university of adelaide · contents abstract i declaration iii acknowledgements iv abbreviations v...

Department of Chemistry

New Methods for the Synthesis of Diynyl, Diyndiyl and Bis(diyndiyl)

Ruthenium(II) Complexes

A Thesis Submitted Towards the Degree of Doctor of Philosophy

By

Nancy Scoleri

B.Sc. (Hons)

July 2008

Contents

Abstract i

Declaration iii

Acknowledgements iv

Abbreviations v

General experimental conditions viii

CHAPTER ONE: Introduction

1.1. The syntheses of diynyl complexes 3

1.1.1. Synthetic strategy one 4

1.1.2. Synthetic strategy two 6

1.1.3. Synthetic strategy three 7

1.1.4. Synthetic strategy four 8

1.1.5. Alternative synthetic strategies 9

1.2. The syntheses of diyndiyl complexes 10

1.2.1. Symmetric diyndiyl complexes 11

1.2.1.1 Synthetic strategy one 12

1.2.1.2. Synthetic strategy two 14

1.2.1.3. Synthetic strategy three 17

1.2.1.4. Synthetic strategy four 18

1.2.2. Asymmetric diyndiyl complexes 19

1.3. The syntheses of trinuclear complexes 24

1.3.1. Organic linkers 24

1.3.2. Organometallic linkers 26

1.4. Molecular wires 30

1.4.1. Evaluation of molecular wires by cyclic voltammetry 33

1.5. Work described in this thesis 41

CHAPTER TWO: The Chemistry of Bis(Diyndiyl) Ruthenium(II) Complexes 2.1. Introduction 43

2.2. Aim of this work 47

2.3. Results and Discussion 48

2.3.1. Symmetric complexes trans-Ru{C4[Ru]}2(dppe)2 48

2.3.2. Asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 51

2.3.3. Asymmetric complexes trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 54

2.3.4. Synthesis of trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 58

2.3.5. Gold reactions 60

2.3.5.1. Synthesis of trans-Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2 62

2.3.5.2. Synthesis of trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-

dppm)(CO)7]}(dppe)2

65

2.3.6. Various reactions of trans-Ru(C4H)2(dppe)2 67

2.3.6.1. Reaction with AuCl(PPh3) 67

2.3.6.2. Reaction with Co3(µ3-CBr)(µ-dppm)(CO)7 68

2.3.6.3. Reaction with TCNE 69

2.3.7. Synthesis of trinuclear copper(I) and silver(I) alkynyl complexes 75

2.4. Electrochemistry 80

2.4.1. trans-Ru{C4[Ru]}2(dppe)2 complexes 80

2.4.2. trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 complexes 85

2.4.3. trans-Ru{C4[Ru]}{C4H}(dppe)2 complexes 88

2.4.4. trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 89

2.4.5. Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 89

2.4.6. [{Cp*(dppe)Ru}(C≡C)2{M3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X]

(M = Cu, Ag; X = PF6, BF4)

90

2.5. Conclusions 94

2.6. Experimental 96

CHAPTER THREE: A New Method for the Synthesis of Diyndiyl Ruthenium(II) Complexes

3.1. Introduction 107



3.3.1. The lithiation of [Ru](C≡CC≡CH) ([Ru] = Ru(dppe)Cp*,

Ru(PPh3)2Cp)

111

3.3.1.1. Synthetic strategy 111

3.3.1.2. NMR study 112

3.3.2. Investigation of the formation of [Ru](C≡CC≡CLi) 113

3.3.2.1. Synthesis of [Ru](C≡CC≡CTMS) 113

3.3.2.2. Synthesis of [Ru]{C≡CC≡C[Au(PPh3)]} 116

3.3.3. Reactions of [Ru](C≡CC≡CLi) with various metal halides 118

3.3.3.1. Reaction with (AuCl)2(µ-dppm) 118

3.3.3.2. Reaction with cis-PtCl2(PPh3)2 121

3.3.3.3. Reactions with GeClPh3 and SnClPh3 121

3.3.3.4. Reaction with [CuCl(PPh3)]4 124

3.3.3.5. Reaction with RhCl(CO)(PPh3)2 128

3.4. Conclusions 131


CHAPTER FOUR: The reactions of Ru(C≡CC≡CLi)(dppe)Cp*


4.1.1. The reaction of nucleophilic complexes with organic reagents 138

4.1.2. The reaction of nucleophilic complexes with polyfluoroaromatic

reagents

139

4.1.3. The nucleophilic ruthenium(II) complex Ru(C≡CC≡CLi)(dppe)Cp* 140



4.3.1. Reactions with organic reagents 143

4.3.1.1. Synthesis of Ru(C≡CC≡CMe)(dppe)Cp* 143

4.3.1.2. Synthesis of Ru{C≡CC≡CC(O)Ph}(dppe)Cp* 145

4.3.1.3. Synthesis of Ru{C≡CC≡CC(O)Me}(dppe)Cp* 146

4.3.1.4. Synthesis of Ru{C≡CC≡CC(O)OMe}(dppe)Cp* 147

4.3.1.5. Synthesis of {Ru(C≡CC≡C)(dppe)Cp*}2(CO)2 147

4.3.1.6. Synthesis of Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* 148

4.3.1.7. Reaction with TCNE 152

4.3.2. Reactions with polyfluoroaromatic reagents 158

4.3.2.1. Synthesis of Ru(C≡CC≡CC6F5)(dppe)Cp* 158

4.3.2.2. Synthesis of Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* 161

4.3.2.3. Synthesis of Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* 162

4.3.2.4. Synthesis of Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* 163

4.3.2.5. Synthesis of Ru(C≡CC≡CC10F7-2)(dppe)Cp* 165

4.3.2.6. Further reactions with Ru(C≡CC≡CC6F5)(dppe)Cp* 172

4.4. Electrochemistry 176

4.4.1. CV of products from the reactions with organic reagents 176

4.4.2. CV of products from the reactions with polyfluoroaromatic

reagents

177



CHAPTER FIVE: Some Chemistry Involving Azide Reagents




5.3.1. Reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = TMS, H, Au(PPh3)) 200

5.3.2. Reactions of Ru(C≡CC≡CH)(PPh3)2Cp 211

5.3.3. Reactions of Ru(C≡CH)(dppe)Cp* 212



General conclusions 220

References 222

Complexes Index 231

i

Abstract

Chapter One outlines the different methods described in the literature for the synthesis

of diynyl, symmetric and asymmetric diyndiyl complexes. The extension to

complexes containing a central bridging group within the carbon chain is also

introduced with the description of two different linking groups, either an organic or

organometallic moiety. A brief overview of molecular electronics and one method of

evaluation of electronic communication, cyclic voltammetry, are also addressed.

Chapter Two describes the synthesis of novel symmetric and asymmetric

bis(diyndiyl) ruthenium(II) complexes of general formula {LnM}-C≡CC≡C-{M”L”p}-

C≡CC≡C-{M’L’m}, featuring two transition metal fragments linked by either a

Ru(dppe)2 moiety or a trinuclear copper(I) or silver(I) cluster M3(µ-dppm)3 (M = Cu,

Ag). Through the use of cyclic voltammetry, it was shown that the inclusion of these

three particular bridging groups allows electronic communication between the two

terminal end-groups. The chemistry of the starting material trans-Ru(C4H)2(dppe)2 (1)

is also described, forming novel complexes when reacted with AuCl(PPh3) or TCNE.

Chapter Three describes a new convenient synthetic route to diynyl and diyndiyl

ruthenium(II) complexes. Lithiation of the ruthenium(II) diynyl complexes

Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp with n-BuLi yields the

lithium complexes Ru(C≡CC≡CLi)(dppe)Cp* and Ru(C≡CC≡CLi)(PPh3)2Cp. The

most favorable conditions for their formation are examined by using NMR

spectroscopy and different assay reactions. These lithium species are further reacted

with a range of metal halides to give new asymmetric diyndiyl complexes of general

formula [Ru](C≡CC≡C){MLn} (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp).

ii

Chapter Four investigates the reactivity of the novel lithium complex

Ru(C≡CC≡CLi)(dppe)Cp* synthesised in Chapter Three. The nucleophilic nature of

this complex is assessed with a range of electrophiles such as organic substrates or

polyfluoroaromatic compounds. A number of new complexes are prepared and single-

crystal X-ray structure determinations are reported for many of the complexes. The

electrochemistry of some of these complexes is also described.

Chapter Five summarises the reactions of diynyl ruthenium(II) complexes

Ru(C≡CC≡CR)(dppe)Cp* (where R = H, TMS, Au(PPh3)) with three azide reagents

TMSN3, TsN3 and AuN3(PPh3). The reactions are suggested to undergo a Huisgen

1,3-alkyne-azide cycloaddition to generate 1,2,3-triazoles which further react to give

the various products. The complexes synthesised are characterised by spectroscopic

methods and, where possible, by X-ray structure determination. Furthermore, the

reactions of the complexes Ru(C≡CC≡CH)(PPh3)2Cp and Ru(C≡CH)(dppe)Cp* with

azides to give the ruthenium azido complexes [Ru]N3 (where [Ru] = Ru(PPh3)2Cp,

Ru(dppe)Cp*) are described.

iii

Declaration This thesis contains no material which has been accepted for the award of any other

degree or diploma in any university, and to the best of my knowledge, contains no

material previously published or written by another person except where due

reference has been made.

I give consent for this thesis to be made available for photocopying and loan if

applicable.

Nancy Scoleri Date: 4th of July 2008

iv

Acknowledgements

First, I would like to thank my supervisor, Professor Michael Bruce for giving me the

opportunity to work on an interesting and challenging project. It has been a unique

experience which I will always remember. I am also grateful for the help of my co-

supervisor Dr Marcus Cole throughout the past few years.

Thank you to Professor Allan White and Dr Brian Skelton for the X-ray structures,

Professor Brian Nicholson for the ES-MS and Dr. Simon Pike for valuable

discussions on NMR spectra and the organic side of my project. I would also like to

thank Professor Jean-François Halet and Dr Stéphane Rigaut for running the DFT

calculations and for their suggestions on the trinuclear project. Thanks also to Phil

Clements, Graham Bull and Peter Apoefis, staff members of our chemistry

department who have helped with instrument failures.

Special thanks to Prof. Michael Bruce, Dr Marcus Cole and Dr. Gary Perkins for

giving their time to read my thesis. Your corrections and advice were greatly

appreciated.

Thanks must go to everyone I have had the pleasure of sharing a lab with: Dr Maryka

Gaudio, Dr Natasha Zaitseva, Dr Cassandra Mitchell, Dr Shirley Xiao-Li Zhao, Dr

Benjamin Hall, Dr Gary Perkins, Dr David Armitt and Christian Parker. Thank you

also to Mable Fong, Renée Morelli, Suzanne Lochet and Alice Granger for their

friendship and for giving me distraction outside my PhD.

Finally, special and most important thanks must go to my family. I am grateful to my

parents for their ongoing encouragements, love and faith in me. I really appreciate

everything you have ever done for me. Thank you also to my brothers, Tony and

Gianny for being there when I needed you. Thank you also to Gary for your love and

support and keeping me focussed on achieving my goals.

v

Abbreviations

General:

° Degrees °C Degrees Celsius Å Ångstrom anal. Analysis Acac Acetylacetonate av. Average Bpy 2,2’-bipyridyl Bu Butyl ca Approximately

Calcd Calculated cm Centimetres Cp Cyclopentadienyl Cp* Pentamethylcyclopentadienyl Cy Cyclohexyl dbu 1,8-diazabicyclo[5.4.0]undec-7-ene DFT Density-functional theory dippe 1,2-bis(diisopropylphosphino)ethane dmpe 1,2-bis(dimethylphosphino)ethane dppe 1,2-bis(diphenylphosphino)ethane dppm Bis(diphenylphosphino)methane e- Electron EH Extended Hückel theory eq Equivalent ESR Electron spin resonance Et Ethyl, -CH2CH3 Et2O Diethyl ether EtOH Ethanol eV Electron volts Fc Ferrocenyl FMO Frontier molecular orbital g Gram h Hour(s) HOMO Highest occupied molecular orbital IR Infrared LDA Lithium Diisopropylamide, LiNPri

2 LUMO Lowest unoccupied molecular orbital Me Methyl, CH3

vi

MeLi Methyl lithium MeOH Methanol mg Milligrams min Minutes MLn General metal-ligand fragment mL Millilitres mm Millimetres mmol Millimoles NMR Nuclear magnetic resonance Na[BPh4] Sodium tetraphenylborate Na[PF6] Sodium hexafluorophosphate NaOMe Sodium methoxide [NBu4]F Tetrabutylammonium fluoride NHEt2 Diethylamine NEt3 Triethylamine OAc Acetate OTf Triflate, trifluoromethanesulfonate, CF3SO3

- ORTEP Oak Ridge Thermal Ellipsoid Plot program Pd(PPh3)4 Palladium(0)tetrakis(triphenylphosphine) ppn Bis(triphenylphosphine)iminium Ph Phenyl, -C6H5 PPh3 Triphenylphosphine Pz Pyrazole Tol Tolyl R General organic group [Ref] Reference r.t. Room temperature Rc Ruthenocenyl s Seconds tBu Tertiary butyl, -C(CH3)3 TCNE Tetracyanoethylene Temp. Temperature THF Tetrahydrofuran TLC Thin layer chromatography tmeda Tetramethylethylenediamine TMS Trimethylsilyl, -Si(CH3)3, SiMe3 Tp’ Hydridotris(3,5-dimethylpyrazolyl)borate Ts Tosyl ∆ Reflux µ Micro X Halide

vii

NMR: br Broad d Doublet dt Doublet of triplet Hz Hertz m Multiplet

nJIJ n bond coupling constant between nuclei I and J ppm Parts per million s Singlet sept Septet t Triplet δ Chemical shift COSY Correlation Spectroscopy IR: br Broad cm-1 Wavenumbers m Medium sh Shoulder w Weak s Strong Mass Spectroscopy: ES-MS Electrospray mass spectrum M Molecular ion m/z Mass per unit charge Electrochemistry: E Potential En Potential of nth redox process E1/2 Half-wave potential ∆E Potential difference ia Anodic peak current ic Cathodic peak current mV Millivolts V Volts CV Cyclic voltammogram

viii

General experimental conditions

All reactions were carried out under dry, high purity nitrogen or argon using standard

Schlenk techniques. Solvents were purified as follows: THF, Et2O, benzene were

distilled from Na/benzophenone; CH2Cl2 was distilled from CaH2; NEt3 was distilled

from KOH; MeOH was distilled from Mg/I2.

Elemental analyses were performed by the Chemical and Micro Analytical Services

(CMAS), Belmont, Victoria, Australia and by Campbell Microanalytical Laboratory,

Chemistry Department, University of Otago, Dunedin, New Zealand.

Chromatography was performed using basic alumina (0.05 - 0.15 mm, pH 9.5 ± 0.5,

Fluka) and silica gel (0.04 - 0.06mm, 230 - 400 mesh). Preparative TLC was carried

out on glass plates (20 x 20 cm) coated with silica (Merck 60 GF254, 0.5 mm thick).

Instrumentation

IR spectra were recorded on a Perkin Elmer Spectrum 1720X FT IR spectrometer

(4000 - 400 cm-1). Nujol mull spectra were collected from samples mounted between

NaCl discs. Solution spectra were obtained using a 0.5 mm path length solution cell

fitted with NaCl windows.

NMR spectra were recorded on either Bruker AM300WB or Varian Gemini 2000

spectrometers (1H at 300.13 MHz, 13C at 75.47 MHz, 19F at 564.24 MHz, 31P at

121.50 MHz). Samples were contained within 5 mm sample tubes. Chemical shifts (δ)

are reported in ppm, relative to an internal standard of tetramethylsilane (0 ppm) for 1H and 13C NMR spectra, an external standard of H3PO4 (0 ppm) for the 31P NMR

spectra and an external standard of C6F6 (164.9 ppm) for the 19F NMR spectra.

ix

Cyclic voltammograms were recorded using either a Maclab/400 supplied by AD

Instruments or a Princeton PAR model 263A potentiostat using a conventional three

electrode cell, using a platinum working electrode, platinum wire counter electrode

and a pseudo-reference electrode. Solutions were made up in CH2Cl2 using a 0.1 M

solution of [Bun4N][PF6] as the supporting electrolyte. All potentials were referenced

against an internal ferrocene standard, [FeCp2]/[FeCp2]+ = + 0.46 V. In all cases, the

current is proportional to the square root of the scan rate.

The ES-MS were recorded on either a VG platform 2 or a Finnigan LCQ

spectrometer. Methanol and acetonitrile solutions were directly infused into the

instrument, using a chemical aids to ionisation as required.

X-ray crystal structures were determined by Professor Allan White and Dr Brian

Skelton, University of Western Australia, Australia. Structural data were received in

CIF format and the ORTEP plots of individual molecules were generated using

Mercury 1.4.2 for windows, with non-essential hydrogen atoms removed for clarity.

Throughout this thesis, ORTEP plots adhere to the following colour scheme:

ruthenium in pink, carbon in grey, phosphorus in orange, hydrogen in pale yellow,

nitrogen in blue, germanium in purple, fluorine in bright green, oxygen in red and

sulfur in darker yellow.

Chapter One

Introduction

2

Carbon is the fourth most abundant chemical element in the universe by mass after

hydrogen, helium, and oxygen. Carbon is found in the sun, stars, comets, and in the

atmospheres of most planets. It exhibits remarkable properties and its different

allotropes include the hardest naturally occurring substance (diamond) and also one of

the softest substances (graphite) known (Figure 1). Moreover, it has a great affinity

for bonding with other small atoms, including other carbon atoms, and is capable of

forming multiple stable covalent bonds with such atoms.

Figure 1: Atomic arrangements of carbon in diamond and graphite

In 1982 the synthesis of a new polymorph of elemental carbon, known as carbyne,

was reported.1 Carbyne is a linear form of carbon, consisting entirely of sp-hybridised

carbon atoms. Carbyne can be represented by three different structures (Figure 2).

Two features alternating triple and single bonds (alkynyl or poly-yndiyl) with either

sp ((A)) or sp3 ((B)) carbon termini and a third consists solely of double bonds

(cumulenic) with sp2 carbon termini ((C)).2

C (C C) C

X

X

X

X

X

X

C (C C) C

X

X

X

X

C (C C) C XX m mm

(A) (B) (C) Figure 2: The different structures of carbyne

3

Furthermore, a new class of complexes containing chains of conjugated carbon triple

bonds capped by different transition metal centres has become of considerable

interest. The synthesis of complexes of the general formula {MLn}-(C≡C)m-{MLn},

where {MLn} represents a metal-ligand fragment has been investigated extensively.3

The carbon atoms associated with the triple bond are sp hybridised and the highly

reactive carbon units can be stabilised by using suitable organometallic building

blocks as end-capping groups. The one-dimensional units are also exceptional linking

ligands in that π-electron delocalisation over all carbons atoms in the chain enables

electron transfer between two transition metal centres to occur. Furthermore, the

bonding between the metal centre and the organic bridge is of σ-bonding nature. This

allows electronic communication between the metal end-groups through the carbon-

carbon triple bond(s). Hence, these carbon-rich bimetallic complexes are of interest

for applications in the fields of non-linear optics,4,5 molecular switches and sensors6-9

or liquid crystals.10,11 Currently, complexes of the general formula {LnM}-(C≡C)m-

{MLn} including carbon chains containing from two up to 28 carbon atoms joining

the two metal-ligand centres are known.3,12,13 The work described in this thesis

focuses on the synthesis of complexes containing a butadiyndiyl chain, that is an

unsaturated carbon chain containing four carbon atoms.

1.1. The syntheses of diynyl complexes

In 1957, the first complex containing a bridging C4 ligand was described,14 followed

by more detailed studies performed by Hagihara and co-workers in the 1970s.15 They

reported the reaction of NiCl(PPh3)Cp with buta-1,3-diyne in the presence of a

Grignard reagent which gave the diynyl complex Ni(C≡CC≡CH)(PPh3)Cp (Scheme

1).15

Cp(Ph3P)Ni C C C C H+ H C CC2H5MgBr

NiCl(PPh3)Cp H2

Scheme 1: The synthesis of Ni(C≡CC≡CH)(PPh3)Cp

4

Since then, many diynyl complexes of general formula {LnM}(C≡CC≡CR) (R =

TMS, H) were reported. They feature a C4 carbon chain capped by a metal-ligand

fragment at one end and a hydrogen atom or other simple organic group at the other.

The syntheses of diynyl complexes are of significant interest as these reagents are

very useful starting materials.

A range of diynyl complexes have been obtained from various synthetic routes. The

four most used methods are:

1) the Cu(I)-catalysed reaction of 1,3-diynes with metal-halide precursors

2) metal exchange with coupling of silyl and stannyl derivatives

3) the reaction of metal-halide precursors with organolithium reagents

4) the reaction of metal-halide with trimethylsilylbutadiyne in the presence of

Na[BPh4] and an amine solvent.

1.1.1. Synthetic strategy one

The most used method for the synthesis of diynyl complexes involves the Cu(I)-

catalysed reaction of 1,3-diynes with metal-halide precursors. This method was first

reported in 1977 for the synthesis of the cis- and trans- isomers of

Pt(C≡CC≡CH)2(PBu3)2.16,17 The mechanism of this reaction is considered to proceed

via a copper(I) alkynyl intermediate which undergoes an alkynyl-halide exchange

with the {LnM}X species and results in the formation of the diynyl complex and

regeneration of the CuX catalyst (Scheme 2).

5

RC C C CH

RC C C CCu

RC C C C{MLn}

HI (HX)

CuI (CuX)

{MLn}X

Scheme 2: Catalytic cycle for the synthesis of diynyl complexes

Many examples of this synthetic route have been reported in the literature. For

instance, the reaction of WCl(CO)3Cp with trimethylsilylbutadiyne gave the diynyl

W(C≡CC≡CTMS)(CO)3Cp in 85% yield (Scheme 3).18

Cp(OC)3W C C C C TMS+W(CO)3CpClCuI

THF/NHEt2H C C TMS

2

Scheme 3: The synthesis of W(C≡CC≡CTMS)(CO)3Cp

Similarly, the reaction of {MLn}Cl (where MLn = W(CO)3Cp’, Mo(CO)3Cp and

Fe(CO)2Cp; Cp’ = Cp or Cp*) with buta-1,3-diyne in the presence of CuI with

diethylamine as solvent gave the yellow diynyl complexes {MLn}(C≡CC≡CH) in

good yield (Scheme 4).19-21

{LnM} C C C C HH C C H+CuI

{MLn}ClTHF/NHEt2

{MLn} = W(CO)3Cp (90%) W(CO)3Cp* (77%) Mo(CO)3Cp (60%) Fe(CO)2Cp (32%)

2

Scheme 4: Synthesis of {MLn}(C≡CC≡CH)

6

1.1.2. Synthetic strategy two

Another method for the synthesis of diynyl complexes is the reaction of silyl and

stannyl derivatives (e.g. TMSC≡CC≡CTMS, Ph3SnC≡CC≡CTMS) with a metal

halide. 1,4-Bis(trimethylsilyl)buta-1,3-diyne, TMSC≡CC≡CTMS, has proved to be a

useful compound in the synthesis of diynyl complexes. For example, the reaction of

ReCl(CO)3(tBu2bpy) with TMSC≡CC≡CTMS in the presence of KF and AgOTf gave

Re(C≡CC≡CTMS)(CO)3(tBu2bpy) (Scheme 5).22

Re C C C C TMS+ TMS C CReCl(CO)2(tBu2bpy)KF, AgOTf

MeOH, ∆TMS2 (bpytBu2)(OC)2

Scheme 5: The synthesis of Re(C≡CC≡CTMS)(CO)3(tBu2bpy)

The diynyl complex Rh(C≡CC≡CTMS)(CO)(PPri3)2 was obtained from the treatment

of trans-Rh(OH)(CO)(PPri3)2 with the mixed silyl-stannyl diyne Ph3SnC≡CC≡CTMS

in benzene (Scheme 6).23

+ Ph3Sn C Ctrans-Rh(OH)(CO)(PPri3)2

Benzene

80oCTMS2 (PPri

3)2(CO)Rh C C TMS2

Scheme 6: Synthesis of Rh(C≡CC≡CTMS)(CO)(PPri

3)2

Similarly, the unsymmetric diyne Me3SnC≡CC≡CTMS was reacted with

PtCl2{P(tol)3}2 in THF to afford the diynyl complex Pt(C≡CC≡CTMS)Cl{P(tol)3}2 in

63% yield. Pt(C≡CC≡CTMS)Cl{P(tol)3}2 is further desilylated using [NBu4]F to give

the complex Pt(C≡CC≡CH)Cl{P(tol)3}2 (Scheme 7).24

Pt C C C C TMS

P(tol)3

P(tol)3

Cl

Pt C C C C H

P(tol)3

P(tol)3

Cl

Me3Sn C C TMS+THF

∆

THF

PtCl2{P(tol)3}2 2

[NBu4]F

Scheme 7: Synthesis of Pt(C≡CC≡CH)Cl{P(tol)3}2

7

1.1.3. Synthetic strategy three

A third method for the preparation of diynyl complexes involves the reaction of a

metal-halide precursor {MLn}X with an organolithium reagent such as

LiC≡CC≡CTMS. LiC≡CC≡CTMS is obtained from the treatment of

TMSC≡CC≡CTMS with one equivalent of methyllithium.25 The precipitation of the

lithium halide LiX drives the reaction to completion (Scheme 8).

{LnM} C C C C TMS+{MLn}X- LiX

Li C C TMS2

Scheme 8: Synthetic strategy three The synthesis of the complexes Fe(C≡CC≡CTMS)(CO)2Cp’ (where Cp’ = Cp, Cp*) is

an example of this route.26,27 These diynyl complexes contain a TMS-protected ligand

which can be further desilylated using potassium fluoride (Scheme 9).28

IFe

OC CO

RR

RR

RC C C CFe

OC CO

RR

RR

RTMS+

THF

R = H or Me

MeOH/THFKF

C C C CFe

OC CO

RR

RR

RH

-80oCLi C C TMS2

Scheme 9: The synthesis of Fe(C≡CC≡CH)(CO)2Cp’ (Cp’ = Cp, Cp*)

Similarly, the reaction of RuCl2(CO)2(PEt3)2 with LiC≡CC≡CTMS at -78oC afforded

the trans-bis(diynyl) complex Ru(C≡CC≡CTMS)2(CO)2(PEt3)2 which can then be

treated with [NBu4]F to give the complex Ru(C≡CC≡CH)2(CO)2(PEt3)2 (Scheme

10).25

8

Li C C TMS+ C CC C(Et3P)2(OC)2Ru TMSTHF

-78oCRuCl2(CO)2(PEt3)2 2

THF [NBu4]F

C CC C(Et3P)2(OC)2Ru H 2

25oC

2

Scheme 10: Synthesis of Ru(C≡CC≡CTMS)2(CO)2(PEt3)2 and Ru(C≡CC≡CH)2(CO)2(PEt3)2

1.1.4. Synthetic strategy four

The reaction of a metal halide with the mono TMS-substituted starting material

trimethylsilylbutadiyne HC≡CC≡CTMS in the presence of Na[BPh4] in an amine

solvent was described as another method for the synthesis of diynyl complexes. For

example, treatment of FeCl(dppe)Cp* with HC≡CC≡CTMS gave the diynyl

Fe(C≡CC≡CTMS)(dppe)Cp* in 82% yield.29 The presence of the non-coordinating

salt Na[BPh4] facilitates the ionisation of the Fe-Cl bond and NEt3 leads to

deprotonation of the intermediate to give the desired complex. The analogous

ruthenium diynyl complexes were also synthesised in very good yields using this

method (Scheme 11).30

+ C CC C{LnM} TMSTHF/NEt3

{LnM} ClNa[BPh4]

{MLn} = Fe(dppe)Cp* (82%) Ru(dppe)Cp* (79%) Ru(PPh3)2Cp (94%)

H C C TMS2

Scheme 11: Synthesis of {MLn}(C≡CC≡CTMS)

Furthermore, proto-desilylation of the two complexes Ru(C≡CC≡CTMS)(dppe)Cp*

and Ru(C≡CC≡CTMS)(PPh3)2Cp with [NBu4]F gave the unsubstituted buta-1,3-diyn-

1-yl complexes Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp,

respectively (Scheme 12).30

9

C CC C[Ru] HTHF

C CC C[Ru] TMS[NBu4]F

[Ru] = Ru(dppe)Cp* (96%) Ru(PPh3)2Cp (74%)

Scheme 12: The synthesis of diynyl [Ru](C≡CC≡CH) complexes

1.1.5. Alternative synthetic strategies

A few alternative methods have also been described in the literature when the

previous routes were unsucessful. The diynyl Fe(C≡CC≡CTMS)(dppe)Cp* was

synthesised by photolysis of Fe(C≡CC≡CTMS)(CO)2Cp* in the presence of dppe

(Scheme 13).28 The two carbonyl groups were substituted by the dppe ligand in this

case. It must be noted that this method is less efficient than the previously described

route (See Section 1.1.4.), Fe(C≡CC≡CTMS)(dppe)Cp* was obtained in 40% yield.

C C C CFe

Ph2P PPh2

TMShv

dppeC C C CFe

OC CO

TMS

Scheme 13: Synthesis of Fe(C≡CC≡CTMS)(dppe)Cp* The synthesis of Re(C≡CC≡CTMS)(NO)(PPh3)Cp* is an example of an alternative

route for the synthesis of diynyl complexes.20 It involves the reaction of the labile

precursor [Re(ClC6H5)(NO)(PPh3)Cp*]+ with HC≡CC≡CTMS, giving the

intermediate [Re(HC≡CC≡CTMS)(NO)(PPh3)Cp*]+ which is then deprotonated with

KOtBu to give the desired complex in 96% yield (Scheme 14).22

10

Re

+

NOPh3PCl

+

H C C TMS2

Re

ONPh3P

ReNOPh3P

KOBut

CCCCH TMS

C C C C TMS

Scheme 14: Synthesis of Re(C≡CC≡CTMS)(NO)(PPh3)Cp*

1.2. The syntheses of diyndiyl complexes

Diyndiyl complexes of general formula {LnM}-C≡CC≡C-{M’L’n’} are composed of

two metal-ligand fragments linked by a butadiyndiyl C4 chain.7 Complexes of this

type can be represented by one of three possible valence structures below (Figure 3).3

Most of the bimetallic complexes are represented by the valence structure A, which

comprises alternating single and triple bonds. Structure B is also based on polyynes,

while C shows a fully double-bonded cumulenic system.

{LnM} C C C C {MLn}

(A) (B)

(C)

{LnM} C C C C {MLn}

{LnM} C C C C {MLn}

Figure 3: Valence structures of diyndiyl complexes

11

The syntheses of bimetallic complexes bridged by diyndiyl ligands have been of

interest in recent times due to their potential applications in material science. Such

complexes have been suggested as components for non-linear optics,4,5 liquid

crystalline devices10,11 and as precursors to one-dimensional molecular wires.6-9

Studies have been concentrated on the synthesis of complexes containing C4 chains

capped at each end by two identical or different MLn groups.31 Although many

examples of symmetric compounds have been described only a few examples of

asymmetric complexes have been prepared.31

1.2.1. Symmetric diyndiyl complexes

Generally symmetrical diyndiyl complexes of the general formula {LnM}-C≡CC≡C-

{MLn} have been prepared by one of four main synthetic methods:

1) Coupling between an organic C4 unit with two equivalents of a metal-ligand

fragment

2) Homo-coupling between two metal ethynyl complexes {LnM}(C≡CH)

3) Coupling of a monometallic diynyl complex {MLn}(C≡CC≡CR) with a single

equivalent of a metal-ligand fragment.

4) Modification of the ligand configuration in an existing diyndiyl complex

C C=

Metal-ligand fragment {MLn}=

Halide=XR = Non-metallic substitution

+ RRX21)

22)

3)

4)

+R X

Metal-ligand fragment {M'Ln'}=

Scheme 15: Synthetic strategies for symmetric diyndiyl complexes

12

Outlined below are some literature examples demonstrating these strategies and the

reaction conditions that have been used to prepare symmetric diyndiyl complexes.

1.2.1.1 Synthetic strategy one

The first method for the synthesis of symmetric diyndiyl complexes involves the

coupling between an organic C4 unit with two equivalents of a metal-ligand fragment.

This is the most frequently used synthetic method due to the large number of

accessible butadiynyl-based starting materials and the wide range of coupling

conditions that can be applied.

Buta-1,3-diyne (HC≡CC≡CH) is the simplest and most reactive diyne molecule. It can

be prepared from the reaction of 1,4-chlorobut-2-yne with concentrated aqueous

potassium hydroxide and trapped in a THF solution.32 This compound tends to

polymerise but it can be stored in solution for up to one week at low temperatures (<

-20oC). Although buta-1,3-diyne must be handled with care, it has been used to

synthesise a number of diyndiyl complexes.

For example, the reaction of {RhCl(PPri3)2}2 or {IrCl(PPri

3)2}2 with buta-1,3-diyne in

hexane at -78°C gave the diyndiyl complexes {(PPri3)2Cl(H)Rh}2(µ-C≡CC≡C) and

{(PPri3)2Cl(H)Ir}2(µ-C≡CC≡C) in 68% yield33 and 85% yield,34 respectively (Scheme

16).

+ M C C C C M-78oC

2 {MCl(PPri3)2}2

M = Rh, Ir

Hexane

H

Cl Cl

H

Pri3P Pri

3P

PPri3 PPri

3

H C C H2

Scheme 16: {(PPri3)2Cl(H)Rh}2(µ-C≡CC≡C) and {(PPri

3)2Cl(H)Ir}2(µ-C≡CC≡C)

1,4-Bis(trimethylsilyl)butadiyne (TMSC≡CC≡CTMS) is a much more stable

derivative of buta-1,3-diyne. This white crystalline solid can be prepared in large

quantities by the oxidative coupling of trimethylsilylacetylene TMSC≡CH under Hay

coupling conditions (CuCl/tmeda/O2) and stored at room temperature.35 It has been

13

used in the preparation of a number of symmetric diyndiyl complexes. For instance,

the treatment of TMSC≡CC≡CTMS with an excess of RuCl(PPh3)2Cp in refluxing

methanol in the presence of KF yielded the desired symmetric complex

{Ru(PPh3)2Cp}2(µ-C≡CC≡C) in 66% yield (Scheme 17).36

TMS C C TMSRu

Ph3P PPh3

Cl +2 C CRu

Ph3P PPh3

C Ru

PPh3Ph3P

C

MeOHKF

∆2

Scheme 17: Synthesis of {Cp(PPh3)2Ru}2(µ-C≡CC≡C)

Similar chemistry occurs with TMSC≡CC≡CTMS and two equivalents of

Rh(OH)(CO)(PPri3)2 to give {Rh(CO)(PPri

3)2}2(µ-C≡CC≡C) in 75% yield (Scheme

18).23

+ Rh C C C C Rh2 Rh(OH)(CO)(PPri3)2 OC CO

Pri3P Pri

3P

PPri3

PPri3

MeOH

∆TMS C C TMS2

Scheme 18: Synthesis of {Rh(CO)(PPri3)2}2(µ-C≡CC≡C)

The gold diyndiyl complexes {Au(PCy3)}2(µ-C≡CC≡C) and {Au[P(tol)3)]}2(µ-

C≡CC≡C) are also prepared by treatment of AuCl(PCy3)37 or AuCl{P(tol)3}38 with

TMSC≡CC≡CTMS in presence of NaOH in a methanol solution (Scheme 19).

+ (R3P)Au C C C C Au(PR3)2 AuCl(PR3)MeOH

NaOHR = Cy or tol

TMS C C TMS2

Scheme 19: Synthesis of {Au(PCy3)}2(µ-C≡CC≡C) and {Au[P(tol)3]}2(µ-C≡CC≡C)

Furthermore, the dilithio derivative of buta-1,3-diyne (LiC≡CC≡CLi) was also used to

prepare diyndiyl complexes. This compound can be synthesised by various routes

such as the addition of n-BuLi to solutions of buta-1,3-diyne or cis-

HC≡CCH=CH(OMe) at low temperatures39,40 or the treatment of TMSC≡CC≡CTMS

14

with an excess of MeLi.41 The reaction of LiC≡CC≡CLi with two equivalents of

FeCl(CO)2Cp gives the corresponding diiron diyndyl complex {Fe(CO)2Cp}2(µ-

C≡CC≡C) with elimination of lithium chloride (Scheme 20).15

FeOC

CO

Cl +2 C CFeOC

CO

C FeCTHF

-25oC

COCO

Li C C Li2

Scheme 20: Synthesis of {Fe(CO)2Cp}2(µ-C≡CC≡C)

The complex {Fe(CO)2Cp}2(µ-C≡CC≡C) can also be synthesised by a method

involving the reaction of the organostannane Me3SnC≡CC≡CSnMe3 (prepared from

the reaction of LiC≡CC≡CLi with SnClMe3) with two equivalents of FeI(CO)2Cp in

the presence of PdCl2(NCMe)2 (Scheme 21).42

FeOC

CO

I +2 C CFeOC

CO

C FeCCO

CO

Me3Sn C C SnMe32PdCl2(NCMe)2

Scheme 21: Second method for the synthesis of {Fe(CO)2Cp}2(µ-C≡CC≡C)

1.2.1.2. Synthetic strategy two

A number of symmetric diyndiyl complexes have been obtained by homo-coupling of

two metal ethynyl complexes {LnM}(C≡CH). For example, Glaser oxidative coupling

conditions [Cu(OAc)2/pyridine/O2] were used to prepare the rhenium diyndiyl

complexes {Re(NO)(PR3)Cp*}2(µ-C≡CC≡C) (R = Ph,43-45 tol,8 C6H4tBu-48) from the

rhenium ethynyls Re(C≡CH)(NO)(PR3)Cp*. Pyridine acts as a base to deprotonate the

bis(vinylidene) obtained in situ (Scheme 22).

15

Re

ON PR3

C CH ON PR3

C

Re

NOR3P

CC

H

H

pyridine

Re

ON PR3

C C Re

NOR3P

CC

2+

Cu(OAc)2

R = Ph, tol, C6H4tBu-4

80oC CRe

Scheme 22: Synthesis of {Re(NO)(PR3)Cp*}2(µ-C≡CC≡C) (R = Ph, tol, C6H4

tBu-4)

However, it was found that these conditions are often too harsh for other complexes.

Thus, alternative reaction conditions were applied in order to synthesise other

diyndiyl complexes. The oxidative coupling of the ethynyls M(C≡CH)(dppe)Cp* (M

= Fe, Ru, Os) at low temperature with [FeCp2][PF6] generates a 17-electron radical

that undergoes a spontaneous carbon-carbon bond formation to afford an intermediate

bis(vinylidene) [{M(dppe)Cp*}2(µ-C=CH-CH=C)]2+. Deprotonation of the

bis(vinylidene) with KOtBu yields the desired symmetric diyndiyls

{M(dppe)Cp*}2(µ-C≡CC≡C) (M = Fe,46 Ru,47 Os48) in good yields (Scheme 23).

16

M

Ph2P PPh2

C CH[FeCp2][PF6]

CH2Cl2

M

Ph2P PPh2

C C

M

PPh2Ph2P

CC

H

H

2+

KOtBu THF

M

Ph2P PPh2

C C M

PPh2Ph2P

CC

M

Ph2P PPh2

C CH M

PPh2Ph2P

CHC

-80oC

M = Fe (92%), Ru (90%), Os (66%)

Scheme 23: Synthesis of {M(dppe)2 Cp*}(µ-C≡CC≡C) (M = Fe, Ru, Os)

The manganese diyndiyl [{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)]+ was prepared in a

similar manner. Desilylation and subsequent deprotonation of

[Mn(dmpe)2(C≡CTMS)2]+ gave the radical complex Mn(dmpe)2(C≡CH)(C≡C.). This

radical undergoes a spontaneous homo-coupling reaction to give

[{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)], which is oxidised by [Mn(dmpe)2(C≡CH)2]+

present in solution to afford [{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)]+ in 65% yield

(Scheme 24).49

17

TMS C C Mn C C TMS

Me2P

Me2P

PMe2

PMe2

[NBu4]FHC C Mn C CH

Me2P

Me2P

PMe2

PMe2

+ - H+

H C C Mn C C

Me2P

Me2P

PMe2

PMe2

C C Mn C CH

Me2P

Me2P

PMe2

PMe2

HC C Mn C C

Me2P

Me2P

PMe2

PMe2

C C Mn C CH

Me2P

Me2P

PMe2

PMe2

HC C Mn C C

Me2P

Me2P

PMe2

PMe2

-e-

+

Scheme 24: Synthesis of [{Mn(dmpe)2(C≡CH)}2(C≡CC≡C)]+

1.2.1.3. Synthetic strategy three

A third useful method for the synthesis of diyndiyl complexes involves the coupling

of a monometallic diynyl complex {MLn}(C≡CC≡CR) with a single equivalent of a

metal-ligand fragment. This synthetic strategy uses complexes that already contain the

butadiyndiyl chain and various conditions were reported.

The first example is the synthesis of the iron diyndiyl {Fe(dippe)Cp*}2(µ-C≡CC≡C)

from the reaction of Fe(C≡CC≡CH)(dippe)Cp* with one equivalent of

FeCl(dippe)Cp* in the presence of K[PF6] and KOtBu (Scheme 25).50

C C C CFe

Pri2P PPri

2

HK[PF6]/KOtBu

MeOH/THF

C C C CFe

Pri2P PPri

2

FeCl(dippe)Cp*Fe

PPri2Pri

2P

Scheme 25: Synthesis of {Fe(dippe)Cp*}2(µ-C≡CC≡C)

18

Alternative coupling conditions were used for the synthesis of tungsten diyndiyl

complexes. Treatment of W(C≡CC≡CH)(CO)3Cp’ with WCl(CO)3Cp’ (where Cp’ =

Cp and Cp*) in the presence of copper iodide and diethylamine gave the complexes

{W(CO)3Cp’}2(µ-C≡CC≡C) in good yield.19,21 Similarly, the reaction of

Fe(C≡CC≡CH)(CO)2Cp* with FeCl(CO)2Cp* in the presence of copper iodide and

NEt3 gave the symmetric diyndiyl {Fe(CO)2Cp*}2(µ-C≡CC≡C) (Scheme 26).26

C CC C{LnM} HCuI/NHEt2

C CC C {MLn}{LnM}{MLn}Cl

{MLn} = W(CO)3Cp (80%) W(CO)3Cp* (90%) Fe(CO)2Cp* (85%)

Scheme 26: Synthesis of {MLn}2(µ-C≡CC≡C)

1.2.1.4. Synthetic strategy four

This synthetic strategy involves the modification of the ligand configuration in an

existing diyndiyl complex. The diyndiyl {Ru(PPh3)2Cp}2(µ-C≡CC≡C) was heated

under reflux in toluene with an excess of PMe3 to afford the mixed phosphine

complex {Ru(PPh3)(PMe3)Cp}2(µ-C≡CC≡C) in 43% yield.7 Similarly, the diyndiyl

complex {Ru(PPh3)2Cp)2(µ-C≡CC≡C) undergoes a ligand exchange in the presence

of dppe at elevated temperature to give the complex{Ru(dppe)Cp}2(µ-C≡CC≡C) in

86% yield (Scheme 27).30

C C C CRuPh2P PPh2

RuPPh2

Ph2P

TolueneC C C CRu

Ph3PPPh3

RuPPh3

PPh3

C C C CRu

Ph3PPMe3

RuPPh3

PMe3PMe3

dppeToluene

Scheme 27: {Ru(PPh3)(PMe3)Cp}2(µ-C≡CC≡C) and {Ru(dppe)Cp}2(µ-C≡CC≡C)

19

1.2.2. Asymmetric diyndiyl complexes

Asymmetric diyndiyl complexes of general formula {LnM}-C≡CC≡C-{M’L’n’} are

composed of two different metal-ligand fragments linked by a butadiyndiyl C4

chain.31 Only a few examples of asymmetric complexes have been prepared. This can

be explained as most symmetric diyndiyl complexes can be prepared in a single-step

reaction while asymmetric diyndiyl complexes require multi-step syntheses.

Generally, asymmetric diyndiyls can be prepared by one main synthetic route. It

involves the initial preparation of a diynyl complex of the general formula

{LnM}(C≡CC≡CR) where R is a hydrogen atom or other simple organic group such

as TMS. The terminal R group of the carbon chain is then substituted with another

metal-ligand fragment under various reaction conditions. Detailed below are some

literature examples that demonstrate the different reaction conditions that have been

used to prepare a range of asymmetric diyndiyl complexes.

First, asymmetric diyndiyl complexes have been synthesised using the CuI-catalysed

coupling of a diynyl complex with a metal halide in amine solvents. For example, the

reaction of W(C≡CC≡CH)(CO)3Cp with various metal halides gave the desired

asymmetric diyndiyl {W(CO)3Cp}(C≡CC≡C){MLn} in good yields (Scheme 28).31

C C C CW

OCCO

HCuI/NHEt2

C C C C {MLn}{MLn}Cl

OC

{MLn} = Mo(CO)3Cp (95%) = Fe(CO)2Cp (65%) = Ru(CO)2Cp (51%) = Rh(CO)(PPh3)2 (74%) = Ir(CO)(PPh3)2 (82%) = Au(PPh3) (97%)

W

OCCO

OC

Scheme 28: The synthesis of various asymmetric diyndiyl {W(CO)3Cp}(C≡CC≡C){MLn}

20

Furthermore, an alternative reaction involves the lithiation of the terminal diynyl

ligand of the complex {LnM}(C≡CC≡CH) with any of a range of organolithium bases,

such as n-, sec- or t-BuLi, or LDA, followed by treatment with a metal halide. The

lithiation of a terminal diynyl complex with a lithium base results in the formation of

a nucleophilic species {LnM}(C≡CC≡CLi) which is subsequently treated with the

metal halide to afford the desired diyndiyl complex (see also Chapter Three).

In 1990, Wong reported the deprotonation of terminal iron diynyl complexes

Fe(C≡CC≡CH)(CO)LCp (L = CO, PPh3) with sec-BuLi and the resulting anions were

trapped with {MLn}Cl to form {Fe(CO)LCp}(C≡CC≡C){MLn} (M = Fe, Mo, W; L =

CO, PPh3; Ln = (CO)2Cp, (CO)3Cp) (Scheme 29).27

C C C C HFe

OC L

C C C C LiFe

OC L

C C C CFe

OC L

Sec-BuLi

-78oC

Fe

COOC

L = CO, PPh3FeCl(CO)2Cp

C C C CFe

OC L

M

OC CO CO

MCl(CO)3Cp

M = Mo, W

Scheme 29: Wong’s methodology for the synthesis of diyndiyl complexes

A few years later, Gladysz and co-workers extended this work to the lithiation of the

diynyl complex Re(C≡CC≡CH)(PPh3)(NO)Cp*.22 The lithiated complex

Re(C≡CC≡CLi)(PPh3)(NO)Cp* was generated and then reacted with trans-

PdCl2(PEt3)2 to give {Re(PPh3)(NO)Cp*}(C≡CC≡C){PdCl(PEt3)2} or with trans-

RhCl(PPh3)2(CO) to give {Re(PPh3)(NO)Cp*}(C≡CC≡C){Rh(PPh3)2(CO)} (Scheme

30).

