed. 47, 3966 (2008).

36. Synthesis of Chloride-Free Ruthenium(II) Hexaaqua Tosylate 155

37. BASIC RUTHENIUM ACETATE AND MIXEDVALENCE DERIVATIVES

Submitted by JOHN C. GOELTZ,* STARLA D. GLOVER,*

JAMES HAUK,* and CLIFFORD P. KUBIAK*


Oxo-centered triruthenium clusters have been the subject of considerable study

because of their extensive redox chemistry.1–9 The triruthenium clusters with a

carbonyl ligand are particularly interesting because infrared lineshape analysis

of the n(CO) bands in various oxidation states illuminates previously unknown

details of rates of very fast intramolecular electron transfer.10–14 The [Ru3(m3-O)(m-OAc)6L3]

þ unit is a versatile building block for extended structures

because each metal center has a single exchangeable coordination site (Fig. 1).

Unlike the corresponding oxo-centered iron triangles,15 ligands coordinated to the

three exchangeable external sites of the Ru3 clusters are typically not labile when

the ligands are pyridines, isocyanides, NO (for RuIII), or CO (forRuII), allowing for

facile preparation and purification of variously substituted mixed ligand com-

plexes. Here, we report the synthesis of the Ru3III,III,III cationic oxo-centered

cluster with three aquo ligands, the facile reduction of the cluster to a neutral

Ru3III,III,II core with either aquo or pyridyl ligands, and introduction of a single

carbon monoxide at the formally RuII site. The latter molecule with one carbonyl

and two semilabile aquo ligands is a very stable and versatile startingmaterial, and

its use in preparing many new complexes is limited only by creativity in bridging

and terminal ligand substitution.7,16,17

A. TRI(AQUO)-m3-OXO-HEXAKIS(m-ACETATE)TRIRUTHENIUMACETATE, [Ru3(m3-O)(m-OAc)6(H2O)3]OAc

3 RuCl3ðH3OÞ3 þ 9 NaOAc!½Ru3ðm3-OÞðm-OAcÞ6ðH2OÞ3�½OAc�þ 2 HOAcþ 9 NaClþ 5 H2O

Procedure

A 500-mL round-bottomed flask is charged with RuCl3�3H2O (6 g, 22.9mmol),

NaOAc�3H2O (12 g, 88.2mmol), a stir bar, 150mL absolute ethanol, and 150mL

*Department ofChemistry andBiochemistry,UniversityofCalifornia at SanDiego,SanDiego,CA92093.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.


glacial acetic acid. The brown solution is refluxed for 4 h, during which time the

color changes to deep forest green. The reaction is cooled to room temperature,

and filtered through filter paper, discarding the insoluble materials. The solvent is

removed from the filtrate in vacuo. The resulting oily residue is taken up in a

minimum of methanol (ca. 25mL) and precipitated with an excess of acetone

(ca. 500mL). The resulting green powder is collected on a glass frit and washed

with 3� 30mL acetone and 1� 30mL diethyl ether. Yield: 9 g. A single recrys-

tallization does not remove all of the sodium acetate, but the product is sufficiently

pure for syntheses in parts B and C.

High-purity samples are obtained by dissolving the green powder in aminimum

amount (ca. 100mg in 10mL) of premixed 1:1 methanol/acetone, cooling to

�40�C (MeCN/dry-ice bath), and collecting the precipitate from the cold solution

by filtration. This recrystallization is repeated two to three times.

Anal. Calcd. for C14H29O19Ru3 (Ru3(m3-O)(m-OAc)6(H2O)3]OAc�H2O):C, 20.90;

H, 3.63. Found:C, 20.76;H, 3.24. IR (KBr pellet): n(OAc)¼ 1572 (sh), 1524, 1427

(sh), 1385 cm�1.

Properties

The product is air stable and soluble in polar organic solvents.

B. TRI(PYRIDINE)-m3-OXO-HEXAKIS(m-ACETATE)TRIRUTHENIUM, Ru3(m3-O)(m-OAc)6(py)3

½Ru3ðm3-OÞðm-OAcÞ6ðMeOHÞ3�OAcþ 3 pyþ 0:25 N2H4

!Ru3ðm3-OÞðm-OAcÞ6ðpyÞ3 þ 0:25 N2 þ 3MeOHþHOAc

O

Ru

O O

Ru

O

ORuO

O

O O

O

OO

O

L

L

L

Figure 1. Structure of basic ruthenium acetate framework.

37. Basic Ruthenium Acetate and Mixed Valence Derivatives 157

Procedure9

In a 100-mL round-bottomed flask equipped with a magnetic stir bar,

[Ru3O(OAc)6(H2O)3]OAc (0.8 g, 0.1mmol) is dissolved in 50mL of methanol

followed by 3mL of pyridine. The reactionmixturewas heated at reflux for 5min

and then allowed to cool to 0�C on an ice bath. To the cooled solution, about 5mL

of 95% N2H4 was added dropwise by pipette until the formation of a green

precipitate was seen in the blue green solution. The suspension is then stirred for

15min before the addition of two further drops of hydrazine. After five additional

minutes, the green solid was collected by filtration and washed with 10mL of

water, 10mL of methanol, and 3� 10mL of diethyl ether. After air dying, the

solid was dried in vacuo. Yield: 0.42 g (46%).

Anal. Calcd. for C27H33N3O13Ru3: C, 35.60; H, 3.65; N, 4.61. Found: C, 34.50; H,

3.35; N, 4.45. 1H NMR (CDCl3): d�OAc 2.09 (18H); d py 7.75 (6H), 7.99 (3H),

9.44 (6H). UV–vis (e in M�1 cm�1): lmax 249.0 (18,000), 402.1 (8400), and 919.9

(6800) nm. IR (KBr pellet): 1558, 1486, 1419, 1344, 764, 689, 631 cm�1. Cyclic

voltammetry (1mM in MeCN with 0.1M Bu4NPF6, vs. Fc/Fcþ ): �450mV

(oxidation).

Properties

The product is air stable and soluble in organic solvents such as CH2Cl2 and

MeCN, but insoluble in methanol.

C. DI(AQUO)-m3-OXO-HEXAKIS(m-ACETATE)CARBONYL-TRIRUTHENIUM(II, III, III), Ru3(m3-O)(m-OAc)6(CO)(H2O)2

½Ru3ðm3-OÞðm-OAcÞ6ðMeOHÞ3�OAcþCOþNaBH4 þ 3 H2O!Ru3ðm3-OÞðm-OAcÞ6ðCOÞðH2OÞ2 þNaBðOAcÞH3 þ 3MeOHþ 0:5 H2

& Caution. The third procedure involves pressurizing a flask with carbon

monoxide. This should be performed carefully in a well-ventilated fume hood.

Procedure

A portion of [Ru3(m3-O)(m-OAc)6(H2O)3]OAc (4.16 g, 5.3mmol) from step A is

dissolved in about 100mL of dry methanol in an oven-dried 500-mL Schlenk

flask. This solution is sparged with N2 for 15min with magnetic stirring, then

while still flushing with N2, NaBH4 (0.262 g, 6.89mmol, 1.3 equiv) is added in

one portion. The flask is fitted with a sturdy rubber septum and secured tightly


with tape or wire. The solution effervesces and changes from dark green to light

green. The Schlenk flask inlet is connected to a CO source, and the flask is

pressurized to ca. 1.3 atm of CO. The reaction is stirred at this pressure of CO for

12–15 h. Longer reaction times lead to lower yields. When the reaction is

complete, the solution has assumed the deep purple color of the product. The

reaction vessel is flushed with nitrogen, and the reaction mixture is then

evaporated on a rotary evaporator at 40�C.*

The product is purified by chromatography on a silica gel column (1.5 cm

� 20 cm) packedwith CHCl3. About 0.5 g of the product is dissolved in about 5mL

of 3: 1 CHCl3/MeOH and loaded on the column. The product is eluted with 96%

CHCl3/4% MeOH. The first band, containing the product, is deep purple in color.

A second teal-colored band elutes after the product. The purple product is collected

and the solvent is removed to yield a dark purple powder. Typical yield is 40–45%.

Anal. Calcd. for C15H30O18Ru3 (Ru3(m3-O)(m-OAc)6(CO)(H2O)2�2 MeOH):

C, 22.48; H, 3.77. Found: C, 22.87; H, 3.88. IR (KBr pellet, cm�1): n(CO)¼ 1962;

n(OAc)¼ 1613, 1576, 1422. 1H NMR (D2O): d�OAc 1.93 (12H), 1.74 (6H).

UV–vis (e in M�1 cm�1): 549 (2900), 379 (1700), 288 (4800) nm.

Properties

The product is soluble in water, but is only sparingly soluble in chloroform and

methylene chloride. It can be solubilized in halogenated solvents by the addition

of small amounts (ca. 5% by volume) ofMeOH, EtOH,MeCN, or THF.Otherwise,

the ancillary ligands are assumed to be H2O or MeOH, depending on the sample’s

history. These coordinated water/methanol ligands are easily substituted over the

course of several hours at room temperature. A variety of pyridyl ligands,10

isocyanides,18 and more complex ligands have been installed.16,17

The product is diamagnetic and is formulated as RuIIRuIIIRuIII with the

carbonyl ligand bound to RuII. It is very stable in air both as a solid and in

solution but is best stored as a solid in a sealed vial in a freezer if long-term storage

(i.e., months to years) is needed. UV light (l <�250 nm) induces CO dissociation.

Degraded product can be repurified by chromatography on silica.

References

1. A. Spencer and G. Wilkinson, J. Chem. Soc., Dalton Trans. 8, 786–792 (1974).

2. S. Uemura, A. Spencer, and G. Wilkinson, J. Chem. Soc., Dalton Trans. 23, 2565–2571 (1973).

* The reaction also proceeds if it is sparged with CO before the addition of the borohydride, but yields

were found to be lower. The checkers used a Fischer–Porter bottle, whichwas operationally convenient,

but gave no improvement in yield.

37. Basic Ruthenium Acetate and Mixed Valence Derivatives 159

3. A. Spencer and G. Wilkinson, J. Chem. Soc., Dalton Trans. 14, 1570–1577 (1972).

4. F. A. Cotton, J. G. Norman, A. Spencer, and G. Wilkinson, J. Chem. Soc. Chem. Commun. 16,

967–968 (1971).

5. J. A. Baumann, S. T.Wilson, D. J., Salmon, P. L. Hood, and T. J.Meyer, J. Am. Chem. Soc. 101, 11,

2916–2920 (1979).

6. H. Uehara, M. Abe, Y. Hisaeda, K. Uosaki, and Y. Sasaki, Chem. Lett. 35, 10, 1178–1179

(2006).

7. M. Abe, Y. Sasaki, Y., Yamada, K. Tsukahara, S. Yano, and T. Ito, Inorg. Chem. 34, 17, 4490–4498

(1995).

8. A. Sato, M. Abe, T. Inomata, T. Kondo, S. Ye, K. Uosaki, and Y. Sasaki, Phys. Chem. Chem. Phys.

3, 16, 3420–3426 (2001).

9. J. A. Baumann, D. J. Salmon, S. T. Wilson, T. J. Meyer, and W. E. Hatfield, Inorg. Chem. 17, 12,

3342–3350 (2002).

10. T. Ito, T. Hamaguchi, H. Nagino, T. Yamaguchi, H. Kido, I. S. Zavarine, T. Richmond, J.,

Washington, and C. P. Kubiak, J. Am. Chem. Soc. 121, 19, 4625–4632 (1999).

11. T. Ito, T. Hamaguchi, H. Nagino, T. Yamaguchi, J. Washington, and C. P. Kubiak, Science 277,

5326, 660–663 (1997).

12. C. H. Londergan and C. P. Kubiak, Chem. Eur. J. 9, 24, 5962–5969 (2003).

13. J. C. Salsman, C. P. Kubiak, and T. Ito, J. Am. Chem. Soc. 127, 8, 2382–2383 (2005).

14. J. C. Goeltz, C. J. Hanson, and C. P. Kubiak, Inorg. Chem. 48, 11, 4763–4767 (2009).

15. F. E. Sowrey, C. J. MacDonald, and R. D. Cannon, J. Chem. Soc., Faraday Trans. 94, 11,

1571–1574 (1998).

16. B. J. Lear and C. P. Kubiak, J. Phys. Chem. B 111, 24, 6766–6771 (2007).

17. B. J. Lear, and C. P. Kubiak, Inorg. Chem. 45, 18, 7041–7043 (2006).

18. K. Ota, H. Sasaki, T. Matsui, T. Hamaguchi, T. Yamaguchi, T. Ito, H. Kido, and C. P. Kubiak,

Inorg. Chem. 38, 18, 4070–4078 (1999).

38. DI-m-CHLORO(ETHYLBENZOATE)DIRUTHENIUM(II),[(h6-etb)RuCl2]2

Submitted by ABRAHA HABTEMARIAM,*

SOLEDAD BETANZOS-LARA,* and PETER J. SADLER*

Checked by ESTER TRUFAN� and RICHARD D. ADAMS�

Dimeric arene complexes of the type [(h6-arene)RuCl2]2 are common starting

materials in ruthenium chemistry. These Ru(II) dimers containing mono- and

disubstituted arenes are generally prepared by reaction of RuCl3�3H2O with the

appropriate 1,3- or 1,4-cyclohexadiene. The Ru(III) is reduced to Ru(II) with

concurrent aromatization and p-binding of the cyclohexadiene.1,2 Coordinated

arenes containing electron-withdrawing groups such as esters are thermally labile,

and this property has been exploited synthetically for a variety of applications.3–7

*Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.�Department of Chemistry, University of South Carolina, Columbia, SC.


Although some cyclohexadienes are readily available, many can be obtained

easily by Birch reduction, which involves reduction with solutions of alkali metals

in liquid ammonia, a source of solvated electrons, in the presence of alcohol as a

proton source.8–10 In previous years, the Bouveault–Blanc procedure, which uses

sodium metal and alcohol in liquid ammonia, was frequently employed for direct

reduction of aromatic esters; however, it gave rise mainly to the corresponding

substituted benzoic acid.11 Rabideau et al. reported a modified procedure;12

however, in our hands, this resulted in the reduction of the ester function to give

benzoic acid. We have found that the Birch reduction of benzoic acid, followed

by esterification, is an efficient procedure for the preparation of the corresponding

1,4-dihydro compound prior to the coordination of the arene to produce functio-

nalized dimeric ruthenium–arene complexes.13

A. ETHYL-1,4-CYCLOHEXADIENE-3-CARBOXYLATE

& Caution. Ammonia is a potent irritant to the respiratory system and the

eyes. Metallic sodium reacts violently with water liberating highly flammable

gases. An efficient fume hood must be used.

C6H5CO2EtþH2 !C6H7CO2Et

Procedure

Liquid ammonia (600mL) is condensed into a 2-L three-necked round-bottomed

flask equipped with a dry ice/acetone condenser fitted with a calcium chloride

guard tube, and a mechanical stirrer. The flask is kept at 198 K by a cooling bath

(dry ice/acetone mixture). Benzoic acid (38.65 g, 0.32mol) is placed into a 250-

mL round-bottomed flask and dry and freshly distilled ethanol (150mL) is added.

This solution is transferred into the ammonia solution bymeans of a cannula. Small

pieces of sodiummetal (21.7 g, 0.94mol), which are kept under hexane, are added

to the reaction mixture with rapid stirring over a period of 30min. The reaction

mixture turned dark blue and is stirred further for about 25min. ThenNH4Cl (35 g)

is added. The color is dischargedwithin about 2min. The reactionmixture is stirred

for a further hour, the cold bath is removed, and the ammonia left to evaporate

underN2flowand allowed to reach ambient temperature overnight. Thewhite solid

in the vessel is dissolved in chilled distilled water (500mL), which is then acidified

by a slow and careful addition of conc. hydrochloric acid (ca. 11M) to pH 1–2.*

* Owing to the presence of residual ammonia, addition of water may result in a very basic solution

requiring that a large quantity of strong acid be added to reach the desired pH. Failure to properly acidify

the solution may result in a highly reduced yield.

38. Di-m-Chloro(Ethylbenzoate)Diruthenium(II) 161

This solution is placed in a separatory funnel and extracted (3� 150mL) with

ether. The ether layers are combined andwashedwith brine solution and dried over

anhydrous magnesium sulfate, filtered, and the solvent taken off on a rotary

evaporator to leave a yellowish oily residue (yield 35.0 g). Vacuum distillation of

the crude oil using a setup containing a fractionating column (13 cm long, diameter

0.5 cm; 0.08mmHg/350–355 K) resulted in a clear colorless oil. 1H NMR

(CDCl3): d 5.94 (m, 2H), 5.87 (m, 2H), 3.80 (m, 1H), 2.72 (m, 2H). 1,4-

Dihydrobenzoic acid (35.0 g) is heated under reflux in dry ethanol (250mL) and

98% sulfuric acid (17mL) under nitrogen for 18 h. The pH is then adjusted to ca. 8

(monitored using an indicator paper) by the addition of a large excess of sodium

hydroxide (25% w/v). This solution is placed onto a separating funnel, and brine

(100mL) is added to improve the layer separation. The solution is extracted with

dichloromethane (3� 150mL). The organic layers are combined, dried over

anhydrous magnesium sulfate, filtered, and the solvent removed on a rotary

evaporator to give an oil. Vacuum distillation of the product using the setup

described above resulted in a clear colorless oil [0.5mmHg/319–321 K].

1H NMR(CDCl3): d 6.86 (m, 2H), 6.30 (m, 2H), 5.82 (m, 3H), 4.30 (q, 2H), 1.32

(t, 3H).*

B. CHLORO(ETHYLBENZOATE)DIRUTHENIUM(II), [(h6-etb)

RuCl2]2

2 C6H7CO2Etþ 2 RuCl3 � ðH2OÞx !½ðC6H5CO2EtÞRuCl2�2 þH2

þ 2 HClþ xH2O

Procedure

RuCl3�xH2O (1.01 g, 4.85mmol assuming x¼ 3) and ethyl-1,4-cyclohexadiene-3-

carboylate (3.69 g, 24.28mmol) are stirred under reflux in dry ethanol (150mL)

under nitrogen for 10 h.�Themixture is allowed to cool to ambient temperature, the

precipitate is filtered off, and the solid washed with minimal cold ethanol and then

with diethyl ether. The solid is collected by filtration and dried in air (1.09 g, 88%).

Anal. Calcd. for C18H20Cl4O4Ru2: C, 33.55; H, 3.13. Found: C, 33.53; H, 3.02.1H

NMR (CDCl3): d 6.39 (d, 2H, J¼ 6Hz), 5.91 (t, 1H, J¼ 6Hz), 5.71 (t, 2H,

* Small amounts of benzoic acid and ethanol were detected by 1H NMRanalysis. The checkers distilled

at 0.25mmHg/309K.� The reaction time is sufficient to produce the dimer in good quality and quantity; prolonged reaction

times (up to 16 h) give the same result.


J¼ 6Hz), 4.40 (q, 2H, J¼ 7Hz), 1.35 (t, 3H, J¼ 7Hz). ESI-MS: 608.9 [Mþ -Cl],304.9 [Mþ -Cl]. mp decomp. ca. 238�C. IR (n, cm�1): 3080 (CAr¼CAr), 1722

(C¼O).

Properties

The [(h6-etb)RuCl2]2 is a fine brick red powder that is readily soluble in chloroform

and dichloromethane to afford yellow solutions that turn green after about 3 h

accompanied by a black precipitate, indicating decomposition. It is also very

soluble in DMF, methanol, and water to give dark yellow solutions, but sparingly

soluble in acetone, ethanol, and ethyl acetate, and insoluble in hexane and other

nonpolar solvents. It can be easily recrystallized from an aqueous solution to give

crystals suitable for X-ray diffraction.

Acknowledgments

We thank WPRS/ORSAS (UK) and CONACyT (Mexico) for studentship support

for S.B.-L.

References

1. R. A. Zelonka and M. C. Baird, Can. J. Chem., 50, 3063–3072 (1972).

2. M. A. Bennett and A. K. Smith, J. Chem. Soc., Dalton Trans., 233–241 (1974).

3. K. Umezawa-Vizzini and T. Randall Lee, Organometallics, 22, 3066–3076 (2003).

4. Y. Miyaki, T. Onishi, S. Ogoshi, and H. Kurosawa, J. Organomet. Chem., 616, 135–139 (2000).

5. B. Therrien, T. R.Ward,M. Pilkington, C. Hoffmann, F. Gilardoni, and J.Weber,Organometallics,

17, 330–337 (1998).

6. A.M.Hayes,D. J.Morris,G. J. Clarkson, andM.Wills, J. Am.Chem. Soc., 127, 7318–7319 (2005).

7. T. J. Geldbach, M. R. H. Brown, R. Scopelliti, and P. J. Dyson, J. Organomet. Chem., 690,

5055–5065 (2005).

8. A. J. Birch and G. S. Rao,in: Advances in Organic Chemistry, Methods and Results, Taylor, E. C.

Ed., Wiley-Interscience, New York, 1972, pp. 1–65.

9. R. G. Harvey, Synthesis, 2, 161–172 (1970).

10. P. W. Rabideau, Tetrahedron, 45, 1579–1603 (1989).

11. H. O. House,inModern Synthetic Reactions, 2nd ed.,W. A. Benjamin, Inc.,Meno Park, CA, 1972,

pp. 150–151.

12. P. W. Rabideau, D. L. Huser, and S. J. Nyikos, Tetrahedron Lett., 21, 1401–1404 (1980).

13. M. Melchart, A. Habtemariam, O. Novakova, S. A. Moggach, F. P. A. Fabbiani, S. Parsons, V.

Brabec, and P. J. Sadler, Inorg. Chem., 46, 8950–8962 (2007).

38. Di-m-Chloro(Ethylbenzoate)Diruthenium(II) 163

Chapter Nine

IRIDIUM COMPLEXES

39. THE DIPHOSPHINE tfepma AND ITS DIIRIDIUMCOMPLEX Ir2

0,II(tfepma)3Cl2

Submitted by THOMAS S. TEETS,* TIMOTHY R. COOK,* and

DANIEL G. NOCERA*

Checked by JOHN C. GOELTZ� and CLIFFORD P. KUBIAK�

The two-electron mixed-valence compound, Ir2(tfepma)3Cl2 (tfepma¼CH3N(P[OCH2CF3]2)2), is synthesized by stoichiometric reaction of the

chloro-1,5-cyclooctadieneiridium(I) dimer with tfepma. The bimetallic complex

undergoes the unusual reaction of reversible addition of hydrogen across a single

metal–metal bond.1–3 The complex contains a trigonal bipyramidal iridium(0)

center and a square planar iridium(II) center. The iridium(II) center is coordina-

tively unsaturated and binds two-electron ligands. The bridging diphosphazane

tfepma ligand is especially effective in supporting two-electron mixed valency of

bimetallic cores comprising late transition metals.4–6 tfepma is prepared in two

steps from commercial precursors. The first synthetic step affords MeN(PCl2)2from the reaction of methylamine hydrochloride with phosphorus trichloride.