21

C CRe

ON PPh3-80oC

n-BuLi

PdCl2(PEt3)2 RhCl(PPh3)2(CO)

C C H C CRe

ON PPh3

C C Li

C CRe

ON PPh3

C C Pd

PEt3

PEt3

Cl C CRe

ON PPh3

C C Rh

PPh3

PPh3

CO

Scheme 30: The reactions of Re(C≡CC≡CH)(PPh3)(NO)Cp* The complex W(C≡CC≡CH)(CO)3Cp was lithiated with LDA at -78oC. The resulting

W(C≡CC≡CLi)(CO)3Cp was then reacted with MnI(CO)5 to give the asymmetric

complex {W(CO)3Cp}(C≡CC≡C){Mn(CO)5} (Scheme 31).31

C CW

OC -78oC

LDAC C H C C C C Li

CO CO

W

OC CO CO

C C C C Mn(CO)5W

OC CO CO

MnI(CO)5

Scheme 31: The synthesis of {W(CO)3Cp}(C≡CC≡C){Mn(CO)5}

Another reaction that can be used for the synthesis of asymmetric complexes involves

the complexation of the diynyl with the metal halide in the presence of both Na[BPh4]

and NEt3/dbu. For example, the heterometallic complex

{Ru(dppe)Cp*}(C≡CC≡C){Fe(dppe)Cp*} was obtained from the reaction of the

complex Ru(C≡CC≡CH)(dppe)Cp* with FeCl(dppe)Cp* (Scheme 32).51

22

C C C C HRu

Ph2P PPh2

FeCl(dppe)Cp*C C CRu

Ph2P PPh2

Fe

PPh2Ph2P

CNa[BPh4]

NEt3/dbu

Scheme 32: The synthesis of {Ru(dppe)Cp*}(C≡CC≡C){Fe(dppe)Cp*}

Some asymmetric complexes containing gold were also synthesised from the reaction

of diynyl complexes with AuCl(PR3) in the presence of K[N(TMS)2]. For example,

the complexes {Ru(L2)Cp’}(C≡CC≡C){Au(PR3)} (Cp’ = Cp, L = PPh3, R = Ph; Cp’

= Cp*, L2 = dppe, R = Ph, tol) were obtained in good yields (Scheme 33).30

C C HCp'(L2)Ru Au(PR3)CC C CCp'(L2)RuAuCl(PR3)

K[N(TMS)2]THF

Cp' = Cp, L = PPh3, R = Ph orCp' = Cp*, L2 = dppe, R = Ph, tol

2

Scheme 33: Synthesis of asymmetric diyndiyls {Ru(L2)Cp’}(C≡CC≡C){Au(PR3)} Furthermore, the TMS-protected diynyl can be used to synthesise several asymmetric

diyndiyl complexes. For example, the complex W(C≡CC≡CTMS)(CO)3Cp reacts

with RuCl(PPh3)2Cp in presence of KF and dbu to afford the asymmetric complex

{W(CO)3Cp}(C≡CC≡C){Ru(PPh3)2Cp} in 61% yield (Scheme 34).18

C CWOC KF/dbu

RuCl(PPh3)2CpC C TMS

OC CO

C C C CWOC

OC COMeOH

Ru

PPh3PPh3

Scheme 34: Synthesis of {W(CO)3Cp}(C≡CC≡C){Ru(PPh3)2Cp} Similarly, the reaction of Ru(C≡CC≡CTMS)(PPh3)2Cp with RuCl(dppe)Cp’ (where

Cp’ = Cp or Cp*) in MeOH, in the presence of KF and dbu, gave the complexes

{Ru(PPh3)2Cp}(C≡CC≡C){Ru(dppe)Cp’} (where Cp’ = Cp or Cp*) in 42% and 45%

yield, respectively (Scheme 35).30

23

C CKF/dbu

RuCl(dppe)Cp'C C TMS C C C C

MeOH

Ru

Ph3PPPh3

Ru

Ph3PPPh3

RuPPh2Ph2P

RR

RR

R

R = H, Me

Scheme 35: Synthesis of {Ru(PPh3)2Cp}(C≡CC≡C){Ru(dppe)Cp’}

The mixed-metal complex Ru(C≡CC≡CFc)(dppe)Cp was obtained from the reaction

between FcC≡CC≡CTMS and RuCl(dppe)Cp in the presence of KF and dbu while the

complex Ru(C≡CC≡CFc)(dppm)Cp was synthesised from a similar reaction but in

presence of K[PF6] instead (Scheme 36).52

C CKF or K[PF6]

C CC C Fc

MeOH

TMS

n = 1, 2

RuPh2P PPh2

(CH2)n

FcRuPh2P PPh2

(CH2)n

Cl+dbu

2

Scheme 36: Synthesis of Ru(C≡CC≡CFc)(dppe)Cp and Ru(C≡CC≡CFc)(dppm)Cp

The mixed-metal complex {Re(PPh3)(NO)Cp*}(C≡CC≡C){Fe(dppe)Cp*} was

synthesised from the reaction of Re(C≡CC≡CTMS)(PPh3)(NO)Cp* with

FeCl(dppe)Cp* in the presence of KF, K[PF6] and 18-crown-6 in MeOH/THF

(Scheme 37).9

C CRe

ON

KF/K[PF6]

FeCl(dppe)Cp*C C TMS

Ph3P18-crown-6

C CRe

ON

C CPh3P

Fe

PPh2Ph2P

Scheme 37: Synthesis of {Re(PPh3)(NO)Cp*}(C≡CC≡C){Fe(dppe)Cp*}

24

1.3. The syntheses of trinuclear complexes

Currently, complexes of the general formula {LnM}-(C≡C)m-{MLn} include carbon

chains containing from two up to 28 carbon atoms joining the two metal-ligand

centres.3,12,13 However, as the chain length increases the synthesis becomes more

difficult and the stability of the compounds slowly decreases, especially with electron-

rich termini. Hence, the focus has been shifted to the introduction of a central bridging

group within the carbon chain. The central bridging group can be either an organic or

organometallic moiety. This is a convenient way to modify the physical properties of

the corresponding complex.

1.3.1. Organic linkers

First, the insertion of an organic moiety into these unsaturated carbon chains was

proposed. The reaction of 1,4-diethynylbenzene with two equivalents of a metal-

ligand fragment afforded, under various conditions, complexes of general formula

1,4-[{LnM}(C≡C)]2C6H4. Several examples have been described in the literature and

are summarised in Scheme 38.53-58 It was found that the insertion of the 1,4-

diethynylbenzene linker improved the stability of the complexes.

C CH C C H C C{LnM} C C {MLn}

{MLn} = RuCl(dppm)2; OsCl(dppm)2; FeCl(depe)2 RuCl(dppe)2; Ru(dppe)Cp*; Ru(dppe)Cp Fe(dppe)Cp*; Ru(PPh3)2Cp; Fc

{MLn}X

Scheme 38: Synthesis of complexes of general formula 1,4-[{LnM}(C≡C)]2C6H4

One example also involved the synthesis of a complex containing two W(CO)3CpC4

groups linked by the 1,4-phenylene unit. The complex 1,4-

[{W(CO)3Cp}(C≡CC≡C)]2C6H4 was synthesised in very good yield from the reaction

between 1,4-diiodobenzene and two equivalents of W(C≡CC≡CH)(CO)3Cp in the

presence of palladium/copper catalyst (Scheme 39).59

25

C CCp(OC)3W C C H + I I

Pd(PPh3)4CuITHF/NHPri

2

C CCp(OC)3W C C CC W(CO)3CpCC

Scheme 39: The synthesis of 1,4-{W(CO)3Cp}(C≡CC≡C)]2C6H4

Other examples of organic linkers are 2,5-thiophenediyl and 9,10-anthracenediyl.

Complexes of general formula 2,5-[{LnM}-C≡C-C4H2S-C≡C-{MLn}] where {MLn}

is Fe(dppe)Cp*,60 RuCl(dppm)2,54 OsCl(dppm)254 and Fc58 have been reported

(Figure 4).

C C{LnM} C C {MLn}

{MLn} = RuCl(dppm)2; OsCl(dppm)2; Fe(dppe)Cp*; Fc

S

Figure 4: Examples of 2,5-[{LnM}-C≡C-C4H2S-C≡C-{MLn}] complexes

A few complexes containing the 9,10-anthracenediyl moiety have also been

synthesised, such as {Cp*(dppe)M}-C≡C-C14H8-C≡C-{M(dppe)Cp*} (where M = Ru

and Fe) and the mixed-metal complex {Cp*(dppe)Fe}-C≡C-C14H8-C≡C-

{Ru(dppe)Cp*}(Figure 5).58,61

C C {MLn}C C{LnM}

{MLn} = Fe(dppe)Cp*; Ru(dppe)Cp*

Figure 5: {Cp*(dppe)M}-C≡C-C14H8-C≡C-{M(dppe)Cp*} (where M = Ru and Fe)

26

1.3.2. Organometallic linkers

Secondly, organometallic linkers can be used as the central bridging unit between two

metal-ligand centers. For example, the two redox-active ferrocene or ruthenocenyl

moieties have been employed as the central bridging group for several complexes of

general formula {LnM}-C≡C-Mc-C≡C-{MLn} (where Mc = 1,1’-M(η-C5H4)2, {MLn}

= Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp) (Figure 6).62,63

C C {MLn}

C C{LnM}

M = Fe, Ru{MLn} = Ru(dppe)Cp*; Ru(dppe)Cp; Ru(PPh3)2Cp

M

Figure 6: {LnM}-C≡C-Mc-C≡C-{MLn} complexes Similarly, the Ru(dppe)2 and Ru(dppm)2 metal-ligand fragments have also been used

as potential bridging groups as shown in Figure 7.58

Fe

C C Ru C C

Fe

PPh2Ph2P

Ph2P PPh2

n

n

n = 1, 2

Figure 7: Example of complexes with a Ru metal-ligand bridging group Furthermore, the synthesis of bis(diyndiyl) complexes of the general formula {LnM}-

C≡CC≡C-M”-C≡CC≡C-{M’Lm} has been developed. These complexes have two

transition metal fragments {LnM}-C≡CC≡C linked by a third metal centre. They have

been synthesised by various methods.

27

For example, two different mercury trimetallic complexes have been synthesised from

the reactions of Ru(C≡CC≡CH)(PR3)2Cp’ [(PR3)2 = dppe, Cp’ = Cp*; PR3 = PPh3,

Cp’ = Cp] and Hg(OAc)2 in THF (Scheme 40).64

RuR

RR

R

R C C C C Hg C C C C Ru R

R

RR

R(PR3)2

(PR3)2

(PR3)2 = dppe, R = Me or PR3 = PPh3, R = H

RuR

RR

R

R C C C C

(PR3)2

Hg(OAc)2THF

∆

H

Scheme 40: Synthesis of Hg{C≡CC≡C[Ru(PR3)2Cp’]}2 complexes

Similarly, the reactions of the diynyl complexes W(C≡CC≡CH)(CO)3Cp and

Au(C≡CC≡CH)(PR3) (where R = Ph, tol) with Hg(OAc)2 also afforded the trimetallic

complexes Hg[C≡CC≡C{MLn}]2 (where {MLn} = W(CO)3Cp, Au(PR3)).31,59

In addition, the reaction of trans-PdCl2(PEt3)2 with Re(C≡CC≡CLi)(PPh3)(NO)Cp*

(obtained from the treatment of Re(C≡CC≡CH)(PPh3)(NO)Cp* and n-BuLi) gives the

palladium complex trans-[{Re(PPh3)(NO)Cp*C4}2Pd(PEt3)2] in 73% yield (Scheme

41).22

28

C Pd C C

ON

PPh3

NO

PEt3

PEt3

Re C C C C C Re

Ph3P

C C C C HReON

(PPh3)

n-BuLi

-80oCTHF

C C C C LiReON

(PPh3)

PdCl2(PEt3)2-80oCTHF

Scheme 41: Synthesis of trans-[{Re(PPh3)(NO)Cp*C4}2Pd(PEt3)2]

Another method for the synthesis of bis(diyndiyl) complexes involves the CuI-

catalysed coupling of bis(diynyl) complex with a metal halide in amine solvents. For

example, the complexes trans-Pt{(C≡CC≡C)[M(PBu3)2Cl]}2(PBu3)2 (M = Pd, Pt)

were synthesised from the reactions of Pt(C≡CC≡CH)2(PBu3)2 with two equivalents

of trans-MCl2(PBu3)2 in the presence of CuI and NHEt2 (Scheme 42).16 Similarly, the

coupling of W(C≡CC≡CH)(CO)3Cp with cis-PtCl2(L2) species gave the complexes

cis-Pt{(C≡CC≡C)[W(CO)3Cp]}2(L2) (where L2 = dppe, dppp; L = PEt3).31

C C C C HPt

PBu3

PBu3

C C C CH

trans-MCl2(PBu3)2CuI/NHEt2

M = Pd (65%), Pt (40%)

C C C C MPt

PBu3

PBu3

C C C CM

PBu3

PBu3

Cl

PBu3

PBu3

Cl

Scheme 42: Synthesis of trans-Pt{(C≡CC≡C)[M(PBu3)2Cl]}2(PBu3)2 (M = Pd, Pt)

29

The reaction of [ppn][Au(acac)2] with diynyl complexes {MLn}(C≡CC≡CH) (where

{MLn} = W(CO)3Cp, Au(PPh3)) in a NHEt2/CH2Cl2 solvent gave the trimetallic

complexes in good yield as shown in Scheme 43.65

C CC C{LnM} H

NHEt2/CH2Cl2

C CC C {MLn}AuCC CC{LnM}

{MLn} = W(CO)3Cp (85%) = Au(PPh3) (73%)

[ppn][Au(acac)2]

ppn

+

Scheme 43: Synthesis of [ppn][Au{C≡CC≡C{MLn}}2]

Finally, the bis(ferrocenylalkynyl)ruthenium complex trans-Ru(C≡CC≡CFc)2(dppe)2

was synthesised by a different method.66 It was obtained from the reaction of

RuCl2(dppe)2 and the terminal alkyne FcC≡CC≡CH in the presence of Na[PF6] and

NEt3 (Scheme 44). This complex possesses a Ru(dppe)2 moiety as the central linking

group between the two carbon chains.

C C C C H

CCC C Ru

Ph2P PPh2

PPh2Ph2P

C C CC

CH2Cl2

Ru

Ph2P PPh2

PPh2Ph2P

Cl

Na[PF6] NEt3

+

Fe

Fe Fe

Cl

Scheme 44: Synthesis of trans-[Ru(C≡CC≡CFc)2(dppe)2] complex

30

1.4. Molecular wires

The miniaturisation of various electronic devices and their components has fascinated

and inspired the scientific community for many years. In 1949, the first digital

computer weighed as much as six elephants and filled a room big enough to hold

twenty of them.67 Less than sixty years later, we are able to make much smaller and

more powerful computers. This revolution in electronics came with the invention of

the integrated circuit which is described as a series of electronic devices layered in a

precise configuration in silicon, a semi-conducting material.68 Continual progress in

this field is driven by the fabrication of ever-smaller devices within the integrated

circuit. However, some limitations to this technology have raised concern and

researchers are now attempting to build new materials using the simplest molecular

building blocks, atoms and molecules. Recently, the field of molecular circuits has

expanded with the synthesis of molecular wires,69-72 switches,73-75 memories76,77 and

diodes.78

Any molecular circuit is composed of molecular wires which allow the current to flow

from one end of the molecule to the other. A molecular wire is defined as a “one

dimensional molecule allowing a through-bridge exchange of an electron/hole

between its remote ends/terminal groups, themselves able to exchange electrons with

the outside world”.69 The three most promising candidates for molecular wires are

conjugated organic molecules,79,80 carbon nanotubes81 and redox-active complexes.82

A wide variety of organic molecular wires with impressive size (up to 128 Å) were

successfully prepared by linking various unsaturated organic units.79,83-87 One

example of such a molecule is shown in Figure 8. The alternating single and multiple

carbon-carbon bonds within these compounds provide a rigid backbone which

facilitates electron transport through their conjugated π-systems.

Et2N3

R R

8

128 Å

TMS

Figure 8: A potential organic molecular wire, R = 3-ethylheptyl

31

Furthermore, the application of carbon nanotubes in molecular electronics has become

very promising.70,88-90 They appear as a sheet of graphite with a hexagonal lattice

rolled into a seamless cylinder. The structural properties of the carbon nanotubes can

be changed, such as the number of layers, the diameter of the cylinder and the

wrapping angle. For example, three different wrapping angles are shown in Figure 9.

Structure (a) is the nanotube in the armchair configuration, while (b) and (c) are the

zigzag and the chiral forms, respectively.91 The conductivity of a carbon nanotube is

dependent on these structural differences.

Figure 9: Structural differences of carbon nanotubes91

Recently, organometallic chemists incorporated metal centres in molecular wires.69

Such organometallic molecular wires attracted interest due to the possibility of “fine-

tuning” the electronic properties of the wire, by varying the ligands on the metal

centres or by changing the oxidation state of the metals. Bimetallic compounds in

which unsaturated elemental carbon chains span two transition metals constitute the

most fundamental class of carbon-based molecular wires. They are described by the

general formula {LxM}-Cn-{M’L’x’} where MLx represents a metal-ligand fragment

and Cn is the conjugated bridging ligand.92 Most of the carbon chains contain yndiyl

32

-C≡C- or poly-yndiyl -{C≡C}n- units which have remarkable versatility and π-density

which allows the delocalisation of electrons. Furthermore, a redox-active molecular

wire works when an unpaired electron is transferred across the entire molecule. This

free electron is obtained by either the loss of an electron from the highest occupied

molecular orbital (HOMO) or the addition of an electron to the lowest unoccupied

molecular orbital (LUMO) of the neutral complex. The two metal termini are left in

different oxidation states, forming a mixed-valence complex. The free electron can

then reside on either metal terminus (Figure 10).

e-

e-

M MConjugated bridge

Figure 10: Schematic representation of electron transfer in a redox-active molecular wire

The Robin-Day classification of mixed-valence compounds can describe the degree of

electronic interactions between both capping redox-active metals of a molecular

wire.93 Consider the bimetallic complex {LxM}-Cn-{MLx} which possesses two

identical redox-active sites linked by a Cn spacer. There are three possibilities under

the Robin-Day classification:

(i) Class I complexes do not allow any communication between the metal

centres as a result of the bridging ligand Cn acting as an insulator. The

charge is totally localised on one of the redox centres.

(ii) Class II materials are complexes with weakly interacting redox centres.

The charge is not localised on one of the metal centres nor is it delocalised

over the whole molecule. This characteristic distinguishes these materials

from Class I and at least one spectroscopic method is able to differentiate

between the two metal termini.

33

(iii) Class III complexes allow communication between the metal termini.

There are very strong interactions between the two metal centres and the

bridging ligand Cn acts as a conductor. Therefore, the charge in this type of

compound is fully delocalised over the whole molecule. Oxidation of

these complexes occurs in a stepwise manner, one electron at a time.

Recently, a fourth class, between Class II and III, has been proposed.94 Complexes in

this class have an inter-valence charge transfer that is not solvent dependent. This

characterises them as class III complexes. However, it is possible to determine some

charge localisation through the use of IR and low temperature X-ray crystallography,

which indicates class II complexes. One such example is the Creutz-Taube ion

[{H3N)5Ru}2(µ-pz)]5+.94

1.4.1. Evaluation of molecular wires by cyclic voltammetry

Many compounds can be suggested as models for molecular wires, hence a given

compound should prove its ability to transfer electrons in order to be considered as a

molecular wire. Cyclic voltammetry is one of the most frequently used

electrochemical methods to evaluate the electronic interaction between two redox-

active centres because of its relative simplicity.95,96

Cyclic voltammetry is a method to evaluate the oxidation potential of molecules and

measure the current response between redox-active metal termini. This technique

employs a three-electrode system. The most important electrode is the working

electrode where the redox reaction of the analyte takes place. The second electrode is

the auxiliary electrode (also known as the counter electrode). Its purpose is to conduct

electricity from the signal source into the solution, maintaining the correct current.

The third electrode is the reference electrode with a known and constant potential

(Figure 11). The basic theory behind cyclic voltammetry is to trace the transfer of

electrons during an oxidation-reduction reaction. At the negative electrode, the anode,

electrons are given off, and oxidation takes place. At the positive electrode, the

cathode, the electrons are collected, and reduction occurs. This giving-and-taking of

electrons creates an electric current and a potentiometer measures the current response

against the voltage.97

34

Figure 11: Cyclic voltammetry experimental set-up: the cell

The cyclic voltammetry experiment involves applying a triangular voltage as shown

in Figure 12. The experiment starts off with an initial potential Einitial at which no

redox reaction can take place. A forward scan is then performed by increasing the

potential linearly until it reaches the switching potential Eswitch and the cathodic

reaction is recorded. At this point, a reverse scan is carried out by decreasing the

potential back to the final potential Efinal measuring the anodic reaction.

Figure 12: Applied waveform used in a cyclic voltammetry experiment

A theoretical trace of a fully reversible one-electron process is shown in Figure 13.

From this trace, it is possible to measure both the cathodic ic and anodic ia peak

currents and the half-wave potential E1/2 which is the average between the anodic

potential Ea and the cathodic potential Ec (Equation 1).98

35

( )Ca EEE += 21

2/1 Equation 1

Figure 13: Theoretical trace of a fully reversible redox event

Furthermore, to obtain accurate voltammograms, measurements must be taken under

the conditions of a stationary working electrode and an unstirred solution. The way in

which redox-active complexes move between the bulk solution and the interface

double layer, called the mass transport, must be controlled by diffusion (Figure 14).98

+

+++

+++++

-----------

Double layer

Electrode

Diffusionlayer

Bulk

SolutionInterface

Figure 14: Enlarged view of the area around the working electrode

36

If the mass transport is controlled by diffusion, the current intensity (peak height of

the relevant redox event) is related to the square-root of the scan rate (Equation 2).98

i α ν Equation 2

A plot of the peak current versus the square root of the scan rate will show a linear

relationship for a fully reversible system. The ratio between the cathodic and anodic

currents will be equal to 1 for a fully reversible process, i.e., ic/ia = 1. In the case of a

partially reversible process, 1 > ic/ia > 0 while for a fully non-reversible event, ic/ia = 0

and is independent of scan rate.

For a symmetric molecular wire of general formula {LxM}-Cn-{MLx}, the difference

between successive oxidation potentials in the cyclic voltammogram is identified as

∆Eo. The value of ∆Eo is determined by the extent of the interactions between the two

termini of the wire: the greater the value, the greater the electronic communication

between the metal termini and the more efficient the complex is as a molecular

wire.69,99,100 Two cases were determined. The first one shows no interaction between

the two redox centres since the spacer acts as an insulator (Class I). Both metal

centres will be oxidised and reduced at the same potential and the cyclic

voltammogram will show a single wave representing a two-electron redox process

(Figure 15a).101 The oxidation potential of the two metal centres will only differ by a

small statistical factor described by ∆Eo = 2(RT/F)ln2, where R is the molar gas

constant, T is the temperature and F is the Faraday constant. The second case involves

a molecule with strong interactions between the two metal centres (Class III). The

cyclic voltammogram will show a minimum of two well-separated waves, each

corresponding to a one-electron process (Figure 15b).10 The formation of the mono-

oxidised species generates the first oxidation wave, while the second wave

corresponds to the formation of the doubly oxidised species. For Class III complexes,

electronic communication is high as ∆Eo is usually greater than 0.2 V. A molecular

wire is therefore a Class III material.69 For a class II complex, the relationship

between ∆Eo and the electron delocalisation becomes complicated as structural

reorganisation, solvation or ion pairing can affect ∆Eo values.

37

Figure 15: Cyclic voltammogram of class I (a) and class III (b) binuclear complexes

The diyndiyl complex {Cp(PPh3)2Ru}(C≡CC≡C){Ru(PPh3)2Cp} is a typical example

of a class III molecule.7 Its cyclic voltammogram shows four waves, each

representing a one-electron redox process, with three waves being fully reversible and

the last being irreversible. The large values of ∆Eo imply that strong interactions occur

between the metal termini and the carbon chain acts as a conductor. The presence of

four oxidation waves suggests that the stepwise oxidation of the neutral molecule to

the +4 state occurs via four one-electron redox events which may be represented by

the structural changes in the carbon bridge shown in Figure 16.7

38

[Ru] C C C C [Ru]

[Ru] C C C C [Ru]

[Ru] C C C C [Ru]

[Ru] C C C C [Ru]

[Ru] C C C C [Ru]

-e-

-e-

-e-

-e-

1+

2+

3+

4+

[Ru] = Ru(PPh3)2Cp

Figure 16: Stepwise oxidation of {Cp(PPh3)2Ru}(C≡CC≡C){Ru(PPh3)2Cp}

39

The molecular orbital (MO) diagram of the model complex {Cp(PH3)2Ru}(C≡C-

C≡C){Ru(PH3)2Cp} was prepared using theoretical calculations (Figure 17). This

diagram offers a better understanding of the bonding occurring between the C4 chain

and the two metal centres. This MO diagram shows that the bonding between the

metal and the carbon chain is of σ- and π-bonding nature.

The σ-type interactions are located between the high-lying metallic frontier molecular

orbitals (FMOs) 3bu and 3ag and the low-lying C4 orbitals 1bu and 2ag. These

interactions contribute to donation of electron density from the carbon chain towards

the metal. The σ-type bonding is complemented by relatively weak π-type back-

bonding from occupied metallic FMOs into the high-lying acceptor C4 FMOs 1au and

2bu. The large energy difference between these orbitals limits the degree to which

these back-bonding interactions may contribute to the metallic and organic fragments

bonding.

The predominant π-type interactions are filled/filled interactions between the FMOs

of the C4 spacer (1bg and 1ag) and the corresponding occupied metallic FMOs with the

same symmetry (1bg and 2ag). These interactions stabilise the C4 orbitals while the

metallic orbitals are destabilised and become the HOMOs of the neutral system. As a

consequence of these π interactions, a large percentage contribution takes place from

the carbons atoms of the C4 chain to the HOMOs of the neutral molecule. Therefore,

the HOMOs are delocalised over the entire six-atom Ru-C4-Ru chain and any

oxidation process which involves loss of electrons from these orbitals will not be

exclusively metal-centered.

In addition, it can be seen in the middle of Figure 17 that the HOMOs are well

separated from the high-lying LUMOs 2au and 3bu (3.37 eV) and the other lower-

lying occupied MOs. Therefore, it is expected that {Cp(PH3)2Ru}(C≡C-

C≡C){Ru(PH3)2Cp} will be able to lose up to four electrons, two from each HOMO,

giving rise to a total of five potential oxidation states. We can assume that similar

results will be obtained for the complex {Cp(PPh3)2Ru}(C≡CC≡C){Ru(PPh3)2Cp} as

the only difference is due to the substitution of PPh3 for PH3 to simplify the

calculations. This was confirmed experimentally by the cyclic voltammogram.7

40

Figure 17: Molecular orbital diagram of {Cp(PH3)2Ru}(C≡CC≡C){Ru(PH3)2Cp}

41

1.5. Work described in this thesis

In this thesis, the effect of inserting a central bridging group within the carbon chain is

investigated with the inclusion of the Ru(dppe)2 and the copper(I) or silver(I) cluster

M3(µ-dppm)3 (M = Cu, Ag) bridging ligands. Several symmetric and asymmetric

bis(diyndiyl) ruthenium(II) complexes of the general formula {LnM}-C≡CC≡C-

{M”L”p}-C≡CC≡C-{M’L’m} were synthesised. The electrochemistry of each of these

complexes is examined to determine if the insertion of the bridge allows or inhibits

the electronic communication between the two terminal redox-active groups. The

electronic interactions are also compared to those of complexes with longer straight

carbon chains.

Furthermore, the development of a synthetic route for the synthesis of diynyl and

diyndiyl ruthenium(II) complexes is described. The lithiation of the ruthenium(II)

diynyl complexes Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp gives

lithio derivatives of assumed formula [Ru](C≡CC≡CLi) (where [Ru] = Ru(dppe)Cp*,

Ru(PPh3)2Cp). These then react further with metal halides, organic and

polyfluoroaromatic reagents to give new diynyl and asymmetric diyndiyl complexes.

This new synthetic route allows the synthesis of several complexes which could not

be obtained from previously known methods. The complexes synthesised were

characterised by spectroscopic methods and where possible X-ray structure

determination. The electrochemistry of some of these complexes is also described.

In addition, the reactions of various diynyl and acetylene ruthenium(II) complexes

with azide reagents are explored. These reactions are expected to be related to “Click

Chemistry”, in particular the Huisgen 1,3-dipolar cycloaddition of the alkynes with

the azides to generate 1,2,3-triazoles. However, the reactions did not proceed as

expected, but gave a range of novel products which are characterised using both

spectroscopic and structural methods.

Chapter 2

The Chemistry of Bis(Diyndiyl) Ruthenium(II) Complexes

43

2.1. Introduction

Metal complexes with a conjugated carbon bridge have currently attracted great

attention because of their potential applications in molecular electronics. Many

diyndiyl compounds {LnM}-C≡CC≡C-{MLn} (where MLn is a metal-ligand fragment)

containing various redox-active metal centers have been prepared with metal termini

including Fe(dppe)Cp*,46 Re(PPh3)(NO)Cp*,44 Ru(PPh3)2Cp7 and Ru(dppe)Cp*102 for

example. These complexes show strong electronic interactions between the two redox-

active metal termini through the conjugated C4 chain (Figure 18a).

An exciting development has been the synthesis of bis(diyndiyl) complexes of the

general formula {LnM}-C≡CC≡C-{M”L”p}-C≡CC≡C-{M’L’m}. These complexes

have two transition metal fragments linked by a third metal centre. It is interesting to

evaluate the electronic properties associated with these types of complexes and to

determine if there is any electronic communication through the central organometallic

moiety or not (Figure 18b).

M Carbon Chain M

e-

(a)

M Carbon Chain M

e-

Carbon Chain M

(b) Figure 18: Electron delocalisation on various molecular wires

Few bis(diyndiyl) complexes have been synthesised until now and their central

bridging group can be classified in two categories. This group can either act as an

insulator by inhibiting the electronic communication through the carbon chain or it

can act as a conductor allowing electronic communication between the two terminal

metals.

One such example of a bis(diyndiyl) complex was synthesised from the reaction

between Ru(C≡CC≡CH)(dppe)Cp* and Hg(OAc)2 in THF to afford the complex

Hg{C≡CC≡C[Ru(dppe)Cp*]}2 (Figure 19).64

44

C C C CRuPh2P

PPh2

Hg C C C C Ru

Ph2P PPh2

Figure 19: The complex Hg{C≡CC≡C[Ru(dppe)Cp*]}2

The electronic structure of this compound was analysed using Extended Hückel (EH)

and Density Functional Theory (DFT) molecular orbital calculations, carried out on

the hydrogen-substituted model complex Hg{C≡CC≡C[Ru(dHpe)Cp*]}2 [dHpe =

H2P-(CH2)2-PH2]. The DFT molecular orbital plot of the HOMO is shown in Figure

20. The theory shows that there is a lack of Hg contribution in the HOMO which

prevents any electronic communication between the ruthenium termini and this was

confirmed by cyclic voltammetry. Hence, it can be concluded that the mercury atom

in Hg{C≡CC≡C[Ru(dppe)Cp*]}2 acts as an insulator.64

Figure 20: DFT molecular orbital plot of the HOMO of Hg{C≡CC≡C[Ru(dHpe)Cp*]}2

The same situation was found to occur when Pt, Pd and Cu metals were incorporated

into the bridging carbon chains.103 For example, the electrochemistry of the palladium

complex trans-[{Re(NO)(PPh3)Cp*C4}2Pd(PEt3)2] (Figure 21) was investigated. In

this instance, the ESR spectra of the monocation showed that the unpaired electron is

localised on the rhenium atom. Hence, the -C≡CC≡C-Pd-C≡CC≡C- linkage does not

45

allow electron delocalisation between the rhenium termini, and it is believed that the

palladium atom provides the principal barrier to delocalisation. This is another

example of a bis(diyndiyl) complex with no communication between the metal

centres.22

C Pd C C

ON

PPh3

NO

PEt3

PEt3

Re C C C C C Re

Ph3P

Figure 21: Molecular structure of trans-[{Re(NO)(PPh3)Cp*C4}2Pd(PEt3)2]

By contrast, bis(alkynyl)ruthenium systems were reported to allow communication

between the two end-groups. For example, the middle ruthenium moiety of the

complexes [cis-Ru(C≡CFc)2(dppm)2]CuI and trans-Ru(C≡CFc)2(PBu3)2(CO)(L) (L =

CO, pyridine or P(OMe)3) allows electronic interactions between the terminal

ferrocenyl groups (Figure 22 and Figure 23).104

Ru

PPh2

PPh2

Ph2P

Ph2P

Fe

Fe

Cu I

Figure 22: [cis-Ru(C≡CFc)2(dppm)2]CuI

Fe

C C Ru C C

Fe

L PBu3

Bu3P CO

L = CO, C5H5N, P(OMe)3

Figure 23: Ru(C≡CFc)2(PBu3)2(CO)(L)

46

Furthermore, in 1998 Dixneuf and co-workers reported the synthesis of a

bis(ferrocenylalkynyl)ruthenium complex trans-[Ru(C≡CC≡CFc)2(dppe)2] which

shows electronic communication from one end of the organometallic complex to the

other.66 This complex possesses a Ru(dppe)2 moiety as the central linking group of the

two carbon chains (Figure 24). It was synthesised from the reaction of RuCl2(dppe)2

and FcC≡CC≡CH in the presence of Na[PF6] and NEt3.

In order to evaluate how the carbon-rich bridges and the Ru(dppe)2 moiety

communicate information from one end of the molecule to the other, the redox

potentials of the ferrocenyl and ruthenium moieties were measured using cyclic

voltammetry. The cyclic voltammogram of trans-[Ru(C≡CC≡CFc)2(dppe)2] is

composed of three redox potentials: two at -0.12 V and +0.01 V corresponding to the

oxidation of the ferrocenyl groups and one at +0.40 V for the RuII/RuIII system.66 Both

ferrocenyl and Ru(dppe)2 groups are reversibly oxidised and the ruthenium(II) moiety

behaves as a strong electron-donating centre. Thus, this study confirmed that the

Ru(dppe)2 moiety allows electronic communication and that the -C≡C-C≡C- bridge is

very efficient in allowing electronic communication from one end of the linear

organometallic molecule to the ferrocenyl group at the other end. This complex shows

the potential of this particular ruthenium fragment as a connector between carbon-rich

systems to mediate electron conduction.

CCC C Ru

Ph2P PPh2

PPh2Ph2P

C C CC

Fe Fe

Figure 24: trans-[Ru(C≡CC≡CFc)2(dppe)2]

47

2.2. Aim of this work

The primary aim of this work is to develop a method for the synthesis of

bis(diyndiyl) ruthenium complexes of the general formula {LnM}-C≡CC≡C-

Ru(dppe)2-C≡CC≡C-{M’L’m}, featuring two transition metal fragments linked by a

trans-(C≡CC≡C)2Ru(dppe)2 moiety. Two different approaches to these complexes can

be taken with a double addition of the transition metal termini giving symmetric

complexes (where LnM = M’L’m) or sequential addition giving rise to the possibility

of asymmetric complexes (where LnM ≠ M’L’m).

An attractive feature of these bis(diyndiyl) ruthenium(II) complexes is the presence of

the Ru(dppe)2 moiety as the central bridging group. It was previously shown that the

Ru(dppe)2 moiety allows electron communication along a carbon chain. Hence, our

objective is to investigate further the electrochemical behavior of the new

bis(diyndiyl) complexes by using cyclic voltammetry and to demonstrate that the

Ru(dppe)2 moiety acts as a conductor in this type of complex.

Secondly, the trinuclear copper(I) or silver(I) clusters M3(µ-dppm)3 (M = Cu, Ag) are

proposed as different central bridging groups to link two ruthenium diynyl fragments.

Complexes of the general formula {Cp*(dppe)Ru}-C≡CC≡C-{M3(µ-dppm)3}-

C≡CC≡C-{Ru(dppe)Cp*} were synthesised and characterised. Cyclic voltammetry

can then be used to determine what effect the inclusion of the copper(I) and silver(I)

cluster has on the electronic communication between the two metal end-groups.

48

2.3. Results and Discussion

2.3.1. Symmetric complexes trans-Ru{C4[Ru]}2(dppe)2

The synthesis of symmetric bis(diyndiyl) complexes trans-Ru{C4[Ru]}2(dppe)2

(where [Ru] = Ru(dppe)Cp*, Ru(dppe)Cp or Ru(PPh3)2Cp) was achieved by the

reaction of trans-Ru(C4H)2(dppe)2 (1) with two equivalents of a chlororuthenium

complex in the presence of an excess of NEt3 and Na[BPh4]. The reaction mixture

was heated in a refluxing mixture of CH2Cl2/MeOH for two hours (Scheme 45). The

presence of the non-coordinating salt Na[BPh4] facilitates the ionisation of the Ru-Cl

bond while treatment with NEt3 leads to deprotonation of the vinylidene intermediate

to give the desired complex.

Ru

Ph2P PPh2

PPh2Ph2P

HC C C CC C C CH

2 eq [Ru]Cl 1:1 CH2Cl2/MeOHNa[BPh4]

Ru

Ph2P PPh2

PPh2Ph2P

[Ru]C C C CC C C C[Ru]

NEt3∆

(1)

[Ru] = Ru(dppe)Cp* (2), Ru(dppe)Cp (3) or Ru(PPh3)2Cp (4)

Scheme 45: Synthetic strategy for symmetric bis(diyndiyl) complexes

49

The symmetric bis(diyndiyl) complex trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2) was

successfully synthesised as a yellow-green powder in 70% yield while the complexes

trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3) and trans-Ru{C4[RuCp(PPh3)2]}2(dppe)2 (4)

were obtained as brown solids in 75% and 77% yields, respectively.

Complexes 2, 3 and 4 each contain three redox-active metal centres bridged by

butadiyndiyl chains. The Ru-C4-Ru-C4-Ru fragment forms an eleven-atom chain. The

central ruthenium has two dppe ligands attached, whereas the terminal rutheniums are

bound to various ligands. These complexes are therefore examples of trinuclear

complexes.

Complexes 2, 3 and 4 were fully characterised by 1H, 31P and 13C NMR, IR, ES-MS

and microanalysis. All the data are summarised in Table 1. The characteristic peaks

for the Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp ligands are present in the 1H, 31P

and 13C NMR spectra. In the 31P NMR spectrum of 2, 3 and 4, a singlet is also present

for the four equivalent phosphorus nuclei on the central ruthenium which indicates a

trans configuration. The carbons of the carbon chains were not observed in the 13C

NMR spectra due to the lack of solubility of the complexes in common NMR

solvents. However, the IR spectra of the three complexes contain ν(C≡C) bands

between 1969 and 2124 cm-1. Further characterisations of 2, 3 and 4 were obtained

from ES-MS which contained ions corresponding to [M]+, a fragment ion at m/z 898

for [Ru(dppe)2]+ and fragment ions for the corresponding Ru(dppe)Cp*, Ru(dppe)Cp

and Ru(PPh3)2Cp groups.

50

Table 1: Spectroscopic data for complexes 2 - 4

Complex IR (cm-1) ν(C≡C)

1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

2 2012 (m) 1969 (w)

7.72-7.04 (m, 80H, Ph); 2.60-2.55, 1.91-1.82 (2 x m, 16H, CH2CH2); 1.46 (s, 30H, Cp*)

135.46-129.61 (m, Ph); 97.80 (s, C5Me5); 31.49-31.15 (m, CH2CH2); 11.53 (s, C5Me5)

76.3 (s, Ru(dppe)Cp*) 53.4 (s, Ru(dppe)2)

2266, [M]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+

3 2124 (m) 2013 (w)

7.67-7.16 (m, 80H, Ph); 4.35 (s, 10H, Cp); 2.23-2.19, 1.91-1.79 (2 x m, 16H, CH2CH2)

136.27-129.37 (m, Ph); 83.85 (s, C5H5); 29.09-28.34 (m, CH2CH2)

80.7 (s, Ru(dppe)Cp) 56.5 (s, Ru(dppe)2)

2123, [M]+; 2122, [M - H]+; 898, [Ru(dppe)2]+; 606, [Ru(NCMe)(dppe)Cp]+; 565, [Ru(dppe)Cp]+

4 2014 (w) 1979 (w)


133.88-127.14 (m, Ph); 83.10 (s, C5H5); 30.09-29.56 (m, CH2CH2)

57.0 (s, Ru(dppe)2) 43.0 (s, Ru(PPh3)2)

2375, [M]+; 1685, [Ru(PPh3)2CpC4Ru(dppe)2C4]+

; 898, [Ru(dppe)2]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+

51

2.3.2. Asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2

The strategy for the synthesis of asymmetric bis(diyndiyl) complexes involved the

reaction of trans-Ru(C4H)2(dppe)2 (1) with one equivalent of a chlororuthenium

complex in a CH2Cl2/MeOH solvent mixture. An excess of Na[BPh4] and NEt3 are

necessary for the ionisation of the Ru-Cl bond and the deprotonation step. The

reaction was complete after a 1 h reflux (Scheme 46).

Ru

Ph2P PPh2

PPh2Ph2P

HC C C CC C C CH

1 eq [Ru]ClCH2Cl2/MeOH

Na[BPh4]

Ru

Ph2P PPh2

PPh2Ph2P

HC C C CC C C C[Ru]

NEt3∆


(1)

Scheme 46: Synthetic strategy for asymmetric bis(diyndiyl) complexes

The asymmetric bis(diyndiyl) complexes trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2

(5) and trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6) were obtained as green solids in

80% and 85% yield, respectively. Trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) was

synthesised in 85% yield as a brown powder.

52

Complexes 5, 6 and 7 were readily identified from their spectroscopic data and

elemental analysis. Table 2 summarises the data obtained. In the 1H, 31P and 13C NMR

spectra, the characteristic peaks for the Ru(dppe)Cp*, Ru(dppe)Cp, Ru(PPh3)2Cp and

Ru(dppe)2 ligands are present. The 1H NMR spectra of 5, 6 and 7 also show a singlet

corresponding to the terminal hydrogen at δ 1.44, 1.41 and 1.40, respectively. The

infrared spectrum of the three complexes contain different bands assigned to ν(C≡C)

and ν(≡CH). The ES-MS of complexes 5, 6 and 7 contain strong [M]+ ions, with

fragmentation ions for Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp.

53


Complex IR (cm-1)

1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

5 ν(≡CH) 3055 (m); ν(C≡C) 2022 (w), 1968 (w)

7.99-7.12 (m, 60H, Ph); 2.47-2.44, 2.10-2.03 (2 x m, 12H, CH2CH2); 1.56 (s, 15H, Cp*); 1.44 (s, H)


70.5 (s, Ru(dppe)Cp*) 46.1 (s, Ru(dppe)2)

1631, [M]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+

6 ν(≡CH) 3053 (w); ν(C≡C) 1995 (m), 1919 (m)

7.42-6.87 (m, 60H, Ph); 4.50 (s, 5H, Cp); 2.55-2.51, 2.11-2.04 (2 x m, 12H, CH2CH2); 1.41 (s, H)

136.01-125.22 (m, Ph); 84.84 (s, C5H5); 30.54-29.27 (m, CH2CH2)

81.5 (s, Ru(dppe)Cp) 56.4 (s, Ru(dppe)2)

1560, [M]+; 898, [Ru(dppe)2]+; 605, [Ru(NCMe)(dppe)Cp]+; 563, [Ru(dppe)Cp]+

7 ν(≡CH) 3055 (w); ν(C≡C) 1981 (m), 1896 (m)

7.76-6.91 (m, 70H, Ph); 4.20 (s, 5H, Cp); 2.39-2.37, 2.10-2.06 (2 x m, 8H, CH2CH2); 1.40 (s, H)

133.97-125.72 (m, Ph); 81.48 (s, C5H5); 31.03-30.22 (m, CH2CH2)

53.0 (s, Ru(dppe)2) 40.0 (s, Ru(PPh3)2Cp)

1685, [M]+; 898, [Ru(dppe)2]+; 690, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+

54

2.3.3. Asymmetric complexes trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2

Previously, diyndiyl complexes of general formula {LnM}-C≡CC≡C-{MLn} have

been synthesised.7 Studies have been concentrated on the synthesis of complexes

containing C4 chains capped at each end by two identical or different MLn groups and

various methods have been described in Chapter One. One synthetic route for the

synthesis of asymmetric complexes is based on the reaction of a diynyl with one

equivalent of a metal halide in presence of a non-coordinating salt and excess of a

base. The use of the salt is very important in this reaction as it assists with the

ionisation of the metal-chloride bond and the presence of excess base allowed the

intermediate to be deprotonated immediately upon formation, thereby preventing any

side reactions from occurring. One such example is the synthesis of mixed ruthenium-

iron diyndiyls shown in Scheme 47.12

C C C CRu

Ph2P PPh2

H + Cl Fe

Ph2P PPh2

(CH2)n

Na[BPh4]/dbu

NEt3

C C C CRu

Ph2P PPh2

Fe

Ph2P PPh2

(CH2)n

Scheme 47: Synthesis of {Cp*(dppe)Ru}(C≡CC≡C){Fe(PP)Cp*} (PP = dppe, dppp)

55

Consequently, the asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 (where

[Ru] = Ru(dppe)Cp* (5), Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)) synthesised in Section

2.3.2 offer a wide range of possibilities for new chemistry. The terminal hydrogen

atom can be readily replaced by different end-groups, giving a new route for the

synthesis of asymmetric trinuclear complexes.

Hence, the reaction of trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] = Ru(dppe)Cp*

(5) or Ru(PPh3)2Cp (7)) with one equivalent of the chlororuthenium complex

RuCl(dppe)Cp in the presence of an excess of NEt3 and Na[BPh4] afforded the

asymmetric complexes trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2 (8)

and trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2 (9) in 77% and 78%

yields, respectively (Scheme 48).