Previous reports did not utilize an exogenous base,7,8 though we have found that in

the presence of pyridine the reaction time can be shortened from 10 days to several

hours, and yields are improved. The second synthetic step involves the reaction of

MeN(PCl2)2 with a slight excess of 2,2,2-trifluoroethanol and triethylamine in


*Department of Chemistry, Massachusetts Institute of Technology, Cambridge,

MA 02139-4307.�Department of Chemistry, University of California at San Diego, San Diego, CA 61801.

164

diethyl ether to furnish tfepma.9,10 The phosphine precursors are each prepared

over the course of 2 dayswhereas the iridiumcomplex described here is prepared in

a few hours.

General

Except when noted, all manipulations were carried out in exclusion of air and

moisture using glovebox and Schlenk techniques. 1,1,2,2-Tetrachloroethane was

dried over anhydrous calcium chloride and filtered prior to use. Other solvents

were dried by passing through an alumina column and sparged with argon.

Methylamine hydrochloride was heated under vacuum at 125�C for 12 h prior

to use. 2,2,2-Trifluoroethanol was dried by storage over molecular sieves, and

triethylamine was dried by distillation from CaH2 under a nitrogen atmosphere.

Anhydrous pyridine and phosphorus trichloride were used as received.

A. BIS(DICHLOROPHOSPHINO)METHYLAMINE

MeNH3Clþ 2 PCl3 þ 3 C5H5N!MeNðPCl2Þ2 þ 3 C5H5NHCl

Procedure

In a nitrogen-filled glovebox, methylamine hydrochloride (41 g, 0.61mol) is

transferred to a 2–L two-necked round-bottomed flask equipped with a large

Teflon-coated stir bar. The flask is fitted with a reflux condenser fitted with a

nitrogen inlet and a rubber septum and removed from the glovebox.* Phosphorus

trichloride (250 g, 1.8mol) is added via cannula to give a colorless suspension,

which is stirred and diluted with 250mL of 1,1,2,2-tetrachloroethane. Pyridine

(147mL, 1.82mmol) is then added via cannula to give a light pink mixture, which

is heated to reflux for 16 h to give an orange, biphasic mixture. The mixture is

allowed to cool to room temperature, causing a large amount of colorless

pyridinium hydrochloride to precipitate from solution. The mixture is stirred at

ca. 65�C until most of the solid redissolves, at which time 350mL of hexanes is

added via cannula. The resulting solution is stirred for 5min and allowed to

separate into two distinct layers. The top hexane layer is cannula transferred to a

1-L Schlenk flask. The extraction process is repeated with an additional 200mL of

hexanes and the top layer is combined with the first extract. The cloudy solution

that results is evaporated. (Caution: Cold trap will contain PCl3.) The remaining

crude product is purified by vacuum distillation at reduced pressure (60�C, 1 Torr)to remove any remaining 1,1,2,2-tetrachloroethane (first fraction). In the glovebox,

* The checkers weighed the hydrochloride quickly in air with no significant loss of yield. The reaction

was conducted on 25% scale.

39. The Diphosphine tfepma and its Diiridium Complex Ir20,II(tfepma)3Cl2 165

the distilled product (second fraction) is filtered through glass wool to remove

residual pyridinium hydrochloride, giving the product as a clear, colorless, low-

viscosity oil. The yield is 84 g (60%).

Anal.Calcd. for CH3Cl4NP2: C, 5.16; H, 1.30; N, 6.02. Found: C, 5.41; H, 1.27; N,

5.85.

Properties

Bis(dichlorophosphino)methylamine is a colorless oil that reacts rapidly with

water; it is best stored frozen in a glovebox freezer. The 31P{1H}NMR spectrum in

CDCl3 shows a singlet at 160.5 ppm vs. 85% D3PO4, and the 1H NMR in CDCl3consists of a triplet at 3.30 ppm (JH–P¼ 3Hz).

B. BIS(BIS(TRIFLUOROETHOXY)PHOSPHINO)METHYLAMINE

(tfepma)

MeNðPCl2Þ2 þ 4 CF3CH2OHþ 4 Et3N!MeN½PðOCH2CF3Þ2�2þ 4 Et3NHCl

Procedure

In the glovebox, bis(dichlorophosphino)methylamine (22.3 g, 95.8mmol) is dis-

solved in 700mL of diethyl ether in a 2-L two-necked round-bottomed flask with a

Teflon-coated stir bar to give a clear, colorless solution. A flow adaptor is connected

to one neck and a pressure-equalizing addition funnel and septum are connected to

the other. The apparatus is removed from the glovebox and placed under a positive

pressure of N2 through the flow adaptor. Triethylamine (60mL, 430mmol) is added

via syringe to the addition funnel and added dropwise to the reactionmixture. If the

triethylamine is not sufficiently dried, the reaction mixture becomes cloudy owing

to a white precipitate, which forms from the hydrolysis of the P–Cl bond. The

apparatus is placed in a cooling bath of dry ice/acetone and allowed to reach�78�C.Once cooled, trifluoroethanol (30.9mL, 431mmol) is added via syringe to the

addition funnel and then added dropwise to the solution over 15min. As the

trifluoroethanol is added, awhite solid forms and results in a thickwhite suspension

upon completion of the addition. The suspension is removed from the cooling bath

and stirred overnight at room temperature. Thewhite solid is collected on a large frit

and washed thoroughly with diethyl ether (4� 500mL). The diethyl ether is

removed via a rotary evaporator to yield a slightly cloudy, colorless oil. The

product is purified by vacuum distillation to remove excess trifluoroethanol,

triethylamine, and residual triethylammonium chloride. At 0.35Torr, the product

fraction distills at a temperature of 60–65�C. The yield is 41 g (88%).

166 Iridium Complexes

Anal. Calcd. for C9H11F12NO4P2: C, 22.19; H, 2.28; N, 2.88. Found: C, 22.31; H,

2.32; N, 2.75.

Properties

The ligand tfepma, also a colorless oil, is air andmoisture stable and can be handled

under ambient atmosphere at room temperature. The 31P{1H} NMR spectrum in

CDCl3 shows a singlet at 149.8 ppm vs. 85% D3PO4. The1H NMR in CDCl3

consists of a multiplet centered at 4.10 ppm (8H), and a triplet at 2.69 ppm

(JH–P¼ 3.9Hz, 3H).

C. Ir20,II(tfepma)3Cl2

½IrðcodÞCl�2þ3MeN½PðOCH2CF3Þ2�2! Ir2Cl2fMeN½PðOCH2CF3Þ2�2g3þ2 cod

Procedure

In the glovebox, an orange solution forms in a 100-mL Schlenk flask upon the

addition of chloro-1,5-cyclooctadieneiridium(I) dimer11 (1.00 g, 1.49mmol) to

50mL of toluene. tfepma (2.25 g, 4.62mmol) is dissolved in 5mL of toluene and

added dropwise to the [Ir(cod)Cl]2 solution, prompting a color change to dark red.

Outside the glovebox, the flask is fitted with a reflux condenser and nitrogen inlet,

and the solution is heated to reflux for 1 h under nitrogen, during which time a dark

greenish-black solid forms and precipitates. Upon cooling to room temperature,

the product settles. The dark yellow supernatant is removed by cannula filtration.

The product is washed with 3� 15mL pentane and dried in vacuo to give a dark

green powder. The yield is 1.84 g (64.6%).

Anal. Calcd. for C27H33F36N3O12P6Ir2Cl2: C, 16.92; H, 1.74; N, 2.19. Found: C,

17.01; H, 1.71; N, 2.16.

Properties

Ir2(tfepma)3Cl2 is isolated as a microcrystalline dark green solid that can be stored

indefinitely in a drybox. The solid dissolves in acetonitrile to give a yellow-orange

solution. The 31P{1H} NMR spectrum of the compound in CD3CN consists of

several broad features. Five distinct resonances are observed: a broad singlet at

33.0 ppm, a broad triplet at 47.8 ppm, and three multiplets centered at 64.5, 70.2,

and 94.0 ppm. The 1H NMR of the iridium compound in CD3CN shows two

distinct methyl peaks: a triplet at 2.58 ppm (JH–P¼ 10.5Hz, 3H) and a broad

singlet at 2.77 ppm (6H). Signals for the methylene protons of the trifluoroethoxy

groups appear as a set of overlapping, broad resonances between 4.0 and 5.5 ppm.

39. The Diphosphine tfepma and its Diiridium Complex Ir20,II(tfepma)3Cl2 167

References

1. A. F. Heyduk and D. G. Nocera, Chem. Commun. 1519 (1999).

2. A. F. Heyduk and D. G. Nocera, J. Am. Chem. Soc. 122, 9415 (2000).

3. T. G. Gray, A. S. Veige, and D. G. Nocera, J. Am. Chem. Soc. 126, 9760 (2004).

4. T. G. Gray and D. G. Nocera, Chem. Commun. 1540 (2005).

5. A. J. Esswein, A. S. Veige, and D. G. Nocera, J. Am. Chem. Soc. 127, 16641 (2005).

6. T. R. Cook, Y. Surendranath, and D. G. Nocera, J. Am. Chem. Soc. 131, 28 (2009).

7. J. F. Nixon, J. Chem. Soc. A 2689 (1968).

8. R. B. King and J. Gimeno, Inorg. Chem. 17, 2390 (1978).

9. M. Ganesan, S. S. Krishnamurthy, and M. Nethaji, J. Organomet. Chem. 570, 247 (1998).

10. M. S. Balakrishna, T. K. Prakasha, S. S. Krishnamurthy, U. Siriwardane, and N. S. Hosmane,

J. Organomet. Chem. 390, 203 (1990).

11. J. L. Herde, J. C. Lambert, and C. V. Senoff, Inorg. Synth. 15, 18 (1974).

40. HETEROLEPTIC CYCLOMETALATEDIRIDIUM(III) COMPLEXES

Submitted by LEONARD L. TINKER,* NEAL D. McDANIEL,*

ERIC D. CLINE,* and STEFAN BERNHARD*


The discovery of novel luminescent transition metal complexes has become the

focus of many research efforts due to their widespread utility in a variety of fields.1

The versatility of such complexes is often determined by their photophysical and

electrochemical properties, which can be ‘‘tuned’’ for a given purpose through

judicious ligandmodification.2 Earlyworks that focus on ruthenium(II) complexes

demonstrate a narrow range of excited-state tuning due to the thermal population of

a quickly relaxing, nonemissive metal-centered (3MC) state. Iridium(III) com-

plexes have an increased ligand field stabilization energy, thus allowing for

increased manipulation of the lowest unoccupied molecular orbital. In addition,

such complexes form a mixed excited triplet state associated with metal-to-ligand

charge transfer and ligand-centered transitions linked to the ancillary and cyclo-

metalating ligands, respectively.3 The mixed nature of the excited state further

facilitates the synthetic tuning of the photophysical and electrochemical properties

of these highly luminescent materials.