Ru

Ph2P PPh2

PPh2Ph2P

HC C C CC C C C[Ru]

1 eq RuCl(dppe)Cp 1:1 CH2Cl2/MeOH

Na[BPh4]

Ru

Ph2P PPh2

PPh2Ph2P

[Ru(dppe)Cp]C C C CC C C C[Ru]

NEt3 ∆

[Ru] = Ru(dppe)Cp* (5) or Ru(PPh3)2Cp (7)

[Ru] = Ru(dppe)Cp* (8) or Ru(PPh3)2Cp (9)

Scheme 48: Synthetic strategy for 8 and 9

56

Complexes 8 and 9 were fully characterised by 1H, 31P and 13C NMR, IR, ES-MS and

microanalysis. The data are summarised in Table 3. In the NMR spectra, the

characteristic peaks for the Ru(dppe)2, Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp

ligands were present for both complexes. The infrared spectra of complexes 8 and 9

show the loss of the ν(≡CH) band and the presence of ν(C≡C) bands. Furthermore,

the ES-MS of 8 and 9 show the fragment ions for the different terminal ligands.

57

Table 3: Spectroscopic data for complexes 8 and 9


1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

8 2021 (m), 1961 (m)

7.88-6.90 (m, 80H, Ph); 4.59 (s, 5H, Cp); 2.98-2.84, 2.24-2.16 (m, 16H, CH2CH2); 1.45 (s, 15H, Cp*)

134.82-127.03 (m, Ph); 99.92 (s, C5Me5); 81.76 (s, C5H5); 30.82-29.97 (m, CH2CH2); 9.89 (s, C5Me5)

80.7 (s, Ru(dppe)Cp) 76.4 (s, Ru(dppe)Cp*) 55.6 (s, Ru(dppe)2)

2194, [M + H]+; 1629, [M - Ru(dppe)Cp]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+; 675, [Ru(NCMe)(dppe)Cp*]+; 565, [Ru(dppe)Cp]+; 605, [Ru(NCMe)(dppe)Cp]+

9 2017 (m),

1888 (w) 7.87-6.93 (m, 75H, Ph); 2.71-2.57, 2.42-2.37 (2 x m, 12H, CH2CH2); 4.58 (s, 5H, Cp); 4.32 (s, 5H, Cp)

135.47-128.56 (m, Ph); 81.25 (s, C5H5); 80.93 (s, C5H5); 30.10-29.20 (m, CH2CH2)

80.7 (s, Ru(dppe)Cp) 55.9 (s, Ru(dppe)2) 42.9 (s, Ru(PPh3)2)

1685, [Ru(PPh3)2CpC4Ru(dppe)2C4]+ ; 1559, [Ru(dppe)CpC4Ru(dppe)2C4]+; 898, [Ru(dppe)2]+; 690, [Ru(PPh3)2Cp]+; 605, [Ru(NCMe)(dppe)Cp]+; 565 [Ru(dppe)Cp]+; 429, [Ru(PPh3)Cp]+

58

2.3.4. Synthesis of trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2

Previously, it was reported that the reaction of cis-RuCl2(dppe)2 with silver triflate

leads to the abstraction of one of the halide ligands to produce the complex cis-

[RuCl(dppe)2]OTf.105 This complex was shown to react with bis(propargylic) alcohols

to form allenylidene ruthenium complexes (Scheme 49).106

OTf

Ru Cl

Ph2P

Ph2P

PPh2

PPh2

Ru

Ph2P

Ph2P

PPh2

PPh2

Cl

Cl

AgOTf

H C C C C C C C C HOH

Ph

OH

Ph

Cl Ru

Ph2P

Ph2P

PPh2

PPh2

C C

Ph

CC

C

Ph

C C C Ru Cl

Ph2P

Ph2P PPh2

PPh2

2 OTf2+

Scheme 49: First example of reaction with cis-[RuCl(dppe)2]OTf Another example is the synthesis of the complex RuCl(C≡CCHPh2)(dppe)2 from

trans-[RuCl(dppe)2]OTf and H-C≡C-CPh2(OH). This reaction is done in two steps.

The first one affords the compound [RuCl(=C=C=CPh2)(dppe)2]OTf which is then

reduced using LiAlH4 to give the desired complex (Scheme 50).107

59

OTf

Ru Cl

Ph2P

Ph2P

PPh2

PPh2

+ H C C C

OH

Ph

Ph

CH2Cl2Cl Ru

Ph2P

Ph2P

PPh2

PPh2

C CPh

CPh

OTf

LiAlH4THF

Cl Ru

Ph2P

Ph2P

PPh2

PPh2

C CPh

CPh

H

Scheme 50: Second example of reaction with trans-[RuCl(dppe)2]OTf These reactions offer possibilities to link a ruthenium fragment to a carbon chain.

Hence, Ru(C≡CC≡CH)(dppe)Cp* reacts with one equivalent of [RuCl(dppe)2]OTf in

a CH2Cl2/NEt3 solvent mixture at room temperature for two days to afford the

complex trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 (10) in 83% yield (Scheme 51).

Ru

Ph2P PPh2

PPh2Ph2P

Cl+C C C CRu

Ph2P PPh2

H

1:1 CH2Cl2/NEt3

C C C CRu

Ph2P PPh2

Ru

Ph2P PPh2

PPh2Ph2P

OTf

(10)

Cl

Scheme 51: Synthesis of 10

Complex 10 was readily identified by elemental analysis and IR, ES-MS and NMR

spectroscopy. The IR spectrum shows two ν(C≡C) bands at 2037 and 1988 cm-1. The 1H NMR spectrum contains a multiplet at δ 7.72-6.90 for the protons of the phenyl

60

groups, two multiplets at δ 3.57-3.54 and 3.49-3.46 for the CH2CH2 protons of the

central Ru(dppe)2 unit and two multiplets at δ 2.86-2.76 and 1.87-1.75 for the

Ru(dppe)Cp* moiety. The 31P NMR spectrum of 10 contains a peak at δ 82.8 for the

phosphorus of the Ru(dppe)Cp* ligand and two equivalent triplets at δ 60.1 (18 Hz)

and 50.6 (18 Hz) for the phosphorus on the central ruthenium. This can be explained

by the phosphorus atoms of the Ru(dppe)2 unit being in different chemical

environment if it is assumed that there is a restricted rotation around the ruthenium.

The 13C NMR spectrum contains resonances assigned to the phenyl groups (δ 133.23-

128.11), Cp* (δ 93.26, 9.82) and CH2 (δ 32.22-31.79). The ES-MS includes a peak for

[M - H]+ at m/z 1615, a peak at m/z 898 for [Ru(dppe)2]+ and a peak at m/z 635 for

[Ru(dppe)Cp*]+.

The successful synthesis of this complex suggests a new route for the potential

synthesis of bis(diyndiyl) complexes as the presence of the chloride atom offers a

possible site for connecting different end-groups. Substitution of the chloride atom on

10 for a Ru(C≡CC≡C)(dppe)Cp* fragment was attempted using various conditions,

but the formation of the expected complex was not observed, only decomposition

products being obtained.

2.3.5. Gold reactions

Gold(I) chemistry has interested researchers for many years. Several gold(I)

complexes have been used as precursors for alkynylgold(I) derivatives. These include

AuCl(L) (L = PPh3, SC4H8),108,109 (AuCl)2(µ-dppm)110 and [ppn][Au(acac)2].111 Some

gold(I) complexes of 1,3-butadiyne have been reported recently by our research

group.65 For example, the copper-catalysed coupling of AuCl(PPh3) and buta-1,3-

diyne under Cadiot-Chodkiewicz conditions results in the formation of

Au(C≡CC≡CH)(PPh3). This complex reacts further with AuCl(PPh3) under similar

conditions to afford {Au(PPh3)}2(µ-C≡CC≡C) (Scheme 52).65

61

+ H C CAuCl(PPh3)Cu(I)

THF/NHEt2(Ph3P)Au C C C CH

THF/NHEt2

(Ph3P)Au C C C C Au(PPh3)

AuCl(PPh3)Cu(I)

H2

Scheme 52: Synthesis of gold(I) complexes Furthermore, diynyl complexes have been shown to react with AuCl(PPh3) to give

heteronuclear diyndiyl complexes, such as the asymmetric diyndiyl

W{C≡CC≡C[Au(PPh3)]}(CO)3Cp synthesised from the reaction between

W(C≡CC≡CH)(CO)3Cp and AuCl(PPh3) (Scheme 53).65

Cp(OC)3W C C C CH

THF/NHEt2

Cu(I)

AuCl(PPh3)Cp(OC)3W C C C C Au(PPh3)

Scheme 53: Synthesis of W{C≡CC≡C[Au(PPh3)]}(CO)3Cp

Similarly, the reactions of Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp

with AuCl(PPh3) in the presence of K[N(TMS)2] afforded two new complexes

(Scheme 54).112

[Ru] C CC CHAuCl(PPh3)

[Ru] C C Au(PPh3)C C

[Ru] = Ru(dppe)Cp*, Ru(PPh3)2CpK[N(TMS)2]

Scheme 54: Synthesis of [Ru]{C≡CC≡C[Au(PPh3)]} In general, diyne complexes of general formula {MLn}(C≡CC≡CH) react with

AuCl(PPh3) to afford complexes of the type {MLn}(C≡CC≡C){Au(PPh3)}. Hence, the

reaction of the asymmetric complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] =

Ru(dppe)Cp* (5), Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)) with AuCl(PPh3) should show

a similar reaction pattern and result in the formation of complexes of the type trans-

Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2.

62

2.3.5.1. Synthesis of trans-Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2

The complexes trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] = Ru(dppe)Cp* (5),

Ru(dppe)Cp (6) or Ru(PPh3)2Cp (7)) react with one equivalent of AuCl(PPh3) in the

presence of NaOMe in a mixture of 1:4 MeOH/THF to give trans-

Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11), trans-Ru{C4[Ru(dppe)Cp]}-

{C4[Au(PPh3)]}(dppe)2 (12) and trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2

(13) as pale yellow complexes in 70%, 62% and 69% yield, respectively (Scheme 55).

Ru

Ph2P PPh2

PPh2Ph2P

C C C CC C C C[Ru] Au(PPh3)

NaOMeAuCl(PPh3)

Ru

Ph2P PPh2

PPh2Ph2P

HC C C CC C C C[Ru]

1:4 MeOH/THF



Scheme 55: Reaction scheme for the synthesis of 11, 12 and 13

63

Complexes 11, 12 and 13 have very similar structures, the difference being the

presence of the different terminal ruthenium ligands. The three complexes were fully

characterised by NMR and infrared spectroscopy, and elemental analysis. All data are

described in Table 4. The NMR analyses confirmed the presence of the different

terminal groups (Ru(dppe)Cp*, Ru(dppe)Cp, Ru(PPh3)2Cp) and the Ru(dppe)2 moiety.

The 31P NMR spectra of complexes 11, 12 and 13 also show the expected peak for the

phosphorus of the Au(PPh3) unit and the Ru(dppe)Cp*, Ru(dppe)Cp and Ru(PPh3)2Cp

groups. The carbon chains on the three complexes are characterised by ν(C≡C) bands

in the infrared spectra.

64



1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

11 2012 (w) 1957 (m)



73.8 (s, Ru(dppe)Cp*) 55.3 (s, Ru(dppe)2) 44.6 (s, Au(PPh3))

2086, [M]+; 2055 [M - P]+; 1626, [M – Au(PPh3)]+

12 2013 (w) 1882 (w)


142.68-122.00 (m, Ph); 84.97 (s, C5H5); 30.83-29.79 (m, CH2CH2)

80.7 (s, Ru(dppe)Cp) 53.3 (s, Ru(dppe)2) 44.6 (s, Au(PPh3))

2018, [M]+; 898, [Ru(dppe)2]+; 565 [Ru(dppe)Cp]+

13 1970 (w) 1899 (w)


136.01-121.85 (m, Ph); 84.05 (s, C5H5); 31.12-29.25 (m, CH2CH2)

53.9 (s, Ru(dppe)2) 51.4 (s, Ru(PPh3)2Cp) 43.2 (s, Au(PPh3))

2113, [M - P]+; 2038, [M - PPh]+; 898, [Ru(dppe)2]+; 429, [Ru(PPh3)Cp]+

65

2.3.5.2. Synthesis of trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2

Recently, it was reported that reactions between aurated poly-ynes and halo-alkynes

result in a facile elimination of AuX(PR3) (X = halide, R = Ph, tol) and the formation

of new C-C bonds.30 The reactions are carried out in ether solvents (THF, Et2O) at

moderate temperatures in the presence of a Pd(0)/Cu(I) catalyst. This reaction may be

considered to be a variant of the well-known Sonogashira reaction.113-115 The

AuX(PR3) may be recovered and re-used. For example, this reaction was used to

make the complex Co3{µ3-C(C≡C)2TMS}(µ-dppm)(CO)7 by coupling

TMS(C≡C)2Au(PPh3) with Co3(µ3-CBr)(µ-dppm)(CO)7 (Scheme 56).30

CuI/Pd(PPh3)4THF

C C C C

(OC)2Co

Co(CO)3

C Co(CO)2

PPh2

Ph2P

(OC)2Co

Co(CO)3

C Co

PPh2

Ph2P

+ (CO)2

TMS

TMS C C Au(PPh3)2 Br

Scheme 56: Synthesis of Co3{µ3-C(C≡C)2TMS}(µ-dppm)(CO)7

The reaction of trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11) with one

equivalent of Co3(µ3-CBr)(µ-dppm)(CO)7 in the presence of CuI and Pd(PPh3)4

afforded trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2 (14) (Scheme

57).

66

CuI/Pd(PPh3)4THF

Ru

Ph2P PPh2

PPh2Ph2P

C C C CC C C C

(OC)2Co

Co(CO)3

C Co(CO)2

PPh2

Ph2P

Ru

Ph2P PPh2

PPh2Ph2P

Au(PPh3)C C C CC C C C +Ru

Ph2P PPh2

Ru

Ph2P PPh2

(11)

(14)

(OC)2Co

Co(CO)3

C Co

PPh2

Ph2P

(CO)2Br

Scheme 57: Reaction scheme for the synthesis of 14

Complex 14 was obtained in 33% yield and characterised by 1H, 31P NMR, IR and

ES-MS. The infrared spectrum has two bands for the ν(C≡C) stretch at 2010 and 1978

cm-1, as well as bands for the ν(CO) stretch. The 1H NMR spectrum shows the

protons associated with the phenyl groups of the dppe and dppm ligands at δ 7.70-

6.83, the protons of the CH2CH2 unit of the dppe ligands as two multiplets at δ 2.85-

2.77 and 2.55-2.45 and these of the dppm ligand at δ 4.45-4.40 and 3.48-3.43. A

singlet at δ 1.51 corresponds to the Cp* ligand. The 31P NMR spectrum of 14 contains

three peaks, one at δ 72.8 for the phosphorus of the end-group ruthenium, one at δ

55.9 for the phosphorus on the middle ruthenium and at δ 30.6 for the phosphorus of

the dppm ligand. In the 13C NMR spectrum, the presence of a multiplet at δ 203.29-

200.02 indicates the CO groups. There are also two multiplets at δ 139.37-132.77 and

30.40-29.63 for the phenyl groups and the CH2CH2 unit of dppe respectively. The

dppm ligand is characterised by a multiplet at δ 33.95-32.22 corresponding to the CH2

group, and the Cp* ligand is confirmed by the presence of a singlet at δ 96.86 for the

C5Me5 atoms and at 10.11 for the methyl groups on the C5Me5 unit. The ES-MS of 14

contained a peak at m/z 2370 corresponding to [M - CO]+, a peak at m/z 898 for

[Ru(dppe)2]+ and a peak at m/z 675 for [Ru(dppe)Cp*]+.

67

Complex 14 is the first example of a complex containing both even- and odd-

numbered carbon chains connected by a Ru(dppe)2 unit. The formation of the new

carbon-carbon bond through the elimination of AuBr gives an odd-numbered C5 chain

connecting the cobalt cluster while the other C4 chain remains unchanged.

2.3.6. Various reactions of trans-Ru(C4H)2(dppe)2

2.3.6.1. Reaction with AuCl(PPh3)

According to previous studies described in Section 2.3.5, it was anticipated that

AuCl(PPh3) would react with the bis(diyndiyl) complex trans-Ru(C4H)2(dppe)2 (1) in

the presence of base. Hence, two equivalents of AuCl(PPh3) and 1 were coupled

together in a simple reaction using sodium methoxide (Scheme 58). This resulted in

the formation of a lemon-yellow complex, Ru{C4[Au(PPh3)]}2(dppe)2 (15), in 89%

yield.

Complex 15 was characterised by NMR, IR, ES-MS and elemental analysis. The

infrared spectrum shows two ν(C≡C) bands at 1974 and 2084 cm-1. The 1H NMR

spectrum of 15 shows a multiplet at δ 7.61-7.07 assigned to the aromatic hydrogens

and two multiplets at δ 3.76-3.59 and 2.61-2.51 which correspond to -CH2CH2-

groups of dppe. The 31P NMR spectrum shows a singlet at δ 53.1 arising from the

phosphorus nuclei coordinated to the ruthenium, and at δ 46.1 from the phosphorus

nucleus coordinated to the gold. In the 13C NMR spectrum, two multiplets were

present at δ 134.53-127.28 for the phenyl groups and at δ 33.27-30.91 for the CH2CH2

group. The ES-MS of this complex shows a peak for the molecular ion [M]+ at m/z

1916 and peaks corresponding to [Au(PPh3)2]+ at m/z 721 and [Au(PPh3)]+ at m/z 459.

68

Ru

Ph2P PPh2

PPh2Ph2P

Au(PPh3)C C C CC C C C(Ph3P)Au

Ru

Ph2P PPh2

PPh2Ph2P

HC C C CC C C CH

NaOMe2 eq AuCl(PPh3) 1:4 MeOH/THF

(1)

(15)

Scheme 58: Reaction scheme for the formation of 15

2.3.6.2. Reaction with Co3(µ3-CBr)(µ-dppm)(CO)7

As described in Section 2.3.5.2, a simple coupling reaction occurs between the

compound {TMS(C≡C)2}Au(PPh3) and the cobalt cluster Co3(µ3-CBr)(µ-dppm)(CO)7

in the presence of a Pd(0)/Cu(I) catalyst to afford the complex Co3{µ3-

C(C≡C)2TMS}(µ-dppm)(CO)7. Hence, the reaction of Co3(µ3-CBr)(µ-dppm)(CO)7

with Ru{C4[Au(PPh3)]}2(dppe)2 (15) at room temperature in THF in the presence of

the Pd(PPh3)4/Cu(I) catalyst mixture afforded trans-Ru{C5[Co3(µ-

dppm)(CO)7]}2(dppe)2 (16) as a bright orange solid in 54% yield. This reaction results

in elimination of two moles of Au(PPh3)Br and the formation of new C-C bonds

yielding a complex with two C5 carbon chains (Scheme 59).

69

Ru

Ph2P PPh2

PPh2Ph2P

C C Au(PPh3)(Ph3P)Au C C

Co(CO)2

Co(CO)3

CCo

Ph2P

PPh2

THF

Ru

Ph2P PPh2

PPh2Ph2P

C C C CC C C C

Co(CO)2

Co(CO)3

CCo

Ph2P

PPh2

(OC)2Co

Co(CO)3

C Co(CO)2

PPh2

Ph2P

(OC)2

(OC)2

CuI/Pd(PPh3)4

+

(16)

(15)

22Br

Scheme 59: Reaction scheme for the formation 16

Complex 16 was identified from its spectroscopic data. The infrared spectrum shows

ν(CO) bands in the terminal region and a ν(C≡C) band at 2084 cm-1. The 1H NMR

spectrum shows a broad multiplet at δ 7.48-6.82 due to the phenyl groups, two

multiplets at δ 2.68-2.56 and 2.32-2.19 assigned to the CH2 groups in dppe and two

multiplets at δ 4.45-4.40 and 3.54-3.48, which correspond to the two hydrogens of the

methylene group in the dppm ligands. In the 31P NMR spectrum, two resonances were

observed at δ 51.0 and 33.2, assigned to the phosphorus atoms of the dppe and dppm

ligands, respectively. In the 13C NMR spectrum, a multiplet at δ 221.31-206.21

indicates the presence of the CO groups and a multiplet at δ 134.56-126.55 shows the

presence of the phenyl groups. There are also two other multiplets for the dppm and

dppe ligands at δ 33.49-32.87 and 30.61-29.40, respectively.

2.3.6.3. Reaction with TCNE

TCNE is an electron-deficient alkene owing to the four electron-withdrawing cyano

groups. Cycloaddition of TCNE to RC≡CM triple bonds to give cyclobutenyl

complexes and subsequent ring-opening to buta-1,3-dien-2-yl complexes are

characteristic reactions of σ-alkynyl or σ-poly-ynyl ligands on transition metals.

These reactions proceed via intermediates which cannot be isolated in all cases, as the

cyclobutene undergoes rapid ring-opening.116,117 For example, the reaction of various

alkynyl complexes with TCNE are illustrated in Scheme 60.59,63

70

{LnM} C C {M'L'n'} {LnM} C C

C C

NCNC

CNCN

{M'L'n'}

{LnM} C C {M'L'n'}

C

CNNC

TCNE

C

NC CN

{MLn} = Fc, W(CO)3Cp

{M'L'n'} = Ru(dppm)Cp Ru(dppe)Cp Os(dppe)Cp Fc

Scheme 60: Cycloaddition of TCNE to {MLn}(C≡C){M’L’n’}

Consequently, TCNE is expected to react with the electron-rich regions of trans-

Ru(C4H)2(dppe)2 (1), possibly adding across one or both of the carbon-carbon triple

bonds. Addition of two equivalents of TCNE to a solution of 1 in dichloromethane

afforded bright purple solid Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) in 93%

yield. It is reasonable to assume that this reaction goes via the formation of a

cyclobutene intermediate which is unstable and transforms rapidly to give the final

product 17 (Scheme 61).

Ru

Ph2P PPh2

PPh2Ph2P

HH C C C CC C C C

C C

NCNC CN

CN

CC CNCNNC

NC

Ru

Ph2P PPh2

PPh2Ph2P

C C CC C C

C

C

CNNC

C

NC

NC H

C

C

C

CN

CN

H

CNNC

CH2Cl2Ru

Ph2P PPh2

PPh2Ph2P

(C C) H(C C)H

Intermediate

22

(17)

TCNE

(1)


71

Complex 17 displayed expected resonances in the 1H, 31P and 13C NMR spectra. The 1H NMR spectrum contained a multiplet at δ 7.43-7.14 assigned to the aromatic

hydrogens of the phenyl groups, two multiplets at δ 3.08-2.99 and 2.25-2.17

corresponding to the hydrogens of -CH2CH2- and a singlet at δ 1.41 due to C-H. The 31P NMR spectrum shows only one peak at δ 47.4 which corresponds to the

phosphorus atoms of dppe. The 13C NMR spectrum shows the resonances for the

carbon atoms of the C4 chains and the resonances for two CN groups were found at δ

115.11 and 113.75 while the two other CN groups were found at δ 111.31 and 110.10.

In the infrared spectrum, one ν(C≡C) band at 1973 cm-1 and one ν(CN) band at 2220

cm-1 were observed. The ES-MS of 17 shows a peak for the molecular ion at m/z 1251

and peaks corresponding to [M - CN]+ at m/z 1225 and [Ru(dppe)2]+ at m/z 898.

Crystals of 17 were grown from a benzene/CH2Cl2 mixture and the molecular

structure was determined by single-crystal X-ray diffraction studies. These studies

confirmed that two molecules of TCNE react with the C≡C triple bonds furthest from

the ruthenium centre probably because of steric hindrance around the Ru(dppe)2

moiety.

The ORTEP diagram is shown in Figure 25 and selected bond distances and angles

are given in Table 5. The Ru-C(1) bond length of 2.002(8) Å is close to the value

expected for a ruthenium carbon single bond (2.01 Å) and the C(1)-C(2) bond length

of 1.24(1) Å confirms the presence of the C≡C triple bond. The C(2)-C(3) and C(3)-

C(4) distances of 1.40(1) Å and 1.47(1) Å respectively, are consistent with the

presence of C-C single bonds. The C(2)-C(3) bond length is shorter than expected

indicating that there is a small amount of electron delocalisation occurring. The angles

Ru-C(1)-C(2) [176.8(7) Å] and C(1)-C(2)-C(3) [178.2(8) Å] in 17 are nearly linear

whereas C(2)-C(3)-C(4) is bent [115.3(6) Å]. This angle can be explained by the

presence of the C(3)-C(30) and the C(4)-C(40) bonds which have typical C=C double

bond lengths.

72

Figure 25: ORTEP view of complex 17

Bond distances (Å) Bond Angles (o)

Ru-C(1) 2.002(8) Ru-C(1)-C(2) 176.8(7)

Ru-P(1) 2.392(2) P(1)-Ru-P(2) 82.64(7)

Ru-P(2) 2.385(2) P(1)-Ru-C(1) 90.9(2)

C(1)-C(2) 1.24(1) P(2)-Ru-C(1) 84.6(2)

C(2)-C(3) 1.40(1) C(1)-C(2)-C(3) 178.2(8)

C(3)-C(4) 1.47(1) C(2)-C(3)-C(4) 115.3(6)

C(30)-C(32) 1.45(1) C(3)-C(4)-C(40) 124.7(7)

C(3)-C(30) 1.38(1) C(30)-C(3)-C(4) 121.5(7)

C(4)-C(40) 1.35(1) C(3)-C(4)-C(40) 124.7(7)

Table 5: Selected bond distances (Å) and angles (o) for 17

73

trans-Ru(C4H)2(dppe)2

Ru{C4[Ru(dppe)Cp*]}2(dppe)2 Ru{C4[RuCp(PPh3)2]}2(dppe)2

Ru{C4[Ru(dppe)Cp]}2(dppe)2

2 RuCl(PPh3)2Cp

2 RuCl(dppe)Cp

2 RuCl(dppe)Cp*

Ru{C4[Au(PPh3)]}2(dppe)2

2 AuCl(PPh3)

Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2

2 Co3(µ3-CBr)(µ-dppm)(CO)7

2 Tcne

Ru{C CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2

(2)

(1)

(17)

(3)

(4)

(15)

(16)

Figure 26: Summary of products synthesised from trans-Ru(C4H)2(dppe)2 (1)

74

Ru(C4H)2(dppe)2Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2

RuCl(PPh3)2Cp

RuCl(dppe)Cp

RuCl(dppe)Cp*

AuCl(PPh3)

Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2

Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2

RuCl(dppe)Cp

Co3(µ3-CBr)(µ-dppm)(CO)7

Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2

Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2

Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2

Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2

Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2

Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2RuCl(dppe)Cp

AuCl(PPh3)

AuCl(PPh3)

(8)

(5)

(11)

(14)

(1)

(7)

(9)

(13)

(6)

(12)

Figure 27: Summary of products synthesised from trans-Ru(C4H)2(dppe)2 (1)

75

2.3.7. Synthesis of trinuclear copper(I) and silver(I) alkynyl complexes

In 1993, Gimeno and co-workers reported the synthesis and crystal structures of

various triangular copper(I) alkynyls such as [Cu3(µ-dppm)3(µ3-η1-C≡CR)2][BF4]

(where R = Ph, tBu, CH2OCH3) (Figure 28).118

CuC CCu

Cu

PP

PPP

P

CC RR

[BF4]

R = Ph, tBu, CH2OCH3

Figure 28: First examples of triangular copper(I) alkynyls

Since then, a number of polynuclear copper(I) and silver(I) alkynyl complexes have

been reported.119-125 They are promising building blocks for the construction of rigid-

rod oligomeric and polymeric materials and exhibit interesting properties such as

luminescence and an ability to mediate electron delocalisation. The trinuclear

copper(I) or silver(I) clusters can be capped by either organic alkynyl fragments

(Figure 29)126 or metal alkynyl fragments (Figure 30).127

MC CM

M

PP

PPP

P

CC RRM = Cu, Ag

+

R = Ph, C6H4-NO2-4, C6H4-OCH3-4

Figure 29: Examples of complexes capped with organic alkynyl fragments

76

MC C C CM

M

PP

PPP

P

CCCC Re

OC CO

CO

N N

Re

OC CO

N N

OC

M = Cu, Ag

+

Figure 30: Examples of complexes capped with metal alkynyl fragments

One method for the synthesis of copper(I) and silver(I) alkynyl complexes of this type

involves the reaction of three equivalents of [M2(µ-dppm)2(NCMe)2][X]2 (M = Cu,

Ag; X = PF6, BF4) with four equivalents of a terminal alkynyl group, in the presence

of an excess of KOH in CH2Cl2/MeOH.127 The complexes [Cu3(µ-dppm)3{µ3-η1-

C≡C(C6H2R2)nC≡C-p-Re(NN)(CO)3}2]+ (NN = bpy, tBu2bpy; R = H, Me; n = 0, 1)

were synthesised by this method (Scheme 62).127

MeCN Cu

P

P

Cu

P

P

NCMe OC Re C C

N N

OC CO

C C H

R

R

KOH

OC Re C C

N N

OC CO

C C

R

R

ReCC

NN

COOC

R

R

Cu CC

Cu

Cu

PP

PP

P

PCO

2+

3 4+

n

+

R = H, n = 1, NN = bpyR = Me, n = 1, NN = bpyR = H, n = 1, NN = tBu2bpyn = 0, NN = bpy

nn

Scheme 62: Synthesis of [Cu3(µ-dppm)3{µ3-η1-C≡C(C6H2R2)nC≡C-p-Re(NN)(CO)3}2]+

77

Similarly, the trinuclear copper(I) alkynyl complex [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-

dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6] (18) was synthesised from the mixture of

Ru(C≡CC≡CH)(dppe)Cp* and [Cu2(µ-dppm)2(NCMe)2][PF6]2. The reagents were

refluxed in an 4:1 THF/NEt3 mixture in the presence of a strong base (Scheme 63).12

CuC C C CRuPh2P PPh2

Cu

Cu

PP

PPP

P

CCCC RuPPh2Ph2P

HC C C CRu

Ph2P PPh2

[Cu2(µ-dppm)2(NCMe)2][PF6]2

THF/NEt3 dbu

∆

+

(18)

[PF6]


Following this work, the binuclear copper(I) complex [Cu2(µ-dppm)2(NCMe)2][BF4]2

would react similarly to give the [BF4]- analogue. Hence, Ru(C≡CC≡CH)(dppe)Cp*

was reacted with [Cu2(µ-dppm)2(NCMe)2][BF4]2 in 4:1 THF/NEt3 in the presence of

dbu and afforded the complex [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-

dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19) as a bright yellow complex in 55% yield.

Complex 19 was readily identified from its spectroscopic data and elemental analysis.

It shows similar characteristics to complex 18; all data are summarised in Table 6.

The characteristic peaks for the Ru(dppe)Cp* and the dppm ligands are present in the 1H, 31P and 13C NMR spectra of 19. The difference between both complexes 18 and 19

is the presence of a different anion. Thus, the infrared spectrum of 19 shows one band

at 1059 cm-1 due to ν(BF) and the 31P NMR spectrum of 19 is missing the septet for

the phosphorus nuclei on [PF6]-.

78

Furthermore, the two compounds [Ag2(µ-dppm)2(NCMe)2][PF6]2 and [Ag2(µ-

dppm)2(NCMe)2][BF4]2 are readily available128 and they should react similarly to the

copper analogues to give new bis-ruthenium complexes linked by a silver cluster.

The complexes Ru(C≡CC≡CH)(dppe)Cp* and [Ag2(µ-dppm)2(NCMe)2][X]2 (X = PF6

or BF4) were refluxed in a 4:1 THF/NEt3 solvent mixture for one hour in presence of

dbu and in the dark. The two complexes [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-

dppm)3}(C≡C)2{Ru(dppe)Cp*}][X] (X = PF6 (20); BF4 (21)) were obtained in 53%

and 51% yields, respectively (Figure 31).

AgC C C CRuPh2P PPh2

Ag

Ag

PP

PPP

P

CCCC RuPPh2Ph2P

+

Figure 31: Representation of 20 and 21

Complexes 20 and 21 were characterised by IR, 1H, 31P, 13C NMR, ES-MS and

microanalysis. All the data are summarised in Table 6. The characteristic peaks for

the Ru(dppe)Cp* and the dppm ligands are present in the 1H, 31P and 13C NMR

spectra of 20 and 21. In the 31P NMR spectrum of 20, a septet is also present at δ -

141.05 (1JPF 711 Hz) for the phosphorus nuclei on PF6. The IR spectra of both

complexes contain ν(C≡C) bands and complex 20 has a band at 838 cm-1 for ν(PF)

while complex 21 has one ν(BF) band at 1052 cm-1.

79


Complex

IR (cm-1)

1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

[Ref]

18 2015 ν(C≡C) (w); 839 ν(PF) (s)

7.16-6.77 (m, 100H, Ph); 3.64-3.52 (m, 6H, dppm); 3.15-3.02, 2.89-2.54 (2 x m, 2 x 4H, CH2CH2); 1.84 (s, 30H, Cp*)

137.10-128.03 (m, Ph) ; 121.79 (t, 2J(CP) = 21 Hz, C1); 118.09 (s, C2); 95.01 (s, C3); 94.55 (s, C5Me5); 65.30 (s, C4); 28.20 (m, CH2CH2); 11.45 (s, C5Me5)

-140.7 (sept, 1JPF 710 Hz, PF6) -7.2 (s, 6P, dppm) 79.4 (s, 4P, dppe)

1355 [M + H]2+

635 [Ru(dppe)Cp*]+

12

19 2021 ν(C≡C)

(w); 1059 ν(BF) (s)


137.10-128.03 (m, Ph); 121.50 (t, 2J(CP) = 21 Hz, C1); 117.15, 95.01, 64.80 (s, C2, C3, C4); 94.19 (s, C5Me5); 28.20-27.96 (m, CH2CH2); 11.45 (s, C5Me5).

-7.3 (s, 6P, dppm) 79.4 (s, 4P, dppe)

1355 [M + H]2+

635 [Ru(dppe)Cp*]+

This work

20 2033 ν(C≡C)

(w); 838 ν(PF) (s)


133.61-127.82 (m, Ph); 123.55, 116.45, 95.79, 51.64 (s, C1, C2, C3, C4); 94.21 (s, C5Me5); 28.71-28.15 (m, CH2CH2); 9.83 (s, C5Me5)

-141.1 (sept, 1JPF 711 Hz, PF6) -1.3 (s, 6P, dppm) 80.7 (s, 4P, dppe)

1421 [M]2+

635 [Ru(dppe)Cp*]+

This work

21 2015 ν(C≡C)

(w); 1052 ν(BF) (s)



-1.2 (s, 6P, dppm) 80.5 (s, 4P, dppe)

1421 [M]2+

635 [Ru(dppe)Cp*]+

This work

80

2.4. Electrochemistry

2.4.1. trans-Ru{C4[Ru]}2(dppe)2 complexes

Due to their interest as possible models for molecular wires, the electronic properties

of complexes 2, 3, and 4 were examined. Density-functional theory (DFT) molecular

orbital calculations were performed on the model complex

Ru{C≡CC≡C[Ru(dHpe)Cp]}2(dHpe)2 [dHpe = H2P(CH2)2PH2].129 The HOMOs

consists of four closely spaced orbitals and there is a large energy gap between the

LUMO and the HOMO of 1.60 eV (Figure 34). It was deduced that eight electrons

could be lost from the HOMOs in a stepwise fashion. Using DFT calculations, a

contour plot of the HOMO and HOMO-1 of the model complex was prepared (Figure

32 and Figure 33).129 The HOMOs extend across the entire eleven-atom chain. An

important consequence of this is that any oxidation process cannot be expected to

occur solely at the metal centres but rather is delocalised across the entire chain.

Figure 32: Contour plot of the HOMO of the model complex

Figure 33: Contour plot of the HOMO-1 of the model complex

81

Figure 34: Partial orbital interaction diagram for the model complex

As mentioned previously, a convenient way to evaluate the electronic communication

in such systems is by using cyclic voltammetry. The cyclic voltammograms of

complexes 2, 3 and 4 were measured in CH2Cl2 under similar conditions, provided in

the general experimental conditions.

The cyclic voltammogram of trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2) shows four

one-electron oxidation waves which are diffusion controlled. The first three waves at -

0.72 V, -0.33 V and +0.21 V are fully-reversible (ia/ic = 1) while a fourth is observed

at +0.70 V, which is partially reversible (ia/ic = 0.6). A fifth wave is present at +0.99

V but can not be assigned due to the preceding partially reversible wave at +0.70 V

(Figure 35). From the DFT calculations, it was deduced that eight electrons could be

lost from the HOMOs in a stepwise fashion. However, only five waves are present in

the cyclic voltammogram because the presence of the solvent front does not allow

further analysis. The differences between successive oxidation potentials ∆Eo are

significant, with values greater than 290 mV (for example, ∆E1/2 = 390 mV).58 This

indicates that there are strong interactions between the metal centres via the carbon

bridge and also that complex 2+ can be classified as a Class III complex by the Robin

and Day classification system.69

82

The cyclic voltammograms of trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3) and trans-

Ru{C4[Ru(PPh3)2Cp]}2(dppe)2 (4) show a very similar pattern to that of complex 2.

Complexes 3 and 4 each show five waves at -0.70 V, -0.25 V, +0.47 V, +0.76 V,

+1.19 V and -0.64 V, -0.12 V, +0.49 V, +0.79 V, +1.26 V, respectively. Complexes 3

and 4 show large peak-to-peak separation with large values of ∆E1/2 of 450 mV for 3

and 520 mV for 4. Hence, complex 3+ and 4+ can be classified as class III complexes

by the Robin and Day classification system.69 Electrochemical data for complexes 2, 3

and 4 are summarised in Table 7.

The successful synthesis of 3 and 4 allows the generation of a series of symmetric

trinuclear complexes of general formula [Ru]-C≡CC≡C-Ru(dppe)2-C≡CC≡C-[Ru].

This allows the direct comparison of their redox properties and to determine the effect

of the exchange of the Ru(dppe)Cp* end-group for a Ru(dppe)Cp or Ru(PPh3)2Cp

moiety (For comparison all CVs were measured using the same potentiostat and cell

setup). From the data summarised in Table 7, it can be noticed that the oxidation

potentials of complex 2 are lower than these of 3 and 4. Hence, complex 2 is more

easily oxidised than complexes 3 and 4. It is also worth mentioning that the oxidation

potentials of complex 3 are intermediate to those observed for 2 and 4. It can also be

deduced that complex 3 will be more easily oxidised compared to complex 4. These

results are consistent with previous theoretical studies which found that the more

electron donating ligand Ru(dppe)Cp* will allow easier oxidation than the less

electron donating groups Ru(dppe)Cp and Ru(PPh3)2Cp. For example, the oxidation

potentials for the related series of diyndiyl complexes of general formula

[Ru](C≡CC≡C)[Ru] are shown in Table 7.12,59

Hence, it can be concluded that the ruthenium(II) moiety Ru(dppe)2 is strongly

electron-donating and acts as a conductor in these three complexes and the -C≡CC≡C-

bridge is very efficient in allowing electronic communication between the terminal

ruthenium groups. Complexes 2, 3 and 4 can therefore be proposed as possible

precursors for molecular wires. This study confirmed the previous research reported

for the complex trans-[Ru(C≡CC≡CFc)2(dppe)2] which found that the Ru(dppe)2

moiety allows electronic communication in this complex. (See Introduction)

83

Figure 35: Cyclic voltammogram of 2

84

In addition, a series of {Cp*(dppe)Ru}-(C≡C)n-{Ru(dppe)Cp*} (n = 1 - 8) complexes

were recently prepared and their cyclic voltammograms were recorded in order to

investigate the influence of chain length on the electronic interactions between two

ruthenium centres.12,55 The separation of the first two waves (∆E1/2) was considered

the best indication of the extent of interactions between the two redox centres.58 Table

7 summarises the values obtained for the various complexes {Cp*(dppe)Ru}-(C≡C)n-

{Ru(dppe)Cp*} (n = 2 - 5). It was deduced that as the chain length is increased, the

interactions between the two ruthenium centres decrease at a steady rate. This trend is

represented graphically in Figure 36, which is a plot of ∆E1/2 against chain length.

Hence, the comparison of the electronic properties of the bis(diyndiyl) ruthenium

complex 2 with these straight chain complexes was investigated. It was found that the

∆E1/2 value of complex 2 is between those of {Cp*(dppe)Ru}-(C≡C)3-

{Ru(dppe)Cp*} and {Cp*(dppe)Ru}-(C≡C)4-{Ru(dppe)Cp*} complexes. Therefore,

it can be concluded that the insertion of the Ru(dppe)2 unit in the C8 carbon chain of

complex 2 has increased the electronic interactions between the two ruthenium

centres compared to the complex with a straight C8 chain.

Figure 36: Chain length effect on ∆E1/2 in the {Cp*(dppe)Ru}2(C≡C)n series

85

2.4.2. trans-Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 complexes

As seen previously, the electronic properties associated with the trinuclear complexes

2, 3 and 4 were of interest. Therefore, the analysis of the cyclic voltammetry

associated with asymmetric complexes of general formula trans-

Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 (where [Ru] = Ru(dppe)Cp* (8) or

Ru(PPh3)2Cp (9)) was also investigated to compare the differences in electronic

properties.

The cyclic voltammograms of 8 and 9 were acquired. Five redox events are present

and are diffusion controlled. Complexes 8 and 9 each show three fully-reversible

waves at -0.70 V, -0.34 V, +0.15 V and -0.52 V, -0.14 V, +0.46 V, respectively. Two

partially reversible waves are also present at +0.59 V, +0.83 V and +0.73 V, +1.15 V,

respectively (Figure 37). All the values are summarised in Table 7. Furthermore, the

∆E1/2 values were found to be equal to 360 mV and 380 mV for 8 and 9 respectively.

These are significant values and indicate that there are strong interactions between the

metal centers. Hence, complex 8+ and 9+ can be classified as Class III complexes by

the Robin and Day classification system.69

The electronic properties of complexes 8 and 9 are very interesting compared to the

values obtained for the other trinuclear complexes 2, 3 and 4. By comparing the

oxidation potentials, it can be deduced that the first and second oxidation potentials of

8 are similar to these obtained for 2 and 3 whereas the E3 and E4 values of 8 are lower.

In the case of 9, the oxidation potentials E3 and E4 are very close to the values of the

complexes 3 and 4. This could be explained by the fact that complexes 8 and 9 are

made of a combination of the different end-group ligands and should therefore show

similarities in their electronic properties. This was also reported from the synthesis of

complexes {Cp(PPh3)2Ru}(C≡CC≡C){Ru(dppe)Cp} and

{Ru(PPh3)2Cp}(C≡CC≡C){Ru(dppe)Cp*} which was found to have oxidation

potentials very comparable to the three complexes {Ru(dppe)Cp*}2(C≡CC≡C),

{Ru(dppe)Cp}2(C≡CC≡C) and {Ru(PPh3)2Cp}2(C≡CC≡C) (Table 7).12,59

86

Complex E1 E2 E3 E4 E5 ∆E1/2 [Ref] 2 -0.72 -0.33 +0.21 +0.70 +0.99 0.39 This work 3 -0.70 -0.25 +0.47 +0.76 +1.19 0.45 This work 4 -0.64 -0.12 +0.49 +0.79 +1.26 0.52 This work 8 -0.70 -0.34 +0.15 +0.59 +0.83 0.36 This work 9 -0.52 -0.14 +0.46 +0.73 +1.15 0.38 This work {Ru(dppe)Cp*}2{C4} -0.43 +0.22 +1.04 +1.54a 0.65 12 {Ru(dppe)Cp}2{C4} -0.24 +0.35 +1.08 +1.44 0.59 59 {Ru(PPh3)2Cp}2{C4} -0.23 +0.41 +1.03 +1.68 0.64 59 {Cp(PPh3)2Ru}{C4}{Ru(dppe)Cp} -0.22 +0.42 +1.07 +1.52 0.64 59 {Cp(PPh3)2Ru}{C4}{Ru(dppe)Cp*} -0.33 +0.34 +1.04 +1.55 0.67 59 {Ru(dppe)Cp*}2{C6} -0.15 +0.33 +1.05 +1.33 0.48 12 {Ru(dppe)Cp*}2{C8} +0.08 +0.43 +1.07 +1.27 0.35 12 {Ru(dppe)Cp*}2{C10} +0.18 +0.45 +1.11 0.26 55

Table 7: Electrochemical data (V), a Peak potential of an irreversible process

87


88

2.4.3. trans-Ru{C4[Ru]}{C4H}(dppe)2 complexes

Electrochemical studies of the asymmetric complexes trans-

Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5), trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2

(6) and trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) were also completed. The

cyclic voltammograms of 5, 6 and 7 show two partially reversible waves and an

irreversible wave at ca 1.0 V (Figure 38). Due to the presence of the first partially

reversible wave it is not possible to calculate the ∆E1/2 values for the three complexes

and therefore assign them a classification.

Figure 38: Cyclic Voltammogram of 5

2.4.4. trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2

The electrochemical properties of complex trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2

(10) using cyclic voltammetry were investigated. The cyclic voltammogram of 10 is

composed of one partially reversible wave at +0.64 V followed by two undefined

waves (Figure 39). Due to the presence of the first partially reversible wave it is not

possible to assign the following waves, which maybe the result of decomposition of

the primary redox product.

89


2.4.5. Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2

The redox potentials for Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) were

measured using cyclic voltammetry. The cyclic voltammogram of 17 shows that the

complex undergoes two oxidation-reduction processes which are diffusion controlled

(Figure 40). The two redox potentials occurring at -0.65 V and +1.21 V are partially

reversible (ia/ic = 0.6 and 0.8, respectively). The reduction at -0.65 V could

correspond to the C-CN groups, which are the most electronegative region of the

complex. The potential at +1.21 V is the oxidation of the Ru(dppe)2 moiety which is

at high potential probably due to the addition of the strongly electron-withdrawing CN

groups to the chain.


90

2.4.6. [{Cp*(dppe)Ru}(C≡C)2{M3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X] (M = Cu,

Ag; X = PF6, BF4)

Density-functional theory (DFT) calculations were made on the model complex

[{Cp(dHpe)Ru}(C≡C)2{M3(µ-dHpm)3}(C≡C)2{Ru(dHpe)Cp}]+ where the dppm,

dppe and Cp* ligands have been replaced by the dHpm, dHpe and Cp ligands for

clarity.130 It was found that there are large energy gaps between the HOMO and the

LUMO of 2.322 eV and 2.288 eV for the copper(I) and the silver(I) complexes,

respectively (Figure 41). Furthermore, contour plots of the HOMO and HOMO-1

orbitals show that these orbitals are delocalised over the entire Ru-C4-M3-C4-Ru chain

(Figure 42 and Figure 43). This suggests that there will be some communication

between the ruthenium end-groups across the copper(I) and silver(I) clusters.130

Figure 41: Partial orbital interaction diagram for the model complex

91

Figure 42: Contour plot of the HOMO of the model complex

Figure 43: Contour plot of the HOMO-1 of the model complex In order to evaluate the electronic properties, the cyclic voltammograms of the

complexes [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19)

and [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X] (X = PF6 (20);

BF4 (21)) were measured in CH2Cl2 under similar conditions. The cyclic

voltammograms of complexes 19, 20 and 21 show two one-electron fully-reversible

oxidation waves (Figure 44). Their redox potentials are summarised in Table 9.

92

Figure 44: Cyclic voltammogram of 19 To this point, the separation of the first two waves (∆E) was considered the best

indication of the extent of interactions between the two redox centres. The difference

between successive oxidation potentials, ∆E1/2, for complex 19 is equal to 220 mV.

The distinction between Class II and Class III systems by the Robin and Day

classification is considered to be at 0.2 V,69 hence complex 19+ is slightly above it and

can be classified as a Class III complex. Therefore, it can be concluded that the

insertion of the trinuclear copper(I) cluster between the two diynyl fragments allow

electronic interactions between the metal termini.

The ∆E1/2 values of complexes 20 and 21 are 160 mV and 170 mV respectively. This

indicates that there are only minimal interactions between the two ruthenium termini

and complexes 20+ and 21+ can be classified as Class II complexes by the Robin and

Day classification system.69 Thus it appears that there is a decrease in the

communication when the trinuclear silver(I) cluster is present in the carbon chain.

93

Complex E1 E2 E3 E4 ∆E1/2 [Ref]

18 +0.15 +0.36 0.23 12

19 +0.17 +0.39 0.22 This work

20 +0.26 +0.43 0.16 This work

21 +0.29 +0.46 0.17 This work

{Ru(dppe)Cp*}2{C8} +0.08 +0.43 +1.07 +1.27 0.35 12

Table 8: Electrochemical data (V)

Therefore it can be deduced that the copper(I) cluster mediates reasonable interactions

between the two ruthenium termini over the carbon chain while the silver(I) cluster

diminishes significantly the ability of electronic communication. This could be

explained by the difference in the contribution to the HOMOs of the copper(I) and the

silver(I) complexes.

Furthermore, the separation of the first two waves (∆E1/2) of complexes 19, 20 and 21

are smaller than the value of the {Cp*(dppe)Ru}-(C≡C)4-{Ru(dppe)Cp*}complex.

Thus, the strength of electronic interactions decreases when the trinuclear copper(I) or

silver(I) clusters are inserted in the chain and makes these complexes less efficient

than a complex with a C8 carbon chain. These results further confirm that the insertion

of a copper(I) or silver(I) cluster makes the oxidation process more difficult and they

are therefore not good linkers for the synthesis of molecular wires.

94

2.5. Conclusions

In summary, symmetric and asymmetric bis(diyndiyl) ruthenium(II) complexes have

been successfully synthesised. It was shown that it is possible to build complexes

containing a Ru(dppe)2 moiety as the central linking group of two butadiyndiyl carbon

chains with metal ligand end-groups. Trans-Ru{C4[Ru]}2(dppe)2 (where [Ru] =

Ru(dppe)Cp* (2), Ru(dppe)Cp (3) and Ru(PPh3)2Cp (4)) and trans-

Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 (where [Ru] = Ru(dppe)Cp* (8) and

Ru(PPh3)2Cp (9)) have been successfully prepared and characterised

spectroscopically.

These complexes have been shown by cyclic voltammetry to undergo a series of five

stepwise one-electron oxidation processes. It was also established that strong

interactions exist between the ruthenium centres with a large separation in the

oxidation waves. The electrochemical studies also confirmed that the Ru(dppe)2 linker

is an effective communicator of electronic information from one termini to the other.

Hence, these bis(diyndiyl) ruthenium (II) compounds may be considered as models

for molecular wires and 2+, 3+, 4+, 8+, 9+ may be classified as Class III complexes by

the Robin-Day classification system.

The synthesis of trans-Ru{C4[Ru]}{C4H}(dppe)2 (where [Ru] = Ru(dppe)Cp* (5),

Ru(dppe)Cp (6) and Ru(PPh3)2Cp (7)) complexes has allowed the synthesis of

asymmetric complexes of general formula trans-

Ru{C4[Ru]}{C4[Ru(dppe)Cp]}(dppe)2 (where [Ru] = Ru(dppe)Cp* (8) and

Ru(PPh3)2Cp (9)) and trans-Ru{C4[Ru]}{C4[Au(PPh3)]}(dppe)2 (where [Ru] =

Ru(dppe)Cp* (11), Ru(dppe)Cp (12) and Ru(PPh3)2Cp (13)). The insertion of the

Au(PPh3) fragment has enabled access to a complex with an extended carbon chain.

For example, complex 11 was further reacted with the cobalt cluster Co3(µ3-CBr)(µ-

dppm)(CO)7 to give complex 14 containing both an even- and odd-numbered alkynyl

linkages. Similar complexes could be prepared using the two complexes 12 and 13.

95

In the same way, the gold reaction between trans-Ru(C4H)(dppe)2 (1) and AuCl(PPh3)

was shown to occur readily and afforded the novel complex trans-

Ru{C4[Au(PPh3)]}2(dppe)2 (15). The reaction of 15 with Co3(µ3-CBr)(µ-dppm)(CO)7

gave a complex with longer carbon chains (C5). It is noteworthy that further reactions

can be performed with complex 15 as Au(PPh3) is a good leaving group.

The reaction of trans-Ru(C4H)(dppe)2 (1) with TCNE afforded the complex

Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) in very good yield. The X-ray

crystal study of 17 has confirmed that it is the second C≡C triple bond out from the

ruthenium centre which is attacked by TCNE as a result of the steric protection of the

inner C≡C bond by the two bulky dppe ligands. It was also shown that the C4 carbon

chains are bent in this complex due to the presence of the double bonds.

Furthermore, the syntheses of three copper(I) and silver(I) alkynyl complexes of

general formula [{Cp*(dppe)Ru}(C≡C)2{M3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][X]

(where M = Cu, Ag and X = PF6, BF4) 19, 20 and 21 were successfully achieved. The

electronic communication in such complexes was evaluated through the use of cyclic

voltammetry. The studies have shown that electronic communication exists between

the two ruthenium centres when a trinuclear copper(I) or a silver(I) cluster is present,

but the electronic interactions become weak.

96

2.6. Experimental

General experimental conditions are detailed on page viii. Reagents: The compounds trans-Ru(C4H)2(dppe)2,131 RuCl(dppe)Cp*,132 RuCl(dppe)Cp,133

RuCl(PPh3)2Cp,134 Ru(C≡CC≡CH)(dppe)Cp*,30 trans-[RuCl(dppe)2]OTf,105 Co3(µ3-

CBr)(µ-dppm)(CO)7,135 AuCl(PPh3),136 [Cu2(µ-dppm)2(MeCN)2][BF4]2,137 [Ag2(µ-

dppm)2(MeCN)2][PF6]2128, [Ag2(µ-dppm)2(MeCN)2][BF4]2

128 and Pd(PPh3)4,12 were

all prepared by standard literature methods. Na[BPh4], CuI, dbu and TCNE were used

as received from Sigma-Aldrich or Fluka.

trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2)

To a suspension of trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol), RuCl(dppe)Cp*

(70 mg, 0.1 mmol), Na[BPh4] (35 mg, 0.1 mmol) and NEt3 (0.02 mL, 0.1 mmol) was

added a 1:1 mixture of CH2Cl2/MeOH and the solution was heated at reflux point for

2 h. The solvent was then removed and the residue dissolved in a minimum amount

of CH2Cl2 and filtered through cotton wool into stirred hexane (40 mL). The yellow-

green precipitate was collected and washed with hexane to yield trans-

Ru{C4[Ru(dppe)Cp*]}2(dppe)2 (2) (76 mg, 67%). Anal. Calcd. (C132H126P8Ru3): C,

70.05; H, 5.61. Found: C, 70.01; H, 5.65. IR (CH2Cl2, cm-1): ν(C≡C) 2012 (m), 1969

(w). 1H NMR (CDCl3): δ 7.72-7.04 (m, 80H, Ph); 2.60-2.55, 1.91-1.82 (2 x m, 16H,

CH2CH2); 1.46 (s, 30H, Cp*). 13C NMR (CD2Cl2): δ 135.46-129.61 (m, Ph); 97.80 (s,

C5Me5); 31.49-31.15 (m, CH2CH2); 11.53 (s, C5Me5). 31P NMR (CDCl3): δ 76.3 (s,

RuCp*dppe); 53.4 (s, Ru(dppe)2). ES-MS (+ve ion, MeOH, m/z): 2266, [M]+; 898,

[Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+.

97

trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3)

Similarly, the reaction between trans-Ru(C4H)2(dppe)2 (1) (50 mg, 0.05 mmol) and

RuCl(dppe)Cp (61 mg, 0.1 mmol) gave trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2 (3) as a

brown powder (32 mg, 75%). Anal. Calcd. (C122H106P8Ru3): C, 69.02; H, 5.03. Found:

C, 69.05; H, 5.09. IR (CH2Cl2, cm-1): ν(C≡C) 2124 (m), 2013 (w). 1H NMR (CDCl3):

δ 7.67-7.16 (m, 80H, Ph); 4.35 (s, 10H, Cp); 2.23-2.19, 1.91-1.79 (2 x m, 16H,

CH2CH2). 13C NMR (CD2Cl2): δ 136.27-129.37 (m, Ph); 83.85 (s, C5H5); 29.09-28.34

(m, CH2CH2). 31P NMR (CDCl3): δ 80.7 (s, Ru(dppe)Cp); 56.5 (s, Ru(dppe)2). ES-

MS (+ve ion, CH3CN, m/z): 2123, [M]+; 2122, [M - H]+; 898, [Ru(dppe)2]+; 606,

[Ru(NCMe)(dppe)Cp]+; 565, [Ru(dppe)Cp]+.

trans-Ru{C4[Ru(PPh3)2Cp]}2(dppe)2 (4)

Similarly, the reaction of trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol) and

RuCl(PPh3)2Cp (75 mg, 0.1 mmol) gave trans-Ru{C4[Ru(PPh3)2Cp]}2(dppe)2 (4) as a


C, 71.84; H, 5.04. IR (CH2Cl2, cm-1): ν(C≡C) 2014 (w), 1979 (w). 1H NMR (CDCl3):

δ 7.71-6.93 (m, 100H, Ph); 4.36 (s, 10H, Cp); 2.31-2.19, 1.93-1.80 (2 x m, 8H,

CH2CH2). 13C NMR (CD2Cl2): δ 133.88-127.14 (m, Ph); 83.10 (s, C5H5); 30.09-29.56

(m, CH2CH2). 31P NMR (CDCl3): δ 57.0 (s, Ru(dppe)2); 43.0 (s, Ru(PPh3)2). ES-MS

(+ve ion, CH3CN, m/z): 2375, [M]+; 1685, [Ru(PPh3)2CpC4Ru(dppe)2C4]+; 898,

[Ru(dppe)2]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.

trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5)

trans-Ru(C4H)2(dppe)2 (1) (50 mg, 0.05 mmol), RuCl(dppe)Cp* (34 mg, 0.05 mmol),

Na[BPh4] (17 mg, 0.05 mmol) and NEt3 (0.01 mL, 0.07 mmol) were combined and a

6:1 mixture of CH2Cl2/MeOH was added. The resulting suspension was heated at

reflux point for 1 h. The solvent was then removed and the resulting green residue

dissolved in a minimum amount of CH2Cl2 and filtered through cotton wool into

stirred hexane (40 mL). The precipitate was collected and washed with hexane to

98

yield trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5) as a green powder (66 mg, 80%).

Anal. Calcd. (C96H88P6Ru2): C, 70.75; H, 5.44. Found: C, 70.73; H, 5.54. IR (CH2Cl2,

cm-1): ν(≡CH) 3055 (m); ν(C≡C) 2022 (w), 1968 (w). 1H NMR (CDCl3): δ 7.99-7.12

(m, 60H, Ph); 2.47-2.44, 2.10-2.03 (2 x m, 12H, CH2CH2); 1.56 (s, 15H, Cp*); 1.44

(s, H). 13C NMR (CD2Cl2): δ 136.32-127.32 (m, Ph); 96.91 (s, C5Me5); 31.51-30.22

(m, CH2CH2); 10.64 (s, C5Me5). 31P NMR (CDCl3): δ 70.5 (s, Ru(dppe)Cp*); 46.1 (s,

Ru(dppe)2). ES-MS (+ve ion, MeOH, m/z): 1631, [M]+; 898, [Ru(dppe)2]+; 635,

[Ru(dppe)Cp*]+.

trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6)

Similarly, from trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol) and RuCl(dppe)Cp

(32 mg, 0.05 mmol) was obtained trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6) as a

green powder (67 mg, 85%). Anal. Calcd. (C91H78P6Ru2): C, 70.08; H, 5.04. Found:

C, 70.11; H, 5.12. IR (CH2Cl2, cm-1): ν(≡CH) 3053 (w); ν(C≡C) 1995 (m), 1919 (m). 1H NMR (C6D6): δ 7.42-6.87 (m, 60H, Ph); 4.50 (s, 5H, Cp); 2.55-2.51, 2.11-2.04 (2

x m, 12H, CH2CH2); 1.41 (s, H). 13C NMR (CD2Cl2): δ 136.01-125.22 (m, Ph); 84.84

(s, C5H5); 30.54-29.27 (m, CH2CH2). 31P NMR (C6D6): δ 81.5 (s, Ru(dppe)Cp); 56.4

(s, Ru(dppe)2). ES-MS (+ve ion, CH3CN, m/z): 1560, [M]+; 898, [Ru(dppe)2]+; 605,

[Ru(NCMe)(dppe)Cp]+; 563, [Ru(dppe)Cp]+.

trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7)

Similarly, from trans-Ru(C4H)2(dppe)2 (1) (51 mg, 0.05 mmol) and RuCl(PPh3)2Cp

(37 mg, 0.05 mmol) was obtained trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) as a


C, 72.03; H, 5.08. IR (CH2Cl2, cm-1): ν(≡CH) 3055 (w); ν(C≡C) 1981 (m), 1896 (m). 1H NMR (CDCl3): δ 7.76-6.91 (m, 70H, Ph); 4.20 (s, 5H, Cp); 2.39-2.37, 2.10-2.06 (2

x m, 8H, CH2CH2); 1.40 (s, H). 13C NMR (CD2Cl2): δ 133.97-125.72 (m, Ph); 81.48

(s, C5H5); 31.03-30.22 (m, CH2CH2). 31P NMR (CDCl3): δ 53.0 (s, Ru(dppe)2); 40.0

(s, (PPh3)2Cp). ES-MS (+ve ion, CH3CN, m/z): 1685, [M]+; 898, [Ru(dppe)2]+; 690,

[Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.

99

trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2 (8)

To a suspension of trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5) (30 mg, 0.018

mmol), RuCl(dppe)Cp (17 mg, 0.027 mmol), Na[BPh4] (9.6 mg, 0.027 mmol) and

NEt3 (0.02 mL, 0.1 mmol) was added a 1:1 mixture of CH2Cl2/MeOH. The resulting

suspension was heated at reflux point for 1 h. The solvent was then removed and the

resulting residue dissolved in a minimum amount of CH2Cl2 and filtered through

cotton wool into stirred hexane (40 mL). The green precipitate was collected and

washed with hexane to yield trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2

(8) (32 mg, 77%). Anal. Calcd (C127H116P8Ru3): C, 69.45; H, 5.33. Found: C, 68.98;

H, 5.33. IR (Nujol, cm-1): ν(C≡C) 2021 (m), 1961 (m). 1H NMR (CDCl3): δ 7.88-6.90

(m, 80H, Ph); 4.59 (s, 5H, Cp); 2.98-2.84, 2.24-2.16 (m, 16H, CH2CH2); 1.45 (s, 15H,

Cp*). 13C NMR (CD2Cl2): δ 134.82-127.03 (m, Ph); 99.92 (s, C5Me5); 81.76 (s,

C5H5); 30.82-29.97 (m, CH2CH2); 9.89 (s, C5Me5). 31P NMR (CDCl3): δ 80.7 (s,

Ru(dppe)Cp); 76.4 (s, Ru(dppe)Cp*); 55.6 (s, Ru(dppe)2). ES-MS (+ve ion, CH3CN,

m/z): 2194, [M + H]+; 1629, [M - Ru(dppe)Cp]+; 898, [Ru(dppe)2]+; 635,

[Ru(dppe)Cp*]+; 675, [Ru(NCMe)(dppe)Cp*]+; 565, [Ru(dppe)Cp]+; 605,

[Ru(NCMe)(dppe)Cp]+.

trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2 (9)

Similarly, trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2 (9) was obtained

from trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) (31 mg, 0.019 mmol),

RuCl(dppe)Cp (12 mg, 0.019 mmol) and Na[BPh4] (7 mg, 0.019 mmol) as a green

powder (33 mg, 78%). Anal. Calcd. (C132H112P8Ru3): C, 70.39; H, 5.02. Found: C,

69.81; H, 5.37. IR (Nujol, cm-1): ν(C≡C) 2017 (m), 1888 (w). 1H NMR (CDCl3): δ

7.87-6.93 (m, 75H, Ph); 2.71-2.57, 2.42-2.37 (2 x m, 12H, CH2CH2); 4.58 (s, 5H, Cp);

4.32 (s, 5H, Cp). 13C NMR (CD2Cl2): δ 135.47-128.56 (m, Ph); 81.25 (s, C5H5); 80.93

(s, C5H5); 30.10-29.20 (m, CH2CH2). 31P NMR (CDCl3): δ 80.7 (s, Ru(dppe)Cp); 55.9

(s, Ru(dppe)2); 42.9 (s, Ru(PPh3)2). ES-MS (+ve ion, CH3CN, m/z): 1685,

[Ru(PPh3)2CpC4Ru(dppe)2C4]+; 1559, [Ru(dppe)CpC4Ru(dppe)2C4]+; 898,

[Ru(dppe)2]+; 690, [Ru(PPh3)2Cp]+; 605, [Ru(NCMe)(dppe)Cp]+; 565 [Ru(dppe)Cp]+;

429, [Ru(PPh3)Cp]+.

100

trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 (10)

A mixture of Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) and [RuCl(dppe)2]OTf

(80 mg, 0.07 mmol) in a 1:1 CH2Cl2/NEt3 mixture was stirred at r.t. for 2 days. The

solvent was then removed and the yellow residue was washed with Et2O (40 mL) and

dried under vacuum to give trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2 (10) as a pale

yellow powder (99 mg, 83%). Anal. Calcd. (C41H42P2Ru): C, 68.37; H, 5.43. Found:

C, 68.54; H, 5.40. IR (CH2Cl2, cm-1): ν(C≡C) 2037 (m), 1988 (w). 1H NMR (CDCl3):

δ 7.72-6.90 (m, 60H, Ph); 3.57-3.54, 3.49-3.46 (2 x m, 8H, CH2CH2); 2.86-2.76, 1.87-

1.75 (2 x m, 4H, CH2CH2); 1.50 (s, 15H, Cp*).13C NMR (CDCl3): δ 133.23-128.11

(m, Ph); 93.26 (s, C5Me5); 32.22-31.79 (m, CH2CH2); 9.82 (s, C5Me5). 31P NMR

(CDCl3): δ 82.8 (s, Ru(dppe)Cp*); 60.1 (t, 18Hz, dppe); 50.6 (t, 18Hz, dppe). ES-MS

(+ve ion, MeOH, m/z): 1615, [M - H]+; 898, [Ru(dppe)2]+; 635, [Ru(dppe)Cp*]+.

trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11)

To a solution of trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2 (5) (50 mg, 0.04 mmol)

and NaOMe (3 mg, 0.15 mmol) in a 1:4 mixture of MeOH/THF was added

AuCl(PPh3) (15 mg, 0.03 mmol). The reaction mixture was stirred at r.t. for 3 h and

the solvent was then evaporated. The residue was dissolved in minimum amount of

CH2Cl2 and dropped into rapidly stirred hexane. The pale yellow precipitate was

collected by filtration, washed with hexane (2 x 20 mL) and air-dried to afford trans-

Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11) (55 mg, 70%). Anal. Calcd.

(C114H102AuP7Ru2): C, 65.58; H, 4.92. Found: C, 65.89; H, 5.20. IR (Nujol, cm-1):

ν(C≡C) 2012 (w), 1957 (m). 1H NMR (CDCl3): δ 7.69-7.04 (m, 75H, Ph); 3.52-3.15,

2.37-2.30 (2 x m, 12H, CH2CH2); 1.57 (s, 15H, Cp*). 13C NMR (CDCl3): δ 139.31-

121.36 (m, Ph); 98.80 (s, C5Me5); 30.63-29.65 (m, CH2CH2); 9.48 (s, C5Me5). 31P

NMR (CDCl3): δ 73.8 (s, Ru(dppe)Cp*); 55.3 (s, Ru(dppe)2); 44.6 (s, Au(PPh3)). ES-

MS (+ve ion, MeOH, m/z): 2086, [M]+; 2055 [M - P]+; 1626, [M - Au(PPh3)]+.

101

trans-Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2 (12)

Similarly, from trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2 (6) (40 mg, 0.03 mmol) and

AuCl(PPh3) (13 mg, 0.03 mmol) was obtained the pale yellow powder trans-

Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2 (12) (33 mg, 62%). Anal. Calcd.

(C109H93AuP7Ru2): C, 64.85; H, 4.64. Found: C, 65.13; H, 5.11. IR (CH2Cl2, cm-1):

ν(C≡C) 2013 (w), 1882 (w). 1H NMR (CDCl3): δ 7.87-6.91 (m, 75H, Ph); 4.57 (s,

5H, Cp); 2.56-2.49, 2.33-2.24 (2 x m, 12H, CH2CH2). 13C NMR (CDCl3): δ 142.68-

122.00 (m, Ph); 84.97 (s, C5H5); 30.83-29.79 (m, CH2CH2). 31P NMR (CDCl3): δ 80.7

(s, Ru(dppe)Cp); 53.3 (s, Ru(dppe)2); 44.6 (s, Au(PPh3)). ES-MS (+ve ion, MeOH,

m/z): 2018, [M]+; 898, [Ru(dppe)2]+; 565 [Ru(dppe)Cp]+.

trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2 (13)

Similarly, trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2 (13) was obtained

from trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2 (7) (41 mg, 0.03 mmol) and

AuCl(PPh3) (13 mg, 0.03 mmol) as a pale yellow powder (36 mg, 69%). Anal. Calcd.

(C119H99P7AuRu2): C, 66.63; H, 4.65. Found: C, 66.95; H, 5.22. IR (CH2Cl2, cm-1):

ν(C≡C) 1970 (w), 1899 (w). 1H NMR (CDCl3): δ 7.79-6.86 (m, 85H, Ph); 4.36 (s,

75H, Cp); 2.30-2.25, 1.99-1.88 (2 x m, 8H, CH2CH2). 13C NMR (CDCl3): δ 136.01-

121.85 (m, Ph); 84.05 (s, C5H5); 31.12-29.25 (m, CH2CH2). 31P NMR (CDCl3): δ 53.9

(s, Ru(dppe)2); 51.4 (s, Ru(PPh3)2Cp); 43.2 (s, Au(PPh3)). ES-MS (+ve ion, MeOH,

m/z): 2113, [M - P]+; 2038, [M - PPh]+; 898, [Ru(dppe)2]+; 429, [Ru(PPh3)Cp]+.

trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2 (14)

Co3(µ3-CBr)(µ-dppm)(CO)7 (16 mg, 0.02 mmol), CuI (7 mg, 0.04 mmol), Pd(PPh3)4

(41 mg, 0.03 mmol) and trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2 (11) (41

mg, 0.02 mmol), were dissolved in THF (30 mL) and stirred at r.t. for 4 h. The

solution was filtered and the solvent was then evaporated. The brown residue was

then dissolved in acetone and filtered through cotton wool into stirred hexane (40

mL). The precipitate was collected and washed with hexane to afford trans-

102

Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2 (14) as a brown powder (15

mg, 33%). Anal. Calcd. (C129H109P8Ru2O7Co3): C, 64.61; H, 4.58. Found: C, 64.66;

H, 4.61. IR (CH2Cl2, cm-1): ν(CO): 2069 (m), 2058 (s); ν(C≡C) 2010 (w); 1978 (m). 1H NMR (CDCl3): δ 7.70-6.83 (m, 80H, Ph); 2.85-2.77, 2.55-2.45 (2 x m, 12H,

CH2CH2); 4.45-4.40 (m, H, CH2); 3.48-3.43 (m, H, CH2); 1.51 (s, 15H, Cp*). 13C

NMR (CDCl3): δ 203.29-200.02 (m, CO); 139.37-132.77 (m, Ph); 96.86 (s, C5Me5);

33.95-32.22 (m, CH2); 30.40-29.63 (m, CH2CH2); 10.11 (s, C5Me5). 31P NMR

(CDCl3): δ 72.8 (s, Ru(dppe)Cp*); 55.9 (s, Ru(dppe)2); 30.6 (s, dppm). ES-MS (+ve

ion, CH3CN, m/z): 2370, [M – CO]+; 898, [Ru(dppe)2]+; 675, [Ru(dppe)Cp*]+.

trans-Ru{C4[Au(PPh3)]}2(dppe)2 (15)

To a solution of trans-Ru(C4H)2(dppe)2 (1) (100 mg, 0.1 mmol) and NaOMe (28 mg,

0.5 mmol) in a 1:4 mixture of MeOH/THF was added AuCl(PPh3) (100 mg, 0.2

mmol). The reaction mixture was stirred at r.t. for 5 h. The bright yellow precipitate

was collected by filtration, washed with hexane (2 x 10 mL) and air-dried to afford

trans-Ru{C4[Au(PPh3)]}2(dppe)2 (15) (0.17 mg, 89%). Anal. Calcd.

(C96H78Au2P6Ru): C, 60.29; H, 4.11. Found: C, 60.31; H, 4.17. IR (CH2Cl2, cm-1):

ν(C≡C) 2084 (w), 1974 (m). 1H NMR (CDCl3): δ 7.61-7.07 (m, 60H, Ph); 3.76-3.59,

2.61-2.51 (2 x m, 8H, CH2CH2). 13C NMR (CDCl3): δ 134.53-127.28 (m, Ph); 33.27-

30.91 (m, CH2CH2). 31P NMR (CDCl3): δ 53.10 (s, Ru(dppe)2); 46.08 (s, Au(PPh3)).

ES-MS (+ve ion, MeOH, m/z): 1916, [M]+; 721, [Au(PPh3)2]+; 459, [Au(PPh3)]+.

trans-Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2 (16)

Co3(µ3-CBr)(µ-dppm)(CO)7 (88 mg, 0.1 mmol), trans-Ru{C4[Au(PPh3)]}2(dppe)2

(15) (110 mg, 0.05 mmol), CuI (18 mg, 0.1 mmol) and Pd(PPh3)4 (137 mg, 0.1 mmol)

were dissolved in THF (50 mL) and stirred at r.t. for 4 h. The solution was filtered and

the solvent was evaporated to dryness. The residue was purified by column

chromatography on silica gel, eluted with a mixture of 3:7 acetone/hexane to afford a

bright orange powder trans-Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2 (16) (70 mg, 54%).

103

Anal. Calcd. (C126H92P8RuO14Co6): C, 59.76; H, 3.66. Found: C, 59.84; H, 3.58. IR

(CH2Cl2, cm-1): ν(C≡C) 2084 (w); ν(CO) 2062 (w), 2057 (s), 2033 (m), 1999 (w). 1H

NMR (CDCl3): δ 7.48-6.82 (m, 80H, Ph); 4.45-4.40 (m, 2H, CH2); 3.54-3.48 (m, 2H,

CH2); 2.68-2.56, 2.32-2.19 (2 x m, 8H, CH2CH2). 13C NMR (CDCl3): δ 221.31-206.21

(m, CO); 134.56-126.55 (m, Ph); 33.49-32.87 (m, CH2); 30.61-29.40 (m, CH2CH2). 31P NMR (CDCl3): δ 51.0 (s, Ru(dppe)2); 33.2 (s, dppm). ES-MS (+ve ion, MeOH,

m/z): 2552, [M + Na]+; 2528, [M - H]+.

Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17)

To a solution of trans-Ru(C4H)2(dppe)2 (1) (50 mg, 0.05 mmol) in CH2Cl2 (40 ml)

was added TCNE (12 mg, 0.09 mmol) and the reaction mixture was stirred at r.t. for

16 h, gradually changing in colour from yellow to purple. The solvent was then

removed and the residue was dissolved in minimum amount of benzene and purified

by preparative TLC, eluted with CH2Cl2 to afford a bright purple powder

Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2 (17) (52.2 mg, 93%) (Rf 0.32). Single

crystals suitable for X-ray studies were grown from CH2Cl2/benzene. Anal. Calcd

(C72H50P4RuN8): C, 69.00; H, 4.02; N, 8.95. Found: C, 68.97; H, 4.14; N, 8.86. IR

(CH2Cl2, cm-1): ν(CN) 2220 (m); ν(C≡C) 1973 (w). 1H NMR (CDCl3): δ 7.43-7.14

(m, 40H, Ph); 3.08-2.99, 2.25-2.17 (2 x m, 8H, CH2CH2); 1.41 (s, 2H, =CH). 13C

NMR (CDCl3): δ 152.78, 142.85, 126.12, 90.82 (s, C1, C2, C3, C4); 134.16-128.64 (m,

Ph); 115.11, 113.75 (2 x s, 2 x CN); 111.31, 110.10 (2 x s, 2 x CN); 30.61, 30.47 (2 x

s, 2 x C(CN)2); 30.47-29.98 (m, CH2CH2). 31P NMR (CDCl3): δ 47.4 (s, Ru(dppe)2).

ES-MS (+ve ion, MeOH, m/z): 1251, [M]+; 1225, [M - CN]+; 898, [Ru(dppe)2]+.

[{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19) To a solution of Ru(C≡CC≡CH)(dppe)Cp* (57 mg, 0.08 mmol) in 4:1 THF/NEt3 (10

mL) was added dbu (35 mg, 0.23 mmol) followed by [Cu2(µ-dppm)2(MeCN)2][BF4]2

(73 mg, 0.06 mmol). The solution was heated at reflux for 1 h before cooling and

solvent was then removed. The product was extracted in CH2Cl2, loaded onto a basic

104

alumina column and eluted with a 4:6 acetone/hexane mixture. The solvent was then

removed and crystallisation from CH2Cl2/hexane gave bright yellow crystalline solid

that was collected and washed with Et2O to give [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-

dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (19) (88 mg, 55%). Anal. Calcd.

(C155H144Cu3BF4P10Ru2): C, 66.58; H, 5.19. Found: C, 66.85; H, 5.11. IR (Nujol, cm-

1): ν(C≡C) 2021 (w); ν(BF) 1059 (s). 1H NMR (C6D6): δ 7.17-6.81 (m, 100H, Ph);

3.17-3.14 (m, 6H, dppm); 3.17-3.04, 2.87-2.56 (2 x m, 2 x 4H, CH2CH2); 1.56 (s,

30H, Cp*). 13C NMR (C6D6): δ 137.10-128.03 (m, Ph); 121.50 (t, 2J(CP) = 21 Hz,

C1); 117.15, 95.01, 64.80 (s, C2, C3, C4); 94.19 (s, C5Me5); 28.20-27.96 (m, CH2CH2);

11.45 (s, C5Me5). 31P NMR (C6D6): δ -7.3 (s, 6P, dppm); 79.4 (s, 4P, dppe). ES-MS

(+ve ion, MeOH, m/z): 1355, [M + H]2+; 635, [Ru(dppe)Cp*]+.

[{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6] (20) To a solution of Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.08 mmol) in 4:1 THF/NEt3 (10

mL) was added dbu (35 mg, 0.23 mmol) followed by [Ag2(µ-dppm)2(MeCN)2][PF6]2

(77 mg, 0.06 mmol). The solution was heated at reflux for 1 h in the dark before

cooling and solvent was then removed. The residue was dissolved in acetone (5 mL)

and added to rapidly stirred Et2O (40 mL). A yellow precipitate was collected and

washed with Et2O to give [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-

dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6] (20) (90 mg, 53%). Anal. Calcd.

(C155H144Ag3F6P11Ru2): C, 62.32; H, 4.86. Found: C, 62.52; H, 5.02. IR (Nujol, cm-1):

ν(C≡C) 2033 (w); ν(PF) 838 (s). 1H NMR (C6D6): δ 7.90-6.87 (m, 100H, Ph); 3.25-

3.22 (m, 6H, dppm); 2.55-2.51, 1.84-1.77 (2 x m, 2 x 4H, CH2CH2); 1.59 (s, 30H,

Cp*). 13C NMR (C6D6): δ 133.61-127.82 (m, Ph); 123.55, 116.45, 95.79, 51.64 (s, C1,

C2, C3, C4); 94.21 (s, C5Me5); 28.71-28.15 (m, CH2CH2); 9.83 (s, C5Me5). 31P NMR

(C6D6): δ -141.1 (sept, 1JPF 711 Hz, PF6); -1.3 (s, 6P, dppm); 80.7 (s, 4P, dppe). ES-

MS (+ve ion, acetone, m/z): 1421, [M]2+; 635, [Ru(dppe)Cp*]+.

105

[{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (21) Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (55 mg, 0.08 mmol) with [Ag2(µ-

dppm)2(MeCN)2][BF4]2 (75 mg, 0.06 mmol) gave the mustard yellow complex

[{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4] (21) (90 mg,

51%). Anal. Calcd. (C155H144Ag3BF4P10Ru2): C, 63.56; H, 4.96. Found: C, 63.77; H,

4.60. IR (Nujol, cm-1): ν(C≡C) 2015 (w); ν(BF) 1052 (s). 1H NMR (C6D6): δ 7.37-

6.79 (m, 100H, Ph); 3.12-3.02 (m, 6H, dppm); 2.59-2.53, 1.87-1.79 (2 x m, 2 x 4H,

CH2CH2); 1.56 (s, 30H, Cp*). 13C NMR (C6D6): δ 133.78-127.97 (m, Ph); 123.62,

116.57, 95.88, 51.72 (s, C1, C2, C3, C4); 94.20 (s, C5Me5); 28.94-28.86 (m, CH2CH2);

9.97 (s, C5Me5). 31P NMR (C6D6): δ -1.2 (s, 6P, dppm); 80.5 (s, 4P, dppe). ES-MS

(+ve ion, acetone, m/z): 1421, [M]2+; 635, [Ru(dppe)Cp*]+.

Chapter Three

A New Method for the Synthesis of

Diyndiyl Ruthenium(II) Complexes

107

3.1. Introduction

As described in Chapter One, diyndiyl complexes have been synthesised by several

methods. Of interest to this work is one particular method which involves the

lithiation of terminal diynyl ligands with any of a range of organolithium bases, such

as n-, sec- or t-BuLi, or LDA, followed by treatment with a metal halide. The

lithiation of a terminal diynyl complex with a lithium base results in the formation of

a nucleophilic species {LnM}(C≡CC≡CLi) which is subsequently treated with the

metal halide to afford the desired diyndiyl complex (Scheme 64).

C C C C {M'L'n'}{LnM}

C C C C H{LnM}

{M'L'n'}Cl

Lithium BaseC C C C{LnM} Li

Scheme 64: The lithiation of a diynyl complex to synthesise diyndiyl complexes This method was first reported in 1990 by Wong,27 followed by Gladysz and co-

workers in 1992. They applied the method to Re(C≡CH)(PPh3)(NO)Cp* and

Re(C≡CH)(PPh3)(NO)Cp for the synthesis of a range of complexes.138,139 For

example, trans-{Cp*(PPh3)(NO)Re}(C≡C){Rh(PPh3)2(CO)} was synthesised from

the treatment of Re(C≡CH)(PPh3)(NO)Cp* with n-BuLi and the subsequent reaction

of the generated lithiated complex Re(C≡CLi)(PPh3)(NO)Cp* with trans-

RhCl(CO)(PPh3)2 (Scheme 65).

C C HRe

ON PPh3-78oC

n-BuLiC C LiRe

ON PPh3

C C {MLn}Re

ON PPh3 C C PdRe

ON PPh3

C C RhRe

ON PPh3

{MLn}Cl

{MLn} = TMS SnPh3

PdCl2(PEt3)2

PEt3

PEt3

Cl

RhCl(PPh3)2(CO)

PPh3

PPh3

CO

Scheme 65: The deprotonation and metalation of the complex Re(C≡CH)(PPh3)(NO)Cp*

108

A few years later, the same group extended their work to the lithiation of the diynyl

complex Re(C≡CC≡CH)(PPh3)(NO)Cp*.22 The lithiated complex

Re(C≡CC≡CLi)(PPh3)(NO)Cp* was generated and then reacted with trans-

PdCl2(PEt3)2 to afford {Cp*(PPh3)(NO)Re}(C≡CC≡C){PdCl(PEt3)2)} or with trans-

RhCl(CO)(PPh3)2 to give {Cp*(PPh3)(NO)Re}(C≡CC≡C){Rh(PPh3)2(CO)} (Scheme

66)

C CRe

ON PPh3-80oC

n-BuLi

PdCl2(PEt3)2 RhCl(PPh3)2(CO)

C C H C CRe

ON PPh3

C C Li

C CRe

ON PPh3

C C Pd

PEt3

PEt3

Cl C CRe

ON PPh3

C C Rh

PPh3

PPh3

CO

Scheme 66: The deprotonation and metalation of Re(C≡CC≡CH)(PPh3)(NO)Cp*

Furthermore, our group applied the lithiation method to the synthesis of two tungsten

complexes. First, it was reported that W(C≡CC≡CH)(CO)3Cp was lithiated with LDA

at -78oC and quenched by TMSCl to afford W(C≡CC≡CTMS)(CO)3Cp.20 Secondly,

the reaction of W(C≡CC≡CLi)(CO)3Cp with MnI(CO)5 gave the complex

{W(CO)3Cp}(C≡CC≡C){Mn(CO)5} (Scheme 67).31

C CW

OC -78oC

LDAC C H C C C C Li

CO CO

W

OC CO CO

C C C C TMSW

OC CO CO

C C C C Mn(CO)5W

OC CO CO

MnI(CO)5TMSCl

Scheme 67: The deprotonation and metalation of the complex W(C≡CC≡CH)(CO)3Cp

109

This method was also employed with the iron complex Fe(C≡CC≡CH)(CO)2Cp*

which was treated with s-BuLi, followed by FeCl(CO)2Cp* to give the complex

{Fe(CO)2Cp*}2(C≡CC≡C).26 Similarly, the lithiation of Ru(C≡CH)(PPh3)2Cp* was

achieved using n-BuLi or t-BuLi in a THF/hexane mixture.140 The lithium

intermediate Ru(C≡CLi)(PPh3)2Cp* then reacted with {MLn}Cl ({MLn} = TMS,

GeMe3 and SnBu3n) to give {Cp*(PPh3)2Ru}(C≡C){MLn} (Scheme 68).

Cp*(PPh3)2Ru C C H Cp*(PPh3)2Ru C C Li

Cp*(PPh3)2Ru C C {MLn}

n-BuLi

-70oC

{MLn}Cl

{MLn} = TMS, GeMe3, SnBu3n

Scheme 68: The deprotonation and metalation of the complex Ru(C≡CH)(PPh3)2Cp*

110


The primary aim of this work was to develop a new methodology that would allow

the synthesis of novel diynyl and diyndiyl complexes. The synthetic route is based on

the method first described by Wong which involves the lithiation of a diynyl complex,

followed by its metallation with a metal halide.

This chapter reports the lithiation of two ruthenium(II) diynyl complexes

Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp and the synthesis of the

lithium complexes Ru(C≡CC≡CLi)(dppe)Cp* and Ru(C≡CC≡CLi)(PPh3)2Cp. The

most favorable conditions for their formation are studied by using assay reactions.

Furthermore, the synthesis and characterisation of new asymmetric diyndiyl

complexes of general formula [Ru](C≡CC≡C){MLn} has been achieved by applying

the new synthetic method.

111


3.3.1. The lithiation of [Ru](C≡CC≡CH) ([Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp)

3.3.1.1. Synthetic strategy

In the Introduction, it was shown that one method for the synthesis of asymmetric

complexes is the lithiation of terminal diynyl ligands with strong organolithium bases

(BuLi, LDA) followed by treatment with a metal halide. According to these studies, it

was anticipated that the diynyl complexes [Ru](C≡CC≡CH) (where [Ru] =

Ru(dppe)Cp*, Ru(PPh3)2Cp) could be lithiated using organolithium bases. Hence,

these complexes were treated with a strong organolithium base (BuLi, LDA, MeLi) in

THF at -78oC and the initial bright yellow solution rapidly changed to a darker

yellow. The solution was then assumed to contain the [Ru](C≡CC≡CLi) species.

Furthermore, it was shown in previous work that nucleophiles similar to

[Ru](C≡CC≡CLi) can be used as reactive intermediates in further syntheses; they

react readily with electrophiles such as transition-metal chlorides. Hence, in order to

assay the [Ru](C≡CC≡CLi) species generated in situ, a two-step reaction was

proposed. The first step is the deprotonation of [Ru](C≡CC≡CH) as described above

and the second step involves the addition of a metal halide (Scheme 69). It is

noteworthy that this is providing a new convenient method for the synthesis of new

diynyl and diyndiyl ruthenium(II) complexes.

C C C C {MLn}[Ru]

C C[Ru] C C H

{MLn}Cl

CC C C[Ru] LiLithium Base

THF in situ-78oC

[Ru] = Ru(dppe)Cp* Ru(PPh3)2Cp

Scheme 69: A two-step reaction for the formation of [Ru](C≡CC≡C){MLn} complexes

112

3.3.1.2. NMR study

Spectroscopic monitoring was attempted on the lithiation reaction of

Ru(C≡CC≡CH)(dppe)Cp*. The 1H and 31P NMR spectra of the lithium complex

Ru(C≡CC≡CLi)(dppe)Cp* were obtained by dissolving Ru(C≡CC≡CH)(dppe)Cp* in

THF-d8 in an NMR tube and then adding n-BuLi at -78oC.

The 31P NMR spectrum of the Ru(C≡CC≡CLi)(dppe)Cp* species shows a single peak

at δ 82.9. The chemical shift for the Ru(C≡CC≡CH)(dppe)Cp* in THF-d8 at -78oC

was at δ 80.7. So, the difference between the neutral and the deprotonated species is a

downfield shift of 2.2 ppm. The 1H NMR spectrum of Ru(C≡CC≡CH)(dppe)Cp* in

THF-d8 at -78oC shows five resonances: one at δ 7.78-7.25 for the phenyl groups, two

multiplets at δ 2.75-2.73 and 2.17-2.15 for the dppe ligand, one singlet at δ 1.59 for

the methyl groups of the Cp* ligand. The most significant resonance in this study is

the presence of the terminal proton as a singlet at δ 1.34. In comparison, the 1H NMR

spectrum of the Ru(C≡CC≡CLi)(dppe)Cp* species also showed a multiplet for the

phenyl groups at δ 7.76-7.23, two multiplets at δ 2.76-2.71 and 2.16-1.93 for the dppe

ligand and one singlet at δ 1.53 for the methyl groups of the Cp* ligand. These values

are very close to those for Ru(C≡CC≡CH)(dppe)Cp*. The most interesting feature is

the shift of the terminal proton to δ 1.68 and the decrease in its relative ratio

compared to the Cp* singlet. The ratio decreased from approximately half of its

original value. More spectra were taken at later time interval but did not show any

major change. When an excess of n-BuLi was added, the studied region become very

broad and no further analysis could be completed.

In conclusion, the efficiency of the synthesis of the Ru(C≡CC≡CLi)(dppe)Cp* species

could not be determined from these spectroscopic studies. The small chemical shift

differences in the 31P and the 1H NMR spectra are not conclusive. There is a decrease

in the intensity of the terminal proton, but it appears that complete metallation has not

occurred. Therefore, the formation of the Ru(C≡CC≡CLi)(dppe)Cp* complex was

further studied by using assay reactions.

113

3.3.2. Investigation of the formation of [Ru](C≡CC≡CLi)

In this Section, the conditions that are the most favorable for the lithiation of the

complexes [Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) are

described. In order to explore this, the syntheses of known complexes

[Ru](C≡CC≡CTMS) (where [Ru] = Ru(dppe)Cp* (22), Ru(PPh3)2Cp (23)) and

[Ru](C≡CC≡C[Au(PPh3)]} (where [Ru] = Ru(dppe)Cp* (24), Ru(PPh3)2Cp (25))

were attempted.

3.3.2.1. Synthesis of [Ru](C≡CC≡CTMS)

The syntheses of [Ru](C≡CC≡CTMS) (where [Ru] = Ru(dppe)Cp* (22),

Ru(PPh3)2Cp (23)) are usually achieved by the reaction of the chlororuthenium

complexes [Ru]Cl with an excess of H-C≡CC≡C-TMS in the presence of Na[BPh4]

in a THF/NEt3 solvent mixture (Scheme 70).30

Cl + C C C C TMSC C TMSHNa[BPh4]

THF/NEt350oC

[Ru][Ru]

[Ru] = Ru(dppe)Cp* (79%) (22) Ru(PPh3)2Cp (94%) (23)

2

Scheme 70: Synthesis of 22 and 23

The new approach for the syntheses of 22 and 23 is based on the lithiation of the

diynyl complexes [Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) with

an organolithium base followed by treatment with the metal halide TMSCl (Scheme

71).

114

C C C C TMS[Ru]

C C[Ru] C C H

TMSCl

CC C C[Ru]Lithium Base

in situ

[Ru] = Ru(dppe)Cp* (22), Ru(PPh3)2Cp (23)

Li

Scheme 71: A new method for the synthesis of 22 and 23 The lithiation of [Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) with a

range of organolithium bases, different solvents, temperatures and reaction times was

tried in order to find the best conditions for the synthesis of [Ru](C≡CC≡CLi) (where

[Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp). The terminal lithium complexes were generated

in situ and subsequent addition of TMSCl allowed the formation of the diynyl

complexes 22 and 23. Some representative experiments are summarised in Table 10.

The best yield 86% of Ru(C≡CC≡CTMS)(dppe)Cp* (22) and 80% of

Ru(C≡CC≡CTMS)(PPh3)2Cp (23) were achieved using two equivalents of n-BuLi, in

THF at -78 oC for 30 min, followed by addition of TMSCl and warming the solution

to room temperature.