A facile route to heteroleptic iridium complexes involves the use of cyclome-

talated 2–arylpyridine derivatives of iridium dimers [Ir(Arpy)2Cl]2.4,5 2-Arylpyr-

idines (Arpy) can be synthesized using the techniques described by Krohnke6

*Department of Chemistry, Princeton University, Princeton, NJ 08544.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 08544.


(illustrated in this section) or by Suzuki coupling.7,8 Cleavage of the dimers

[Ir(Arpy)2Cl]2 with neutral ligands is a reliable route to a range of heteroleptic

iridium complexes.

A. DI-m-CHLOROTETRAKIS[2-(2-PYRIDINYL-N)PHENYL-C]DIIRIDIUM(III), [Ir(ppy)2Cl]2

2 IrCl

4

3 nH2ON

Ir

N

Ir

N

N

Cl

Cl

N

(racemic)

.

In a 5-mL round-bottomed flask equipped with a reflux condenser is dissolved

2-phenylpyridine (46.1mg, 297mmol) in 2-methoxyethanol (1.8mL)before adding

water (0.6mL) and IrCl3�nH2O (n¼ 4, 50.0mg, 135mmol). Themixture is heated to

120�C for 16 h, during which time a bright yellow product appears. The completed

reaction is then cooled to room temperature and poured into water (10mL). The

product is isolated by vacuum filtration, washed with water (2� 10mL), and dried

under reduced pressure. The reaction yields [Ir(ppy)2Cl]2 as a yellow solid that is

typically triturated with hexanes followed by drying under reduced pressure and

usedwithout further purification.Yield: 63mg, 59mmol (87%). [Ir(ppy)2Cl]2 canbe

recrystallized by extraction into CH2Cl2 (10mL) and clarifying the solution by

filtering through a sintered glass frit. Hexanes (50mL) are slowly added to the

resulting solution. Cooling the solution below 5�C for at least 16 h affords the bright

yellow product, which is isolated by vacuum filtration, washed with hexanes

(2� 10mL), and dried under reduced pressure. Yield of recrystallization: 44mg,

41mmol (70%).

Anal. Calcd. for C44H32Cl2Ir2N4: C, 49.29; H, 3.01; N, 5.23. Found: C, 48.81; H,

2.81; N, 5.12. 1H NMR (CD2Cl2): d 9.25 (d, 4H, J¼ 5.5Hz), 7.94 (d, 4H,

J¼ 8.0Hz), 7.80 (t, 4H, J¼ 8.0Hz), 7.56 (d, 4H, J¼ 7.5Hz), 6.82 (m, 8H),

6.60 (t, 4H, J¼ 7.5Hz), 5.87 (d, 4H, J¼ 8.0Hz). 13C NMR (CD2Cl2): d 168.57,

152.04, 145.40, 144.57, 137.23, 130.93, 129.64, 124.22, 123.15, 121.95, 119.28.*

* The checkers treated the completed reaction with�5mL of ice and isolated the bright yellow solid by

gravity filtration, rinsing the reaction flask and the solid with�5mL ofmethanol followed by ether. The

crude product was judged pure by NMR spectroscopy.

40. Heteroleptic Cyclometalated Iridium(III) Complexes 169

B. (2,20-BIPYRIDINE-kN1, kN10)BIS[2-(2-PYRIDINYL-kN)PHENYL-

kC]–IRIDIUM(III) HEXAFLUOROPHOSPHATE, [Ir(ppy)2bpy]PF6

N NPF6Ir

N

Ir

N

N

Cl

Cl

N

Ir

N

N

N

NNH4PF6

2

2

(racemic) (racemic)

Toa5-mLround-bottomedflaskareadded[Ir(ppy)2Cl]2 (26.8mg,25.0 mmol),2,20-bipyridine (9.0mg,57.6mmol), andethyleneglycol (850 mL).Themixture isheated

at 150�C for 12 h. The cooled reactionmixture is combinedwithwater (20mL) in a

separatory funnel, and the aqueous solution is washed with diethyl ether (3� 10

mL). The aqueous solution is heated to 70�C and treatedwith a solution of NH4PF6(81.5mg,500 mmol) inwater (0.5mL).Thesolution iscooled to�5�Cforat least1 h

prior to isolating the crudeproductbyvacuumfiltration.Theproduct iswashedwith

water (2� 10mL) and dried under reduced pressure. The product is then recrys-

tallized bydissolving into acetonitrile (700 mL) in a20-mLvial,which is placed in a

secondary container of diethyl ether (20mL). After at least 12 h, the product is

isolated by decanting the supernatant, washing with diethyl ether (2� 5mL), and

drying under reduced pressure. Yield: 36mg, 45 mmol (90%).

Anal. Calcd. forC32H24IrN4PF6:C,47.94;H,3.02;N,6.99.Found:C,47.83;H,2.91;

N, 6.98. 1H NMR(acetone-d6):d 8.85 (dt, 2H, J¼ 8.0, 1.0Hz), 8.30 (ddd, 2H, J¼ 8.0,

7.5, 1.5Hz), 8.24 (m, 2H), 8.11 (ddd, 2H, J¼ 5.5, 1.5, 0.5Hz), 7.96 (ddd, 2H, J¼ 8.0,

7.5, 1.5Hz), 7.90 (dd, 2H, J¼ 8.0, 1.0Hz), 7.84 (ddd, 2H, J¼ 6.0, 1.5, 0.5Hz), 7.71

(ddd, 2H, J¼ 8.0, 5.5, 1.0Hz), 7.16 (ddd, 2H, J¼ 7.5, 6.0, 1.5Hz), 7.04 (ddd, 2H,

J¼ 8.0, 7.5, 1.0Hz), 6.92 (dt, 2H, J¼ 7.5, 1.5Hz), 6.35 (ddd, 2H, J¼ 7.5, 1.0, 0.5Hz).13C NMR (acetone-d6): d 168.71, 156.99, 151.62, 151.38, 150.18, 144.99, 140.54,

139.61, 132.55, 131.33, 129.55, 125.90, 125.77, 124.54, 123.45, 120.87.

Properties

The UV–vis absorption spectrum of a 25mM solution of [Ir(ppy)2bpy]PF6 in

acetonitrile exhibits maxima (lmax, nm (emax, M�1 cm�1)) at 209 (3.5� 104), 258

(4.3� 104), 308sh (2.0� 104), 379sh (5400), 414sh (3000), and 472sh (480). The

emission spectrum with 337 nm excitation shows a maximum at 585nm (F¼0.0622) with a 390 ns lifetime. [Ir(ppy)2(bpy)]PF6 shows a reversible one-electron

Ir(III/IV) oxidation wave (Ep¼ 1.24V vs. SCE, DEp¼ 84mV) and a reversible one-

electron bpy0/bpy�1 reduction wave (Ep¼�1.41V vs. SCE, DEp¼ 66mV).


C. 2-(4-FLUOROPHENYL)-5-METHYL-PYRIDINE, F–mppy

O

Br

Br

N

O

H

N

F

F

O

F

N

NH4OAc

To a 100-mL round-bottomed flask are added 2–bromo–40–fluoroacetophenone(4.87 g, 22.4mmol) and pyridine (50mL). After stirring the mixture vigorously at

room temperature for 1 h, the white pyridinium salt is collected by vacuum

filtration and washed with diethyl ether (3� 20mL) (6.00 g, 20.3mmol, 90%

yield). In a 500-mL round-bottomed flask equipped with a reflux condenser, the

pyridinium salt (5.00 g, 16.9mmol) is dissolved in methanol (100mL) before

adding 2–methylacrolein (1.18 g, 16.8mmol) and ammonium acetate (6.97 g,

90.5mmol). Themixture is heated at reflux for 18 h during which time the reaction

turns dark red. The reactionmixture is cooled to room temperature and then poured

intowater (400mL). The colorless product is isolated by vacuumfiltration,washed

with water (150mL), and dried under reduced pressure. This procedure yields

F-mppy as a white solid. Yield: 1.69 g, 9.03mmol (54%). TLC (silica, Sorbent

1624147, 10% ethyl acetate in hexanes, F–mppy Rf¼ 0.18) and NMR analyses

indicate that further purification is not necessary.

Anal. Calcd. for C12H10FN: C, 76.99; H, 5.38; N, 7.48. Found: C, 76.86; H, 5.47;

N, 7.54. 1H NMR (CDCl3): d 8.48 (d, 1H, J¼ 2.0Hz), 7.92 (dd, 2H, J¼ 8.5,

5.5Hz), 7.56 (d, 1H, J¼ 8.0Hz), 7.53 (dd, 1H, J¼ 8.0, 2.0Hz), 7.12 (dd, 2H,

J¼ 9.5, 7.5Hz), 2.35 (s, 3H). 13C NMR (CDCl3): d 163.38 (d, JC–F¼ 248.0Hz),

153.64, 149.77, 137.81, 135.21, 131.80, 128.56 (d, JC–F¼ 8.5Hz), 119.97, 115.71

(d, JC–F¼ 21.5 Hz), 18.23.

D. DI-m-CHLOROTETRAKIS[5-FLUORO-2-(5-METHYL-2-

PYRIDINYL-N)PHENYL-C]DIIRIDIUM(III), [Ir(F–mppy)2Cl]2

IrCl3.nH2O2

4N

Ir

N

Ir

N

N

Cl

Cl

N

F F

F F

F

(racemic)

40. Heteroleptic Cyclometalated Iridium(III) Complexes 171

In a 5-mL round-bottomed flask equipped with a reflux condenser is added a

solution of F–mppy (55.5mg, 297mmol) in 2–ethoxyethanol (2.14mL) followed

by water (0.24mL) and IrCl3�nH2O (n¼ 4, 50.0mg, 135 mmol). The mixture is

heated at 135�C for 16 h. The reaction mixture is cooled to room temperature

and poured into water (10mL). The precipitate is isolated by vacuum filtration,

washed with water (2� 10mL), and dried under reduced pressure. The reaction

yields [Ir(F–mppy)2Cl]2 as a yellow powder that is typically triturated with

hexanes followed by drying under reduced pressure, and used without further

purification. Yield: 75mg, 63 mmol (93%). The [Ir(F–mppy)2Cl]2 can be recrys-

tallized by dissolving in refluxing CH2Cl2 (150mL) that is allowed to cool for 1 h

while stirring. The solution is then clarified by filtration. The filtrate is heated to

40�C and concentrated to 10mL under reduced pressure. The resulting solution is

treated slowly with 10–20mL of hexanes while stirring and then cooled to

below 5�C for 16 h. An additional 10–20mL of hexanes is added to the cooled

solution and the product is allowed to crystallize at �5�C for another 16 h. The

recrystallized product is isolated by vacuum filtration, washed with hexanes

(2� 10 mL), and dried under reduced pressure. Yield of recrystallization: 59mg,

49mmol (81%).

Anal. Calcd. for C48H36Cl2F4Ir2N4: C, 48.04; H, 3.02; N, 4.67. Found: C, 47.65; H,

2.89; N, 4.54. 1H NMR (CD2Cl2): d 9.02 (s, 4H), 7.79 (d, 4H, J¼ 8.5Hz), 7.70 (dd,

4H, J¼ 8.0, 1.5 Hz), 7.53 (dd, 4H, J¼ 8.5, 6.0 Hz), 6.55 (dt, 4H, J¼ 8.5, 2.5Hz),

5.42 (dd, 4H, J¼ 10.0, 2.5Hz), 2.02 (s, 12H). 13C NMR (CD2Cl2): d 165.10,

162.72 (d, JC–F¼ 252.0Hz), 151.75, 147.10 (d, JC–F¼ 6.0Hz), 140.90, 138.79,

132.22, 125.46 (d, JC–F¼ 9.5Hz), 118.73, 116.71 (d, JC–F¼ 18.0Hz), 109.03 (d,

JC–F¼ 23.0Hz), 18.90.*

Related Compounds

Cleavage of [Ir(F–mppy)2Cl]2 by 2,20–bipyridine gives [Ir(F–mppy)2(bpy)]þ .