Complexes 22 and 23 were characterised by 1H and 31P NMR spectroscopy and the

data were consistent with the literature values.12,59 The 1H NMR spectrum of 22

shows a singlet at δ 0.29 confirming the presence of the trimethylsilyl group, a singlet

at δ 1.56 corresponding to the Cp* ligand, multiplets at δ 2.56-2.52 and 1.88-1.81

corresponding to the hydrogens of the -CH2CH2- group in dppe and a broad multiplet

at δ 7.87-7.02 for the phenyl groups. The 31P NMR spectrum of 22 shows one singlet

at δ 81.3 assigned to the phosphorus nuclei bound to the ruthenium. In the 1H NMR

spectrum of complex 23, a multiplet at δ 7.59-6.91 for the phenyl groups, a singlet at

δ 4.36 which corresponds to the cyclopentadienyl Cp ligand and a singlet at δ 0.28 for

the TMS group are present. In the 31P NMR spectrum, one resonance at δ 50.8 was

assigned to the phosphorus atoms coordinated to the ruthenium.

115

Reagents Solvent Temp. (oC) Reaction Time Yield (%)

Ru(C≡CC≡CH)(dppe)Cp*

n-BuLi (1 eq)

TMSCl

THF -78 1 h (-78oC), then

to r.t.

78


n-BuLi (2 eq)

TMSCl

THF -78 30 min (-78oC),

then to r.t.

86

Ru(C≡CC≡CH)(PPh3)2Cp

n-BuLi (1 eq)

TMSCl

1 : 1

THF/hexane

-40 1 h (-40oC), then

to r.t.

74


n-BuLi (2 eq)

TMSCl

THF -78 30 min (-78oC),

then to r.t.

80


t-BuLi (1 eq)

TMSCl

1 : 1

THF/Et2O

-80 1 h (-80oC), then

to r.t.

75


MeLi (1 eq)

TMSCl

2 : 1

THF/hexane

-20 1 h (-20oC), then

to r.t.

74


MeLi (2 eq)

TMSCl

1 : 1

THF/hexane

0 30 min (0oC), then

to r.t.

70


n-BuLi (1 eq) + TMEDA

TMSCl

2 : 1

THF/hexane

-80 2 h (-80oC), then

to r.t.

64


LDA (1 eq)

TMSCl

THF -78 2 h (-78oC), then

to r.t.

59

Table 9: Summary of experiments for the synthesis of 22 and 23

116

3.3.2.2. Synthesis of [Ru]{C≡CC≡C[Au(PPh3)]}

The synthesis of two known complexes [Ru](C≡CC≡C[Au(PPh3)]} [where [Ru] =

Ru(dppe)Cp* (24), Ru(PPh3)2Cp (25)] was attempted in order to assay further the

synthesis of Ru(C≡CC≡CLi)(PPh3)2Cp.

It was reported previously that the reaction of [Ru](C≡CC≡CH) (where [Ru] =

Ru(dppe)Cp*, Ru(PPh3)2Cp) with the chlorogold precursor AuCl(PPh3) in the

presence of K[N(TMS)2] afforded the complexes Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp*

(24) and Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25) (Scheme 72).30

C C[Ru] C C C[Ru] C Au(PPh3)THF

AuCl(PPh3)THF

AuCl(PPh3)K[N(TMS)2]

C C H[Ru] +

[Ru] = Ru(dppe)Cp* (69%) (24) Ru(PPh3)2Cp (93%) (25)

2

Scheme 72: Synthesis of 24 and 25

The new synthetic method was applied in order to synthesise complexes 24 and 25

(Scheme 73) but also to find what conditions are most favorable for the synthesis of

[Ru](C≡CC≡CLi) (Table 11). It was found that the treatment of [Ru](C≡CC≡CH)

with two equivalents of n-BuLi at -78oC followed by addition of one equivalent of

AuCl(PPh3) gives the best yields, 85% for Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp* (24)

and 70% for Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25).

C C C C Au(PPh3)[Ru]

C C[Ru] C C H

AuCl(PPh3)

CC C C[Ru]Lithium Base

in situ

[Ru] = Ru(dppe)Cp* (24), Ru(PPh3)2Cp (25)

Li

Scheme 73: A new method for the synthesis of 24 and 25

117

Reagents Solvent Temp. (oC) Reaction Time Yield (%)


n-BuLi (1 eq)

AuCl(PPh3)

THF -78 30 min (-78oC),

then to r.t.

60


n-BuLi (2 eq)

AuCl(PPh3)

THF -78 30 min (-78oC),

then to r.t.

85


n-BuLi (1 eq)

AuCl(PPh3)

1 : 1

THF/hexane

-80 1 h (-80oC), then

to r.t.

65


n-BuLi (2 eq)

AuCl(PPh3)

THF -78 30 min (-78oC),

then to r.t.

70


LDA (1 eq)

AuCl(PPh3)

1 : 1

THF/hexane

-78 1 h (-78oC), then

to r.t.

62


MeLi (1 eq)

AuCl(PPh3)

1 : 1

THF/Et2O

-20 1 h (-20oC), then

to r.t.

56


MeLi (2 eq)

AuCl(PPh3)

2 : 1

THF/hexane

-20 30 min (-20oC),

then to r.t.

64

Table 10: Summary of experiments for the synthesis of 24 and 25

Complexes 24 and 25 were readily identified from their spectroscopic data, which are

consistent with the literature values.12,141 Both 1H NMR spectra show a multiplet

assigned to the phenyl groups and the characteristic peaks for the Ru(dppe)Cp* and

the Ru(PPh3)2Cp ligands. In the 31P NMR spectra of 24 and 25, two singlets were

present in a 2:1 ratio corresponding to the phosphorus nuclei bound to the ruthenium

and the phosphorus nucleus coordinated to the gold.

118

In conclusion, the best conditions for the lithiation of diynyl complexes

[Ru](C≡CC≡CH) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) involve the addition of

two equivalents of n-BuLi at –78oC, followed by the addition of a metal halide. The

percentage yield for the test reactions with TMSCl and AuCl(PPh3) are very high.

This indicates that the [Ru](C≡CC≡CLi) species is successfully formed and reacted

efficiently with metal halides. It is also noteworthy that complexes 22 and 24 were

obtained in better yields than from the previous reported methods (86% and 85%

yield versus 79% and 69% yield, respectively).30 Furthermore, the availability of these

two nucleophilic complexes [Ru](C≡CC≡CLi) (where [Ru] = Ru(dppe)Cp*,

Ru(PPh3)2Cp) offers a new synthetic route for the synthesis of a range of diynyl and

diyndiyl complexes.

3.3.3. Reactions of [Ru](C≡CC≡CLi) with various metal halides

3.3.3.1. Reaction with (AuCl)2(µ-dppm)

In 1993, the synthesis of the gold(I) alkynyl complex Au2(µ-dppe)(C≡CPh)2 was

reported.142 This compound was found to emit luminescence (Figure 45).

P

P

PhPh

Ph Ph

Au C C

Au C C

Figure 45: Representation of Au2(µ-dppe)(C≡CPh)2

Several gold(I) complexes have been used as precursors for alkynylgold(I)

derivatives. These include AuCl(L) (L = PPh3, SC4H8),108,109 [ppn][Au(acac)2]111 and

(AuCl)2(µ-dppm)110. In 2002, our research group reported the reactions of various

gold(I) complexes. For example, the diynyl complex {Au(C≡CC≡CH)}2(µ-dppm) was

119

synthesised from the reaction of (AuCl)2(µ-dppm) and HC≡CC≡CH under Cadiot-

Chodkiewicz conditions. Similarly, the complex {Au(C≡CC≡C[W(CO3)Cp])}2(µ-

dppm) was obtained from W(C≡CC≡CH)(CO3)Cp and (AuCl)2(µ-dppm) (Scheme

74).65

R C C C C H

R C C C C Au

R C C C C Au

PPh2

PPh2

CuI NHEt2

+ (AuCl)2(µ-dppm)

R = H or W(CO)3Cp

Scheme 74: Two examples of gold(I) complexes

Following these two examples, it was suggested that a new complex containing two

{Ru(dppe)Cp*}C≡CC≡C moieties linked by the gold(I) fragment Au2(µ-dppm) could

be synthesised. It was found that this compound could not be obtained under Cadiot-

Chodkiewicz conditions. Hence, the new synthetic method involving the lithiation of

Ru(C≡CC≡CH)(dppe)Cp* was proposed as an alternative route.

Two equivalents of Ru(C≡CC≡CH)(dppe)Cp* dissolved in THF were treated with n-

BuLi at -78oC. The gold(I) compound (AuCl)2(µ-dppm) was then added to the

Ru(C≡CC≡CLi)(dppe)Cp* species generated in situ. After warming-up the mixture to

room temperature and work-up the complex {Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-

dppm) (26) was obtained in 90% yield (Scheme 75).

120

Cp*(dppe)Ru C C C C Au


PPh2

PPh2

C C C C Lin-BuLi

THF

(AuCl)2(µ-dppm)



PPh2

PPh2

n-BuLi

(26)

Cp*(dppe)RuC C C C HCp*(dppe)Ru


Complex 26 was fully characterised by 1H, 31P and 13C NMR, IR, ES-MS and

microanalysis (Table 14). In the 1H and 13C NMR spectra, the characteristic peaks for

the Ru(dppe)Cp* and dppm ligands are present. The carbons of the carbon chains

were not observed in the 13C NMR spectrum due to the lack of solubility of complex

26 in solvents suitable for NMR spectroscopy. However, two ν(C≡C) bands at 2106

and 1982 cm-1 were observed in the infrared spectrum. The 31P NMR spectrum of 26

shows two resonances at δ 82.0 and 35.6 in a 2:1 ratio which were assigned to the

phosphorus atoms on the ruthenium and the gold, respectively. Further

characterisation of 26 was obtained from the ES-MS which contains a fragment ion

corresponding to [M - H]+ at m/z 2143.

Crystals suitable for an X-ray study have not yet been obtained to confirm the exact

conformation of 26. Previously, it was found that the complex {Au(C≡CtBu)}2(µ-

dppm) has a U-shaped geometry, with an intramolecular Au…Au contact of 3.331(1)

Å, each Au(I) centre being approximately linearly coordinated by the phosphorus

atom and the alkynyl group.143 Furthermore, in the case of

{Au(C≡CC≡C[W(CO3)Cp])}2(µ-dppm), it was speculated that the increased steric

bulk of the W(CO)3Cp moieties is likely to result in breaking of the intramolecular

Au…Au contact, with twisting of the Au-phosphine backbone.65 It is likely that

complex 26 will show a very similar structure to that of

{Au(C≡CC≡C[W(CO3)Cp])}2(µ-dppm) since the Ru(dppe)Cp* moieties are also

bulky.

121

3.3.3.2. Reaction with cis-PtCl2(PPh3)2

The reaction of Ru(C≡CC≡CH)(dppe)Cp* with n-BuLi at -78oC afforded the

nucleophilic species Ru(C≡CC≡CLi)(dppe)Cp* which was reacted in situ with one

equivalent of cis-PtCl2(PPh3)2. Complex trans-Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp*

(27) was isolated from this reaction in 40% yield (Scheme 76).

C C C CRu

Ph2P PPh2

H

n-BuLi /THF

C C C CRu

Ph2P PPh2

Pt-78oC

PtCl2(PPh3)2

PPh3

Ph3P

ClC C CRu

Ph2P PPh2

H C C C CRu

Ph2P PPh2

Pt-78oC

PPh3

Ph3P

Cl

(27)


Complex 27 was identified from its spectroscopic data (Table 13). The characteristic

peaks for the Ru(dppe)Cp* group are present in the 1H and 31P NMR spectra. The 1H

NMR spectrum also shows a broad multiplet at δ 8.02-6.83 due to the phenyl groups

while in the 31P NMR spectrum a resonance was observed at δ 22.2 for the

phosphorus atoms of the PPh3 groups. Further characterisation of 27 was obtained

from the ES-MS which contained a peak corresponding to [M]+ at m/z 1437 and

fragmentation ions [M - H]+ at m/z 1436 and [Ru(dppe)Cp*]+ at m/z 635.

3.3.3.3. Reactions with GeClPh3 and SnClPh3

In Section 3.3.2.1, it was described that Ru(C≡CC≡CLi)(dppe)Cp* reacts with the

silyl halide TMSCl. Following these results, the reaction of

Ru(C≡CC≡CLi)(dppe)Cp* with tin and germanium halides, two other group 14

metalloids, was suggested in order to synthesise complexes that have not been made

by already established methods.

122

The first step of the reaction involved the generation in situ of

Ru(C≡CC≡CLi)(dppe)Cp* which was obtained from the lithiation of

Ru(C≡CC≡CH)(dppe)Cp* with n-BuLi at -78oC. This was then followed by the

addition of one equivalent of either GeClPh3 or SnClPh3.

Ru(C≡CC≡CGePh3)(dppe)Cp* (28) and Ru(C≡CC≡CSnPh3)(dppe)Cp* (29) were

obtained in 82% and 70% yield as a yellow crystalline solids, respectively (Scheme

77).

C C C CRu

Ph2P PPh2

Hn-BuLi

THFC C C CRu

Ph2P PPh2

Li

{MLn}Cl

C C C CRu

Ph2P PPh2

{MLn}

-78oC

{MLn} = GePh3 (28) SnPh3 (29)

Scheme 77: Synthesis of complex 28 and 29

Complexes 28 and 29 were identified from their spectroscopic data and elemental

analysis. All the data are summarised in Table 14. In the 1H, 31P and 13C NMR

spectra, the characteristic peaks for the Ru(dppe)Cp* ligand are present. The 13C

NMR spectra of 28 and 29 also contain the resonances for the carbon atoms of the C4

chain. The ES-MS of complex 28 contains a [M + Na]+ peak at m/z 1009, while the

spectrum for complex 29 has a [M]+ peak at m/z 1033.

Single crystals suitable for X-ray studies of complex 28 were grown from

THF/hexane. Figure 46 shows the ORTEP plot of 28, while selected structural data

are collected in Table 12. The Ru-C(1) bond length is equal to 1.975(3) Å. This value

is close to the one found for complex Ru(C≡CC≡CTMS)(dppe)Cp* (22) [1.983(2)

Å].1 The C(1)-C(2) bond length is equal to 1.224(3) Å, the C(2)-C(3) distance is

1.377(3) Å and the C(3)-C(4) distance is 1.209(3) Å. The expected alternating short

123

C(1)-C(2), long C(2)-C(3) and short C(3)-C(4) bonds are consistent with the diynyl

nature of the bonds. The C(4)-Ge distance is equal to 1.881(3) Å, which is a slighlty

longer bond than the C(4)-Si bond [1.822(2) Å]30 in complex 22 reflecting the

different atomic radii (Si = 1.17, Ge = 1.22 Å). The angles Ru-C(1)-C(2) [176.5(2) o],

C(1)-C(2)-C(3) [176.2(3) o] and C(2)-C(3)-C(4) [179.0(3) o] and C(3)-C(4)-Ge

[165.5(2) o] in 28 are close to linear.

Figure 46: ORTEP view of 28


Ru-C(1) 1.975(3) Ru-C(1)-C(2) 176.5(2)

Ru-P(1) 2.278(7) P(1)-Ru-P(2) 82.7(2)

Ru-P(2) 2.273(7) P(1)-Ru-C(1) 79.2(7)

Ru-C(Cp*) 2.241(2) - 2.286(2) P(2)-Ru-C(1) 89.0(7)

Ru-C(Cp*) (av.) 2.258(2) C(1)-C(2)-C(3) 176.2(3)

C(1)-C(2) 1.224(3) C(2)-C(3)-C(4) 179.0(3)

C(2)-C(3) 1.377(3) C(3)-C(4)-Ge 165.5(2)

C(3)-C(4) 1.209(3)

C(4)-Ge 1.881(3)


124

Electrochemical studies of complexes 28 and 29 were also completed. The cyclic

voltammograms of complexes 28 and 29 show a single fully-reversible process at

+0.41 V and +0.40 V, respectively. These redox processes are diffusion controlled. It

must be noted that in the case of complex 22, a single irreversible process was

observed at ca +0.43 V.30 Hence, the comparison of the electrochemical properties of

the three analogous complexes 22, 28 and 29 shows that these complexes have very

similar oxidation potentials.

3.3.3.4. Reaction with [CuCl(PPh3)]4

The metal halide [CuCl(PPh3)]4 is readily available,144 so following the work done

with the AuCl(PPh3) metal halide (Section 3.3.2.2.), a similar reaction between

Ru(C≡CC≡CH)(dppe)Cp* and [CuCl(PPh3)]4 was proposed. The first step of the

reaction involved the generation in situ of Ru(C≡CC≡CLi)(dppe)Cp* as previously

described, followed by addition of the metal halide [CuCl(PPh3)]4. This reaction

should afford the complex Ru(C≡CC≡C[Cu(PPh3)])(dppe)Cp*. However, the

expected product was not obtained. Instead, a complex containing two Ru(dppe)Cp*

units linked by a C8 carbon chain {Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*}

(30) was formed in 85% yield (Scheme 78).

C C C C HRu

Ph2P PPh2

C C C C LiRu

Ph2P PPh2

n-BuLi

THF

[CuCl(PPh3)]4

C C CRu

Ph2P PPh2

C C C C Cu(PPh3)Ru

Ph2P PPh2

C C C C C Ru

PPh2Ph2P

[CuCl(PPh3)]4

C C C C HRu

Ph2P PPh2

C C C C LiRu

Ph2P PPh2

n-BuLi

THF

[CuCl(PPh3)]4

C C CRu

Ph2P PPh2

C C C CRu

Ph2P PPh2

C C C C C Ru

PPh2Ph2P

[CuCl(PPh3)]4

(30)

Scheme 78: The reaction of Ru(C≡CC≡CH)(dppe)Cp* with [CuCl(PPh3)]4

125

A possible explanation can be suggested for the formation of complex 30. According

to previous studies, it was found that under Hay coupling conditions (CuCl/tmeda/O2

or air) an oxidative coupling of 1-alkynes containing MLn groups, {MLn}(C≡C)mH,

doubles the chain length to give {MLn}2(µ-C≡C)2m. For example, oxidative coupling

of M(C≡CC≡CH)(CO3)Cp (M = Mo, W) gives {M(CO3)Cp}2{µ-(C≡C)4}(Scheme

79).3

C C C C H{LnM} C C C CC C C C {MLn}{LnM}[Cu(tmeda)]+

O2

{MLn} = Mo(CO)3Cp; W(CO)3Cp

Scheme 79: Oxidative coupling of {MLn}(C≡C)mH

In our reaction, [CuCl(PPh3)]4 might have acted as a catalyst allowing the oxidative-

coupling of the {Cp*(dppe)Ru}-C≡CC≡C- unit via spontaneous C-C bond formation

giving the complex {Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*} (30).

Complex 30 had been previously synthesised from the reaction of the chloro-

ruthenium complex Ru(dppe)Cp*Cl with half an equivalent of TMS-(C≡C)4-TMS in

the presence of KF (Scheme 80).12

Ru

Ph2P PPh2

Cl TMS C C TMS4

KF

MeOHC C CRu

Ph2P PPh2

C C C C C Ru

PPh2Ph2P

Ru

Ph2P PPh2

Cl + TMS C C TMS4

KF

MeOHC C CRu

Ph2P PPh2

C C C C C Ru

PPh2Ph2P(30)

Scheme 80: Previously reported method for the synthesis of 30

Complex 30 was characterised by 1H and 31P NMR spectroscopy, IR and ES-MS and

the data collected are consistent with the literature values (Table 14).12 The

Ru(dppe)Cp* ligands were characterised by typical peaks in the 1H and 31P NMR

spectra. In the IR spectrum, two ν(C≡C) bands at 2101 and 1949 cm-1 were observed

and in the ES-MS [M]+ at m/z 1366 and [Ru(dppe)Cp*]+ at m/z 635 were present.

126

Although complex 30 was synthesised previously, no crystals suitable for X-ray

diffraction were obtained. However in this work, single crystals suitable for X-ray

studies were grown from CH2Cl2/hexane. Figure 47 shows the ORTEP plot of

complex 30 and selected bond distances and angles are given in Table 13. The Ru-

C(1) bond length of 2.006(3) Å is close to the value expected for a ruthenium carbon

single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.230(4) Å, the C(3)-C(4)

distance of 1.226(5) Å, the C(2)-C(3) distance is 1.370(4) Å, and are therefore

consistent with being C≡C triple and C-C single bonds, respectively. The angles Ru-

C(1)-C(2) [177.6(2) o], C(1)-C(2)-C(3) [177.0(3) o] and C(2)-C(3)-C(4) [177.6(3) o] in

30 are nearly linear.



Ru(1)-C(1) 2.006(3) Ru-C(1)-C(2) 177.6(2)

Ru(1)-P(1) 2.258(6) P(1)-Ru-P(2) 83.3(2)

Ru(1)-P(2) 2.275(5) P(1)-Ru-C(1) 84.0(7)

Ru-C(Cp*) 2.223(1) - 2.267(3) P(2)-Ru-C(1) 84.9(6)

Ru-C(Cp*) (av.) 2.252(3) C(1)-C(2)-C(3) 177.0(3)

C(1)-C(2) 1.230(4) C(2)-C(3)-C(4) 177.6(3)

C(2)-C(3) 1.370(4)

C(3)-C(4) 1.226(5)


127

Subsequently, Ru(C≡CC≡CH)(PPh3)2Cp was treated with n-BuLi at -78oC and

[CuCl(PPh3)]4 was added to the lithio intermediate Ru(C≡CC≡CLi)(PPh3)2Cp. After

removal of the solvent and column chromatography, the yellow product

{Cp(Ph3P)2Ru}(C≡CC≡C){Cu(PPh3)} (31) was obtained in 40% yield (Scheme 81).

-78oCCu(PPh3)C C C CRu

Ph3P PPh3

HC C C CRu

Ph3P PPh3[CuCl(PPh3)]4

n-BuLi

C C C CRu

Ph3P PPh3

HC C C CRu

Ph3P PPh3[CuCl(PPh3)]4 (31)

THF


Complex 31 was characterised by elemental analysis, IR, 1H and 31P NMR and ES-

MS (Table 15). The 1H and 31P NMR spectra of 31 confirm the presence of the

Ru(PPh3)2Cp ligand. In the 31P NMR, one singlet is also present at δ 38.5 for the

phosphorus associated with the copper moiety. The ES-MS shows one [M + MeOH]+

at m/z 1096, one fragment for [Ru(PPh3)2Cp]+ at m/z 691 and one fragment at m/z 429

for the [Ru(PPh3)Cp]+ moiety.

In comparison to the reaction of Ru(C≡CC≡CH)(dppe)Cp* and [CuCl(PPh3)]4, this

reaction gave the expected product and there was no indication of the presence of an

oxidative coupling product. The difference between the two reactions is the two

different ruthenium metal-ligand moiety (Ru(PPh3)2Cp vs Ru(dppe)Cp*). Hence, it

can be assumed that the more electron donating ruthenium ligand Ru(dppe)Cp* has an

influence on the synthesis of complex 30.

128

3.3.3.5. Reaction with RhCl(CO)(PPh3)2

Similarly, the complex {Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2} (32) was

obtained from the reaction of Ru(C≡CC≡CH)(PPh3)2Cp treated with n-BuLi at -78oC,

followed by adddition of one equivalent of RhCl(CO)(PPh3)2 (Scheme 82).

n-BuLi-78oC

RhCl(CO)(PPh3)2

Rh(CO)(PPh3)2C C C CRu

Ph3P PPh3

HC C C CRu

Ph3P PPh3(32)

THF


Complex 32 displayed the expected resonances in the 1H, 31P NMR, IR, microanalysis

and ES-MS (Table 15). In the 1H and 31P NMR spectra, the characteristic peaks for the

Ru(PPh3)2Cp ligand are present. The phosphorus atoms on the Rh(CO)(PPh3)2 ligand

are observed at δ 38.5 in the 31P NMR spectrum. In the infrared spectrum, two

ν(C≡C) bands at 1978 and 1955 cm-1 and one ν(CO) band at 2108 cm-1 were

observed. The ES-MS of 32 shows a peak for the molecular ion at m/z 1394 and

fragmentation ions corresponding to [Ru(PPh3)2Cp]+at m/z 691 and [Ru(PPh3)Cp]+at

m/z 429.

129



1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

26 2106 (m) 1982 (m)

7.95-6.85 (m, 60H, Ph); 3.23 (s, 2H, CH2); 2.89-2.80, 1.92-1.81 (2 x m, 8H, CH2CH2); 1.56 (s, 15H, Cp*)

133.76-127.64 (m, Ph); 93.12 (s, C5Me5); 43.33 (s, CH2); 30.12-29.86 (m, CH2CH2); 10.08 (s, C5Me5)

82.0 (s, dppe) 35.6 (s, dppm)

2143, [M - H]+; 1366, [M - Au2(dppm)]+; 675, [Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+.

27 2105 (m) 1984 (m)

8.02-6.83 (m, 50H, Ph); 2.39-2.20, 1.90-1.84 (2 x m, 2 x 2H, CH2CH2); 1.54 (s, 15H, Cp*)

81.9 (s, dppe) 22.2 (s, PPh3)

1437, [M+]; 1436, [M - H]+ ; 635, [Ru(dppe)Cp*]+

28 2106 (m) 2000 (m)


137.76-127.64 (m, Ph); 99.42, 93.46, 86.85, 62.40 (s, C1, C2, C3, C4); 93.22 (s, br, C5Me5); 30.12-29.62 (m, CH2CH2); 10.17 (s, C5Me5)

81.0 (s, dppe) 1009, [M + Na]+; 988, [M + H]+; 675, [Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+

29 2081 (m) 1977 (m)

7.89-7.01 (m, 35H, Ph); 2.55-2.52, 1.81-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*


81.2 (s, dppe) 1033, [M]+; 675, [Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+

30 2101 (m) 1949 (m)


80.1 (s, dppe) 1366, [M]+; 635, [Ru(dppe)Cp*]+

130

Table 14: Spectroscopic data for complexes 31 and 32

Complex

IR (cm-1)

1H NMR (δ)

31P NMR (δ)

ES-MS (m/z)

31 ν(C≡C) 2106 (m),

1994 (m) 7.76-6.89 (m, 45H, Ph); 4.24 (s, 5H, Cp)

50.8 (s, Ru(PPh3)2) 38.5 (s, Cu(PPh3))

1096, [M + MeOH]+; 691,

[Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+

32 ν(C≡C) 2108 (m), 1978 (m); ν(CO) 1955 (m)

7.17-6.92 (m, 60H, Ph); 4.35 (s, 5H, Cp)

50.6 (s, Ru(PPh3)2) 38.5 (s, Rh(PPh3)2)

1394, [M]+; 691, [Ru(PPh3)2Cp]+; 429,

[Ru(PPh3)Cp]+.

131

3.4. Conclusions

In summary, this work has demonstrated that the diynyl complexes [Ru](C≡CC≡CH)

(where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) can be lithiated using organolithium

bases. Two different assay reactions which involved the addition of TMSCl and

AuCl(PPh3) were studied. It was found that the lithiation of the complexes

[Ru](C≡CC≡CH) is most favorable under the presence of two equivalents of the

lithium base n-BuLi at -78oC. In addition, the generated lithium complexes

[Ru](C≡CC≡CLi) were reacted with metal halides from a range of metal groups (Si,

Au, Ge, Sn, Pt, Cu and Rh) and afforded new asymmetric complexes.

This is the first example of the lithiation of ruthenium(II) diynyl complexes and this

new synthetic route will allow the synthesis of a wide range of novel diynyl and

symmetric or asymmetric ruthenium(II) diyndiyl complexes.

132

3.5. Experimental

General experimental conditions are detailed on page viii. Reagents:

The compounds Ru(C≡CC≡CH)(dppe)Cp*,30 Ru(C≡CC≡CH)(PPh3)2Cp,30

AuCl(PPh3),136 (AuCl)2(µ-dppm),143 CuCl(PPh3),144 RhCl(CO)(PPh3)2,145

PtCl2(PPh3)2146 were all prepared by standard literature methods. n-BuLi, TMSCl,

GeClPh3, SnClPh3 was used as received from Sigma-Aldrich.

Ru(C≡CC≡CTMS)(dppe)Cp* (22)

A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was

treated with n-BuLi (0.14 mL, 1.045 M solution in THF) and stirred for 30 min at -

78oC. An aliquot of TMSCl (18 µL, 0.14 mmol) was added and the reaction was

allowed to warm to r.t. over 2 h. Solvent was removed to give a yellow residue which

was then dissolved in hexane (70 mL) and the solution was filtered via cannula and

evaporated to dryness to give Ru(C≡CC≡CTMS)(dppe)Cp* (22) as a bright yellow

powder (47 mg, 86%). 1H NMR (C6D6): δ 7.87-7.02 (m, 20H, Ph); 2.56-2.52, 1.88-

1.81 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*); 0.29 (s, 9H, TMS). 31P NMR

(C6D6): δ 81.3 (s, dppe). Literature 1H NMR (C6D6): δ 7.86-6.89 (m, 20H, Ph); 2.49-

1.78 (2 x m, 2 x 2H, CH2CH2); 1.53 (s, 15H, Cp*); 0.23 (s, 9H, TMS). 31P NMR

(C6D6): δ 81.3 (s, dppe).12

Ru(C≡CC≡CTMS)(PPh3)2Cp (23)

Similarly, from Ru(C≡CC≡CH)(PPh3)2Cp (51 mg, 0.07 mmol) and TMSCl (17 µL,

0.14 mmol) was obtained Ru(C≡CC≡CTMS)(PPh3)2Cp (23) as a bright yellow

powder (45 mg, 80%). 1H NMR (CDCl3): δ 7.59-6.91 (m, 30H, Ph); 4.36 (s, 5H, Cp);

0.28 (s, 9H, TMS). 31P NMR (CDCl3): δ 50.8 (s, PPh3). Literature 1H NMR (CDCl3):

133

δ 7.58-6.92 (m, 30H, Ph); 4.30 (s, 5H, Cp); 0.26 (s, 9H, TMS). 31P NMR (CDCl3): δ

50.7 (s, PPh3).59

Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp* (24)

Similarly, Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) was reacted with

AuCl(PPh3) (39 mg, 0.07 mmol) and afforded Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp*

(24) as a bright yellow powder (72 mg, 85%). 1H NMR (C6D6): δ 7.86-6.96 (m, 35H,

Ph); 2.76-2.73, 2.20-2.14 (2 x m, 2 x 2H, CH2CH2); 1.54 (s, 15H, Cp*). 31P NMR

(C6D6): δ 80.6 (s, dppe); 43.1 (s, PPh3). Literature 1H NMR (C6D6): δ 7.76-7.04 (m,

35H, Ph); 2.77-2.15 (2 x m, 2 x 2H, CH2CH2); 1.52 (s, 15H, Cp*). 31P NMR (C6D6): δ

80.8 (s, dppe); 42.5 (s, PPh3).12

Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25)

Similarly, from Ru(C≡CC≡CH)(PPh3)2Cp (51 mg, 0.07 mmol) and AuCl(PPh3) (68

mg, 0.14 mmol) was obtained Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp (25) as a bright

yellow powder (57 mg, 70%). IR (Nujol, cm-1): ν(C≡C) 2073 (m), 1983 (m). 1H NMR

(CDCl3): δ 7.64-6.86 (m, 45H, Ph); 4.40 (s, 5H, Cp). 31P NMR (CDCl3): δ 51.2 (s,

Ru(PPh3)2); 33.9 (s, Au(PPh3)). Literature IR (Nujol, cm-1): ν(C≡C) 2072 (m), 1981

(m). 1H NMR (CDCl3): δ 7.59-7.08 (m, 45H, Ph); 4.38 (s, 5H, Cp). 31P NMR

(CDCl3): δ 49.9 (s, Ru(PPh3)2); 32.5 (s, Au(PPh3)).141

{Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-dppm) (26)


treated with n-BuLi (0.14 mL, 1.045 M solution in THF) and stirred for 1 h at -78oC.

(AuCl)2(µ-dppm) (60 mg, 0.07 mmol) was added and the reaction was allowed to

warm to r.t. over 2 h. Hexane (20 mL) was added and a yellow precipitate was

collected and washed with hexane to give {Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-dppm)

(26) (135 mg, 90%). Anal. Calcd. (C105H100P6Au2Ru2): C, 58.83; H, 4.70. Found: C,

134

58.88; H, 4.75. IR (Nujol, cm-1): ν(C≡C) 2106 (m); 1982 (m). 1H NMR (C6D6): δ

7.95-6.85 (m, 60H, Ph); 3.23 (s, 2H, CH2); 2.89-2.80, 1.92-1.81 (2 x m, 8H,

CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.76-127.64 (m, Ph); 93.12 (s,

C5Me5); 43.33 (s, CH2); 30.12-29.86 (m, CH2CH2); 10.08 (s, C5Me5). 31P NMR

(C6D6): δ 82.0 (s, dppe); 35.6 (s, dppm). ES-MS (+ve ion, CH3CN, m/z): 2143, [M -

H]+; 1460, [M - C4Ru(dppe)Cp*]+; 1366, [M - Au2(dppm)]+; 675,

[Ru(NCMe)(dppe)Cp]+; 635, [Ru(dppe)Cp*]+.

Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp* (27)

Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and

Pt(PPh3)2Cl2 (59 mg, 0.07 mmol) gave Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp* (27) as

a bright yellow powder (43 mg, 40%). Anal. Calcd. (C76H69P4PtClRu): C, 63.48; H,

4.84. Found: C, 63.60; H, 5.18. IR (Nujol, cm-1): ν(C≡C) 2105 (m), 1984 (m). 1H

NMR (C6D6): δ 8.02-6.83 (m, 50H, Ph); 2.39-2.20, 1.90-1.84 (2 x m, 2 x 2H,

CH2CH2); 1.54 (s, 15H, Cp*). 31P NMR (C6D6): δ 81.9 (s, Ru(dppe)); 22.2 (s,

Pt(PPh3)2). ES-MS (+ve ion, MeOH, m/z): 1437, [M+]; 1436, [M - H]+ ; 635,

[Ru(dppe)Cp*]+.

Ru(C≡CC≡CGePh3)(dppe)Cp* (28)


treated with n-BuLi (50 µL, 2.3 M solution in hexane) and stirred for 30 min at -78oC.

GeClPh3 (31 mg, 0.07 mmol) was added and the reaction was allowed to warm to r.t.

over 3 h. The solvent was then removed and the yellow residue extracted with hexane

(60 mL) and filtered via cannula. The solvent was evaporated to dryness to give

Ru(C≡CC≡CGePh3)(dppe)Cp* (28) as a yellow crystalline powder (62 mg, 82%).

Single crystals suitable for X-ray studies were grown from THF/hexane. Anal. Calcd.

(C58H54P2GeRu): C, 70.60; H, 5.52. Found: C, 70.61; H, 5.55. IR (Nujol, cm-1):

ν(C≡C) 2106 (m), 2000 (m). 1H NMR (C6D6): δ 7.85-6.89 (m, 35H, Ph); 2.53-2.50,

135

1.79-1.75 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 137.76-

127.64 (m, Ph); 99.42, 93.46, 86.85, 62.40 (s, C1, C2, C3, C4); 93.22 (s, br, C5Me5);

30.12-29.62 (m, CH2CH2); 10.17 (s, C5Me5). 31P NMR (C6D6): δ 81.0 (s, dppe). ES-

MS (+ve ion, CH3CN, m/z): 1009, [M + Na]+; 988, [M + H]+; 675,


Ru(C≡CC≡CSnPh3)(dppe)Cp* (29)

Similarly, from Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and SnClPh3 (45 mg,

0.11 mmol) was obtained Ru(C≡CC≡CSnPh3)(dppe)Cp* (29) as a yellow crystalline

powder (54 mg, 70%). Anal. Calcd. (C58H54P2SnRu): C, 67.45; H, 5.27. Found: C,

67.97; H, 5.51. IR (Nujol, cm-1): ν(C≡C) 2081 (m), 1977 (m). 1H NMR (C6D6): δ

7.89-7.01 (m, 35H, Ph); 2.55-2.52, 1.81-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H,

Cp*). 13C NMR (C6D6): δ 134.02-127.84 (m, Ph); 103.22, 99.05, 86.85, 74.82 (s, C1,

C2, C3, C4); 91.87 (s, C5Me5); 30.01-29.86 (m, CH2CH2); 10.21 (s, C5Me5). 31P NMR

(C6D6): δ 81.2 (s, dppe). ES-MS (+ve ion, CH3CN, m/z): 1033, [M]+; 675,


{Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*} (30)



78oC. A solution of [CuCl(PPh3)]4 (28 mg, 0.07 mmol) in THF (5 mL) was added via

cannula and the reaction was allowed to warm to r.t. over 3 h. A red-orange

precipitate was collected and washed with hexane to give

{Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*} (30) (86 mg, 85%). Single

crystals suitable for X-ray studies were grown from CH2Cl2/hexane. IR (CH2Cl2, cm-

1): ν(C≡C) 2101 (m); 1949 (m). 1H NMR (C6D6): δ 7.75-7.03 (m, 40H, Ph); 2.55-

2.40, 2.00-1.89 (2 x m, 8H, CH2CH2); 1.53 (s, 30H, Cp*). 31P NMR (C6D6): δ 80.1 (s,

dppe). ES-MS (+ve ion, MeOH) (m/z): 1366, [M]+; 635, [Ru(dppe)Cp*]+. Literature

136

IR: ν(C≡C) 2107 (m); 1951 (m). 1H NMR: δ 7.66-7.09 (m, 40H, Ph); 2.67, 2.09 (2 x

m, 8H, CH2CH2); 1.49 (s, 30H, Cp*). 31P NMR: δ 80.0 (s, dppe). ES-MS (m/z): 1366,

[M]+; 635, [Ru(dppe)Cp*]+.12

{Cp(Ph3P)2Ru}(C≡CC≡C){Cu(PPh3)} (31)

A solution of Ru(C≡CC≡CH)(PPh3)2Cp (52 mg, 0.07 mmol), in THF (10 mL) was


78oC. [CuCl(PPh3)]4 (25 mg, 0.07 mmol) was added and the reaction was allowed to

warm to r.t. over 2 h. The solvent was then removed. The residue was dissolved in

minimum CH2Cl2 and loaded onto a basic alumina column eluting with a 3:7

acetone/hexane mixture. A yellow band was collected and solvent removed to give

{Cp(Ph3P)2Ru}C≡CC≡C{Cu(PPh3)} (31) (30 mg, 40%). Anal. Calcd.

(C63H50P3RuCu): C, 71.04; H, 4.74. Found: C, 71.08; H, 4.79. IR (CH2Cl2, cm-1):

ν(C≡C) 2106 (m), 1994 (m). 1H NMR (C6D6): δ 7.76-6.89 (m, 45H, Ph); 4.24 (s, 5H,

Cp). 31P NMR (C6D6): δ 50.8 (s, Ru(PPh3)2), 38.5 (s, Cu(PPh3)). ES-MS (+ve ion,

MeOH, m/z): 1096, [M + MeOH]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.

{Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2} (32)

Similarly, {Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2} (32) was obtained as a yellow

powder (49 mg, 50%) from the reaction between Ru(C≡CC≡CH)(PPh3)2Cp (53 mg,

0.07 mmol) and RhCl(CO)(PPh3)2 (49 mg, 0.07 mmol). Anal. Calcd.

(C82H65OP4RhRu): C, 70.64; H, 4.70. Found: C, 70.73; H, 4.76. IR (CH2Cl2, cm-1):

ν(C≡C) 2108 (m), 1978 (m); ν(CO) 1955 (m). 1H NMR (C6D6): δ 7.17-6.92 (m, 60H,

Ph); 4.35 (s, 5H, Cp). 31P NMR (C6D6): δ 50.6 (s, Ru(PPh3)2), 38.5 (s, Rh(PPh3)2).

ES-MS (+ve ion, MeOH, m/z): 1394, [M]+; 691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.

Chapter Four

The Reactions of

Ru(C≡CC≡CLi)(dppe)Cp*

138

4.1. Introduction

4.1.1. The reaction of nucleophilic complexes with organic reagents

In 2001, the lithiated tungsten carbide Tp’(CO)2W(≡CLi) was generated from the

treatment of the complex Tp’(CO)2(W≡CH) with n-BuLi. Subsequently,

Tp’(CO)2W(≡CLi) was reacted with a range of electrophiles in order to trap the

anionic complex. First, it was reacted with iodomethane and iodine to give the

complexes Tp’(CO)2W(≡CMe) and Tp’(CO)2W(C≡CI) (Scheme 83).147

Tp'(OC)2W C Hn-BuLi

THFTp'(OC)2W C Li

-78oC

Tp'(OC)2W C MeTp'(OC)2W C I

I2 MeI

Scheme 83: The lithiation of Tp’(CO)2W(≡CH)

Then, Tp’(CO)2W(≡CLi) was reacted with other electrophiles such as benzophenone,

benzaldehyde and benzoyl bromide. The complexes Tp’(CO)2W[≡CCPh2(OH)],

Tp’(CO)2W[≡CHPh(OH)] and Tp’(CO)2W(≡CC(O)Ph) were obtained, respectively

(Scheme 84).147

Tp'(OC)2W C I

Tp'(OC)2W C C

Tp'(OC)2W C

R

OH

Ph

PhC

O

R = Ph or H

Ph Br

O

Ph R

O

H2O

1)

2)

Scheme 84: Reactions of Tp’(CO)2W(≡CLi) with electrophiles

139

Furthermore, Gladysz and co-workers reported the reaction of

Re(C≡CH)(NO)(PPh3)Cp* with n-BuLi to synthesise the lithium complex

Re(C≡CLi)(NO)(PPh3)Cp*.138 The nucleophilic complex was further reacted with

iodomethane to generate the methylated complex Re(C≡CMe)(NO)(PPh3)Cp*.

Similarly, the reaction of Re(C≡CC≡CH)(NO)(PPh3)Cp* with n-BuLi afforded

Re(C≡CC≡CLi)(NO)(PPh3)Cp*, which was trapped with iodomethane to give

Re(C≡CC≡CMe)(NO)(PPh3)Cp* (Scheme 85).22

C CRe

ON PPh3-80oC

n-BuLiH C CRe

ON PPh3

Li

C CRe

ON PPh3

Me

MeI

n n

n

n = 1, 2

Scheme 85: The synthesis of Re{(C≡C)nMe}(NO)(PPh3)Cp*

4.1.2. The reaction of nucleophilic complexes with polyfluoroaromatic reagents

The availability of polyfluoroaromatic compounds has resulted in many investigations

of their reactivity. It is now well known that fluorocarbons have increased

susceptibility to nucleophilic attack owing to withdrawal of electron density onto the

fluorine atoms.148

In 1967, Wiles and Massey reported the synthesis of several fluoroaromatic

acetylenes using the lithium derivatives of mono-substituted alkynes (Scheme 86).149

The acetylene group introduced activates the fluorine atom para to it, so that

RC≡C(C6F5) reacted further to give the disubstituted compounds 1,4-(RC≡C)2C6F4 in

high yield (Scheme 86).149

140

R C C H R C C Li

R C C C6F5R C C Li

R C C C6F4 RCC

BuLiTHF

C6F6

+

R = H, Ph, SiEt3

Scheme 86: The synthesis of RC≡C(C6F5) and 1,4-(RC≡C)2C6F4

The complexes Ru(C≡CC6F5)(dppe)Cp* and Ru(C≡CC6F5)(dppe)Cp were synthesised

by a different method.55 The trimethylsilyl-substituted alkyne, TMS(C≡C)C6F5, reacts

with the chlororuthenium complex in the presence of potassium fluoride (Scheme 87).

Similarly, the diruthenium complexes 1,4-{Cp(PPh3)2Ru(C≡C)}2C6F4 and 1,4-

{Cp(dppe)Ru(C≡C)}2C6F4 were obtained from the reactions of 1,4-

{TMS(C≡C)}2C6F4 under the same conditions (Scheme 88).55

TMS C C C6F5 Cp'(dppe)Ru C C C6F5+KF

MeOH∆ Cp' = Cp* or Cp

RuCl(dppe)Cp'

Scheme 87: The synthesis of Ru(C≡CC6F5)(dppe)Cp’

TMS C C C6F4 +KF

THF/MeOH∆

[Ru] C C C6F4 [Ru]CC[Ru]Cl

[Ru] = Ru(dppe)Cp or Ru(PPh3)2Cp2

Scheme 88: The synthesis of 1,4-{[Ru](C≡C)}2C6F4

4.1.3. The nucleophilic ruthenium(II) complex Ru(C≡CC≡CLi)(dppe)Cp*

In Chapter Three, the ruthenium(II) diynyl complex Ru(C≡CC≡CH)(dppe)Cp* was

successfully lithiated with a strong base n-BuLi, which resulted in the formation of a

nucleophilic complex Ru(C≡CC≡CLi)(dppe)Cp*. This complex was further reacted

with metal halides to afford new asymmetric ruthenium(II) diyndiyl complexes

(Scheme 89).

141

C C C C Hn-BuLi

THF-78oC

C C C CRu

Ph2P PPh2

Ru

Ph2P PPh2

{MLn}Cl

in situ

C C C C {MLn}Ru

Ph2P PPh2

Li

Scheme 89: The lithiation and metalation of Ru(C≡CC≡CH)(dppe)Cp*

This reaction has allowed the formation of a new nucleophilic species,

Ru(C≡CC≡CLi)(dppe)Cp*. This complex shows similar characteristics to the

complexes Tp’(CO)2W(≡CLi), Re(C≡CLi)(NO)(PPh3)Cp* and

Re(C≡CC≡CLi)(NO)(PPh3)Cp* described previously. Hence, it can be proposed that

Ru(C≡CC≡CLi)(dppe)Cp* will react similarly with a range of electrophiles and

therefore be a precursor for new complexes for which the parent alkynes are either not

available or synthesised with difficulty.

142


In this chapter, the reactivity of the lithium complex Ru(C≡CC≡CLi)(dppe)Cp*

synthesised in Chapter Three is further investigated. The nucleophilic nature of this

complex makes it a valuable starting material. Hence, the primary aim of this work

was to react Ru(C≡CC≡CLi)(dppe)Cp* with a range of electrophiles such as organic

substrates or polyfluoroaromatic compounds and to analyse and characterise the

products obtained.

143


4.3.1. Reactions with organic reagents

All the complexes described in this Section were fully characterised by 1H, 31P and 13C NMR, IR, ES-MS and microanalysis and the data are summarised in Table 17.

4.3.1.1. Synthesis of Ru(C≡CC≡CMe)(dppe)Cp*

Ru(C≡CC≡CH)(dppe)Cp* was treated with two equivalents of n-BuLi at -78oC. After

stirring for 30 min, iodomethane was added to the solution, which was then allowed to

warm to room temperature. After work-up, the complex Ru(C≡CC≡CMe)(dppe)Cp*

(33) was obtained in 70% yield (Scheme 90).