Relative to the ppy derivative, the fluorinated complex exhibits an increased

emission energy, excited-state lifetime, and quantum yield of emission.9

* The checkers dissolved F-mppy (255mg, 1.34mmol) in 2-ethoxyethanol (9.6mL) before adding

water (1.2mL). This solution is heated to reflux and then cooled back to room temperature

under nitrogen prior to adding IrCl3�nH2O (232mg, 0.626mmol). The cooled reaction mixture was

worked up by addition of �30mL of ice. After the ice had dissolved, the product was isolated by

gravity filtration using filter paper and washed with 2mL of cold methanol followed by ether to yield

the yellow powder, which was judged pure by 1H NMR spectroscopy. Yield: 292mg, 0.243mmol

(78%).


References

1. M. S. Lowry and S. Bernhard, Chem. Eur. J. 12, 7970 (2006).

2. M. S. Lowry, W. R. Hudson, R. A. Pascal, and S. Bernhard, J. Am. Chem. Soc. 126, 14129 (2004).

3. M. S. Lowry, J. I. Goldsmith, J. D. Slinker, R. Rohl, R. A. Pascal, G. G. Malliaras, and S. Bernhard,

Chem. Mater. 17, 5712 (2005).

4. S. Sprouse, K. A. King, P. J. Spellane, and R. J. Watts, J. Am. Chem. Soc. 106, 6647 (1984).

5. F. O.Garces, K.Dedeian, N. L.Keder, andR. J.Watts,ActaCrystallogr. C:Cryst. Struct. Commun.

49, 1117 (1993).

6. F. Krohnke, Synthesis 1, 1 (1976).

7. O. Lohse, P. Thevenin, and E. Waldvogel, Synlett. 1, 45 (1999).

8. N. Miyaura, T. Yanagi, and A. Suzuki, Synth. Commun. 11, 513 (1981).

9. J. I. Goldsmith, W. R. Hudson, M. S. Lowry, T. H. Anderson, and S. Bernhard, J. Am. Chem. Soc.

127, 7502 (2005).

41. OXYGEN AND CARBON BOUNDACETYLACETONATO IRIDIUM(III) COMPLEXES

Submitted by STEVEN M. BISCHOF* and ROY A. PERIANA*

Checked by MARK R. RINGENBERG� and THOMAS B. RAUCHFUSS�

Tris(acetylacetonato-O,O) iridium(III) is a coordinatively saturated, stable

species that has been examined spectroscopically1,2 and used in metal vapor

deposition studies.3,4 Removal of one acac ligand (acac¼ acetylacetonato or

2,4-pentanedionate) generates a family of bis-(acac-O,O) iridium(III) complexes

exhibiting rich coordination chemistry. In 1976, Bennett and Mitchell isolated

these (acac-O,O)2Ir(III)(R)(L) complexes as intermediates in yielding

preparations of the (acac-O,O)3Ir(III) complex from the reaction of acetylace-

tone with IrCl3.5

In 2000, the catalytic properties of (acac-O,O)2Ir(III)(R)(L) were discovered as

a part of a program on developing thermally stable, group VIII metal complexes

containing O-donor ligands. For example, [Ir(m-acac-O,O,C3)(acac-O,O)(acac-

C3)]2 catalyzes the anti-Markovnikov hydroarylation of benzenewith propylene to

yield n-propylbenzene via a well-defined CH activation reaction.6

*The Scripps Energy Laboratories, The Scripps Research Institute, Jupiter, FL 33458.�Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

41. Oxygen and Carbon Bound Acetylacetonato Iridium(III) Complexes 173

The (acac-O,O)2Ir(acac-C3)(H2O) and [Ir(m-acac-O,O,C3)(acac-O,O)(acac-

C3)]2 complexes are readily prepared, synthetically flexible starting materials for

this class of compounds as shown previously byBennett and Periana.5,7–9 Reacting

either (acac-O,O)2Ir(acac-C3)(H2O) or [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2

with pyridines, alkyl amines, water, methyl or phenylating agents (Me2M or Ph2M

where M¼Zn or Hg), mesitylene, benzene, cyclohexane, n-octane, and other

organic reagents yields the alkyl or aryl derivatives, which exhibit rich coordina-

tion and reaction chemistry.

A. trans-BIS-(ACETYLACETONATO-O,O)(ACETYLACETONATO-

C3)AQUO IRIDIUM(III), (acac-O,O)2Ir(acac-C3)(H2O)

IrCl3 þ 3 NaHCO3 þ 3 CH3COCH2COCH3 !ðacac-O;OÞ2Irðacac-C3ÞðH2OÞþ 3 NaClþ 3 CO2 þ 2 H2O

Procedure

Iridium trichloride hydrate (2.00 g, 5.67mmol based on IrCl3.3H2O), sodium

bicarbonate (2.00 g, 23.8mmol, �4.2 equiv.), and acetylacetone (2,4-pentane-

dione, 20mL, 196mmol, �35 equiv.) are loaded into a 50-mL round-bottomed

flask equipped with a magnetic stir bar and a water-cooled reflux condenser. The

reaction mixture is refluxed for 48 h (acetylacetone bp� 140�C) under argon (thereaction can also be carried out under air with an oil bubbler attached to the

condenser). The reaction mixture is then cooled to room temperature and diluted

with 25mL of dichloromethane to precipitate a yellow solid, which is filtered with

a sintered glass filter frit. Often, the yellow solid adheres to the walls of the flask,


requiring removal by a metal spatula to load material on the frit for washing. The

solid is washed with dichloromethane (2� 25mL) to remove remaining acety-

lacetone and (acac-O,O)3Ir. Isolation of (acac-O,O)3Ir can be done by workup of

the dichloromethane layer; however, higher yielding procedures have now been

reported.10 The isolated yellow solid (continue on to procedure B if interested in

making [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2) is dissolved in �250mL of

deionized H2O at room temperature with vigorous stirring in a 500-mL round-

bottomed flask, and the resulting solution is filtered. The solution is concentrated

in vacuo to yield 0.86–1.30 g (1.70–2.55mmol, 30–45%) of trans-(acac-O,O)2Ir

(acac-C3)(H2O) as a yellow-orange powder. Care should be taken to not apply

significant heat (>40�C) to remove the water in the vacuum concentration step as

the product can be converted to [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 at

increased temperatures.

Anal. Calcd. C, 35.50%; H, 4.57%. Found: C, 35.20%; H, 4.39%. 1H NMR

(D2O): d 5.53 (s, 2H), 5.47 (s, 1H), 1.90 (s, 12H), and 1.73 (s, 6H). 13C NMR (90%

D2O/10% CD3OD, 100MHz): d 217.9, 188.0, 104.5, 50.0, 33.2, and 28.3. IR

(diamond/ZnSe crystal, cm�1): 2970, 1738, 1678, 1556, 1516, 1386, 1275, 1200,

1014, 943, and 782.

Properties

The compound (acac-O,O)2Ir(acac-C3)(H2O) is quite soluble in water and metha-

nol. It is slightly soluble in dichloromethane, chloroform, benzene, THF, toluene,

and acetonitrile as well as acetic and trifluoroacetic acids. It is insoluble in hexanes

and diethyl ether. The complex is air and water stable; however, when stored as a

solid for long periods, a glovebox or desiccator should be utilized as the complex is

slightly hygroscopic. Synthetically, (acac-O,O)2Ir(acac-C3)(H2O) is the precursor

for procedureB aswell as numerous other Ir(acac)motifs. Reactionwith pyridines,

alkyl amines, water, methyl or phenylating agents (Me2M or Ph2M where M¼Zn

or Hg), mesitylene, benzene, cyclohexane, n-octane, and other organic reagents

yields the alkyl or aryl derivative.

B. BIS-(m-ACETYLACETONATO-O,O,C3)-BIS-

(ACETYLACETONATO-O,O)-BIS-(ACETYLACETONATO-C3)

DIIRIDIUM(III), [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2

2 IrCl3þ6 NaHCO3þ6 CH3COCH2COCH3!½Irðm-acac-O;O;C3Þðacac-O;OÞðacac-C3Þ�2þ6 NaClþ6 CO2þ6 H2O


Procedure

The yellow solid from preparationA is loaded into a 500-mL round-bottomed flask

with reflux condenser and dissolved in�250mLof deionizedwater. Themixture is

refluxed for 4 h yielding a bright orange homogeneous solution. The water is

removed in vacuo to yield an orange residue. The product is purified by elutionwith

CHCl3 through a 6� 45 cm column of neutral alumina. The fast-moving yellow/

orange band of the product (Rf� 0.16) is followed by two by-products atRf� 0.25

and 0.29. Removal of the solvent yielded 0.69–1.33 g (0.71–1.36mmol, 25–48%)

of [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2.

Anal. Calcd. C, 36.80%; H, 4.32%. Found: C, 36.69%; H, 4.41%. 1H NMR

(CDCl3): d 5.35 (s, 2H), 5.10 (s, 2H), 5.09 (s, 2H), 2.01 (s, 12H), 1.98 (s, 12H), and1.93 (s, 12H). 13C NMR (CDCl3): d 212.9, 203.4, 184.9, 103.4, 62.0, 39.7, 32.4,

30.2, and 27.4. IR (diamond/ZnSe crystal, cm�1)¼ 2970, 1738, 1649, 1634, 1516,

1384, 1353, 1276, 1166, 1019, 938, 778, and 669.

Properties

[Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 shows excellent solubility in most or-

ganic solvents such as chloroform, dichloromethane, methanol, DMSO, and

acetone. It is also soluble in many acids such as acetic, trifluoroacetic, and

methanesulfonic acids. The thermally robust compound is stable to air and water.

Samples have been stored for over 1 year without decomposition. Single crystals

can be obtained by diffusion of alkane or aromatic solvents into chloroform or

dichloromethane solutions of the complex. Heating [Ir(m-acac-O,O,C3)(acac-O,O)

(acac-C3)]2 for extended periods in organic or acidic media leads to isolation of [Ir

(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 or precipitation of iridium black. No evi-

dence has been seen for formation of (acac-O,O)Ir(III) on prolonged heating.

Reaction with pyridines, alkyl amines, water, methyl or phenylating agents (Me2M

or Ph2M where M¼Zn or Hg), mesitylene, benzene, cyclohexane, n-octane, and

other organic reagents yields the alkyl or aryl derivative. C�H activation reactions

can be performed in organic or acidic solvents. Hydroarylation with [Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2 occurs in benzene with primary alkenes.

C. trans-BIS-(ACETYLACETONATO-O,O)(ACETYLACETONATO-

C3)PYRIDINE IRIDIUM(III), (acac-O,O)2Ir(acac-C3)PYRIDINE

ðacac-O;OÞ2Irðacac-C3ÞðH2OÞþ pyridine!ðacac-O;OÞ2Irðacac-C3ÞpyridineþH2O


½Irðm-acac-O;O;C3Þ2ðacac-O;OÞðacac-C3Þ�2 þ pyridine!2ðacac-O;OÞ2Irðacac-C3Þpyridine

Procedure

A100-mL Schlenk tube under an argon purge is loaded with 1.00 g (1.97mmol) of

(acac-O,O)2Ir(acac-C3)(H2O), procedure A, or 1.00 g (1.02mmol) [Ir(m-acac-O,

O,C3)(acac-O,O)(acac-C3)]2, procedure B, 40mL (492mmol) of CHCl3, and

10mL (124mmol) of pyridine. The mixture is heated at 60�C for 15min to afford

a homogeneous light yellow solution,which is allowed to cool to room temperature

before filtering through a sintered glass filter frit. Removal of solvent gave >1.00 g(1.77mmol, >90%) of trans-(acac-O,O)2Ir(acac-C

3)pyridine.

Anal. Calcd. C, 42.24%; H, 4.61%; N, 2.46%. Found: C, 41.95%; H, 4.65%; N,

2.74%. 1H NMR (CDCl3): d 8.29 (d, J¼ 5.0Hz, 2H, pyridyl), 7.83 (t, J¼ 7.7Hz,

1H, pyridyl), 7.35 (t, J¼ 7.0Hz, 2H, pyridyl), 5.30 (s, 2H), 5.26 (s, 1H), 1.97

(s, 6H), 1.94 (s, 12H). 13C NMR (CDCl3) d 213.2, 184.8, 149.3, 138.4, 124.9,

102.6, 39.9, 31.5, and 27.1. IR (diamond/ZnSe crystal, cm�1)¼ 2970, 1738, 1669,

1639, 1548, 1535, 1382, 1354, 1276, 1235, 1159, 1061, 1028, 935, 776, 701,

and 671.

Properties

The (acac-O,O)2Ir(acac-C3) pyridine complex is quite soluble in methanol,

dichloromethane, and chloroform, and moderately soluble in THF. It is slightly

soluble in water, benzene, and toluene. The complex is also soluble in acetic and

trifluoroacetic acids. It is insoluble in hexanes and diethyl ether. The complex is air

and water stable for extended periods. Addition of pyridine to complex from

procedure A or B in organic or acid media leads to formation of (acac-O,O)2Ir

(acac-C3)pyridine in situ, which drastically inhibits C–H activation; however, it

does not stop it completely. Pyridine binds strongly through s-donation to help

stabilize the electrophilic iridium(III).

References

1. R. J. Watts and D. Missimer, J. Am. Chem. Soc. 100, 5350 (1978).

2. V. G. Isakova, I. A. Baidina, N. B. Morozova, and I. K. Igumenov, Polyhderon 19, 1097 (2000).

3. E. F€arm, M. Kemell, M. Ritala, and M. Leskel€a, J. Phys. Chem. C 112, 15791 (2008).

4. R. J. Silvennoinen, O. J. Jylh€a, M. Lindbald, H. Osterholm, and A. O. I. Krause, Catal. Lett. 114,

135 (2007).

5. M. A. Bennett and T. R. B. Mitchell, Inorg. Chem. 15, 2936 (1976).

6. T. Matsumoto, D. J. Taube, R. A. Periana, H. Taube, and H. Yoshida, J. Am. Chem. Soc. 122, 7414

(2000).


7. R. A. Periana, X. Y. Liu, and G. Bhalla, Chem. Commun. 3000 (2002).

8. A. G. Wong-Foy, G. Bhalla, X. Y., Liu, and R. A. Periana, J. Am. Chem. Soc. 125, 14292 (2003).

9. G. Bhalla, X. Y. Liu, J. Oxgaard, W. A. GoddardIII, and R. A. Periana, J. Am. Chem. Soc. 127,

11372 (2005).

10. J. E. Collins, M. P. Castellani, A. L. Rheingold, E. J. Miller, W. E. Geiger, A. L. Rieger, and

P. H. Rieger, Organometallics 14, 1232 (1995).


CONTRIBUTOR INDEX

Adhikari, Debashis, 8, 24

Armanasco, Nicole L., 109

Badiei, Yosra, 50

Baker, Murray V., 109

Barnes, Alison G., 109

Bernhard, Stefan, 168

Bischof, Steven M., 173

Blackmore, Karen J., 92

Brown, David H., 109

Caporali, Maria, 96

Chen, Chien-Hong, 129

Chianese, Anthony, 84

Chiang, Karen P., 13, 41

Chung, Young Keun, 114

Clayton, Joshua, 56

Cline, Eric D., 168

Comba, Peter, 70

Cook, Timothy R., 164

Cowley, Ryan E., 13

Crabtree, Robert H., 84, 88

Ding, Keying, 43

Døssing, Anders, 67

Douvris, Christos, 56

DuBois, Daniel L., 132

Dudek, Lisa, 102

Dugan, Thomas R., 43, 48

Fete, Matthew G., 56

Frey, Anne Mette, 67

Garrett, Benjamin R., 84

Goeltz, John C., 164

Gonsalvi, Luca, 96

Hawthorne, M. Frederick, 63

Hayes, Paul G., 20

Hesler, Valerie J., 109

Heyduk, Alan F., 92

Hitomi, Yutaka, 74

Holland, Patrick L., 1, 13, 38, 41,

43, 48, 53

Jakob, Maik, 70

Jalisatgi, Satish, 63

Kajita, Yuuji, 74

Kerscher, Marion, 70

Kim, Sang Bok, 114

King, Benjamin T., 56

Kishima, Yoshihisa, 74

Kl€aui, Wolfgang, 120

Kodera, Masahito, 74

Kogut, Elzbieta, 45

Kubiak, Clifford P. 164

Kunz, Peter C., 120

Lee, Mark W., 63

Letko, Christopher S., 84

Leung, Chin Hin, 84

Liaw, Wen-Feng, 129

Lotz, Simon, 114

MacAdams, Leonard A.,

30

Mack, Amanda E., 143

Matos, Karl, 56

McDaniel, Neal D., 168

Melzer, Marie M., 45

Michl, Josef, 56

Mindiola, Daniel J., 1, 8, 24,

Nakagawa, Tomoyuki, 74

Nguyen, Andy I., 92

Nocera, Daniel G., 164

North, Michael R., 109


179

Ohki, Yasuhiro, 137

Ohta, Shun, 137

Periana, Roy A., 173

Peruzzini, Maurizio, 96

Piers, Warren E., 20

Pike, Robert D., 114

Puttnual, Chuleeporn, 30

Radius, Udo, 78

Rakowski DuBois, Mary,

132

Rauchfuss, Thomas B., 143

Roesky, Herbert W., 34

Ruckerbauer, David, 120

Safronov, Alexander V., 63

Sanchez Cabrera, Gloria, 8

Schaub, Thomas, 78

Stubbert, Bryan D., 38

Sun, Shouheng, 114

Sweigart, Dwight A., 114

Tachi, Yoshimitsu, 74

Tatsumi, Kazuyuki, 137

Teets, Thomas S., 164

Theopold, Klaus H., 30

Tinker, Leonard L., 168

Tran, Ba L., 8

Tranchemontagne, David J., 102

Val�asek, Michal, 56

Varonka, Matthew S., 4, 45

Volkis, Victoria, 56

Voutchkova, Adelina, 88

Warren, Timothy H., 1, 4, 45, 50

Wielandt, J. Wolfram, 120

Wiese, Stefan, 45

Yaghi, Omar M., 102

Zanobini, Fabrizio, 96

Zharov, Ilya, 56

Zuno-Cruz, Francisco J., 8

180 Contributor Index

SUBJECT INDEX

(acac-O,O)2Ir(acac-C3)(H2O), trans-bis-

(acetylacetonato-O,O)(acetylacetonato-C3)

aquo iridium(III), 174–175

(acac-O,O)2Ir(acac-C3)pyridine, trans-bis-

(acetylacetonato-O,O)(acetylacetonato-C3)

pyridine iridium(III), 176–177

Acenaphthene(tricarbonyl)manganese(I) salt,

35:117–118

trans-bis(acetylacetonato-O,O)

(acetylacetonato-C3)aquo iridium(III),

35:174–175

trans-bis(acetylacetonato-O,O)

(acetylacetonato-C3)pyridine iridium(III),

35:176–177

N-Aryl diketiminates, 35:2–3

Arylthiolates, iron complexes, 35:137–142

Basic ruthenium acetate, 35:156

Bipidone (dimethyl-(3,7-dimethyl-9-oxo-2,4-bis

(2-pyridyl)-3,7-diazabicyclo[3.3.1]

nonane)-1,5-dicarboxylate), 35:72

(2,20-Bipyridine)bis[2-(2-pyridinyl)phenyl-iridium(III) hexafluorophosphate, 35:170

Bis(bis(diethylphosphinomethyl)methylamine)

nickel(0), 35:134

Bis(bis(trifluoroethoxy)phosphino)methylamine

(tfepma), 35:166–167

Bis[bis(trimethylsilyl)amido]iron(II),

35:138–140

Bromide, salt of methylenebis(N-(t-butyl)

imidazolium), 35:84–85

cyanocarbonyl iron derivative, 35: 131

Bromotricarbonylcyanoferrate(II), 35:131

Carbon-bound acetylacetonato iridium(III)

complexes, 35:173–177

Cesium

salt of 1-methylcarba-closo-dodecaborate(�),

35:57–58

salt of dodecahydroxy-closo-dodecaborate,

35:63–65

Chelating N-heterocyclic carbene ligand,

35:84–87

Chloro(1,5-cyclooctadiene)(1,3-

dimethylimidazolium-2-ylidene) rhodium

(I), 35:89

Chromium

tricarbonyl 1,3,5-trimethyl-1, 3,5-

triazacyclohexane complex, 35:111–112

acetonitrile nitrosyl complex, 35:67–69

aqua nitrosyl complex, 35:67–69

Cobalt

Cyclopentadienyl)tris(dimethylphosphito

derivative

diketiminate complexes, 35:30–33


Copper


tetradentate bispidine ligand dimethyl-(3,7-

dimethyl-9-oxo-2,4-bis(2-pyridyl)-3,7-

diazabicyclo[3.3.1]nonane)-1,5-

dicarboxylate, 35:70–73

tris(2-picolinyl)methane, complex, 35:74–76

Copper(II) bipidone complex, 35:72–73

Copper tert-butoxide, 35:51–52

Cr(CO)3(Me3TACH), tricarbonyl(1,3,5-

trimethyl-1,3,5-triazacyclohexane)

chromium(0), 111–112

Cyanide

tetraethylammonium (1,3-propanedithiolato)

pentacarbonyldiiron derivative,

35:146

tetraethylammonium (1,3-propanedithiolato)

tetracarbonyldiiron derivative, 35:145

Cyclometalated iridium(III) complexes,

35:168–172

bis(1,5-Cyclooctadiene)nickel(0), 35:123–124


181

(1,5-Cyclooctadiene)(bis-1,3-

dimethylimidazole-2-ylidene)iridium(I)

hexafluorophosphate, 35:90

(Cyclopentadienyl)tris(dimethylphosphito-P)

cobaltate(III), sodium salt, 35:125–128

1,3-Dialkyl-imidazol-2-ylidenes, 35:78–83

Di(aquo)-m3-oxo-hexakis(m-acetate)carbonyl-

triruthenium(II,III,III), 35:158–159

cis-Dichlorotetrakis(dimethylsulfoxide)

ruthenium(II), 35:150–151

Dichloro(ethylbenzoate)ruthenium(II) dimer,

35:162–163

trans-Dichlorotetrakis(dimethylsulfoxide)