C C C C Hn-BuLi

THF-78oC

C C C CRu

Ph2P PPh2

Ru

Ph2P PPh2

MeI

in situ

C C C C MeRu

Ph2P PPh2

Li

(33)

Scheme 90: The synthesis of Ru(C≡CC≡CMe)(dppe)Cp* (33)

In the 1H, 31P and 13C NMR spectra of complex 33, the characteristic peaks for the

Ru(dppe)Cp* ligand are observed. The methyl group is characterised by a singlet δ

1.73 in the 1H NMR spectrum and a singlet at δ 21.03 in the 13C NMR spectrum. The

resonances for the carbon atoms of the C4 chain are also present in the 13C NMR at δ

124.69, 91.73, 76.86 and 52.46. Two ν(C≡C) bands at 2029 and 1908 cm-1 were

144

observed in the infrared spectrum. Further characterisation of 33 was obtained from

an ES-MS which contained ions corresponding to [M + MeOH]+ at m/z 732 and at m/z

635 for [Ru(dppe)Cp*]+.

Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. The

ORTEP plot of compound 33 is shown in Figure 48 and selected bond distances and

angles are given in Table 16. The Ru-C(1) bond length of 2.029(3) Å is close to the

value expected for a ruthenium carbon single bond (2.01 Å). The C(1)-C(2) bond

length is equal to 1.166(4) Å, the C(3)-C(4) distance is 1.193(5) Å, the C(2)-C(3)

distance is 1.419(5) Å, and the C(4)-C(5) distance is 1.472(5) Å. They are therefore

consistent with being C≡C triple and C-C single bonds, respectively. The carbon

chain in 33 is essentially linear, the angles C(1)-C(2)-C(3), C(2)-C(3)-C(4) and C(3)-

C(4)-C(5) being 173.9(3) o, 177.8(4) o and 175.9(4) o, respectively.


Ru-C(1) 2.029(3) Ru-C(1)-C(2) 177.8(3)

Ru-P(1) 2.262(7) P(1)-Ru-P(2) 82.6(3)

Ru-P(2) 2.273(9) P(1)-Ru-C(1) 82.3(8)

Ru-C(Cp*) 2.233(4) - 2.271(3) P(2)-Ru-C(1) 86.0(1)

Ru-C(Cp*) (av.) 2.259(3) C(1)-C(2)-C(3) 173.9(3)

C(1)-C(2) 1.166(4) C(2)-C(3)-C(4) 177.8(4)

C(2)-C(3) 1.419(5) C(3)-C(4)-C(5) 175.9(4)

C(3)-C(4) 1.193(5)

C(4)-C(5) 1.472(5)

C(5)-H(5A) 0.953(4)

C(5)-H(5B) 0.966(5)

C(5)-H(5C) 0.951(5)


145


4.3.1.2. Synthesis of Ru{C≡CC≡CC(O)Ph}(dppe)Cp*

Benzoyl chloride is susceptible to nucleophilic attack at the carbonyl carbon. Hence,

the reaction of Ru(C≡CC≡CLi)(dppe)Cp* with benzoyl chloride was attempted. First,

Ru(C≡CC≡CLi)(dppe)Cp* was generated in situ as described previously. Then,

benzoyl chloride was added at -78oC and an immediate colour change from yellow to

red was observed. The complex Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34) was obtained

in 75% yield as a red powder. A proposed mechanism for the reaction involves the

attack of the anion Ru(C≡CC≡C-)(dppe)Cp* at the carbonyl carbon. The intermediate

formed then loses the chloride to form complex 34 which possesses a ketone

substituent (Scheme 91).

The same trend as complex 33 is observed in the 1H, 31P and 13C NMR spectra with

the presence of peaks for the Ru(dppe)Cp*C4 fragment. The CO group is

characterised by a singlet at δ 206.41 in the 13C NMR spectrum and one ν(CO) band

at 1716 cm-1 in the IR spectrum. The phenyl groups are present as multiplets at δ

7.28-7.05 and 133.63-127.63 in the 1H and 13C NMR spectra, respectively. Finally the

ES-MS contains [M + Na]+ at m/z 811, [M]+ at m/z 788 and [Ru(dppe)Cp*]+ at m/z

635.

146

CC C C C

O

Ph

Ph Cl

O

C C C C C Cl

Ph

O

C C C C Hn-BuLi

THFC C C C Li

- LiCl

-78oC

Ru

Ph2P PPh2

Ru

Ph2P PPh2

Ru

Ph2P PPh2

Ru

Ph2P PPh2 (34)

Scheme 91: Proposed mechanism for the synthesis of complex 34

4.3.1.3. Synthesis of Ru{C≡CC≡CC(O)Me}(dppe)Cp*

Similarly, the reaction of Ru(C≡CC≡CLi)(dppe)Cp* with acetyl chloride afforded the

complex Ru{C≡CC≡CC(O)Me}(dppe)Cp* (35) as a bright yellow crystalline powder.

The reaction is similar to that giving complex 34 since both reactions involved the

reaction of the nucleophilic Ru(C≡CC≡CLi)(dppe)Cp* with an acid chloride (Scheme

92).

CC C C C

O

MeRu

Ph2P PPh2

Me Cl

O

C C C C LiTHF

-78oC

Ru

Ph2P PPh2 (35)

Scheme 92: The synthesis of complex 35

The 1H NMR spectrum of complex 35 shows the presence of a singlet at δ 2.14 for the

protons of the methyl group. In the 13C NMR of 35, the resonance for the CO group

was found as a singlet at δ 201.57 while the resonance for the methyl group was

present as a singlet at δ 33.35. The IR spectrum of 35 also confirms the presence of

the CO group with a ν(CO) band at 1710 cm-1. In the ES-MS, a [M]+ ion was found at

m/z 725 with a [Ru(dppe)Cp*]+ fragment ion at m/z 635.

147

4.3.1.4. Synthesis of Ru{C≡CC≡CC(O)OMe}(dppe)Cp*

The complex Ru{C≡CC≡CC(O)OMe}(dppe)Cp* (36) was obtained from the reaction

of Ru(C≡CC≡CLi)(dppe)Cp* with methyl chloroformate as a yellow powder in 40%

yield (Scheme 93).

CC C C C

O

OMeMeO Cl

O

C C C C LiTHF

-78oC

Ru

Ph2P PPh2

Ru

Ph2P PPh2 (36)


The presence of the Ru(dppe)Cp* fragment is confirmed in the 1H and 31P NMR

spectra of complex 36. The OMe group is characterised by one singlet at δ 1.68 in the 1H NMR spectrum, which is unusual when compared to purely organic methyl esters.

One ν(CO) band at 1723 cm-1 is also present in the IR spectrum. The ES-MS

confirmed the formulation of this complex, containing [M]+ at m/z 743 and one

fragment ion at m/z 635 corresponding to [Ru(dppe)Cp*]+. Due to the poor yields and

instability of this complex in concentrated solutions it could not be satisfactorily

characterised by 13C NMR or microanalysis.

4.3.1.5. Synthesis of {Ru(C≡CC≡C)(dppe)Cp*}2(CO)2

Two equivalents of Ru(C≡CC≡CH)(dppe)Cp* dissolved in THF were treated with n-

BuLi at -78oC. Oxalyl choride was then added to Ru(C≡CC≡CLi)(dppe)Cp*

generated in situ and the colour of the solution changed from yellow to bright orange.

After warming up to room temperature and work-up the complex

{Ru(C≡CC≡C)(dppe)Cp*}2(CO)2 (37) was obtained in 55% yield as an orange

powder (Scheme 94).

148

C C LiRu

Ph2P PPh2

2 THF-78oC

Cl Cl

O

O

C CRu

Ph2P PPh2

2 CC Ru

PPh2Ph2P

2C

O

C

O(37)


The presence of the CO groups is confirmed by a singlet at δ 213.74 in the 13C NMR

spectrum and one ν(CO) band at 1655 cm-1 in the IR spectrum of complex 37. In the 1H and 13C NMR spectra, the resonances for the Ru(dppe)Cp* ligands are present as

described for previous complexes. The 31P NMR spectrum shows one resonance at δ

80.1 for the equivalent phosphorus atoms on the dppe ligands. The ES-MS confirmed

the formulation of 37 with [M + MeOH]+ at m/z 1453.

4.3.1.6. Synthesis of Ru{C≡CC≡CCHPh(OH)}(dppe)Cp*

Furthermore, Ru(C≡CC≡CH)(dppe)Cp* was treated with n-Buli at -78oC and

Ru(C≡CC≡CLi)(dppe)Cp* generated in situ was further reacted with benzaldehyde.

An immediate colour change from yellow to bright orange was observed and the

reaction was then quenched with water. The complex

Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38) was obtained in 76% yield. The proposed

mechanism involves the attack of the anionic complex Ru(C≡CC≡C-)(dppe)Cp* on

the carbonyl carbon of benzaldehyde. The intermediate is then protonated with water

to afford complex 38 (Scheme 95).

149

Ph H

O

C C C C C H

Ph

O

C C C C Hn-BuLi

THFC C C C Li

C C C C C H

Ph

OH- LiOH

-78oC

H O H

Ru

Ph2P PPh2

Ru

Ph2P PPh2

Ru

Ph2P PPh2

Ru

Ph2P PPh2

(38)

Scheme 95: Proposed mechanism for the formation of complex 38 Similarly to the previous complexes, the 1H, 31P and 13C NMR spectra of complex 38

show the presence of the Ru(dppe)Cp*C4 moiety. In the 1H NMR spectrum, the

presence of the OH group is characterised by a singlet at δ 5.52 while the proton on

the CH group is present as a singlet at δ 1.66. The infrared spectrum also shows one

ν(OH) band at 3303 cm-1. The 13C NMR spectrum of 38 shows one singlet at δ 79.89

which is assigned to the terminal carbon C(H)PhOH. The ES-MS of 38 contains a [M

+ Na]+ at m/z 813, a [M]+ ion at m/z 790 and one fragmentation ion at m/z 635

[Ru(dppe)Cp*]+.

150

C C C C Li[Ru*]

IMe

C C C C Me[Ru*]

Me Cl

O

C C C C[Ru*] C

O

Me

Ph Cl

O

C C C C[Ru*] C

O

Ph

MeO Cl

O

C C C C[Ru*] C

O

OMe

C C[Ru*] 2 CC [Ru*]2C

O

Ph H

O

C C C C C H

Ph

OH

[Ru*]

[Ru*] = Ru(dppe)Cp*

(37)

(38)

(33)

(36)

(35)

(34)

Cl Cl

O

O

C

O

Figure 49: Summary of products synthesised

151

Complex IR (cm-1) 1H NMR (δ) 13C NMR (δ) 31P NMR (δ) ES-MS (m/z) 33 ν(C≡C)

2029, 1908 7.28-6.89 (m, 20H, Ph); 2.65-2.62, 2.01-1.87 (2 x m, 2 x 2H, CH2CH2); 1.73 (s, 3H, CH3); 1.60 (s, 15H, Cp*)

133.96-127.42 (m, Ph); 124.69, 91.73, 76.86, 52.46 (s, C1, C2, C3, C4); 93.25 (s, C5Me5); 29.88-29.27 (m, CH2CH2); 21.03 (s, CH3); 10.12 (s, C5Me5)

81.6 (s, dppe) 731, [M + MeOH]+; 635,

Ru(dppe)Cp*]+

34 ν(C≡C) 2109, 2000; ν(CO) 1716


206.41 (s, CO); 133.63-127.63 (m, Ph); 112.17, 101.00, 95.59, 63.08 (s, C1, C2, C3, C4); 94.13 (t, 2J(CP) 2 Hz, C5Me5); 30.12-29.23 (m, CH2CH2); 10.02 (s, C5Me5)

80.5 (s, dppe) 811, [M + Na]+; 788, [M]+;

635, [Ru(dppe)Cp*]+

35 ν(C≡C) 2048

(m), 2004 (m); ν(CO) 1710 (m)

7.23-7.02 (m, 20H, Ph); 2.68-2.61, 1.85-1.78 (2 x m, 2 x 2H, CH2CH2); 2.14 (s, 3H, C(O)CH3); 1.58 (s, 15H, Cp*)

201.57 (s, CO); 134.51-126.96 (m, Ph); 121.86, 119.52, 102.13, 90.15 (s, C1, C2, C3, C4); 94.38 (s, C5Me5); 33.35-33.29 (m, C(O)CH3); 30.83-30.13 (m, CH2CH2); 10.83 (s, C5Me5)

81.7 (s, dppe) 725, [M]+; 635, [Ru(dppe)Cp*]+

36 ν(C≡C) 2008, 197; ν(CO) 1723

7.26-7.02 (m, 20H, Ph); 2.43-2.38, 2.13-2.06 (2 x m, 2 x 2H, CH2CH2); 1.68 (s, 3H, C(O)CH3); 1.53 (s, 15H, Cp*)

80.6 (s, dppe) 743, [M]+; 635,

[Ru(dppe)Cp*]+

37 ν(C≡C) 2095 (m), 1999 (m); ν(CO) 1655


213.74 (s, CO); 133.80-127.61 (m, Ph); 123.62, 100.28, 69.53, 55.62 (s, C1, C2, C3, C4); 90.62 (s, C5Me5); 30.01-29.75 (m, CH2CH2); 9.94 (s, C5Me5)

80.1 (s, dppe) 1453, [M + MeOH]+; 635, [Ru(dppe)Cp*]+

38 ν(OH) 3303 (w); ν(C≡C) 2106 (m), 2000 (m)

7.29-7.03 (m, 25H, Ph); 5.52 (s, 1H, OH); 2.58-2.56, 1.80-1.74 (2 x m, 2 x 2H, CH2CH2); 1.66 (s, 1H, CH); 1.57 (s, 15H, Cp*)

133.74-127.68 (m, Ph); 122.10, 99.22, 88.72, 65.85 (s, C1, C2, C3, C4); 93.24 (s, br, C5Me5); 79.89 (s, C(H)PhOH); 29.90-29.29 (m, CH2CH2); 10.07 (s, C5Me5)

81.3 (s, dppe) 813, [M + Na]+; 790, [M]+;

635, [Ru(dppe)Cp*]+


152

4.3.1.7. Reaction with TCNE

TCNE is an electron deficient alkene and is a very useful reagent since it undergoes

reaction with the electron rich carbon-carbon triple bonds of transition-metal alkynyl

complexes to give cyclobutenyl complexes and subsequent ring-opening to buta-1,3-

dien-2-yl complexes.116,117

The complex Ru(C≡CC≡CLi)(dppe)Cp* was reacted with one equivalent of TCNE in

THF at -78oC. The colour changed immediately from yellow to dark green. After

purification, {Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C} (39) was isolated

as the major product in 32% yield. The proposed mechanism for the synthesis of

complex 39 is shown in Scheme 96. The reaction is suggested to undergo [2 + 2]-

cycloaddition, followed by ring opening. This intermediate then attacked the β-carbon

of Ru(C≡CC≡CLi)(dppe)Cp* and elimination of lithium acetylide gives complex 39.

C[Ru*] C C

C

LiC

C

NC CNCN CN

C[Ru*]C C

C

C

C

NC CNCN CN

CC

[Ru*]

[Ru*] LiC C C C

C C

NCNC CN

CN

[Ru*] LiC C C C

[Ru*]Li CCCC

-Li2C2

THF

TCNE

[Ru*] = Ru(dppe)Cp* -78oC

(39)

Scheme 96: The reaction of Ru(C≡CC≡CLi)(dppe)Cp* with TCNE

Complex 39 was previously synthesised from the reaction of

{Cp*(dppe)Ru}2(C≡CC≡CC≡C) with TCNE in CH2Cl2 at room temperature. An X-

ray crystal structure was also reported and showed that complex 39 is bent due to the

presence of the C=C double bonds.12 As expected, the spectroscopic features of 39

were similar to those found previously.12 The 1H NMR spectrum contained typical

153

peaks for the Ru(dppe)Cp* moieties. The 31P NMR shows two doublets at δ 81.3 (d, 3J(PP) 13 Hz) and at δ 79.9 (d, 3J(PP) 13 Hz) which corresponds to the two

magnetically inequivalent phosphorus atoms of each dppe ligand. The most

interesting feature in the infrared spectrum is the appearance of two ν(CN) bands at

2208 and 2075 cm-1. The ES-MS of 39 shows a peak for the molecular ion [M+ Na]+

at m/z 1493 and a fragment ion corresponding to [Ru(dppe)Cp*]+ at m/z 635.

From the same reaction, another product was collected and characterised by X-ray

crystallography and spectroscopically. Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp*

(40) was obtained as a blue band in 20% yield. A possible mechanism for the

formation of 40 is shown in Scheme 97.

C CNH2

CN

O

NC CN

Ru

Ph2P PPh2

C CNH2

CNO

NC CN

Ru

Ph2P PPh2

C C C

C H

C

NC

NC CN

Ru

Ph2P PPh2

C C C C LiTCNE

THF-78oC

Ru

Ph2P PPh2

CN

H

C CNH

CN

O

NC CN

Ru

Ph2P PPh2 H

(40)


154

The 31P NMR spectrum of complex 40 shows one singlet at δ 72.9 assigned to the

phosphorus nuclei bonded to the ruthenium and the 1H NMR spectrum shows the

characteristic peaks for the Ru(dppe)Cp* group. The infrared spectrum of 40 also

contains ν(NH) at 3058 cm-1, ν(C≡C) at 1954 cm-1, ν(C=C) at 1603 cm-1, a broad

ν(CN) at 2212 cm-1 and ν(CO) at 1716 cm-1. The ES-MS of 40 contains fragment

ions corresponding to [Ru(dppe)Cp*C2]+ at m/z 659 and [Ru(dppe)Cp*]+ at m/z 635.

A high resolution mass spectrum of 40 was also obtained. The molecular formula

found was C46H40N4NaOP2Ru which corresponds to [M + Na]+ at m/z 851.1624

(calcd. 851.1626). These values are very close to each other confirming the

formulation of complex 40.

Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. Figure 50

shows the ORTEP plot of compound 40, while selected structural data are collected in

Table 18. The Ru-C(1) bond length of 1.96(1) Å is close to the value expected for a

ruthenium carbon single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.22(1)

Å which is consistent with C≡C triple bond and the C(2)-C(3) bond length is equal to

1.43(1) Å due to a C-C single bond. The C(6)-O(6) bond length is equal to 1.26(1) Å

which is consistent with being a C=O group. The angles Ru-C(1)-C(2) [175.2(8) o],

C(1)-C(2)-C(3) [166.9(1) o] in 40 are close to linear whereas the C(2)-C(3)-C(4)

[124.8(1) o] angle is bent.


155


Ru-C(1) 1.960(1) Ru-C(1)-C(2) 175.2(8)

Ru-P(1) 2.302(2) P(1)-Ru-P(2) 81.6(9)

Ru-P(2) 2.272(3) P(1)-Ru-C(1) 85.5(3)

Ru-C(Cp*) 2.235(9) - 2.29(1) P(2)-Ru-C(1) 89.1(3)

Ru-C(Cp*) (av.) 2.264(9) C(1)-C(2)-C(3) 166.9(1)

C(1)-C(2) 1.220(1) C(2)-C(3)-C(4) 124.8(1)

C(2)-C(3) 1.430(1) C(2)-C(3)-C(7) 129.1(1)

C(3)-C(4) 1.420(1) C(4)-C(3)-C(7) 106.1(1)

C(3)-C(7) 1.430(1)

C(6)-O(6) 1.260(1)

C(71)-N(71) 1.140(1)

Table 17: Selected bond distances (Å) and angles (o) for complex 40

Finally, from the same reaction another minor product was collected as a bright

orange band in 16% yield and characterised as

Ru{C≡CC4N(NH)H(Me)C(CN)2)}(dppe)Cp* (41) (Figure 51).

C CRu

Ph2P PPh2N

NH

CH3

NC

CN

Figure 47: Representation of complex 41

Elemental analyses and the ES-MS confirmed the formulation of this complex,

supported by spectroscopic data. A ν(NH) band at 3060 cm-1, a ν(C≡C) band at 2024

cm-1, a ν(CH) band at 2926 cm-1, a ν(CN) band at 2204 cm-1 and a ν(C=C) band at

1644 cm-1 were observed in the IR spectrum. In the 1H NMR spectrum, resonances for

156

the aromatic protons, the dppe and Cp* ligands are present as for complex 40. Three

singlets at δ 4.19 for NH group, at δ 2.17 for the methyl group and at δ 1.26 for the

CH group are also present. Further characterisation of 41 was obtained from an ES-

MS which contained the molecular ion [M]+ at m/z 816 and one fragment ion at m/z

635 for [Ru(dppe)Cp*]+. A high resolution mass spectrum of 41 was also obtained.

The molecular formula found was C46H45N4P2Ru which corresponds to a [M + H]+ at

m/z 817.211 (calcd. 817.216). Thus, these values are close to each other confirming

the formulation of complex 41.

The structure of complex 41 was determined from an X-ray structure determination of

crystals obtained after recrystallisation from CH2Cl2/hexane (Figure 52). Selected

structural data are collected in Table 19. The Ru-C(1) bond length of 1.962(2) Å is

consistent with the value for a ruthenium carbon single bond. The C(1)-C(2) bond

length is equal to 1.232(3) Å which is consistent with C≡C triple bond and the C(2)-

C(3) bond length is equal 1.388(4) Å due to a C-C single bond. The carbon chain in

41 is essentially linear, with angles Ru-C(1)-C(2) equal to 178.3(2) o and C(1)-C(2)-

C(3) equal to 168.3(3) o.


157


Ru-C(1) 1.962(2) Ru-C(1)-C(2) 178.3(2)

Ru-P(1) 2.273(6) P(1)-Ru-P(2) 83.9(2)

Ru-P(2) 2.287(6) P(1)-Ru-C(1) 81.8(7)

Ru-C(Cp*) 2.220(2) - 2.284(2) P(2)-Ru-C(1) 87.4(7)

Ru-C(Cp*) (av.) 2.255(2) C(1)-C(2)-C(3) 168.3(3)

C(1)-C(2) 1.232(3) C(2)-C(3)-C(8) 135.7(3)

C(2)-C(3) 1.388(4) C(2)-C(3)-N(4) 109.4(3)

C(3)-C(8) 1.284(4) C(8)-C(3)-N(4) 114.8(3)

C(3)-N(4) 1.457(4)


The mechanism for the formation of 41 is not obvious. However, the analysis of the

structure of 41 suggests that the insertion of one TCNE occurred (presence of 4

nitrogens). If it is assumed that the TCNE insertion was at the terminal carbons, then

the first step of the reaction can be the usually described [2 +2]-cycloaddition of

TCNE to the carbon chain which is then followed by ring opening (Scheme 98).

TCNE

[Ru*] = Ru(dppe)Cp*

[Ru*] LiC C C C

C C

NCNC CN

CN

Intermediate

[Ru*] LiC C C C C[Ru*] C C

C Li

C

NC

NC CN

CN

Scheme 98: Proposed first step for the synthesis of 41

However, this intermediate must have reacted further to give complex 41. It is not

known if this occurred during the reaction or during the isolation of the product on

TLC plates. These plates are acidic and could have been a factor in the synthesis of

the two different complexes 40 and 41. In order to eliminate this possibility, the

method for the isolation of the product from this reaction should be changed.

Furthermore, isotopic labeling of the carbon atoms of the chain of

Ru(C≡CC≡CH)(dppe)Cp* would allow identification of the position of these carbons

in the final product. In particular, the labeling of C3 and C4 should give a doublet in

158

the 13C NMR if they are sequential in the product. Similarly, the two central carbons

of TCNE could be labeled and analysis of their positions in the final product should

give an indication on how the reaction proceeded. This could also give an explanation

for the presence of the CH3 group. Two possibilities for its formation can be

proposed: the carbon corresponds to the initial carbon chain of

Ru(C≡CC≡CH)(dppe)Cp* which has undergone fragmentation or it can come from

the THF used as solvent in the reaction. In order to refute this, the reaction should be

done in different solvents. In addition, the complex

Ru(C≡CC[=C(CN)2]CH[=C(CN)2])(dppe)Cp* was previously obtained from the

reaction of Ru(C≡CC≡CH)(dppe)Cp* with TCNE.150 This complex could be

dissolved in THF and the reaction could be monitored to determine if complex 41 is

formed from it. If not, the reaction mixture could be put on TLC plates and if complex

41 is obtained this will indicate that its formation is due to the isolation technique

used.

4.3.2. Reactions with polyfluoroaromatic reagents

In the Introduction, it was described that polyfluoroaromatic compounds are

susceptible to nucleophilic substitution. Hence, it was suggested that the nucleophilic

complex Ru(C≡CC≡CLi)(dppe)Cp* should readily react with these compounds. All

the compounds described in this Section were fully characterised by 1H, 31P and 13C

NMR, IR, ES-MS and microanalysis and the data are summarised in Table 21.

4.3.2.1. Synthesis of Ru(C≡CC≡CC6F5)(dppe)Cp*

The first step of the reaction involved the generation in situ of

Ru(C≡CC≡CLi)(dppe)Cp* from the treatment of Ru(C≡CC≡CH)(dppe)Cp* with n-

BuLi at -78oC. Hexafluorobenzene was then added and an immediate colour change

from yellow to orange was observed. Ru(C≡CC≡CC6F5)(dppe)Cp* (42) was obtained

as an orange crystalline powder in 80% yield. The reaction is assumed to involve the

addition of the attacking nucleophile to the C6F6 ring to form a negatively charged

intermediate and F- is then eliminated in the second step. This is an example of a

nucleophilic aromatic substitution (Scheme 99).

159

C C C C

C C C C Li F

F F

F

FF

F F

F

FF

F F

F

FFF

F F

FF

F F

F F

F

FF

- F-

Ru

Ph2P PPh2

C C C CRu

Ph2P PPh2F

Ru

Ph2P PPh2

C C C CRu

Ph2P PPh2

C C C CRu

Ph2P PPh2(42)

Scheme 99: Proposed mechanism for the synthesis of 42

The characteristic peaks for the Ru(C4)(dppe)Cp* fragment are present in the 1H, 31P

and 13C NMR spectra of complex 42. In the infrared spectrum, two bands for the ν(C-

F) stretch were present at 1376 and 1261 cm-1. The ES-MS of 42 shows a peak for the

[M + Na]+ ion at m/z 873 and one fragmentation ion corresponding to [Ru(dppe)Cp*]+

at m/z 635.

In the 19F NMR spectrum, three resonances are observed from the AA’MXX’spin

system. The meta and ortho fluorines of 42 are observed as multiplets at δ -166.63 – -

166.72 and -141.40 – -141.46, respectively. The para fluorine is observed as a triplet

at δ -161.79, due to coupling with the meta fluorines, with a coupling constant of 22

Hz which is also reflected in the meta fluorine resonances. A 19F COSY NMR of 42

was obtained and is shown in Figure 53. There are two main cross-peaks in the

spectrum. The peak for the meta fluorine at δ -166.63 – -166.72 is coupled to the para

fluorine at δ -161.79 and to the ortho fluorine at δ -141.40 – -141.46.

160

Figure 53: 19F COSY NMR of complex 42

The structure of 42 was confirmed by X-ray studies of crystals grown from

CH2Cl2/hexane (Figure 54). Selected structural data are collected in Table 22. The

Ru(dppe)Cp* fragment has the expected geometry, with Ru-P(1) and Ru-P(2) equals

to 2.281(1) Å and 2.270(3) Å, respectively and the Ru-C(Cp*) distances of 2.180(2) -

2.35(1) Å. The Ru-C(1) bond length of 1.993(8) Å is close to the value expected for a

ruthenium carbon single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.18(1)

Å, the C(2)-C(3) distance is 1.39(1) Å and the C(3)-C(4) distance is 1.21(1) Å. The

expected alternating short C(1)-C(2), long C(2)-C(3) and short C(3)-C(4) bonds are

consistent with the diynyl nature of the bonds. The C(4)-C(41) distance is equal to

161

1.45(1) Å, reflecting the presence of a single bond. The average length for the C(n)-

F(n) (n = 42 - 46) bond is equal to 1.34(1) Å. The angles Ru-C(1)-C(2) [175.1(9) o],

C(1)-C(2)-C(3) [170.5(8) o] and C(2)-C(3)-C(4) [179.2(8)o] and C(3)-C(4)-(C41)

[166.4(1) o] indicates that the carbon chain in 42 is essentially linear.


4.3.2.2. Synthesis of Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp*

Complex Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43) was obtained from a similar

reaction, where Ru(C≡CC≡CLi)(dppe)Cp* was reacted with the compound C6F5NO2.

This reaction is an example of a C-F cleavage occurring on the fluoroarene C6F5NO2.

Complex 43 was obtained as a purple powder in 80% yield (Scheme 100).

NO2C C C CC6F5NO2

Ru

Ph2P PPh2

Li

THF-78oC C C C C

F F

NO2

FF

Ru

Ph2P PPh2 (43)

Scheme 100: The synthesis of 43

The NMR spectroscopic analyses of complex 43 confirmed the presence of the

Ru(dppe)Cp* ligand. The IR spectrum contains a broad ν(NO) band at 1634 cm-1 and

162

two ν(C-F) bands at 1259 and 1016 cm-1. Elemental analysis and the ES-MS

confirmed the formulation of complex 43 with [M]+ found at m/z 878.

In the 19F NMR the ortho and meta fluorines form a AA’XX’ spin system and are

found as multiplets at δ -140.26 – -140.34 and -151.88 – -151.96. This is consistent

with 1,4 substitution.

4.3.2.3. Synthesis of Ru(C≡CC≡CC6F4CN-4)(dppe)Cp*

C6F5CN is another available fluoroarene which contains an electron-withdrawing CN

substituent. Hence, Ru(C≡CC≡CLi)(dppe)Cp* was reacted with C6F5CN and an

immediate colour change from yellow to bright orange was observed. After work-up,

Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44) was obtained in 90% yield (Scheme 101).

C C C CC6F5CN

Ru

Ph2P PPh2

Li

THF-78oC

C C C C

F F

CN

FF

Ru

Ph2P PPh2 (44)

Scheme 101: The synthesis of 44 Similarly to complexes 42 and 43, the 1H, 31P and 13C NMR spectra of complex 44

show the presence of the Ru(dppe)Cp* unit and the carbons of the chain. The 13C

NMR of complex 44 also shows the presence of one resonance for the CN group

found as a singlet at δ 111.21. The infrared spectrum contains one band at 2214 cm-1

due to ν(CN) stretch and two bands at 1380 and 1264 cm-1 are present for the ν(C-F)

stretch.

In the 19F NMR, two multiplets at δ -138.72 – -138.83 and -139.68 – -139.79 are

observed and correspond to the two sets of equivalent fluorine atoms, as expected due

to the 1,4-substitution. The structure of 44 was also confirmed by the ES-MS which

contains [M + H]+ at m/z 858 and the fragmentation ion [Ru(dppe)Cp*]+ at m/z 635.

163

The molecular structure of 44 was confirmed by single-crystal X-ray studies on

crystals grown from benzene/hexane. The ORTEP diagram is shown in Figure 55 and

selected bond distances and angles are given in Table 22. The Ru-C(1) bond length of

1.957(1) Å is consistent for a ruthenium carbon single bond. The C(1)-C(2) bond

length of 1.231(2) Å and C(3)-C(4) bond length of 1.212(2) Å confirms they are C≡C

triple bond. The C(2)-C(3) and C(4)-C(41) distances of 1.361(2) Å and 1.416(2) Å

respectively, are consistent with being C-C single bonds. The average length for the

C(n)-F(n) (n = 42 - 46) bond is equal to 1.34(1) Å. The carbon chain is essentially

linear with angles Ru-C(1)-C(2) [171.8(1)o], C(1)-C(2)-C(3) [168.1(1) o], C(2)-C(3)-

C(4) [178.2(1) o] and C(3)-C(4)-C(41) [167.4(1) o]. Similarly, the angle C(44)-

C(441)-N(441) is equal to 178.2(2) o which is nearly linear.

Figure 55: ORTEP view of complex 44 4.3.2.4. Synthesis of Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp*

Two methods were proposed in order to synthesise the complex

Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45). The first is the lithiation of

Ru(C≡CC≡CH)(dppe)Cp* with n-BuLi to generate the species

Ru(C≡CC≡CLi)(dppe)Cp*, followed by addition of C6F5OMe (Scheme 102). This is

the previously described lithiation method. From this reaction, 45 was obtained as an

orange powder in 60% yield.

164

C C C CC6F5OMe

Ru

Ph2P PPh2

Li C C C C

F F

OMe

FF

Ru

Ph2P PPh2

C C C CRu

Ph2P PPh2

Li

THF-78oC

C C C C

F F

OMe

FF

Ru

Ph2P PPh2 (45)

Scheme 102: First method for the synthesis of 45

The second method involves the reaction of the previously synthesised complex

Ru(C≡CC≡CC6F5)(dppe)Cp* (42) with sodium methoxide at room temperature. The

fluorine atom in the para position is replaced by an OMe group to give the desired

complex 45 (Scheme 103). The yield of this reaction is higher with 45 being obtained

in 87% yield.

NaOMeC C C C

F F

OMe

FF

Ru

Ph2P PPh2

C C C C

F F

F

FF

Ru

Ph2P PPh2 (45)(42)

Scheme 103: Second method for the synthesis of 45

The 1H and 13C NMR spectra of 45 contained all the typical resonances for the

Ru(dppe)Cp* group. The OMe group gives a singlet at δ 3.30 in the 1H NMR

spectrum and at δ 74.00 in the 13C NMR spectrum. Two resonances were present in

the 19F NMR spectrum as two multiplets at δ -142.07 – -142.18 and -161.51 – -161.62

which is expected due to the 1,4-substitution. This is also a AA’XX’ spin system.

In the infrared spectrum, one ν(CO) band at 1711 cm-1 was observed and two ν(C-F)

bands at 1377 and 1263 cm-1. The ν(CO) band is at a higher frequency in comparison

to an ordinary organic ether linkage. Finally, the ES-MS contains [M + Na]+ at m/z

885, the molecular ion [M]+ at m/z 862 and the fragmentation ion [Ru(dppe)Cp*]+ at

m/z 635.

Crystals of 45 were grown from a CH2Cl2/hexane mixture and the molecular structure

was determined by single-crystal X-ray diffraction studies. The ORTEP diagram is

shown in Figure 56 and selected bond distances and angles are given in Table 22. The

165

Ru(dppe)Cp* fragment has the expected geometry, with Ru-P(1) and Ru-P(2) equals

to 2.269(1) Å and 2.281(1) Å, respectively and the Ru-C(Cp*) distances of 2.241(4) -

2.278(4) Å. The Ru-C(1) bond length of 1.991(4) Å is close to the value expected for

a ruthenium carbon single bond (2.01 Å) and the C(1)-C(2) bond length of 1.227(5) Å

and the C(3)-C(4) bond length of 1.206(5) Å confirms the presence of the C≡C triple

bonds. These bonds are alternated with C-C single bonds C(2)-C(3) [1.373(6) Å] and

C(4)-C(41) [1.49(1) Å]. The average length for the C(n)-F(n) (n = 42 - 46) bond is

equal to 1.342(9) Å. The angles Ru-C(1)-C(2) [173.8(3) o], C(1)-C(2)-C(3) [176.1(4) o], C(2)-C(3)-C(4) [179.7(5) o] and C(3)-C(4)-C(141) [175.7(6) o] in 45 are nearly

linear. The presence of the oxygen atom gives a bent angle with C(144)-O(144)-

C(147) equal to 107.2(5) o.


4.3.2.5. Synthesis of Ru(C≡CC≡CC10F7-2)(dppe)Cp*

The reaction of Ru(C≡CC≡CLi)(dppe)Cp* with C10F8 gave the complex

Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46) as an orange powder in 35% yield (Scheme

104).

C C C CRu

Ph2P PPh2

Li C C C CRuPh2P PPh2

F F

F

FFF

F

C C C CRu

Ph2P PPh2

Li

THF-78oC

C C C CRuPh2P PPh2

F F

FF

F

(46)

C10F8

Scheme 104: The synthesis of 46

166

Two ν(C≡C) bands at 2138 and 2008 cm-1 were observed in the infrared spectrum of

complex 46 as well as two ν(C-F) bands at 1263 and 1197 cm-1. The Ru(dppe)Cp*C4

unit was characterised by similar peaks to previous complexes in the 1H, 31P and 13C

NMR spectra. Finally, the ES-MS of complex 46 in MeOH contained [M + MeOH]+

at m/z 969, [M]+ at m/z 937 and [Ru(dppe)Cp*]+ at m/z 635.

In the 19F NMR spectrum, three doublets of triplets are present at δ -147.33 (3JFF = 18

Hz, 4JFF = 65 Hz), -149.28 (3JFF = 18 Hz, 4JFF = 58 Hz) and -153.04 (3JFF = 18 Hz, 4JFF

= 58 Hz) and two triplets at δ -158.97 (3JFF = 20 Hz) and -160.05 (3JFF = 19 Hz). Five

of the seven expected fluorine resonances are present and it is assumed that the other

two are hidden below the peaks at δ -158.97 and -160.05 as the integrals are higher

for these peaks (47 vs 29). The strong deshielding caused by the presence of the

Ru(dppe)Cp* ligand enabled the ortho fluorines to be assigned, and the presence of

two low-field signals indicates that 2-substitution had occurred. A 19F COSY NMR

spectrum of 46 was also obtained and is shown in Figure 57. This spectrum further

enables to assign the fluorine resonances. The peak at δ -147.33 is coupled to -160.05,

-153.04 and -149.28 and the peak at -149.28 is coupled to -158.97, -153.04 and -

147.33. Then, the peak at δ -153.04 is coupled to -158.97, -160.05 and -147.33 and

the peak at -158.97 is coupled to -160.05, -153.04 and -149.28. And, the peak at δ -

160.05 is coupled to -158.97 and -147.33. Those peaks indicate the interaction of the

adjacent fluorine atoms present on the rings. The fluorine in the 1 and 3 positions are

present at δ -160.05, the fluorines in the 4 and 8 positions at δ -158.97, the one in the

5 position is at δ -153.04, the one at the 6 position is at δ -149.28 and the one at the 7

position is at δ -147.33.

167

Figure 57: 19F COSY NMR of complex 46

Single crystals suitable for X-ray studies were grown from toluene/hexane. The


angles are given in Table 22. This confirms the substitution on the 2-position.The Ru-

C(1) bond length of 1.976(2) Å is close to the value expected for a ruthenium carbon

single bond (2.01 Å). The C(1)-C(2) bond length is equal to 1.209(3) Å, the C(3)-C(4)

distance of 1.199(3) Å, the C(2)-C(3) distance is 1.373(3) Å, and the C(4)-C(42)

distance is 1.421(3) Å. They are therefore consistent with being C≡C triple bonds and

168

C-C single bonds. The average length for the C(n)-F(n) (n = 41 - 48) bond is equal to

1.337(3) Å. The carbon chain in 46 is essentially linear, the angles C(1)-C(2)-C(3),

C(2)-C(3)-C(4) and C(3)-C(4)-C(42) being 174.3(2) o, 178.2(3) o and 173.5(3) o,

respectively.


From the data summarised in Table 20 there are several interesting comparisons that

can be drawn from the 19F NMR spectra. It can be observed that the addition of the

Ru(dppe)Cp*-C≡CC≡C- moiety has shifted the chemical shifts of the ortho fluorines

(F-2,6) downfield in complexes 42, 43, 44 and 45 compared to the unsubstituted

reagents. For example, the difference in chemical shift between C6F6 and complex 42

is 24 ppm downfield. This was also observed for the complex

Ru(C≡CC6F5)(dppe)Cp*. The chemical shifts of complex 42 are also shifted

downfield compare to Ru(C≡CC6F5)(dppe)Cp*, which can be explained by the

presence of the extra C≡C triple bond in complex 42.

Furthermore, complex 42 has a triplet for the para fluorine atom while in complexes

43, 44 and 45, this fluorine atom has been replaced by various groups. This has

affected the fluorine atoms in meta position (F-3,5) and it can be noted that the

chemical shift is shifted downfield for the different substituents. The smaller

difference in the chemical shift is obtained with the OMe substituent (5 ppm) while

the electron withdrawing groups NO2 and CN gave a larger difference (15 ppm for 43

and 27 for ppm for 44).

169

Complex F-2,6 (δ) F-3,5 (δ) F-4 (δ) [Ref]

C6F6

-164.9 / / This work

C6F5NO2 -150.70 – -

150.86 -162.44 – -163.10

-155.21 (t, 3JFF = 22 Hz, 1F)

This work

C6F5CN -150.57 – -

150.62 -177.07 – -177.10

-166.47 (t, 3JFF = 21 Hz, 1F)

This work

C6F5OMe -144.09 – -

144.15 -150.90 – -150.98

-145.73 (t, 3JFF = 20 Hz, 1F)

This work

Ru(C≡CC6F5)(dppe)Cp* -145.8

(m, 2F) -168.9 (m, 2F)

-169.1 (t, 3JFF = 21 Hz, 1F)

151

42 -141.40 – -

141.46 (m, 2F)

-166.63 – -166.72 (m, 2F)

-161.79 (t, 3JFF = 22 Hz, 1F)

This work

43 -140.26 – -

140.34 (m, 2F)

-151.88 – -151.96 (m, 2F)

/ This work

44 -138.72 – -

138.83 (m, 2F)

-139.68 – -139.79 (m, 2F)

/ This work

45 -142.07 – -

142.18 (m, 2F)

-161.51 – -161.62 (m, 2F)

/ This work

Table 19: 19F NMR data for complexes 42 - 45

170

Complex IR (cm-1) 1H NMR (δ) 13C NMR (δ) 31P NMR (δ) MS (m/z) 42 ν(C≡C) 2151

(m), 2005 (m); ν(C-F) 1376 (m), 1261 (m)


134.48-127.75 (m, Ph); 126.48, 99.23, 89.37, 53.27 (s, C1, C2, C3, C4); 93.80 (t, 2J(CP) 2 Hz, C5Me5); 30.11-29.85 (m, CH2CH2); 10.05 (s, C5Me5)

80.8 (s, dppe) 873, [M + Na]+; 635, [Ru(dppe)Cp*]+

43 ν(C≡C) 2126 (m), 1998 (m); ν(NO) 1634 (w); ν(C-F) 1259 (m), 1016 (m)



80.4 (s, dppe) 901, [M + Na]+; 878,

[M]+; 635,

[Ru(dppe)Cp*]+

44 ν(CN) 2214 (m);

ν(C≡C) 2128 (m), 1995 (m); ν(C-F) 1380 (m), 1264 (m)


133.68-127.63 (m, Ph); 99.39, 94.75, 75.49, 59.48 (s, C1, C2, C3, C4); 94.25 (s, C5Me5); 85.03 (s, CN); 31.95-30.04 (m, CH2CH2); 10.01 (s, C5Me5)

80.2 (s, dppe) 858, [M + H]+; 635,

[Ru(dppe)Cp*]+

45 ν(C≡C) 2149 (m), 2005 (m); ν(CO) 1711 (m); ν(C-F) 1377 (m), 1263 (m)

7.37-7.02 (m, 20H, Ph); 3.30 (s, 3H, C(O)CH3); 2.48-2.41, 1.79-1.74 (2 x m, 2 x 2H, CH2CH2); 1.54 (s, 15H, Cp*)

136.78-127.64 (m, Ph); 100.28, 92.54, 89.95, 53.26 (s, C1, C2, C3, C4); 93.71 (s, C5Me5); 74.00 (s, C(O)CH3); 30.11-29.87 (m, CH2CH2); 10.08 (s, C5Me5)

80.8 (s, dppe) 885, [M + Na]+; 862,

[M]+; 635,

[Ru(dppe)Cp*]+

46 ν(C≡C) 2138 (m), 2008 (m); ν(C-F) 1263 (m), 1197 (m)



80.7 (s, dppe) 969, [M + MeOH]+; 937, [M]+; 635, [Ru(dppe)Cp*]+


171

Complex 42 44 45 46

Bond Distances (Å)

Ru-P(1)

2.281(1) 2.265(6) 2.269(1) 2.268(6) Ru-P(2)

2.270(3) 2.275(9) 2.281(1) 2.282(6) Ru-C(Cp*)

2.180(2) - 2.35(1) 2.229(1) - 2.290(1) 2.241(4) - 2.278(4) 2.232(2) - 2.272(2) (av.)

2.270(1) 2.265(1) 2.257(4) 2.255(2) Ru-C(1)

1.993(8) 1.957(1) 1.991(4) 1.976(2) C(1)-C(2)

1.180(1) 1.231(2) 1.227(5) 1.209(3) C(2)-C(3)

1.390(1) 1.361(2) 1.373(6) 1.373(3) C(3)-C(4)

1.210(1) 1.212(2) 1.206(5) 1.199(3) C(4)-C(41)

1.450(1) 1.416(2) 1.490(1) 1.421(3) C(n)-F(n) (n = 41- 48)

1.330(1) - 1.340(1) 1.340(1) - 1.340(1) 1.289(9) - 1.378(9) 1.314(3) - 1.354(3)

C(n)-F(n) (av.) 1.340(1) 1.340(1) 1.342(9) 1.337(3) Bond Angles (˚)

P(1)-Ru-P(2)

83.2(8) 80.1(3) 83.4(4) 83.3(2) P(1)-Ru-C(1)

83.9(1) 86.0(5) 79.8(1) 80.5(6) P(2)-Ru-C(1)

86.9(3) 85.7(6) 91.2(1) 87.1(6) Ru-C(1)-C(2)

175.1(9) 171.8(1) 173.8(3) 178.7(2) C(1)-C(2)-C(3)

170.5(8) 168.1(1) 176.1(4) 174.3(2) C(2)-C(3)-C(4)

179.2(8) 178.2(1) 179.7(5) 178.2(3) C(3)-C(4)-C(41)

166.4(1) 167.4(1) 175.7(6) 173.5(3)

Table 21: Selected structural data for complexes 42, 44, 45 and 46

172

4.3.2.6. Further reactions with Ru(C≡CC≡CC6F5)(dppe)Cp*

Previously, the reaction between substituted alkynes and vinylidenes was found to occur via

the cycloaddition of the C≡C bond of the alkyne to the C=C of the vinylidene to form

cyclobutenylidene complexes.152 A ruthenium cyclobutenylidene complex was reported from

the reaction of the butatrienylidene [Ru(C=C=C=CH2)(dppe)Cp*]+ with the diynyl

Ru(C≡CC≡CTMS)(dppe)Cp* (Scheme 105).12

C C C CRu

Ph2P PPh2

TMS

CCCC Ru

PPh2Ph2P

H

H +

+

C C CC

Ru

Ph2P PPh2

CCCC

Ru

PPh2Ph2P

H H

TMS

Scheme 105: Proposed mechanism for the formation of the ruthenium cyclobutenylidene

Therefore, the complex Ru(C≡CC≡CC6F5)(dppe)Cp* (42) was treated with HBF4.OEt2 at

room temperature and the cyclobutenylidene complex

[{Cp*(dppe)Ru(C≡C)}2{C4(C6F5)2H}]BF4 (47) was obtained as a bright blue product in 84%

yield. The characteristic peaks for the Ru(dppe)Cp* groups are present in the 1H, 31P and 13C

NMR spectra of complex 47. The 1H NMR spectrum also shows a singlet at δ 2.02 for a

single proton while in the infrared spectrum, one ν(CH) band at 2924 cm-1 and two ν(C-F)

bands at 1264 and 1158 cm-1 were observed. Further characterisation of 47 was obtained from

the ES-MS which contained ions corresponding to [M - H]+ at m/z 1700 and [Ru(dppe)Cp*]+

at m/z 635.

The 19F NMR spectrum obtained shows interesting features due to the asymmetry of the

molecule. The two C6F5 groups are inequivalent and are in different chemical environments.

This gives two multiplets for the meta fluorine atoms at δ -163.73 – -163.61 and -165.19 – -

173

165.26 while two multiplets for the ortho fluorine are present at δ -137.77 – -137.80 and at -

143.77 – -143.64. The para fluorine atoms are assigned to two triplets at δ -156.59 (3JFF = 22

Hz) and -157.33 (3JFF = 22 Hz).

The formation of [(Cp*(dppe)Ru(C≡C)2{C4(C6F5)2H}]BF4 (47) can be explained by the [2 +

2]-cycloaddition of the C≡C triple bond of diynyl 42 with the C=C double bond of

[Ru{C=C=C=C(C6F5)H}(dppe)Cp*]+ probably formed in situ (Scheme 106).

C C C CRu

Ph2P PPh2

C6F5

CCCC Ru

PPh2Ph2P

H

C6F5 +

C C C

C

Ru

Ph2P PPh2

CCC

C

Ru

PPh2Ph2P

H C6F5

C6F5

(47)

+

Scheme 106: Proposed mechanism for the formation of 47

In addition, the complex Ru(C≡CC≡CC6F5)(dppe)Cp* (42) reacts with the electron deficient

alkene TCNE. The cycloaddition of TCNE to one of the C≡C triple bonds is followed by ring-

opening to give Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48) in 97% yield (Scheme

107). It is noteworthy that neither the other isomer nor the bis(adduct) were obtained when an

excess of TCNE was used in the reaction.

174

C C C C

F F

F

FF

Ru

Ph2P PPh2

CH2Cl2

C C C C

F F

F

FF

Ru

Ph2P PPh2

F F

F

FF

Ru

Ph2P PPh2

C C

CNCN

CNNC

CC

NC CN

NC CN

C C C C

F F

F

FF

Ru

Ph2P PPh2

C C C C

F F

F

FF

Ru

Ph2P PPh2

F F

F

FF

Ru

Ph2P PPh2

C C

CNCN

CNNC

CC

NC CN

NC CN

(48)

TCNE

(42)

Intermediate


The IR spectrum of 48 shows one ν(CN) band at 2211 cm-1, one ν(C≡C) band at 1964 cm-1

and two ν(C-F) bands at 1262 and 1196 cm-1. The 1H, 31P and 13C NMR spectra shows the

typical resonances for the Ru(dppe)Cp* unit. The 13C NMR spectrum of 48 shows the four

CN resonances at δ 116.53, 116.33, 111.30 and 110.62. The resonances for the carbon atoms

of the C4 chains were found as four singlets at δ 154.01, 101.00, 92.81 and 78.91. They could

not be assigned to the individual carbons as it could not be determined which triple bond was

attacked by the TCNE. It can only be suggested that the TCNE was added on the C≡C triple

bond adjacent to the fluorine ring due to steric hindrance around the Ru(dppe)Cp* ligand.

In the 19F NMR spectrum two multiplets were present at δ -135.50 – -136.00 and -159.86 – -

160.28 corresponding to the ortho and meta fluorines respectively and a triplet at δ -148.54

(3JFF = 22 Hz) was assigned to the para fluorine. Furthermore, in the ES-MS of 48, ions

corresponding to [M + Na]+ at m/z 1001 and [Ru(dppe)Cp*]+ at m/z 635 were present.

175

F F

F

FF

[Ru*] C C CC

NC CN

NC CN

C C

F F

F

FF

[Ru*] C C

F F

F F

FF

C C LiC C[Ru*]

C C C C[Ru*]

F F

NO2

FFF

F F

CN

FF

C C C C[Ru*]

F F

CN

FF

FF

F

F F

OMe

F

F

F F

NO2

F

C C C C[Ru*]

F F

OMe

FF

C[Ru*] C [Ru*]C CC

CCC

H C6F5

C6F5

+

HBF4

[Ru*] = Ru(dppe)Cp*

TCNE

NaOMe

(44)

(45)

(47)

(42)

(43)

(48)

C C C C[Ru*]

F FF

FFF

F

(46)

F

F

FF

F

F

F F

Figure 59: Summary of polyfluoroaromatic products synthesised

176

4.4. Electrochemistry

4.4.1. CV of products from the reactions with organic reagents

The redox properties of the complexes Ru(C≡CC≡CMe)(dppe)Cp* (33),

Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34) and Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38)

were studied. Their cyclic voltammograms show single fully-reversible processes at

+0.27 V, at +0.25 V and at +0.21 V, respectively. The cyclic voltammogram of 33 is

shown as an example in Figure 60. The cyclic voltammogram of complex

Ru(C≡CC≡CH)(dppe)Cp* shows one single process at + 0.44V.30 Hence, the

oxidation potentials of complexes 33, 34 and 38 are lower than that for

Ru(C≡CC≡CH)(dppe)Cp*. This can be explained by the terminal proton being

replaced by the different end-groups.


Complex {Cp*(dppe)Ru(C≡CC≡C)}2(COCO) (37) has a very interesting structure

since it is composed of a C10 carbon chain which contains two CO groups in the

centre. The redox properties of this complex were investigated. In the CV of 37 one

two-electron partially reversible process is observed at +0.31 V (ia/ic = 0.8) and is

diffusion controlled. Another wave is also present and is most likely due to the

unstability of the starting material which could have decompose in the cell (Figure

61). The two electron process was determined by comparing the difference between

177

Ea and Ec for ferrocene, which undergoes a one electron process, to 37. The two-

electron redox process indicates that there is no communication between the two end-

groups, the two rutheniums are oxidised and reduced at the same potential. Thus, the

insertion of the COCO group has broken the π-conjugation and results in a loss of

electronic interaction between the ruthenium termini.


4.4.2. CV of products from the reactions with polyfluoroaromatic reagents

The redox properties of complexes Ru(C≡CC≡CC6F5)(dppe)Cp* (42),

Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44) and Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46)

were studied. Their cyclic voltammograms show single partially reversible processes

at +0.56 V (ia/ic = 0.8), +0.50 V (ia/ic = 0.8), +0.51 V (ia/ic = 0.5), respectively (Figure

62). These processes are diffusion controlled. Comparison of 42, 44 and 46 with

Ru(C≡CC≡CH)(dppe)Cp* shows oxidation events occurring at higher redox

potentials. This can be explained as the proton has been replaced by the electron

withdrawing groups C6F5, C6F4CN and C10F7 in these complexes.

178


The cyclic voltammogram of complex Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43) was

also acquired. One irreversible process is observed at – 1.45 V and one partially

reversible process is observed at +0.52 V (ia/ic = 0.7) (Figure 63). The wave at –1.45

V is a reduction process while the one at +0.52 V is the oxidation of the Ru(dppe)Cp*

moiety. If the oxidation wave of complex 43 is compared with that of

Ru(C≡CC≡CH)(dppe)Cp*, it can be seen that it occurs at a higher potential, which is

consistent with the presence of the electron withdrawing C6F4NO2 group.


179

Furthermore, the cyclic voltammogram of Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45)

shows two partially reversible processes at +0.17 V (ia/ic = 0.5) and +0.34 V (ia/ic =

0.4) (Figure 64). These redox processes are diffusion controlled. The first oxidation

wave of complex 45 is at +0.17 V, which is at lower potential than that of

Ru(C≡CC≡CH)(dppe)Cp*. One possible explanation is due to the presence of the

C6F4OMe group which produces a combination of two different effects: the first effect

is the inductive effect of the electron-poor fluorine atoms (electron withdrawing)

while the second effect is the resonance effect of the OMe group (electron donating).

The resonance effect is the most important contributor to the redox potential of

complex 45.


Finally, the cyclic voltammogram of the complex

Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48) was obtained. It shows two

partially reversible processes at -0.89 V (ia/ic = 0.7) and -0.52 V (ia/ic = 0.8) which are

diffusion controlled. These correspond to reduction waves usually observed with

TCNE adducts where the electron is delocalised onto the electron-withdrawing CN

group. One fully reversible process is also observed at +0.86 V (ia/ic = 0.9) which

corresponds to the oxidation of the Ru(dppe)Cp* moiety (Figure 65).

180

Figure 65: Cyclic voltammogram of 48 The oxidation potential of complex 48 is higher than the first oxidation potential of

the complex Ru(C≡CC≡CH)(dppe)Cp* and 42 as a consequence of the addition of

TCNE, another electron withdrawing group.

181

4.5. Conclusions

In conclusion, the nucleophilic complex Ru(C≡CC≡CLi)(dppe)Cp* was reacted

successfully with a range of organic reagents to afford new diynyl complexes of

general formula Ru(C≡CC≡CR)(dppe)Cp* where R is an organic group (33 - 38). The

electrochemical studies show that minimal electronic communication between the

terminal end-groups is present in these complexes. The reaction of

Ru(C≡CC≡CLi)(dppe)Cp* with TCNE also afforded three different complexes.

Furthermore, Ru(C≡CC≡CLi)(dppe)Cp* was reacted with polyfluoroaromatic

reagents to afford complexes 42 - 46 in very good yields. Complex

Ru(C≡CC≡CC6F5)(dppe)Cp* (42) was further involved in two reactions: the first gave

the cyclobutenylidene complex [{Cp*(dppe)Ru(C≡C)}2{C4(C6F5)2H}]BF4 (47) while

the reaction with TCNE afforded the complex

Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48).

Therefore, based upon the successful results described in this chapter, the complex

Ru(C≡CC≡CLi)(dppe)Cp* is certain to see increasing use in the preparation of

diverse types of complexes.

182

4.6. Experimental General experimental conditions are detailed on page viii. Reagents: The compounds Ru(C≡CC≡CH)(dppe)Cp*30 was prepared by standard literature

methods. n-BuLi, TCNE, C10F8, HBF4.OEt2 were used as received from Sigma-

Aldrich. MeI, benzoyl chloride, acetyl chloride, methyl chloroformate, oxalyl

chloride, benzaldehyde, C6F6, C6F5NO2, C6F5CN, C6F5OCH3 were freshly distilled

under nitrogen.

Ru(C≡CC≡CMe)(dppe)Cp* (33) A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (5 mL) was


An aliquot of MeI (32 µL, 0.51 mmol) was added and the reaction was allowed to

warm to r.t. over 3 h. The solvent was then removed and the yellow residue extracted

with hexane (60 mL) and filtered via cannula. The solvent was evaporated to dryness

to give Ru(C≡CC≡CMe)(dppe)Cp* (33) as a bright yellow powder (40 mg, 70%).

Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. Anal.

Calcd. (C41H42P2Ru): C, 70.47; H, 6.06. Found: C, 70.45; H, 5.99. IR (CH2Cl2, cm-1):

ν(C≡C) 2029 (m), 1908 (m). 1H NMR (C6D6): δ 7.28-6.89 (m, 20H, Ph); 2.65-2.62,

2.01-1.87 (2 x m, 2 x 2H, CH2CH2); 1.73 (s, 3H, CH3); 1.60 (s, 15H, Cp*). 13C NMR

(C6D6): δ 133.96-127.42 (m, Ph); 124.69, 91.73, 76.86, 52.46 (s, C1, C2, C3, C4);

93.25 (s, C5Me5); 29.88-29.27 (m, CH2CH2); 21.03 (s, CH3); 10.12 (s, C5Me5). 31P

NMR (C6D6): δ 81.6 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 731, [M + MeOH]+;

635, [Ru(dppe)Cp*]+.

183

Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34)

Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) with benzoyl

chloride (17 µL, 0.14 mmol) gave Ru{C≡CC≡CC(O)Ph}(dppe)Cp* (34) as a red

powder (43 mg, 75%). Anal. Calcd. (C47H44P2ORu): C, 71.65; H, 5.63. Found: C,

71.76; H, 5.60. IR (Nujol, cm-1): ν(C≡C) 2109 (m), 2000 (m); ν(CO) 1716 (m). 1H

NMR (C6D6): δ 7.28-7.05 (m, 25H, Ph); 2.54-2.50, 2.18-2.08 (2 x m, 2 x 2H,

CH2CH2); 1.51 (s, 15H, Cp*). 13C NMR (C6D6): δ 206.41 (s, CO); 133.63-127.63 (m,

Ph); 112.17, 101.00, 95.59, 63.08 (s, C1, C2, C3, C4); 94.13 (t, 2J(CP) 2 Hz, C5Me5);

30.12-29.23 (m, CH2CH2); 10.02 (s, C5Me5). 31P NMR (C6D6): δ 80.5 (s, dppe). ES-

MS (+ve ion, MeOH, m/z): 811, [M + Na]+; 788, [M]+; 635, [Ru(dppe)Cp*]+.

Ru{C≡CC≡CC(O)Me}(dppe)Cp* (35)

A solution of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) in THF (2.5 mL) was


Acetyl chloride (26 µL, 0.36 mmol) was added, the reaction was stirred at -78oC for 1

h and then allowed to warm to r.t. over 1 h. Hexane (20 mL) was added dropwise to

the rapidly stirred solution and a precipitate was filtered to give

Ru{C≡CC≡CC(O)Me}(dppe)Cp* (35) as a bright yellow crystalline powder (34 mg,

60%). Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane.

Anal. Calcd. (C42H42P2ORu): C, 69.40; H, 5.83. Found: C, 69.36; H, 5.92. IR (Nujol,

cm-1): ν(C≡C) 2048 (m), 2004 (m); ν(CO) 1710 (m). 1H NMR (C6D6): δ 7.23-7.02

(m, 20H, Ph); 2.68-2.61, 1.85-1.78 (2 x m, 2 x 2H, CH2CH2); 2.14 (s, 3H, C(O)CH3);

1.58 (s, 15H, Cp*). 13C NMR (C6D6): δ 201.57 (s, CO); 134.51-126.96 (m, Ph);

121.86, 119.52, 102.13, 90.15 (s, C1, C2, C3, C4); 94.38 (s, C5Me5); 33.35 (s,

C(O)CH3); 30.83-30.13 (m, CH2CH2); 10.83 (s, C5Me5). 31P NMR (C6D6): δ 81.7 (s,

dppe). ES-MS (+ve ion, MeOH, m/z): 725, [M]+; 635, [Ru(dppe)Cp*]+.

184

Ru{C≡CC≡CC(O)OMe}(dppe)Cp* (36)

Similarly, from Ru(C≡CC≡CH)(dppe)Cp* (51 mg, 0.07 mmol) and methyl

chloroformate (12 µL, 0.15 mmol) was obtained Ru{C≡CC≡CC(O)OMe}(dppe)Cp*

(36) as a yellow powder (20 mg, 40%). IR (Nujol, cm-1): ν(C≡C) 2008 (m), 1971 (m);

ν(CO) 1723 (m). 1H NMR (C6D6): δ 7.26-7.02 (m, 20H, Ph); 2.43-2.38, 2.13-2.06 (2

x m, 2 x 2H, CH2CH2); 1.68 (s, 3H, C(O)CH3); 1.53 (s, 15H, Cp*). 31P NMR (C6D6):

δ 80.6 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 743, [M]+; 635, [Ru(dppe)Cp*]+.

{Cp*(dppe)Ru(C≡CC≡C)}2(COCO) (37)



An aliquot of oxalyl chloride (3 µL, 0.03 mmol) was added and the reaction was

allowed to warm to r.t. over 3 h. The solvent was then evaporated to only few mls and

hexane (30 mL) was added dropwise to the rapidly stirred solution and a precipitate

was filtered to give {Cp*(dppe)Ru(C≡CC≡C)}2(COCO) (37) as an orange powder (23

mg, 55%). Anal. Calcd. (C82H78O2P4Ru2): C, 69.28; H, 5.53. Found: C, 69.57; H,

5.09. IR (CH2Cl2, cm-1): ν(C≡C) 2095 (m), 1999 (m); ν(CO) 1655 (m). 1H NMR

(C6D6): δ 7.99-6.89 (m, 24H, Ph); 2.20-2.14, 2.02-1.91 (2 x m, 2 x 2H, CH2CH2);

1.59 (s, 15H, Cp*). 13C NMR (C6D6): δ 213.74 (s, CO); 133.80-127.61 (m, Ph);

123.62, 100.28, 69.53, 55.62 (s, C1, C2, C3, C4); 90.62 (s, C5Me5); 30.01-29.75 (m,

CH2CH2); 9.94 (s, C5Me5). 31P NMR (C6D6): δ 80.1 (s, dppe). ES-MS (+ve ion,

MeOH, m/z): 1453, [M + MeOH]+; 635, [Ru(dppe)Cp*]+.

Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38)



Benzaldehyde (15 µL, 0.14 mmol) was added and the solution was stirred for 30 min.

185

The solution was then quenched with water and allowed to warm to r.t. over 2 h.

Solvent was removed to give an orange residue which was then dissolved in hexane

(60 mL) and the solution was filtered via cannula and evaporated to dryness to give

Ru{C≡CC≡CCHPh(OH)}(dppe)Cp* (38) as a bright orange crystalline powder (44

mg, 76%). Anal. Calcd. (C47H46P2ORu): C, 71.37; H, 5.87. Found: C, 70.92; H, 5.87.

IR (Nujol, cm-1): ν(OH) 3303 (w); ν(C≡C) 2106 (m), 2000 (m). 1H NMR (C6D6): δ

7.29-7.03 (m, 25H, Ph); 5.52 (s, 1H, OH); 2.58-2.56, 1.80-1.74 (2 x m, 2 x 2H,

CH2CH2); 1.66 (s, 1H, CH); 1.57 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.74-127.68

(m, Ph); 122.10, 99.22, 88.72, 65.85 (s, C1, C2, C3, C4); 93.24 (s, br, C5Me5); 79.89 (s,

C(H)PhOH); 29.90-29.29 (m, CH2CH2); 10.07 (s, C5Me5). 31P NMR (C6D6): δ 81.3 (s,

dppe). ES-MS (+ve ion, MeOH, m/z): 813, [M + Na]+; 790, [M]+; 635,

[Ru(dppe)Cp*]+.

{Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C} (39)



TCNE (9 mg, 0.07 mmol) was added and the reaction was stirred at -78oC for 30 min

and then at r.t. for 4 h. The solvent was removed and the residue was dissolved in

minimum amount of CH2Cl2 and purified by preparative TLC, eluted with CH2Cl2 to

afford a red product as {Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C} (39)

(Rf 0.33) (35 mg, 32%). Anal. Calcd. (C84H78N4P4Ru2): C, 68.65; H, 5.35; N, 3.81.

Found: C, 68.71; H, 5.79; N, 3.72. IR (CH2Cl2, cm-1): ν(CN) 2208 (w), 2075 (w);

ν(C≡C) 1967 (sh), 1866 (m). 1H NMR (CDCl3): δ 7.33-6.92 (m, 40H, Ph); 2.34-2.26,

2.18-2.14 (2 x m, 2 x 4H, CH2CH2); 1.58 (s, 30H, Cp*). 31P NMR (CDCl3): δ 81.3 (d, 3J(PP) 13 Hz, dppe), 79.9 (d, 3J(PP) 13 Hz, dppe). ES-MS (m/z): 1493 [M + Na]+;

635, [Ru(dppe)Cp*]+. Literature IR: ν(CN) 2208 (w), 2193 (w); ν(C≡C) 1973 (sh),

1959 (m). 1H NMR: δ 7.71-6.77 (m, 40H, Ph); 2.44, 1.98 (2 x m, 2 x 4H, CH2CH2);

1.51 (t, 4J(HP) 2 Hz, 30H, Cp*). 31P NMR: δ 79.9 (d, 3J(PP) 13 Hz, dppe), 76.0 (d, 3J(PP) 13 Hz, dppe). ES-MS (m/z): 1493 [M + Na]+.12

186

Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp* (40)

From the same reaction, a second blue band was collected to afford

Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp* (40) (Rf 0.27) (10 mg, 20%). Single

crystals suitable for X-ray studies were grown from CH2Cl2/hexane. Anal. Calcd.

(C46H40N4OP2Ru): C, 66.65; H, 4.87; N, 6.76. Found: C, 66.54; H, 5.44; N, 6.44. IR

(CH2Cl2, cm-1): ν(NH) 3058 (w); ν(CN) 2212 (w); ν(C≡C) 1954 (m); ν(CO) 1716

(m); ν(C=C) 1603 (w). 1H NMR (CDCl3): δ 7.62-7.23 (m, 20H, Ph); 2.74-2.68, 1.83-

1.76 (2 x m, 2 x 2H, CH2CH2); 1.68 (s, 15H, Cp*). 31P NMR (CDCl3): δ 72.9 (s,

dppe). ES-MS (+ve ion, MeOH, m/z): 659, [Ru(dppe)Cp*C2]+ ; 635, [Ru(dppe)Cp*]+.

High resolution MS (m/z): 851.1624, [M + Na]+.

Ru{C≡CC4N(NH)H(Me)C(CN)2)}(dppe)Cp* (41)

From the same reaction, a third band was collected to afford a bright orange product

Ru{C≡CC4N(NH)H(Me)C(CN)2)}(dppe)Cp* (41) (Rf 0.23) (8 mg, 16%). Single

crystals suitable for X-ray studies were grown from CH2Cl2/hexane. IR (CH2Cl2, cm-

1): ν(CH) 2926 (m); ν(CN) 2204 (m); ν(C≡C) 2024 (m); ν(C=C) 1644 (w); ν(NH)

1529 (w). 1H NMR (CDCl3): δ 7.07-7.63 (m, 20H, Ph); 2.31-2.27, 2.18-2.13 (2 x m, 2

x 2H, CH2CH2); 4.19 (s, H, NH); 2.17 (s, 3H, CH3); 1.54 (s, 15H, Cp*); 1.26 (s, H,

CH). 31P NMR (CDCl3): δ 79.7 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 816, [M]+ ;

635, [Ru(dppe)Cp*]+. High resolution MS (m/z): 817.211, [M + H]+.

Ru(C≡CC≡CC6F5)(dppe)Cp* (42)


treated with n-BuLi (91 µL, 1.6 M solution in hexane) and stirred at -78oC for 30 min.

C6F6 (17 µL, 0.14 mmol) was then added and the reaction was stirred at -78oC for 1 h

before being allowed to warm to r.t. over 3 h. Solvent was then removed to give a

residue which was then dissolved in hexane (90 mL) and the solution was filtered via

187

cannula and evaporated to dryness to give Ru(C≡CC≡CC6F5)(dppe)Cp* (42) as an

orange crystalline powder (50 mg, 80%). Single crystals suitable for X-ray studies

were grown from CH2Cl2/hexane. Anal. Calcd. (C46H39F5P2Ru): C, 64.93; H, 4.62.

Found: C, 64.72; H, 4.90. IR (Neat, cm-1): ν(C≡C) 2151 (m), 2005 (m); ν(C-F) 1376

(m), 1261 (m). 1H NMR (C6D6): δ 7.42-7.01 (m, 20H, Ph); 2.49-2.44, 1.79-1.73 (2 x

m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 134.48-127.75 (m, Ph);

126.48, 99.23, 89.37, 53.27 (s, C1, C2, C3, C4); 93.80 (t, 2J(CP) 2 Hz, C5Me5); 30.11-

29.85 (m, CH2CH2); 10.05 (s, C5Me5). 19F NMR (C6D6): δ -141.40 – -141.46 (m, 2F,

o-F); -161.79 (t, 3JFF = 22 Hz, 1F, p-F); -166.63 – -166.72 (m, 2F, m-F). 31P NMR

(C6D6): δ 80.8 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 873, [M + Na]+; 635,

[Ru(dppe)Cp*]+.

Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43)

Similarly, from Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and C6F5NO2 (30 µL,

0.14 mmol) was obtained Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp* (43) as a purple powder

(52 mg, 80%). Anal. Calcd. (C46H39F4NO2P2Ru): C, 63.01; H, 4.48; N, 1.60. Found:

C, 63.07; H, 4.52, N, 1.63. IR (Neat, cm-1): ν(C≡C) 2126 (m), 1998 (m); ν(NO) 1634

(w); ν(C-F) 1259 (m), 1016 (m). 1H NMR (C6D6): δ 7.42-7.04 (m, 20H, Ph); 2.40-

2.35, 1.83-1.78 (2 x m, 2 x 2H, CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ

133.77-126.44 (m, Ph); 100.25, 94.40, 89.38, 76.28 (s, C1, C2, C3, C4); 94.26 (t, 2J(CP) 2 Hz, C5Me5); 31.89-30.11 (m, CH2CH2); 10.22 (s, C5Me5). 19F NMR (C6D6): δ

-140.26 – -140.34 (m, 2F); -151.88 – -151.96 (m, 2F). 31P NMR (C6D6): δ 80.4 (s,

dppe). ES-MS (+ve ion, MeOH, m/z): 901, [M + Na]+; 878, [M]+; 635,

[Ru(dppe)Cp*]+.

Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44)

Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) with n-BuLi

(0.17 mL, 0.86 M solution in hexane) and C6F5CN (19 µL, 0.14 mmol) gave

188

Ru(C≡CC≡CC6F4CN-4)(dppe)Cp* (44) as a bright orange powder (58 mg, 90%).

Single crystals suitable for X-ray studies were grown from benzene/hexane. Anal.

Calcd. (C47H39F4NP2Ru): C, 65.80; H, 4.59; N, 1.63 Found: C, 65.70; H, 4.61, N,

1.63. (Neat, cm-1): ν(CN) 2214 (m); ν(C≡C) 2128 (m), 1995 (m); ν(C-F) 1380 (m),

1264 (m). 1H NMR (C6D6): δ 7.27-7.06 (m, 20H, Ph); 2.53-2.54, 2.01-1.98 (2 x m, 2

x 2H, CH2CH2); 1.53 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.68-127.63 (m, Ph);

99.39, 94.75, 75.49, 59.48 (s, C1, C2, C3, C4); 94.25 (s, C5Me5); 111.21 (s, CN);

31.95-30.04 (m, CH2CH2); 10.01 (s, C5Me5). 19F NMR (C6D6): δ -138.72 – -138.83

(m, 2F); -139.68 – -139.79 (m, 2F). 31P NMR (C6D6): δ 80.2 (s, dppe). ES-MS (+ve

ion, MeOH, m/z): 858, [M + H]+; 635, [Ru(dppe)Cp*]+.

Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45)

1st method:

Similarly, the reaction of Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) with n-BuLi

(91 µL, 1.6 M solution in hexane) and C6F5OCH3 (21 µL, 0.14 mmol) afforded

Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp* (45) as an orange powder (38 mg, 60%).

2nd method:

Ru(C≡CC≡CC6F5)(dppe)Cp* (42) (31 mg, 0.04 mmol) was dissolved in thf (10 mL)

and NaOMe (1.2 mg Na in 2 mL of MeOH, 0.05 mmol) was added. The solution was

stirred at r.t. for 16 h. The solvent was removed and the residue was dissolved in

hexane (60 mL) and then evaporated to dryness to afford Ru(C≡CC≡CC6F4OMe-

4)(dppe)Cp* (45) as an orange powder (27 mg, 87%). Single crystals suitable for X-

ray studies were grown from CH2Cl2/hexane. Anal. Calcd. (C47H42F4OP2Ru): C,

65.42; H, 4.91. Found: C, 65.39; H, 5.03. IR (Neat, cm-1): ν(C≡C) 2149 (m), 2005

(m); ν(CO) 1711 (m); ν(C-F) 1377 (m), 1263 (m). 1H NMR (C6D6): δ 7.37-7.02 (m,

20H, Ph); 3.30 (s, 3H, OCH3); 2.48-2.41, 1.79-1.74 (2 x m, 2 x 2H, CH2CH2); 1.54 (s,

15H, Cp*). 13C NMR (C6D6): δ 136.78-127.64 (m, Ph); 100.28, 92.54, 89.95, 53.26

189

(s, C1, C2, C3, C4); 93.71 (s, C5Me5); 74.00 (s, OCH3); 30.11-29.87 (m, CH2CH2);

10.08 (s, C5Me5). 19F NMR (C6D6): δ -142.07 – -142.18 (m, 2F); -161.51 – -161.62

(m, 2F). 31P NMR (C6D6): δ 80.8 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 885, [M +

Na]+; 862, [M]+; 635, [Ru(dppe)Cp*]+.

Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46)

Similarly to complex 44, from Ru(C≡CC≡CH)(dppe)Cp* (50 mg, 0.07 mmol) and

C10F8 (22 mg, 0.07 mmol) was obtained Ru(C≡CC≡CC10F7-2)(dppe)Cp* (46) as an

orange powder (24 mg, 35%). Single crystals suitable for X-ray studies were grown

from toluene/hexane. Anal. Calcd. (C50H39F7P2Ru): C, 64.17; H, 4.20. Found: C,

64.19; H, 4.19. IR (Neat, cm-1): ν(C≡C) 2138 (m), 2008 (m); ν(C-F) 1263 (m), 1197

(m). 1H NMR (C6D6): δ 7.54-6.89 (m, 20H, Ph); 2.62-2.49, 1.98-1.78 (2 x m, 2 x 2H,

CH2CH2); 1.56 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.94-127.75 (m, Ph); 126.56,

95.93, 89.49, 75.48 (s, C1, C2, C3, C4); 94.06 (t, 2J(CP) 2 Hz, C5Me5); 30.25-29.59 (m,

CH2CH2); 10.17 (s, C5Me5). 19F NMR (C6D6): δ -147.33 (dt, 3JFF = 18 Hz, 4JFF = 65

Hz, 1F); -149.28 (dt, 3JFF = 18 Hz, 4JFF = 58 Hz, 1F); -153.04 (dt, 3JFF = 18 Hz, 4JFF =

58 Hz, 1F); -158.97 (t, 3JFF = 20 Hz, 2F); -160.05 (t, 3JFF = 19 Hz, 2F). 31P NMR

(C6D6): δ 80.7 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 969, [M + MeOH]+; 937,

[M]+; 635, [Ru(dppe)Cp*]+.

[{Cp*(dppe)Ru(C≡C)2}{C4(C6F5)2H}]BF4 (47)

To a solution of Ru(C≡CC≡CC6F5)(dppe)Cp* (42) (31 mg, 0.04 mmol) in THF (15

mL) was added HBF4.O(CH2CH3)2 (6 µL, 0.04 mmol) and the reaction was stirred at

r.t. for 16 h. The solvent was removed and the blue residue was dissolved in minimum

amount of CH2Cl2 and was added to a rapidly stirred hexane solution (40 mL). A

precipitate was collected on a sintered funnel and washed with hexane to afford

[{Cp*(dppe)Ru(C≡C)2}{C4(C6F5)2H}]BF4 (47) as a bright blue powder (23 mg, 84%).

Single crystals suitable for X-ray studies were grown from CHCl3/Et2O. Anal. Calcd.

(C92H79BF14P4Ru2): C, 61.73; H, 4.45. Found: C, 61.50; H, 4.38. IR (Neat, cm-1):

190

ν(CH) 2924 (m), ν(C≡C) 1965 (m), 1897 (m); ν(C-F) 1264 (m), 1158 (m). 1H NMR


2.02 (s, 1H, H); 1.70 (s, 15H, Cp*). 13C NMR (CDCl3): δ 320.72, 201.55, 116.7,

102.07, 99.32 (s, C1, C2, C3, C4, C5); 132.59-127.36 (m, Ph); 97.77 (s, C5Me5); 30.01-

29.37 (m, CH2CH2); 9.27 (s, C5Me5). 19F NMR (CDCl3): δ -137.77 – -137.80 (m, 2F,

o-F); -143.77 – -143.64 (m, 2F, o-F); -156.59 (t, 3JFF = 22 Hz, 1F, p-F); -157.33 (t, 3JFF = 22 Hz, 1F, p-F); -163.73 – -163.61 (m, 2F, m-F); -165.19 – -165.26 (m, 2F, m-

F). 31P NMR (C6D6): δ 81.0 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 1700, [M - H]+;

635, [Ru(dppe)Cp*]+.

Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48)

To a suspension of Ru(C≡CC≡CC6F5)(dppe)Cp* (42) (31 mg, 0.04 mmol) in benzene

(15 mL) was added TCNE (5 mg, 0.04 mmol) resulting in an immediate colour

change from yellow to green. The mixture was stirred at r.t. for 7 h. The solvent was

removed and the residue was extracted in minimum CH2Cl2 and purified by

preparative TLC plates using 1:1 CH2Cl2/Et2O as eluant to give a green band (Rf 0.54)

identified as Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp* (48) (41 mg, 97%).

Anal. Calcd. (C52H39F5N4P2Ru): C, 63.79; H, 4.02; N, 5.73. Found: C, 63.43; H, 4.51;

N, 5.41. IR (Neat, cm-1): ν(CN) 2211 (m); ν(C≡C) 1964 (m); ν(C-F) 1262 (m), 1196

(m). 1H NMR (CDCl3): δ 7.45-7.15 (m, 20H, Ph); 2.78-2.69, 2.31-2.23 (2 x m, 2 x

2H, CH2CH2); 1.53 (s, 15H, Cp*). 13C NMR (CDCl3): δ 132.88-128.29 (m, Ph);

154.01, 139.14, 92.81, 78.91 (s, C1, C2, C3, C4); 116.53, 116.33 (2 x s, 2 x CN);

111.30, 110.62 (2 x s, 2 x CN); 97.37 (t, 2J(CP) 2 Hz, C5Me5); 29.98-29.63 (m,

CH2CH2); 9.95 (s, C5Me5). 19F NMR (CDCl3): δ -159.86 – -160.28 (m, 2F, m-F); -

148.54 (t, 3JFF = 22 Hz, 1F, p-F); -135.50 – -136.00 (m, 2F, o-F). 31P NMR (CDCl3): δ

81.1 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 1001, [M + Na]+; 635, [Ru(dppe)Cp*]+.

Chapter Five

Some Chemistry Involving Azide

Reagents

192

5.1. Introduction

The molecules produced by living systems on Earth have always fascinated and

inspired synthetic chemists. Following Nature’s lead, they have endeavored to

develop a set of highly reliable and selective reactions for the rapid synthesis of useful

new compounds. One of the most rapidly growing areas of this research is the

approach named “Click Chemistry”. This concept was introduced by Kolb, Finn and

Sharpless in 2001 and it was defined as a new way of categorising organic reactions

that are modular in nature, highly efficient (high yields), mild and stereospecific.153

The required process characteristics involve simple reaction conditions, readily

available starting materials and reagents, the use of no solvent or a solvent that is

benign or easily removed and simple product isolation. In summary, a “Click”

reaction is easy to perform and work up, with a high yield.153 Click Chemistry not

only allows particular materials to be prepared, it also opens up new avenues for

materials in general to be prepared more efficiently. To date, Click Chemistry has

been used in a broad range of applications, including functionalising biological

molecules154 and monolayers,155-157 advance drug discovery,158-160 solubilising carbon

nanotubes,161 synthesising various dendrimers162,163 and polymers.164,165 These

examples illustrate the diverse range of functional groups and conditions that are

tolerated by Click Chemistry and demonstrate its powerful possibilities.

The most well documented Click reaction is the Huisgen 1,3-dipolar cycloaddition of

terminal alkynes with an azide to generate a 1,2,3-triazole. The potential of organic

azides as highly energetic functional groups for synthesising heterocyclic compounds

was highlighted and their dipolar cycloaddition with alkynes was placed among the

top reactions fulfilling the Click criteria.166,167

However, the cycloaddition of azides with terminal acetylenes was first described to

require elevated temperatures for prolonged periods. The cycloaddition was non-

regiospecific with two possible isomers (1,4 and 1,5) being formed (Scheme

108).166,167 Some control of regiospecificity was obtainable as electron-withdrawing

groups on the acetylene favour production of 1,4 products, and electron-withdrawing

groups on the azide favour production of the 1,5 isomer. However, mixtures were

193

obtained and exclusive production of one isomer by cycloaddition proved elusive.168

Thus, this reaction in this form was not suitable for the requirements of a Click

reaction.

N N N

R160 - 120 oC

hours - days

NN

N

R2

R1

+ NN

NR1

R2

+ H R2

1,4 regioisomer 1,5 regioisomer

Scheme 108: The 1,3-cycloaddition of an azide and terminal alkyne to give 1,2,3-triazoles

The turning point for the Huisgen 1,3-dipolar cycloaddition came with the discovery

in 2002 that copper(I) catalysis accelerates the reaction of azides with terminal

alkynes and also promotes the regiospecificity with exclusive production of the 1,4-

triazole isomer (Scheme 109).166,167,169 The Cu-catalysed azide-alkyne 1,3-dipolar

cycloaddition (CuAAC) is believed to occur by formation of a three-coordinate

copper(I) acetylide that reacts with an azide coligand, proceeding through a carbenoid

intermediate to yield a C-bound copper(I) triazolate. Protonation at carbon affords the

final 1,2,3 triazole.

N N N

R1

NN

N

R2

R1

+ H R2

Cu catalyst

r.t., min - h

Scheme 109: Copper(I)-mediated cycloaddition to give the 1,4-regioisomer

Since its discovery, the copper-catalysed azide-alkyne 1,3-dipolar cycloaddition has

been established as one of the most reliable means for the covalent assembly of

complex molecules. It has enabled a number of applications in medicinal

chemistry,160,170 materials and surface science167,171,172 and molecular biology.173,174

194

The popularity of this method can be explained by several reasons. First, the reaction

is not significantly affected by the steric and electronic properties of the groups

attached to the azide and alkyne reactive centers. The reaction is unaffected by water

and most organic and inorganic functional groups, thus eliminating the need for

protecting-group chemistry. The rate of the Cu-catalysed process is approximately 107

times that of the uncatalysed version, making the reaction conveniently fast in the

temperature range of 0 to 25oC.167 Furthermore, the 1,2,3-triazole unit that results

from the reaction has several advantageous properties: high chemical stability, an

aromatic character and a good hydrogen-bond accepting ability.

However, it must be noted that the need for azides can be a drawback to the reaction.

Azides are highly energetic materials and potentially explosive. This is particularly so

of low-molecular-weight azides which should be handled with extreme caution.

Furthermore, sodium azide has a similar toxicity to sodium cyanide. Other sources of

risk are the use of metals and halogenated solvents with azides which make the

knowledge of working safely with azides imperative. Furthermore, additional research

has revealed that although the speed of the reaction has improved over non-copper

catalysed cycloaddition, the reaction can appear rather slow with overnight reaction

times at room temperature frequently required. A variant to the method involves the

heating of solutions in order to obtain faster reaction times, but this may not be

suitable when biological conjugation is desired.

One example of the application of the copper-catalysed 1,3-dipolar cycloaddition

involves the reaction of sulfonyl azides with alkynes as shown in Scheme 110.167

Depending on the conditions and reagents, the formation of different products may be

observed. For example, N-sulfonylazides are converted to N-sulfonylamidines when

the reaction is conducted in the presence of amines while, under aqueous conditions,

N-acetylsulfonamides are the major products. However, when the reaction is

performed in chloroform in the presence of 2,6-lutidine, N-sulfonyltriazoles are

obtained in good yields.

195

N N N

R2SO2

NN

N

R1

SO2R2

+

H R1

CuI, CHCl3

12 h, 0oC

R1

NHSO2R2

O

N

R1

R3 R4

NSO2R2

CuI, Pyridine

MeCN, r.t., 16h

R3 NR4

CuI, H2O-CHCl3

12 h, r.t.

2,6-lutidineR1 = Ph, TMS, CO2EtR2 = CH2Ph, CH3R3 = Ph, tBuR4 = Ph, CH3OCH2

Scheme 110: The reaction of sulfonyl azides with alkynes

Further examples involve the copper(I)-catalysed 1,3-dipolar cycloaddition of

terminal alkynes and organic azides to give 1,4-disubstituted 1,2,3 triazoles in very

good yields (Scheme 111).175

N N N

R1

H R2+N

NN

R2

R1CuSO4.5H2O

H2O/ tBuOHr.t., 6 - 12 h

R1 = Ph(CH2)2O(CO); R2 = Ph (92%)R1 = (CO)OH, R2 = (CH2)2OPh (88%)

Scheme 111: Copper(I)-catalysed 1,3-dipolar cycloadditions of terminal alkynes

Recently, an analogous method to the Huisgen dipolar addition of azides and alkynes

has been developed and involves a metal-mediated cycloaddition. One such example

involves the cycloaddition of aryl azides to alkynes in the presence of a {Cp*RuCl}4

catalyst (Scheme 112). It was found that such reactions give higher yields, cleaner

products and shorter reaction times than the copper(I) catalysed reaction. In addition,

the copper(I)-catalysed process produces 1,4-disubstituted 1,2,3 triazoles whereas this

new method allows the formation of 1,5-disubstituted 1,2,3 triazoles.

196

N3+

Cl

N

N

[Cp*RuCl]4

DMFCl N N

NN

N

Scheme 112: Ruthenium-mediated cycloaddition

The [3 + 2]-cycloaddition of (triphenylphosphine)gold(I) azide with terminal alkynes

superficially resembles the copper-catalysed chemistry. The reaction proceeds with

the preformed azide complex to give the organo-gold product (Scheme 113). 176

H R N

NN

R

H

(Ph3P)AuN3 Au(PPh3) +Toluene

r.t.

R = Ph (78%)R = p-C6H5F (74%)

Scheme 113: The reaction of AuN3(PPh3) with terminal alkynes

In a variant of this reaction, triazolato complexes can be generated by cycloaddition of

gold(I) alkynyls to azides. Hence, gold(I) alkynyl complexes react with trimethylsilyl

azide at room temperature in the presence of MeOH to afford new gold complexes in

very good yields (Scheme 114).176

(Ph3P)Au R N

NN

R

H

(Ph3P)AuTMSN3+MeOH

r.t.

R = Ph (71%); p-C6H4F (87%) t-Bu (85%); p-Tol (90%)

Scheme 114: Reaction of gold(I) alkynyl with TMSN3

197

In addition, the synthesis of a ruthenium azide complex was reported in 2003. The

reaction of the chlororuthenium complex RuCl(dppe)Cp with NaN3 in ethanol at

reflux for 4 h gave the ruthenium complex Ru(N3)(dppe)Cp (Scheme 115).177

ClRu

Ph2PPPh2

+ NaN3EtOH

∆N3Ru

Ph2PPPh2

Scheme 115: The synthesis of Ru(N3)(dppe)Cp

This complex was further reacted with alkynes and was shown to undergo

cycloaddition reactions to produce triazolates. The reaction is suggested to proceed by

[3 + 2]-cycloaddition of the C≡C bond to the azido group. Two examples are shown

in Scheme 116. The first involves the reaction of Ru(N3)(dppe)Cp with methyl

propiolate while the second is with dimethyl acetylenedicarboxylate. Both reactions

proceed at room temperature in CH2Cl2 and afford the triazole complexes in very

good yields.177

H CO2CH3

H3CO2C CO2CH3

N

N

N

H

Ru

Ph2P PPh2 CO2CH3

N3Ru

Ph2P PPh2

CH2Cl2, r.t. 8 h

N

N

N

CO2CH3

Ru

Ph2P PPh2 CO2CH3

73%

90%

CH2Cl2, r.t. 8 h

Scheme 116: The synthesis of Ru{N3C2HCO2Me}(dppe)Cp and Ru{N3C2(CO2Me)2}(dppe)Cp

198

Furthermore, in 2004 our group reported that the chlororuthenium complex

RuCl(dppe)Cp* reacts with TMSC≡C(TMS)C=NNHTs in MeOH and in the presence

of KF. After heating at reflux for 3 h, the pyrazole complex

Ru{C3H2NNTs}(dppe)Cp* was obtained (Scheme 117).178

KF / MeOHRu

Ph2P PPh2

NC

C

CN

H

HTs

Ru

Ph2P PPh2

Cl + TMS C C C

N

TsHN

TMS∆

Scheme 117: The synthesis of Ru{C3H2NNTs}(dppe)Cp*

199


The primary aim of this work was to react various diynyl ruthenium(II) complexes of

general formula [Ru](C≡CC≡CR) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp; R = H,

TMS, Au(PPh3)) with the three different azide reagents TMSN3, TsN3 and

AuN3(PPh3). It was suggested that a Huisgen 1,3-dipolar cycloaddition of the alkynes

with the azides would take place to generate 1,2,3-triazoles as shown in Scheme 118.

N N NR1

C C

NN

NR1

CCR2 [Ru]+C C C C R2[Ru] C C R2[Ru] CC

NN

NR1

[Ru] = Ru(dppe)Cp*; Ru(PPh3)2CpR1 = TMS, Ts, Au(PPh3)R2 = H, TMS, Au(PPh3)

1,4 regioisomer 1,5 regioisomer

Scheme 118: Expected reaction of diynyl ruthenium(II) complexes with azides

200


5.3.1. Reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = TMS, H, Au(PPh3))

First, the reaction of Ru(C≡CC≡CH)(dppe)Cp* with TMSN3 in THF at room

temperature afforded the complex Ru{C2N3(CN)(CH3)}(dppe)Cp* (49) as a yellow

powder in 37% yield (Scheme 119). This complex was also obtained from the

reaction of Ru(C≡CC≡CTMS)(dppe)Cp* with TMSN3 in a similar yield.

C C C CRu

Ph2P PPh2

RTMSN3

THFCH3

C

Ru

Ph2P PPh2

C

CN

N

N

N

R = H, TMS(49)


Complex 49 was characterised by 1H, 31P and 13C NMR, IR. Solution IR spectroscopy

revealed one ν(C≡N) band at 2218 cm-1 and one ν(C=N) band at 1724 cm-1. The

Ru(dppe)Cp* ligand shows all characteristic peaks in the 1H, 31P and 13C NMR

spectra. The addition of the methyl group is confirmed by the presence of a singlet at

δ 1.46 in the 1H NMR spectrum. In the 13C NMR spectrum, the methyl group gives a

singlet at δ 58.74 while the CN group gives a singlet at δ 113.91. The two carbons of

the ring are assigned to two singlets at δ 147.24 and 135.45. The ES-MS of 49 shows

ions corresponding to [M + H]+ at m/z 743 and at m/z 635 for [Ru(dppe)Cp*]+.


found was C40H42N4P2RuNa which corresponds to a [M + Na]+ at m/z 765.2112. The

calculated value is 765.1825. This value is consistent with the X-ray structure

obtained, confirming the formulation of complex 49.