ruthenium(II), 35:151

bis(Dichlorophosphino)methylamine,

35:165–166

bis(Diethylphosphinomethyl)methylamine,

nickel complexes, 35:133–134

1,3-Diisopropyl-imidazol-2-ylidene, 35:80–82

1,3-Diisopropyl-imidazolium chloride, 35:79–80

Diketiminate ligands, 35:1–3

Diketiminate complexes, 35:3–19

chromium complexes, 35:32–33

cobalt complexes, 35:43–44

copper complexes, 35:50–55

iron complexes, 35:38–42

manganese complexes, 35:34–36

nickel complexes, 35:45–48

scandium complexes, 35:22–23

titanium complexes, 35:24–28

vanadium complexes, 35:30–32

zinc complexes, 35:36–37

Di-m-chlorotetrakis[2-(2-pyridinyl-N)phenyl-C]

diiridium(III), 35:169–170

Di-m-chlorotetrakis[5-fluoro-2-(5-methyl-2-

pyridinyl-N)phenyl-C]diiridium(III),

35:171–172

2,6-Dimesitylbenzenethiol, 35:140–141

h6-N,N-Dimethylaniline, complex with

(tricarbonyl)manganese(I), 35:118–119

1,3-Dimethyl imidazol-2-ylidene, 35:82–83

1,3-Dimethyl imidazolium iodide, 35:80

N,N0-Dimethylimidazolium-2-carboxylate,

35:88–89

Dimethylsulfoxide

cis-dichlorotetrakis(dimethylsulfoxide)

ruthenium(II), 35:150–151

trans-dichlorotetrakis(dimethylsulfoxide)

ruthenium(II), 35:151

Di(n-butyl)magnesium, 35:122–123

DIPPN¼C(Me)tBu, 16–17

DIPPN(C¼O)(tBu), 15–16

[DIPPN¼C(tBu)]2CH2, 17–18

DIPPNHC(O)tBu, N-pivaloyl-2,6,-

diisopropylanilide, 14–15

2,4-Di-tert-butyl-6-(tert-butylamino)phenol,

35:93–94

2,4-Di-tert-butyl-6-(tert-butylimino)quinone,

35:94–95

Dodecahydroxydodecaborate, 35: 63.

Dodecamethylcarba-closo-dodecaboranyl

radical, 35:61–62

Dodecamethylcarba-closo-dodecaborate(�)

anion, 35:56–62

Ethyl-1,4-cyclohexadiene-3-carboxylate,

35:161–162

Fe[SC6H3-2,6-(mesityl)2]2, 141–142

2-(4-Fluorophenyl)-5-methyl-pyridine, 35:171

Hexaaquaruthenium tosylate, 35:152-155

Hexakis(acetylacetonato)trinickel(II),

35:121–122

Hydridobis(PNP)nickel(II)

hexafluorophosphate, 35:134–135

Imidazolium carboxylates, N-heterocyclic

carbene precursors, 35:88–90

Iminoquinone complexes, 35:92–96

Iodide

1,3-dimethyl-imidazolium salt, 35:80

1-methyl-3-isopropyl-imidazolium salt, 35:80

7-methyl-1,3,5-triaza-7-

phosphoniaadamantane salt, 35:100

tris(hydroxymethyl)methyl phosphonium salt,

35:99

Iridium

(h2:h2-bis(1,3-dimethylimidazole-2-ylidene)

complex, 35:90

cyclometalated complexes, 35:168–172

diphosphine (tfepma) complex, 35:164–167

N-heterocyclic carbene complexes, 35:88–90

acetylacetonato complexes, 35:173–177

Iron

arylthiolates, 35:137–142

cyanocarbonyl complexes, 35:129–131,

145–146

Diketiminate complexes, 35:38–42

182 Subject Index

bis[bis(trimethylsilyl)amido] complex,

35:138–140

(1,3-Propanedithiolato) derivatives,

35:143–145

Ir2(tfepma)3Cl2, tfepma, iridium complex, 167

[Ir(F-mppy)2Cl]2, di-m-chlorotetrakis[5-fluoro-

2-(5-methyl-2-pyridinyl-N)phenyl-C]-

diiridium(III), 171–172

[Ir(m-acac-O,O,C3)(acac-O,O)(acac-C3)]2,

175–176

[Ir(ppy)2bpy]PF6, (2,20-bipyridine-kN1, kN10)

bis[22-(2-pyridinyl-kN)phenyl-kC]-

iridium(III) hexafluorophosphate, 170

[Ir(ppy)2Cl]2, 169

Lithium

2,4-bis(2,6-diisopropylphenylimido)pentyl

derivative, 35:10–11

dodecamethylcarba-closo-dodecaborates(�)

salt, 35:58–61

diketiminate derivative, 35:18–19

zinc diketiminate complex, 35:36–37

Low-coordinate diketiminate

complexes, 35:2–3

Magnesium, dibutyl derivative, 35:122–123

Manganese

acenaphthene(tricarbonyl) complex,

35:117–118


N,N-dimethylaniline(tricarbonyl)-complex,

35:118–119

naphthalene(tricarbonyl) complex, 35:118

tricarbonyl transfer agents, 35:114–119

Me2Im, 1,3-dimethyl-imidazol-3-ylidene,

82–83

Me2ImHI, 1,3-dimethyl-imidazolium iodide, 80

MeiPrIm, 1-methyl-3-isopropyl-imidazol-2-

ylidene, 82–83

MeiPrImHI, 1-methyl-3-isopropyl-imidazolium

iodide, 80

2,4-Bis(mesitylimido)pentane, 35:5–6

nickel derivatives, 35:45–48

thallium derivatives, 35:6–7

Metal-organic frameworks

MOF-5: Zn4O(terephthalate)3, 35:103–105

MOF-177: Zn4O(1,3,5-benzenetribenzoate)2,

35:106–107

Methylenebis(N-(t-butyl)imidazolium) bromide,

35:84–85

Methylenebis(N-(t-butyl)imidazol-2-ylidene),

(1,5-cyclooctadiene)rhodium(I) derivative,

35:86–87

1-Methyl-3-isopropyl-imidazol-2-ylidene,

35:82–83

1-Methyl-3-isopropylimidazolium iodide, 35:80

7-Methyl-1,3,5-triaza-7-phosphoniaadamantane

iodide, 35:100

Molybdenum, tricarbonyl 1,3,5-trimethyl-1,3,5-

triazacyclohexane complex, 35:112–113

Naphthalene, complex with (tricarbonyl)-

manganese(I), 35:118

Nickel

acetylacetonato complex, 35:121–122

bis(diethylphosphinomethyl)methylamine


bis(1,5-cyclooctadiene) derivative,

35:123–124

diketiminate complexes, 35:45-50

Ni(PNP)2, bis(bis(diethylphosphinomethyl)-

methylamine)nickel(0), 134

Oxygen-bound acetylacetonato iridium(III)


Pentaaquanitrosylchromium sulfate, 35:67–69

7-Phospha-3-methyl-1,3,5-triazabicyclo[3.3.1]

nonane, water-soluble bidentate (P,N)

ligand PTN(Me), 35:100–101

bis(2-Picolinyl)methane, 35:75–76

Piperidone (dimethyl-(1-methyl-4-oxo-2,6-bis

(2-pyridyl)piperidine)-3,5-dicarboxylate),

35:70–72

N-Pivaloyl-2,6-diisopropylanilide, 35:14–17

Potassium, 2,2,6,6-tetramethyl-3,5-bis(2,6-

diisopropylphenylimido)heptyl, 35:11–12

[PPN][Fe(CO)4(CN)], iron cyanocarbonyl

complexes, 129–131

[PPN][Fe(CO)4(CN)], PPN salt of

tetracarbonylcyanoferrate(0), 130

[PPN][FeIIBr(CO)3(CN)2], bis PPN salt of

bromotricarbonylcyanoferrate(II), 131nPr2Im, 1,3-di-n-propyl-imidazol-2-ylidene,

80–82nPr2ImHCl, 1,3-di-n-propyl-imidazolium

chloride, 79–80

1,3-Di-n-propyl-imidazolium chloride, 35:79–80

1,3-Di-n-propyl-imidazol-2-ylidene, 35:80–82

PTN(Me)

Subject Index 183

7-phospha-3-methyl-1,3,5-triazabicyclo-

[3.3.1]nonane, 35:100–101

Radical, dodecamethylcarba-closo-

dodecaboranyl, 35:56–62

Rhodium

chelating N-heterocyclic carbene derivatives,

35:84–87

chloro(1,5-cyclooctadiene)(1,3-

dimethylimidazol-2-ylidene) complex,

35:89

{methylenebis(N-(t-butyl)imidazol-2-

ylidene)}(1,5-cyclooctadiene) complex,

35:86–87

N-heterocyclic carbene complexes, 35:88–90

[(h6-etb)RuCl2]2dichloro(ethylbenzoate)ruthenium(II) dimer,

162–163

Ru3(m3-O)(m-OAc)6(CO)(H2O)2, di(aquo)-m3-

oxo-hexakis(m-acetate)carbonyl-

triruthenium(II, III, III), 158–159

[Ru3(m3-O)(m-OAc)6(H2O)3]OAc, tria(aquo)-

m3-oxo-hexakis(m-acetate)triruthenium

acetate, 156–157

Ru3(m3-O)(m-OAc)6(py)3, tri(pyridine)-m3-oxo-

hexakis(m-acetate)triruthenium, 157–158

Ruthenium

acetates, 35:156–159

hexaaquo complex, 35:132–133

dimethylsulfoxide complexes, 35:148–151

ethylbenzoate complex, 35:162–163

tetroxide, 35:153

Scandium diketiminate complexes, 35:21–23

Scandium trichloride tris(tetrahydrofuran),

35:20–21

ScCl3(THF)3 scandium trichloride tris

(tetrahydrofuran), 20–21

Silver-NHC reagent, 35:84–87

Na[(C5H5)Co{P(O)(OMe)2}3], sodium (h5-

cyclopentadienyl)tris(dimethylphosphito-

P)cobaltate(III), 125–128

Sodium, salt of (h5-cyclopentadienyl)tris

(dimethylphosphito-P)cobaltate(III),

35:125–128

Tetracarbonylcyanoferrate(0), 35:130

Tetrakis(hydroxymethyl)phosphonium chloride,

35:97–98

2,2,6,6-Tetramethyl-3,5-bis(2,6-

diisopropylphenylimido)heptane, 35:17–18

2,2,6,6-Tetramethyl-3,5-bis(2,6-

diisopropylphenylimido)heptyl

cobalt complex, 35:43–44

iron complex, 35:41–42

scandium derivatives, 35:22–23

titanium derivatives, 35:27–28

vanadium derivatives, 35:28–29

tfepma, bis(bis(trifluoroethoxy)phosphino)

methylamine, 35:166–167

Thallium diketiminate derivatives, 35:4–7

Titanium diketiminate complexes, 35:24–28

1,3,5-Trimethyl-1,3,5-triazacyclohexane


Tri(pyridine)-m3-oxo-hexakis(m-acetate)

triruthenium, 35:157–158

Tris(hydroxymethyl)methyl phosphonium

iodide, 35:99

Tris(hydroxymethyl)phosphine, 35:98

Tris(2-picolinyl)methane, copper(I) complex,

35:74–76

Tungsten, tricarbonyl 1,3,5-trimethyl-1,3,5-

triazacyclohexane complex, 35:113

Vanadium diketiminate complexes, 35:28–29

Water-soluble bidentate (P,N) ligand PTN(Me),

35:96–101

W(CO)3(Me3TACH), tricarbonyl(1,3,5-

trimethyl-1,3,5-triazacyclohexane)tungsten

(0), 113

Zinc


metal organic frameworks, 35, 103–107.

Zirconium(IV) bis(aminophenolate) complexes,

35:92–96

Zn4O(terephthalate)2metal-organic framework-5, 103–105

metal-organic framework-177, 106–107

184 Subject Index

FORMULA INDEX

AgC15H24F6N4P, [Ag(CH2(t-BuC3H3N2)2]PF6,

86

B11C2H14Cs, Cs[MeCB11H11], 57

B11C12H36, Me12CB11, 61

B11C12H36Cs, Cs[Me12CB11], 58

B11C12H36Li, Li[Me12CB11], 60

B11C16H48N, NMe4[Me12CB11], 59

B12H12Cs2, Cs2[B12H12], 63

B12H12Cs2O12, Cs2[B12(OH)12], 63

C13H36B11, dodecamethylcarba-closo-

dodecaboranyl radical, 61–62

and dodecamethylcarba-closo-

dodecaborate(�), 56–62

C5H8N2, Me2Im, 82

C6H8N2O2, Me2ImCO2, 88

C6H15N3, TACH, 111

C7H12N2, 1-Pr-3-MeIm, 81

C7H12N2, t-BuC3H3N2, 84

C7H13N2l, 1-Pr-3-MeImHl, 80

C9H12O2, C6H7CO2Et, 161

C9H18ClN2, 1,3-Pr2ImHCl, 76

C12H10FN, 4-FC6H4-2-py-5-Me, 171

C15H26Br2N4, CH2(t-BuC3H3N2)2Br2, 84

C17H27NO, 2,6-(i-Pr)2C6H3NHC(O)CMe3, 14

C18H29NO, (t-Bu)2C6H4(O)N-t-Bu, 95

C18H31NO, (t-Bu)2C6H4(OH)NH-t-Bu, 93

C19H19N3, HC(6-(2-picolinyl))3, 75

C20H21N3O5, piperidone, 71

C21H26N2, HLMe,Me2, 6

C22H26NCl, 2,6-(i-Pr)2C6H3NC(Cl)CMe3, 15

C23H28N4O5, bispidine, 72

C23H29N, 2,6-(i-Pr)2C6H3NC(Me)CMe3, 16

C23H30N2, HLMe,Me3, 5

C27H18O6, 1,3,5-benzenetribenzoic acid, 106

C29H42N2, LMe,iPr2H, 9

C35H54N2, LtBu,iPr2H, 17

CoC11H23NaO9P3, Na{(C5H5)Co[P(O)-

(OMe)]3}3, 127

CoC35H53ClN2, (LtBu,iPr2)CoCl, 44

Co3C22H46O18P6, Co{(C5H5)Co[P(O)-

(OMe)2]3}2, 126

CrB2F8C10H15N6O, [Cr(MeCN)5(NO)](BF4)2,

68

CrC9H15N3O3, Cr(TACH)(CO)3, 111

CrC25H34N2Cl2, (LMe,Me2)CrCl2(THF), 32

CrH10NSO10, [Cr(H2O)5(NO)]SO4, 68

CsB11CH14, Cs[MeCB11H11], 57

CsB11C12H36, Cs[Me12CB11], 58

Cs2B12H12O12, Cs2[B12(OH)12], 63

CuC4H9O, CuO-t-Bu, 51

CuC21H22BF4N4, {[HC(6-(2-picolinyl))3]Cu-

(MeCN)}BF4, 76

CuC23H32Cl2N4O7, (bispidinate)CuCl, 73

CuC29H41ClN2, (LMe,iPr2)CuCl, 54

Cu2C53H65N4, [(LMe,Me3)Cu]2(toluene), 52

FC12H11N, 2-(4-fluorophenyl)-5-methyl-

pyridine, 171

F12C9H11NO4P2, MeN(P(OCH2CF3)2)2, 166

FeC5NNaO4, Na[Fe(CN)(CO)4], 130

FeC6H12Cl2O1.5, FeCl2(THF)1.5, 39

FeC30H34NSSi2, [C6H3-2-6-(mes)2S]FeN-

(SiMe3)2, 142

FeC41H34BrN3O3P2, PPN[FeBr(CN)2(CO)3],

131

FeC41H34N2O4P2, PPN[Fe(CN)(CO)4], 130

FeC48H50S2, [C6H3-2-6-(mes)2S]2Fe, 141

Fe2C9H6O6S2, Fe2(pdt)(CO)6, 144

Fe2C17H26N2O5S2, Et4N[Fe2(pdt)(CN)(CO)5],

146

Fe2C24H72N4Si8, {Fe[N(SiMe3)2]2}2, 138

Fe2C58H82Cl2N4, (LMe,iPr2)2Fe2Cl2, 42


185

IrC15H23O7, Ir(acac)2(C-acac)(H2O), 174

Ir2C27H33Cl2F36N3O2P6, [MeN(P-

(OCH2CF3)2)2]3Ir2Cl2, 167

Ir2C30H42O12, [Ir(acac)2(C-acac)]2, 175

Ir2C44H32F4N4, [Ir(2-Phpy-H)2Cl]2, 169

Ir2C48H40Cl2F4N4, [Ir(FC6H3-2-py-5-Me)2Cl]2,

172

IrC18H28F6N4P, [Ir(cod)(Me2Im)2]PF6, 90

IrC20H20NO6, Ir(acac)2(C-acac)(pyridine), 176

IrC32H24F6N4P, [Ir(2-Phpy-H)2(bipy)]PF6,

170

KC35H53N2, LtBu,iPr2K, 11

LiC12B11H36, Li[Me12CB11], 60

LiC29H41N2, LMe,iPr2Li, 10

LiC39H61N2O, LtBu,iPr2Li(THF), 18

LiC13H36B11, Li[CB11Me12], lithium

dodecamethylcarba-closo-dodecaborates

(–), 58–61

LMe,iPr2H, 9–10

LMe,iPr2Li, 10–11

(LtBu,iPr2)ScCl2, 22–23

(LMe,iPr2)ScCl2(THF), 21–22

(LtBu,iPr2)TiCl2, 27–28

(LMe,iPr2)TiCl2(THF), 25–26

(LMe,iPr2)VCl2, 28–29

(LMe,iPr2)CuCl, 53–54

(LMe,iPr2)2Fe2Cl2, 38–39

(LMe,iPr2)2Mn2I2, 35–36

(LMe,iPr2)MnI(THF), 34–35

(LMe,iPr2)2Ni Cl2, 48–49

(LMe,iPr2)ZnCl2Li(OEt2)2, 36–37

(LMe,Me2)CrCl2(THF)2, 32–33

(LMe,Me2)VCl2, 31–32

(LMe,Me3Cu)2(h2:h2-C7H8), 50–51

(LMe,Me3)Ni(2,4-lutidine), 46–47

(LMe,Me3)NiI(2,4-lutidine), 45–46

(LtBu,iPr2)CoCl, 43–44

(LtBu,iPr2)FeCl, 41–42

LtBu,iPr2K, 11–12

LtBu,iPr2H, 17–18

LtBu,iPr2Li, THF adduct, 18–19

MgC8H18, Mg(C4H9)2, 122

MnC11H11BF4NO3, [(Me2NC6H5)Mn(CO)3]-

BF4, 119

MnC13H8BF4O3, [(naphthalene)Mn(CO)3]BF4,

118

MnC15H10BF4O3, [(acenaphthene)Mn(CO)3]-

BF4, 117

MnC33H49ION2, (LMe,iPr2)MnI(THF), 34

Mn2C58H82I2N4, (LMe,iPr2)2Mn2I2, 35

MoC9H15N3O3, Mo(TACH)(CO)3, 112

NaC11H23CoO9P3, Na{(C5H5)Co[P(O)-

(OMe)2]3}, 127

NiC16H24, Ni(cod)2, 123

NiC22H54B2F8N2P4, {Ni-[(Et2PCH2)2NMe]2}

(BF4)2, 136

NiC22H54N2P4, Ni[(Et2PCH2)2NMe]2, 134

NiC22H55F6N2P5, HNi[(Et2PCH2)2NMe]2PF6,

135

NiC30H38N3, (LMe,Me3)Ni(2,4-lutidine), 46

NiIN3, (LMe,Me3)NiI(2,4-lutidine), 45

Ni2C58H82Cl2N4, (LMe,iPr2)Ni2Cl2, 49

Ni3C30H42O12, [Ni(acac)2]3, 121

O4Ru, ruthenium tetroxide, 153

O12C14H26RuS2, [Ru(H2O)6](OTs)2, 150–151

P2C9H11F12NO4, MeN(P(OCH2CF3)2)2, 166

P2C11H27N, (Et2PCH2)2NMe, 133

P2CH3Cl4N, MeN(PCl2)2, 165

PC3H9O3, P(CH2OH)3, 98

PC4H12ClO4, [P(CH2OH)4]Cl, 97

PC4H12IO3, [MeP(CH2OH)3]I, 99

PC7H15IN3, 100

PC7H16N3, MePC5N2H10NMe, 100

RhC18H28F6N4P, [(cod)Rh(Me2Im)2]Cl, 89

RhC23H36F6N4P, [Rh(cod)(CH2-

(t-BuC3H2N2)2)]PF6, 86

RuC8H24Cl2O4S4, RuCl2(dmso)4, 150–151

RuC14H26O12S2, [Ru(H2O)6](OTs)2, 150–151

Ru2C18H20Cl4O4, (C6H5CO2Et)2Ru2Cl4, 162

Ru3C13H22O16, Ru3O(OAc)6(H2O)2(CO), 158

Ru3C14H27O18, [Ru3O(OAc)6(H2O)3]OAc, 156

Ru3C27H33N3O13, Ru3O(OAc)6(pyridine)3, 157

RuO4, 153

ScC12H24Cl3O3, ScCl3(THF)3, 20

ScC29H41Cl2N2, LMe,iPr2ScCl2, 22

ScC33H49Cl2N2O, LMe,iPr2ScCl2(THF), 21

SC24H26, C6H3-2,6-(mes)2SH, 140

S2C25H46Fe2N4O4, (Et4N)2[Fe2(pdt)-

(CN)2(CO)4], 145

S4C8H24Cl2O4Ru, RuCl2(dmso)4, 150–151

186 Formula Index

TiC3H49Cl2N2O, (LMe,iPr2)TiCl2(THF), 25

TIC23H29N2, TILMe,Me3, 6

TiC35H53Cl2N2, (LtBu,iPr2)TiCl2, 27

VC25H34Cl2N2, (LMe,Me2)VCl2(THF), 31

VC29H41Cl2N2, (LMe,iPr2)VCl2, 28

WC9H15N3O3, W(TACH)(CO)3, 113

ZnC33H51Cl2LiN2O, (LMe,iPr2)ZnCl2(Et2O),

36

Zn4C24H12O13, Zn4O(terephthalate)3, 4,

103

Zn4C54H30O13, Zn4O(1,3,5-

benzenetribenzoate)2, 107

ZrC44H74N2O2, [(t-Bu)2C6H4(O)(N-t-Bu)]2Zr

(THF)2, 96

Formula Index 187

inorganic syntheses volume 35the ﬁrst chemistry monograph that i ever bought was inorganic...

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