201

Single crystals suitable for X-ray studies were grown from CH2Cl2/hexane. The


angles are given in Table 23. The Ru(dppe)Cp* fragment has the expected geometry,

with Ru-P(1) and Ru-P(2) equal to 2.290(6) Å and 2.291(6) Å, respectively and the

Ru-C(Cp*) distances of 2.219(2) - 2.246(2) Å. The Ru-N(1) bond length of 2.106(1)

Å is slightly longer than a ruthenium carbon single bond (2.01 Å). The C(31)-N(31)

bond length of 1.149(3) Å is consistent with being a C≡N triple bond. The distances

of N(5)-C(4) [1.336(3) Å] and N(2)-C(3) [1.358(3) Å] are consistent with being N-C

single bond. The N(1)-N(2) bond length [1.321(2) Å] is nearly equal to N(1)-N(5)

[1.358(2) Å]. The angle C(3)-C(31)-N(31) in 49 is 177.4(3) o which is essentially

linear.


202


Ru-N(1) 2.106(1) Ru-N(1)-N(5) 122.7(1)

Ru-P(1) 2.290(6) Ru-N(1)-N(2) 124.8(1)

Ru-P(2) 2.291(6) P(1)-Ru-P(2) 83.40(2)

Ru-C(Cp*) 2.219(2) - 2.246(2) P(1)-Ru-N(1) 86.05(5)

Ru-C(Cp*) (av.) 2.235(2) P(2)-Ru-N(1) 87.31(5)

N(1)-N(2) 1.321(2) C(3)-C(31)-N(31) 177.4(3)

N(1)-N(5) 1.358(2)

N(5)-C(4) 1.336(3)

N(2)-C(3) 1.358(3)

C(3)-C(4) 1.385(3)

C(31)-N(31) 1.149(3)


Structural analysis of complex 49 shows that there is one extra nitrogen, the presence

of a CH3 group and that the Ru(dppe)Cp* ligand is connected to a nitrogen atom. Few

pathways for the formation of 49 can be proposed.

First, it can be assumed that the [3 + 2]-cycloaddition reaction occurred either on the

terminal carbons or on the carbons adjacent to the Ru(dppe)Cp* ligand and gave the

two products shown in Figure 67. From there, either molecule could have undergone

fragmentations of various C-C bond and C-N bonds and rearrangement to give

complex 49. However, at present it is not clear how these processes may have

happened and how the C≡N and CH3 groups were formed.

C C

NN

NTMS

C C R[Ru] CC

NN

NTMS

CCR [Ru]

1,4 regioisomer 1,5 regioisomer Figure 67: First possibility for the formation of 49

203

A second proposal is that the [3 + 2]-cycloaddition reaction did not occur and that

instead the azide group added directly to the Ru(dppe)Cp* moiety followed by a

cleavage of the carbon chain. The carbon atoms C2 and C3 of the chain then re-

attached to the nitrogen atoms (Scheme 120). From this intermediate, it can be

assumed that the CH might undergo reduction to give the CH3 moiety but the source

of the extra nitrogen is not known.

C C C C R[Ru]

[Ru] = Ru(dppe)Cp*R = H, TMS

N N NTMS

[Ru] N N N

TMS

+ C C C C R

CR

C

[Ru]C

CN

N

N

Scheme 120: Second possibility for the formation of 49

A third proposal involves the double addition of TMSN3 to the carbon chain. This

process can either be one addition after the other or the double addition can occur

simultaneously. The intermediate obtained is shown in Scheme 121.

N N NTMS

C C C C R[Ru]

[Ru] = Ru(dppe)Cp*R = H, TMS

NNNTMS

C C R[Ru] CC

NN

NTMS

NN

NTMS

Scheme 121: Third possibility for the formation of 49 From this intermediate, the molecule might undergo rearrangement with breaking of

N-N and N-C bonds. A loss of dinitrogen might also occur and could explain the

presence of the extra nitrogen. This could also explain the presence of the two double

bonds in complex 49. This intermediate also induces the migration of the

Ru(dppe)Cp* group onto one of the nitrogens. A possible non-planar rearrangement

of the molecule can be proposed to allow close proximity of the nitrogen atom and the

Ru(dppe)Cp* group. However, it is not obvious how these fragmentations and

204

rearrangements might occur. In addition, it can be suggested that the CH3 group

comes from the THF used as solvent in both reactions. It must be noted that when the

reaction was done in different solvents such as toluene, benzene and hexane, this

product was not obtained. Furthermore, when the reaction was attempted with two

equivalents of TMSN3, the same product was obtained in a better yield of 45%. This

could indicate that the product is more easily formed in the presence of an excess of

azide reagent.

Furthermore, the reaction of Ru(C≡CC≡CH)(dppe)Cp* with another azide reagent

AuN3(PPh3) was attempted. After stirring at 50oC for 24 h in THF, a yellow powder

was obtained as Ru{C2N3(CH3)H}(dppe)Cp* (50) in 41% yield (Scheme 122). It was

found that if the diyndiyl complex Ru(C≡CC≡C[Au(PPh3)])(dppe)Cp* was treated

with TMSN3 and stirred at room temperature for 48 h, the same product was obtained

in a lower yield of 35%.

AuN3(PPh3)

C C C CRu

Ph2P PPh2

RTMSN3

CH3

H

Ru

Ph2P PPh2

C

CN

N

N

R = H, Au(PPh3) (50)

or

Scheme 122: First method for the synthesis of complex 50

Complex 50 displayed the expected resonances in the NMR analysis, IR and ES-MS.

The characteristic peaks for the Ru(dppe)Cp* ligand are present in the 1H, 31P and 13C

NMR spectra. In the 1H NMR spectrum, two singlets are also present at δ 2.18 and

1.26 for the protons of the CH and the CH3 groups, respectively. In the 13C NMR

spectrum, three singlets are present, at δ 133.7 for C-CH3, at 130.92 for the CH unit

and at 58.63 for the CH3 group. In the infrared spectrum, one band was present at

1712 cm-1 for the ν(C=N) stretch. Finally, the ES-MS of 50 shows a peak for the [M]+

ion at m/z 717 and one fragmentation ion corresponding to [Ru(dppe)Cp*]+ at m/z

635.

205


found was C39H43N3P2Ru which corresponds to a [M]+ at m/z 717.1967 (calcd.

717.1975), confirming the formulation of complex 50.

It must be noted that complex 50 has a very similar backbone to that of complex 49,

the only difference is the presence of a CH group instead of a C≡N group in 49.

Hence, the mechanism of the reaction for the formation of 50 can be suggested to be

very similar to that for the formation of 49. However, the azide reagents used have

different properties (Au(PPh3) versus TMS) and might induce different chemical

behaviour which can explain the absence of the C≡N group in 50. Furthermore, the

two pathways described for the synthesis of 50 converge and give the same product.

This could imply that the presence of the Au(PPh3) unit has an important role in these

reactions. The reaction was also attempted with two equivalents of AuN3(PPh3)

giving the same product in a better yield of 44%. It could again be suggested that an

excess of azide reagent facilitates the synthesis of complex 50.

In addition, Ru(C≡CC≡CH)(dppe)Cp* reacts in toluene with a third azide reagent

TsN3 to afford the complex Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp* (51) as a bright

yellow crystalline powder in 43% yield (Scheme 123).

C C C CRu

Ph2P PPh2

HTsN3

TolueneN C

NN S

N

O

O

CH3

SO

O

CH3

Ru

Ph2P PPh2

(51)

Scheme 123: Synthesis of complex 51

206

This complex was characterised by spectroscopic techniques. A ν(C-H) band at 2977

cm-1, a ν(C≡N) band at 2229 cm-1, a ν(C=N) band at 1703 cm-1 and a ν(SO) band at

1179 cm-1 were observed in the infrared spectrum. The 1H spectrum of 51 contained

all the typical resonances for the aromatic protons, the -CH2CH2- bridge of dppe and

the Cp* ligand. The aromatic protons of the Ts groups were found as a pair of

doublets at δ 7.68 (2J(HH) 8 Hz) and 6.61 (2J(HH) 8 Hz) while the methyl group was

found as a singlet at δ 2.25. The pyrazole ring proton gives a singlet at δ 1.23.

Similarly, the 13C NMR spectrum of 51 has characteristic peaks for the Ru(dppe)Cp*

ligand. The Ts groups are confirmed by the presence of different peaks: four singlets

at δ 145.17, 144.89, 138.84 and 134.87 for C6H4, and a singlet at δ 21.14 for the CH3

group. The three ring carbons were found at δ 116.63, 122.85 and 58.52 but could not

be assigned to individual carbons. The ES-MS of complex 51 contained [M + Na]+ at

m/z 1073, [M + H]+ at m/z 1051, and [Ru(dppe)Cp*]+ at m/z 635.


found was C54H55N4O4P2RuS2 which corresponds to a [M + H]+ at m/z 1051.224. The

calculated value is 1051.219. The molecular formula is consistent with the X-ray

structure obtained, confirming the formulation of complex 51.

Single crystals suitable for X-ray studies were grown from THF/hexane. The ORTEP

diagram of 51 is shown in Figure 68 and selected bond distances and angles are given

in Table 24. The Ru(dppe)Cp* fragment has the expected geometry, with Ru-P(1) and

Ru-P(2) bond lengths of 2.300(1) Å and 2.305(1) Å, respectively and the Ru-C(Cp*)

distances of 2.206(4) - 2.226(4) Å. The Ru-N(1) bond length of 2.006(3) Å is smaller

than the value obtained previously with complex 49 and is very close to a ruthenium

carbon single bond (2.01 Å). The distances of N(7)-C(3) [1.332(6) Å] and N(6)-C(5)

[1.373(6) Å] are consistent with being N-C single bonds. The C(2)-C(3), C(3)-C(4)

and C(4)-C(5) distance of 1.438(6) Å, 1.426 (6) Å and 1.368(6) Å respectively, are

consistent with the presence of C-C single bonds. The angles Ru-N(1)-C(2)

[173.4(4)o] and N(1)-C(2)-C(3) [179.2(5) o] are nearly linear.

207



Ru-N(1) 2.006(3) Ru-N(1)-C(2) 173.4(4)

Ru-P(1) 2.300(1) N(1)-C(2)-C(3) 179.2(5)

Ru-P(2) 2.305(1) P(1)-Ru-P(2) 83.2(4)

Ru-C(Cp*) 2.206(4) - 2.226(4) P(1)-Ru-N(1) 85.1(1)

Ru-C(Cp*) (av.) 2.217(4) P(2)-Ru-N(1) 85.1(1)

N(1)-C(2) 1.147(5) C(4)-C(3)-N(7) 113.9(4)

C(2)-C(3) 1.438(6) N(7)-N(6)-S(6) 116.5(4)

C(3)-C(4) 1.426(6)

C(4)-C(5) 1.368(6)

C(3)-N(7) 1.332(6)

C(5)-N(6) 1.373(6)

N(6)-N(7) 1.340(5)

N(4)-S(4) 1.566(4)

S(4)-O(41) 1.459(3)


208

The analysis of the structure of 51 shows that two Ts groups are present and hence

indicates that a double addition has occurred. The intermediate shown in Scheme 124

can be proposed and two possible pathways for its formation can be suggested. First

the reaction starts with the addition of the two azides followed by fragmentations and

rearrangements. In the second case, there is a [3 + 2]-cycloaddition of only one azide,

followed by fragmentation and rearrangements. The second azide is then added and

further rearrangements might take place to give complex 51. It must also be noted that

in complex 51, a nitrogen atom is connected between the Ru(dppe)Cp* ligand and a

carbon atom. The mechanistic pathways for the fragmentations and rearrangements of

the intermediate to give complex 51 are not obvious.

N N NTs

C C C C H[Ru]

[Ru] = Ru(dppe)Cp*

NNNTs

C C H[Ru] CC

NN

NTs

NN

NTs

Scheme 124: Proposed first step for the formation of 51 In summary, the reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = H, TMS, Au(PPh3)) with

TMSN3, TsN3 and AuN3(PPh3) generated products with three different structural

features. All the data are summarised in Table 25. Only suggestions can be proposed

on the formation of these complexes. The Click reaction seems to occur as the [3 + 2]-

cycloaddition of the azide(s) onto the alkyne is suggested as a possible first step. But,

it appears that the reaction does not stop at this point suggesting that the intermediates

must be very reactive and undergo further chemistry. This second step is not obvious

and more experiments should be done to try to understand what is happening then.

One suggestion will be the isotopic labeling in order to identify which parts of the

reagents are present in the final products. Labelling of the nitrogen atoms of the azide

reagent might help understand if there is double substitution in the case of complexes

49 and 50. Similarly, the carbon atoms of the carbon chain of

Ru(C≡CC≡CR)(dppe)Cp* can be specifically radiolabelled to determine if the

209

carbons present in the final products 49, 50 and 51 are from this starting material.

Furthermore, in order to understand how the CH3 group is formed in complexes 49

and 50, THF-d8 could also be used as solvent and if deuterium atoms are present on

the carbon, this will indicate that it is formed due to this solvent. If not, this

hypothesis could be refuted. Another method to try to describe the presence of this

group or the H atom on complex 50 will be to do the reaction with

Ru(C≡CC≡CD)(dppe)Cp* as starting material in THF and analyse where the

deuterium atom is present on the final product.

210


Complex IR (cm-1)

1H NMR (δ)

13C NMR (δ)

31P NMR (δ)

ES-MS (m/z)

49 ν(C≡N) 2218 (m) ν(C=N) 1724 (m)

7.47-7.08 (m, 20H, Ph); 2.37-2.31, 2.13-2.11 (2 x m, 2 x 2H, CH2CH2); 1.46 (s, 3H, CH3); 1.26 (s, 15H, Cp*)

133.09-127.60 (m, Ph); 147.24 (s, C-CN); 135.45 (s, C-CH3); 113.91 (s, CN); 91.88 (s, C5Me5); 58.74 (s, CH3); 28.39–28.10 (m, CH2CH2); 9.82 (s, C5Me5)

75.1 (s, dppe) 743, [M+ H]+;

635, [Ru(dppe)Cp*]+

50 ν(C=N) 1712 (m) 7.48-6.87 (m, 20H, Ph); 3.14-3.10, 2.73-2.69 (2 x m, 2 x 2H, CH2CH2); 2.18 (s, H, CH); 1.64 (s, 15H, Cp*); 1.26 (s, 3H, CH3)

134.52-127.62 (m, Ph); 133.7 (s, C-CH3); 130.92 (s, CH); 93.02 (s, C5Me5); 58.63 (s, CH3); 30.10–29.77 (m, CH2CH2); 10.28 (s, C5Me5)

75.0 (s, dppe) 717, [M]+; 635, [Ru(dppe)Cp*]+

51 ν(C-H) 2977 (m) ν(C≡N) 2229 (m) ν(C=N) 1703 (m) ν(SO) 1179 (m)

7.68 (d, 2J(HH) 8 Hz, 2H, C6H4); 7.23-6.95 (m, 20H, Ph); 6.61 (d, 2J(HH) 8 Hz, 2H, C6H4); 2.25 (s, 6H, CH3); 2.04-1.99, 1.89-1.85 (2 x m, 8H, CH2CH2); 1.49 (s, 15H, Cp*); 1.23 (s, H, CH)

145.17, 144.89, 138.84, 134.87 (4 x s, C6H4); 130.39-127.06 (m, Ph); 116.63 (s, C); 122.85 (s, C); 92.27 (s, C5Me5); 58.52 (s, C); 28.77-28.18 (m, CH2CH2); 21.14 (s, CH3); 9.79 (s, C5Me5)

74.3 (s, dppe) 1073, [M + Na]+; 1051, [M + H]+; 635, [Ru(dppe)Cp*]+

211

5.3.2. Reactions of Ru(C≡CC≡CH)(PPh3)2Cp

The complex Ru(C≡CC≡CH)(PPh3)2Cp is easily accessible and it was suggested that

this complex should also react with azide reagents and possibly undergo Click

Chemistry. However, it was also assumed that these reactions could behave as shown

in the previous Section since the only difference is the metal ligand moiety

(Ru(PPh3)2Cp vs Ru(dppe)Cp*). This could help understand how the previous

reactions proceeded.

Therefore, the diynyl complex Ru(C≡CC≡CH)(PPh3)2Cp was reacted with the azide

reagent TMSN3 in THF at room temperature for 72 h to give the complex

Ru(N3)(PPh3)2Cp (52) as a yellow-brown powder in 57% yield. Complex 52 was also

obtained from the reaction of Ru(C≡CC≡CH)(PPh3)2Cp with TsN3 stirred in THF at

room temperature for 72 h in slightly higher yield (60%) (Scheme 125).

THF

TMSN3

N3Ru

Ph3P PPh3

Ru

Ph3P PPh3

C C C C HTsN3

or

(52)

Scheme 125: Two methods for the synthesis of complex 52

Complex 52 was characterised by 1H, 31P and 13C NMR, IR and ES-MS. One ν(N3)

band at 1981 cm-1 was observed in the infrared spectrum. In the 1H NMR spectrum, a

multiplet at δ 7.70-6.79 for the phenyl groups and a singlet at δ 4.26 which

corresponds to the cyclopentadienyl Cp ligand are present. In the 13C NMR spectrum,

one multiplet at δ 134.04-125.97 was assigned to the phenyl groups while the singlet

at δ 86.03 was found for the carbons of the Cp ligand. The 31P NMR spectrum of 52

has one resonance at δ 43.3 assigned to the coordinated phosphorus atoms on the

ruthenium. Further characterisation of 52 was obtained from the ES-MS which

contained ions corresponding to [M]+ at m/z 733, and fragmentation ions at m/z 691

for [Ru(PPh3)2Cp]+ and at m/z 429 for [Ru(PPh3)Cp]+.

212

These results indicate that Ru(C≡CC≡CH)(PPh3)2Cp does not undergo [3 + 2]-

cycloaddition nor enter into the reactions described in Section 5.3.1. A proposed

mechanism for these reactions is shown below. It involves the direct attack of the

azide reagent onto the Ru(PPh3)2Cp moiety and cleavage of the carbon chain. This is

the simplest explanation suggested at this time and it should be noted that the -C≡CC≡CH moiety appears to be easier to cleave than first thought (Scheme 126).

C C C C HRu

Ph3P PPh3 NNNR

R = TMS, Ts

Ru

Ph3P PPh3

N3 + C C C C H

(52)

Scheme 126: Proposed mechanism for the formation of 52

In summary, the reactions of Ru(C≡CC≡CH)(PPh3)2Cp with TMSN3 and TsN3 both

gave the ruthenium complex Ru(N3)(PPh3)2Cp (52). These results differ from the

reactions of Ru(C≡CC≡CH)(dppe)Cp* with TMSN3 and TsN3 and it can be assumed

that the presence of the two different ruthenium metal-ligand moiety (Ru(PPh3)2Cp vs

Ru(dppe)Cp*) is the influential factor for this divergence. In addition, complex 52

shows a similar structure to the ruthenium complex Ru(N3)(dppe)Cp reported by

Chang and co-workers.177

5.3.3. Reactions of Ru(C≡CH)(dppe)Cp*

Following the previous results, the reactions of the complex Ru(C≡CH)(dppe)Cp*

with various azide reagents were also investigated. First, Ru(C≡CH)(dppe)Cp* was

reacted with TMSN3 in toluene at room temperature for 72 h. The complex

Ru(N3)(dppe)Cp* (53) was obtained as a yellow powder in 63% yield. The reaction of

Ru(C≡CH)(dppe)Cp* with TsN3 in THF at room temperature for 48 h gave the same

complex in 65% yield (Scheme 127).

213

TsN3 in THF

C C HRu

Ph2P PPh2

TMSN3 in tolueneRu

Ph2P PPh2

N3

(53)

or

Scheme 127: Two methods for the synthesis of complex 53

The 1H NMR spectrum of 53 contained all characteristic peaks for the Ru(dppe)Cp*

ligand with the aromatic protons found as a multiplet at δ 7.25-7.07, the CH2CH2

bridge in dppe as two multiplets at δ 2.37-2.35 and 1.98-1.85 and the protons of the

Cp* ligand as a singlet at δ 1.53. The 31P NMR spectrum shows one singlet at δ 77.7

assigned to the phosphorus nuclei of the Ru(dppe)Cp* fragment. In the IR spectrum,

one ν(N3) band was present at 2035 cm-1. Finally the ES-MS contains [M + Na]+ at

m/z 700 and [Ru(dppe)Cp*]+ at m/z 635.

It should be pointed out that another member of our group carried out the reaction of

Ru(C≡CH)(dppe)Cp* with AuN3(PPh3) and also obtained complex 53.150 All

spectroscopic data obtained agreed with those reported for 53. Single crystals suitable

for X-ray studies were grown and showed that the azide fragment is composed of

N=N double bonds. The molecule is also bent as the angle Ru-N(1)-N(2) is equal to

122.8(8) o as shown in Figure 69.150

Ru

Ph2P PPh2

N

NN

Figure 69: Representation of 53

214

These reactions gave a similar result to the reaction of Ru(C≡CC≡CH)(PPh3)2Cp with

TMSN3 and TsN3 and indicate that Ru(C≡CH)(dppe)Cp* does not undergo [3 + 2]-

cycloaddition. Complexes 53 and 52 only differ by the ligands on the ruthenium atom,

thus it can expected that they will have a similar structure. They can also be related to

the ruthenium complex Ru(N3)(dppe)Cp.177

Furthermore, these reactions could give an indication of what is happening in the

reactions of Ru(C≡CC≡CR)(dppe)Cp* (R = H, TMS, Au(PPh3)) with azides described

in Section 5.3.1. It is possible that complex 53 is formed in these cases. It has then

undergone further chemistry maybe due to the presence of the by-products in solution

and the complexes 49, 50 and 51 are obtained.

215

5.4. Conclusions

In this chapter, the reactions of diynyl ruthenium(II) complexes

Ru(C≡CC≡CR)(dppe)Cp* (where R = H, TMS, Au(PPh3)) with three readily

available azide reagents (TMSN3, TsN3 and AuN3(PPh3)) afforded three different

products, which were characterised spectroscopically and by X-ray analyses. The

mechanisms of formation of these complexes are not apparent but it was suggested

that a Huisgen 1,3-alkyne-azide cycloaddition could have taken place to generate

1,2,3-triazoles as intermediates which then further react to afford complexes 49, 50

and 51.

In addition, the reactions of the complex Ru(C≡CC≡CH)(PPh3)2Cp with two azides

gave the complex Ru(N3)(PPh3)2Cp (52). A similar product was obtained when

Ru(C≡CH)(dppe)Cp* was reacted with azide reagents, generating Ru(N3)(dppe)Cp*

(53) in a good yield. These complexes only differ by the ruthenium moiety and should

have analogous structures. It was also suggested that they were formed from a similar

mechanism.

216

5.5. Experimental

General experimental conditions are detailed on page viii. Reagents: The compounds Ru(C≡CC≡CH)(dppe)Cp*,30 Ru(C≡CC≡CTMS)(dppe)Cp*,30

Ru(C≡CC≡CH)(PPh3)2Cp,30 AuN3(PPh3),179 Ru(C≡CC≡C[Au(PPh3)])(dppe)Cp*,30

Ru(C≡CH)(dppe)Cp*,47 TsN3,180 were all prepared by standard literature methods.

TMSN3 was used as received from Sigma-Aldrich. Despite several attempts accurate

elemental analyses could not be obtained for complexes 49 - 51 and 53.

Ru{C2N3(CN)(CH3)}(dppe)Cp* (49)

1st method:


treated with TMSN3 (10 µL, 0.07 mmol) and stirred at r.t. for 48 h. The solvent was

then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow

precipitate formed and was filtered on sintered funnel and washed with hexane to give

Ru{C2N3(CN)(CH3)}(dppe)Cp* (49) as a bright yellow powder (20 mg, 37%).

2nd method:

Similarly, Ru(C≡CC≡CTMS)(dppe)Cp* (51 mg, 0.07 mmol) and TMSN3 (9 µL, 0.07

mmol) gave Ru{C2N3(CN)(CH3)}(dppe)Cp* (49) (21 mg, 38%). IR (CH2Cl2, cm-1):

ν(C≡N) 2218 (m); ν(C=N) 1724 (m). 1H NMR (C6D6): δ 7.47-7.08 (m, 20H, Ph);

2.37-2.31, 2.13-2.11 (2 x m, 2 x 2H, CH2CH2); 1.46 (s, 3H, CH3); 1.26 (s, 15H, Cp*). 13C NMR (C6D6): δ 133.09-127.60 (m, Ph); 147.24 (s, C-CN); 135.45 (s, C-CH3);

113.91 (s, CN); 91.88 (s, C5Me5); 58.74 (s, CH3); 28.39–28.10 (m, CH2CH2); 9.82 (s,

217

C5Me5). 31P NMR (C6D6): δ 75.1 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 743, [M+

H]+; 635, [Ru(dppe)Cp*]+. High resolution MS (m/z): 765.2112, [M + Na]+.

Ru{C2N3(CH3)H}(dppe)Cp* (50)

1st method:


treated with AuN3(PPh3) (37 mg, 0.07 mmol) and stirred at 50oC for 24 h. The solvent

was then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow


Ru{C2N3(CH3)H}(dppe)Cp* (50) as a bright yellow powder (13 mg, 41%).

2nd method:

Complex Ru{C2N3(CH3)H}(dppe)Cp* (50) was also obtained (11 mg, 35%) from a

similar reaction between Ru(C≡CC≡C[Au(PPh3)])(dppe)Cp* (50 mg, 0.04 mmol) and

TMSN3 (5 µL, 0.07 mmol) at r.t. for 48 h. IR (CH2Cl2, cm-1): ν(C=N) 1712 (m). 1H

NMR (C6D6): δ 7.48-6.87 (m, 20H, Ph); 3.14-3.10, 2.73-2.69 (2 x m, 2 x 2H,

CH2CH2); 2.18 (s, 1H, CH); 1.64 (s, 15H, Cp*); 1.26 (s, 3H, CH3). 13C NMR (C6D6):

δ 134.52-127.62 (m, Ph); 133.7 (s, C-CH3); 130.92 (s, CH); 93.02 (s, C5Me5); 58.63

(s, CH3); 30.10–29.77 (m, CH2CH2); 10.28 (s, C5Me5). 31P NMR (C6D6): δ 75.0 (s,

dppe). ES-MS (+ve ion, MeOH, m/z): 717, [M]+; 635, [Ru(dppe)Cp*]+. High

resolution MS (m/z): 717.1967, [M]+.

Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp* (51)

A solution of Ru(C≡CC≡CH)(dppe)Cp* (31 mg, 0.05 mmol) in toluene (10 mL) was

treated with TsN3 (28 mg, 0.14 mmol) and stirred at r.t. for 18 h. The solvent was then

evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow precipitate

formed and was filtered on sintered funnel and washed with hexane to give

218

Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp* (51) as a bright yellow crystalline powder (33

mg, 43%). Single crystals suitable for X-ray studies were grown from THF/hexane.

IR (CH2Cl2, cm-1): ν(C-H) 2977 (m); ν(C≡N) 2229 (m); ν(C=N) 1703 (m); ν(SO)

1179 (m). 1H NMR (C6D6): δ 7.68 (d, 2J(HH) 8 Hz, 2H, C6H4); 7.23-6.95 (m, 20H,

Ph); 6.61 (d, 2J(HH) 8 Hz, 2H, C6H4); 2.25 (s, 3H, CH3); 2.04-1.99, 1.89-1.85 (2 x m,

2 x 2H, CH2CH2); 1.49 (s, 15H, Cp*); 1.23 (s, 1H, CH). 13C NMR (C6D6): δ 145.17,

144.89, 138.84, 134.87 (4 x s, C6H4); 130.39-127.06 (m, Ph); 116.63 (s, C); 122.85 (s,

C); 92.27 (s, C5Me5); 58.52 (s, C); 28.77-28.18 (m, CH2CH2); 21.14 (s, CH3); 9.79 (s,

C5Me5). 31P NMR (C6D6): δ 74.3 (s, dppe). ES-MS (+ve ion, MeOH, m/z): 1073, [M +

Na]+; 1051, [M + H]+; 635, [Ru(dppe)Cp*]+. High resolution MS (m/z): 1051.224, [M

+ H]+.

Ru(N3)(PPh3)2Cp (52) 1st method:

A solution of Ru(C≡CC≡CH)(PPh3)2Cp (51 mg, 0.07 mmol) in THF (10 mL) was


then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow-

brown precipitate formed and was filtered on sintered funnel and washed with hexane

to give Ru(N3)(PPh3)2Cp (52) as a yellow-brown powder (29 mg, 57%).

2nd method:

Complex Ru(N3)(PPh3)2Cp (52) was also obtained (31 mg, 60%) from a similar

reaction between Ru(C≡CC≡CH)(PPh3)2Cp (50 mg, 0.07 mmol) and TsN3 (14 mg,

0.07 mmol). IR (CH2Cl2, cm-1): ν(N3) 1981 (m). 1H NMR (CDCl3): δ 7.70-6.79 (m,

30H, Ph); 4.26 (s, 5H, Cp). 13C NMR (CDCl3): δ 134.04-125.97 (m, Ph); 86.03 (s,

C5H5). 31P NMR (CDCl3): δ 43.3 (s, PPh3). ES-MS (+ve ion, MeOH, m/z): 733, [M]+;

691, [Ru(PPh3)2Cp]+; 429, [Ru(PPh3)Cp]+.

219

Ru(N3)(dppe)Cp* (53)

1st method:

A solution of Ru(C≡CH)(dppe)Cp* (51 mg, 0.08 mmol) in toluene (10 mL) was


then evaporated to ca 2 mL and hexane (30 mL) was added dropwise. A yellow


Ru(N3)(dppe)Cp* (53) as a yellow powder (37 mg, 63%).

2nd method:

Complex Ru(N3)(dppe)Cp* (53) was also obtained (35 mg, 65%) from a similar

reaction between Ru(C≡CH)(dppe)Cp* (51 mg, 0.08 mmol) and TsN3 (15 mg, 0.08

mmol) in THF (10 mL) at r.t. for 48 h. IR (CH2Cl2, cm-1): ν(N3) 2035 (s). 1H NMR


1.53 (s, 30H, Cp*). 31P NMR (C6D6): δ 77.7 (s, dppe). ES-MS (+ve ion, MeOH, m/z):

700, [M+ Na]+; 635, [Ru(dppe)Cp*]+. Literature150 IR (CH2Cl2, cm-1): ν(N3) 2036 (s). 1H NMR (C6D6): δ 7.32-7.05 (m, 20H, Ph); 2.40-2.38, 1.81-1.78 (2 x m, 2 x 2H,

CH2CH2); 1.50 (s, 30H, Cp*). 31P NMR (C6D6): δ 77.7 (s, dppe). ES-MS (+ve ion,

MeOH, m/z): 677, [M]+; 635, [Ru(dppe)Cp*]+.

220

General conclusions

In summary, this thesis describes the development of new methods for the synthesis

of novel diynyl, diyndiyl and bis(diyndiyl) ruthenium(II) complexes which could not

been obtained from previously known methods.

The first method presented allowed the synthesis of novel symmetric and asymmetric

bis(diyndiyl) ruthenium (II) complexes of the general formula {LnM}-C≡CC≡C-

{M”L”p}-C≡CC≡C-{M’L’m}, featuring two butadiyndiyl carbon chains with metal

ligand end-groups linked by either a Ru(dppe)2 moiety or a trinuclear copper(I) or

silver(I) cluster M3(µ-dppm)3 (M = Cu, Ag). These complexes were studied by cyclic

voltammetry which has enabled the electronic interactions between the two metal

termini along the bridge to be evaluated and to examine the effect of insertion of the

different bridging groups. It was found that the insertion of the Ru(dppe)2 moiety

allows electronic interactions between the terminal groups and these interactions were

increased when compared to the straight-chain analogues. When a trinuclear copper(I)

or silver(I) cluster was inserted, electronic communication was still present between

the metal ligand end-groups, but the electronic interactions were found to diminish

compared to straight-chain analogues.

Furthermore, this work looked at the lithiation of two ruthenium(II) diynyl complexes

Ru(C≡CC≡CH)(dppe)Cp* and Ru(C≡CC≡CH)(PPh3)2Cp. The most favorable

conditions for the synthesis of the lithium complexes Ru(C≡CC≡CLi)(dppe)Cp* and

Ru(C≡CC≡CLi)(PPh3)2Cp were determined. The nucleophilic nature of these

complexes made them valuable starting materials for the synthesis of novel diynyl and

diyndiyl ruthenium(II) complexes. Therefore, the generated lithium complexes

[Ru](C≡CC≡CLi) (where [Ru] = Ru(dppe)Cp*, Ru(PPh3)2Cp) were reacted with

metal halides from a range of metal groups and various electrophiles such as organic

substrates or polyfluoroaromatic compounds. This is the first example of the lithiation

of ruthenium(II) diynyl complexes and this new synthetic route has allowed the

synthesis of a wide range of novel diynyl and symmetric or asymmetric ruthenium(II)

diyndiyl complexes.

221

This thesis also describes the reaction of various diynyl ruthenium(II) complexes with

the three different azide reagents TMSN3, TsN3 and AuN3(PPh3). It was suggested

that a Huisgen 1,3-dipolar cycloaddition of the alkynes with the azides will take place

to generate 1,2,3-triazoles. However, the reactions did not proceed as expected giving

a range of products. This Section of the work has never been explored previously and

exposed a very interesting opportunity for further chemistry.

222

References (1) Smith, P. P. K.; Buseck, P. R. Science 1982, 216, 984.

(2) Eisler, S.; Slepkov, A. D.; Elliot, E.; Luu, T.; McDonald, R.; Hegmann, F. A.;

Tykwinski, R. R. J. Am. Chem. Soc. 2005, 127, 2666.

(3) Bruce, M. I.; Low, P. J. Adv. Organomet. Chem. 2004, 50, 179.

(4) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc, M. Adv.

Organomet. Chem. 1998, 42, 291.

(5) Whittall, I. R.; McDonagh, A. M.; Humphrey, M. G.; Samoc, M. Adv.


(6) Bruce, M. I.; Low, P. J. Adv. Organomet. Chem. 2002, 48, 71.

(7) Bruce, M. I.; Low, P. J.; Costuas, K.; Halet, J.-F.; Best, S. P.; Heath, G. A. J.

Am. Chem. Soc. 2000, 122, 1949.

(8) Meyer, W. E.; Amoroso, A. J.; Horn, C. R.; Jaeger, M.; Gladysz, J. A.

Organometallics 2001, 20, 1115.

(9) Paul, F.; Meyer, W. E.; Toupet, L.; Jiao, H.; Gladysz, J. A.; Lapinte, C. J. Am.

Chem. Soc. 2000, 122, 9405.

(10) Alejos, P.; Coco, S.; Espinet, P. New J. Chem. 1995, 19, 799.

(11) Hudson, S. A.; Maitlis, P. M. Chem. Rev. 1993, 93, 861.

(12) Ellis, B. G., Ph.D. Thesis, The University of Adelaide, 2003.

(13) Zheng, Q.; Gladysz, J. A. J. Am. Chem. Soc. 2005, 127, 10508.

(14) Nast, R.; Urban, F. Z. Anorg. Allg. Chem. 1957, 289, 244.

(15) Kim, P. J.; Masai, H.; Sonogashira, K.; Hagihara, N. Inorg. Nucl. Chem. Lett.,

1970, 6, 181.

(16) Sonogashira, K.; Kataoka, S.; Takahashi, S.; Hagihara, N. J. Organomet.

Chem. 1978, 160, 319.

(17) Sonogashira, K.; Yatake, T.; Tohda, Y.; Takahashi, S.; Hagihara, N. J. Chem.

Soc., Chem. Commun. 1977, 291.

(18) Bruce, M. I.; Low, P. J.; Ke, M.; Kelly, B. D.; Skelton, B. W.; Smith, M. E.;

White, A. H.; Witton, N. B. Aust. J. Chem. 2001, 54, 453.

(19) Bruce, M. I.; Ke, M.; Low, P. J. J. Chem. Soc., Chem. Commun. 1996, 2405.

(20) Bruce, M. I.; Ke, M.; Low, P. J.; Skelton, B. W.; White, A. H.


223

(21) Roberts, R. L.; Puschmann, H.; Howard, J. A. K.; Yamamoto, J. H.; Carty, A.

J.; Low, P. J. J. Chem. Soc., Dalton Trans. 2003, 1099.

(22) Weng, W.; Bartik, T.; Brady, M.; Bartik, B.; Ramsden, J. A.; Arif, A. M.;

Gladysz, J. A. J. Am. Chem. Soc. 1995, 117, 11922.

(23) Gevert, O.; Wolf, J.; Werner, H. Organometallics 1996, 15, 2806.

(24) Zheng, Q.; Hampel, F.; Gladysz, J. A. Organometallics 2004, 23, 5896.

(25) Sun, Y.; Taylor, N. J.; Carty, A. J. J. Organomet. Chem. 1992, 423, C43.

(26) Akita, M.; Chung, M.-C.; Sakurai, A.; Sugimoto, S.; Terada, M.; Tanaka, M.;

Moro-oka, Y. Organometallics 1997, 16, 4882.

(27) Wong, A.; Kang, P. C. W.; Tagge, C. D.; Leon, D. R. Organometallics 1990,

9, 1992.

(28) Coat, F.; Guillevic, M.-A.; Toupet, L.; Paul, F.; Lapinte, C. Organometallics

1997, 16, 5988.

(29) Coat, F.; Thominot, P.; Lapinte, C. J. Organomet. Chem. 2001, 629, 39.

(30) Bruce, M. I.; Ellis, B. G.; Gaudio, M.; Lapinte, C.; Melino, G.; Paul, F.;

Skelton, B. W.; Smith, M. E.; Toupet, L.; White, A. H. Dalton Trans. 2004,

1601.

(31) Bruce, M. I.; Hall, B. C.; Low, P. J.; Smith, M. E.; Skelton, B. W.; White, A.

H. Inorg. Chim. Acta 2000, 300-302, 633.

(32) Brandsma, L. Preparative Acetylenic Chemistry; 2nd ed.; Elsevier:

Amsterdam, 1988.

(33) Rappert, T.; Nurnberg, O.; Werner, H. Organometallics 1993, 12, 1359.

(34) Werner, H.; Lass, R. W.; Gevert, O.; Wolf, J. Organometallics 1997, 16, 4077.

(35) Jones, G. E.; Kendrick, D. A.; Holmes, A. B. Org. Synth. 1993, VIII, 63.

(36) Bruce, M. I.; Hall, B. C.; Kelly, B. D.; Low, P. J.; Skelton, B. W.; White, A.

H. J. Chem. Soc., Dalton Trans. 1999, 3719.

(37) Che, C.-M.; Chao, H.-Y.; Miskowski, V. M.; Li, Y.; Cheung, K.-K. J. Am.

Chem. Soc. 2001, 123, 4985.

(38) Bruce, M. I.; Jevric, M.; Skelton, B. W.; Smith, M. E.; White, A. H.; Zaitseva,

N. N. J. Organomet. Chem. 2006, 691, 361.

(39) Shostakovskii, M. F.; Bogdanova, A. V. The Chemistry of Diacetylenes;

Wiley: New York, 1974.

(40) Zweifel, G.; Rajagopalan, S. J. Am. Chem. Soc. 1985, 107, 700.

224

(41) Holmes, A. B.; Jennings-White, C. L. D.; Schulthess, A. H.; Akinde, B.;

Walton, D. R. M. J. Chem. Soc., Chem. Commun. 1979, 840.

(42) Crescenzi, R.; Sterzo, C. L. Organometallics 1992, 11, 4301.

(43) Brady, M.; Weng, W.; Gladysz, J. A. J. Chem. Soc., Chem. Commun. 1994,

2655.

(44) Brady, M.; Weng, W.; Zhou, Y.; Seyler, J. W.; Amoroso, A. J.; Arif, A. M.;

Bohme, M.; Frenking, G.; Gladysz, J. A. J. Am. Chem. Soc. 1997, 119, 775.

(45) Zhou, Y.; Sweyler, J. W.; Weng, W.; Arif, A. M.; Gladysz, J. A. J. Am. Chem.

Soc. 1993, 115, 8509.

(46) Le Narvor, N.; Toupet, L.; Lapinte, C. J. Am. Chem. Soc. 1995, 117, 7129.

(47) Bruce, M. I.; Ellis, B. G.; Low, P. J.; Skelton, B. W.; White, A. H.


(48) Bruce, M. I.; Costuas, K.; Davin, T.; Halet, J.-F.; Kramarczuk, K. K.; Low, P.

J.; Nicholson, B. K.; Perkins, G. J.; Roberts, R. L.; Skelton, B. W.; Smith, M.

E.; White, A. H. J. Chem. Soc., Dalton Trans. 2007, 5387.

(49) Fernandez, F. J.; Blacque, O.; Alfonso, M.; Berke, H. J. Chem. Soc., Chem.

Commun. 2001, 1266.

(50) Guillemot, M.; Toupet, L.; Lapinte, C. Organometallics 1998, 17, 1928.

(51) Bruce, M. I.; Costuas, K.; Davin, T.; Ellis, B. G.; Halet, J.-F.; Lapinte, C.;

Low, P. J.; Smith, M. E.; Skelton, B. W.; Toupet, L.; White, A. H.


(52) Bruce, M. I.; de Montigny, F.; Jevric, M.; Lapinte, C.; Skelton, B. W.; Smith,

M. E.; White, A. H. J. Organomet. Chem. 2004, 689, 2860.

(53) Bruce, M. I.; Hall, B. C.; Low, P. J.; Skelton, B. W.; White, A. H. J.


(54) Colbert, M. C. B.; Lewis, J.; Long, N. J.; Raithby, P. R.; Younus, M.; White,

A. J. P.; Williams, D. J.; Payne, N. N.; Yellowlees, L.; Beljonne, D.;

Chawdhury, N.; Friend, R. H. Organometallics 1998, 17, 3034.

(55) Gaudio, M., Ph.D. Thesis, The University of Adelaide, 2006.

(56) Klein, A.; Lavastre, O.; Fiedler, J. Organometallics 2006, 25, 635.

(57) Lavastre, O.; Pass, J.; Bachmann, P.; Guesmi, S.; Moinet, C.; Dixneuf, P. H.


(58) Low, P. J.; Roberts, R. L.; Cordiner, R. L.; Hartl, F. J. Solid State

Electrochem. 2005, 9, 717.

225

(59) Smith, M. E., Ph.D. Thesis, The University of Adelaide, 2002.

(60) Le Stang, S.; Paul, F.; Lapinte, C. Organometallics 2000, 19, 1035.

(61) Perkins, G. J., Ph.D. Thesis, The University of Adelaide, 2006.

(62) Bruce, M. I.; Jevric, M.; Perkins, G. J.; Skelton, B. W.; White, A. H. J.

Organomet. Chem. 2007, 692, 1757.

(63) Bruce, M. I.; Low, P. J.; Hartl, F.; Humphrey, P. A.; de Montigny, F.; Jevric,

M.; Lapinte, C.; Perkins, G. J.; Roberts, R. L.; Skelton, B. W.; White, A. H.


(64) Bruce, M. I.; Halet, J.-F.; Le Guennic, B.; Skelton, B. W.; Smith, M. E.;

White, A. H. Inorg. Chim. Acta 2003, 350, 175.

(65) Bruce, M. I.; Hall, B. C.; Skelton, B. W.; Smith, M. E.; White, A. H. Dalton

Trans. 2002, 995.

(66) Lebreton, C.; Touchard, D.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf,

P. H. Inorg. Chim. Acta 1998, 272, 188.

(67) Klarreich, E. Science Notes; State University of New York, 2001.

(68) Wassel, R. A.; Gorman, C. B. Angew. Chem., Int. Ed. Engl. 2004, 43, 5120.

(69) Paul, F.; Lapinte, C. Coord. Chem. Rev. 1998, 178-180, 431.

(70) Robertson, N.; McGowan, C. A. Chem. Soc. Rev. 2003, 32, 96.

(71) Tour, M. J.; Rawlett, A. M.; Kozaki, M.; Yao, Y.; Jagessar, R. C.; Dirk, S. M.;

Price, D. W.; Reed, M. A.; Zhou, C. W.; Chen, J.; Wang, W.; Campbell, I.

Chem. Eur. J. 2001, 7, 5118.

(72) Ward, M. D. Chem. Ind. 1996, 568.

(73) Donhauser, Z. J.; Mantooth, B. A.; Kelly, K. F.; Bumm, L. A.; Monnell, J. D.;

Stapleton, J. J.; Price Jr, D. W.; Rawlett, A. M.; Allara, D. L.; Tour, J. M.;

Weiss, P. S. Science 2001, 292, 2303.

(74) Fraysse, S.; Coudret, C.; Launay, J. P. Eur. J. Inorg. Chem. 2000, 1581.

(75) Ward, M. D. Chem. Ind. 1997, 650.

(76) Chen, J.; Reed, M. A.; Rawlett, A. M.; Tour, J. M. Science 1999, 286, 1550.

(77) Roth, K. M.; Dontha, N.; Dabke, R. B.; Gryko, D. T.; Clausen, C.; Lindsey, J.

S.; Bocian, D. F.; Kuhr, W. G. J. Vac. Sci. Technol. B 2000, 18, 2359.

(78) Morales, G. M.; Jiang, P.; Yuan, S.; Lee, Y.; Sanchez, A.; You, W.; Yu, L. J.

Am. Chem. Soc. 2005, 127, 10456.

(79) Tour, J. M. Chem. Rev. 1996, 96, 537.

226

(80) Valasek, M.; Pecka, J.; Jindrich, J.; Calleja, G.; Craig, P. R.; Michl, J. J.


(81) Seifert, G.; Kohler, T.; Frauenheim, T. Appl. Phys. Lett. 2000, 77, 1313.

(82) Launay, J. P. Chem. Soc. Rev. 2001, 30, 386.

(83) Cygan, M. T.; Dunbar, T. D.; Arnold, J. J.; Bumm, L. A.; Shedlock, N. F.;

Burgin, T. P.; Jones II, L.; Allara, D. L.; Tour, J. M.; Weiss, P. S. J. Am.

Chem. Soc. 1998, 120, 2721.

(84) Fan, F.-R. F.; Yang, J.; Cai, L.; Price Jr, D. W.; Dirk, S. M.; Kosynkin, D. V.;

Yao, Y.; Rawlett, A. M.; Tour, J. M.; Bard, A. J. J. Am. Chem. Soc. 2002, 124,

5550.

(85) James, D. K.; Tour, J. M. AldrichimicaActa 2006, 39, 47.

(86) Reed, M. A.; Zhou, C.; Muller, C. J.; Burgin, T. P.; Tour, J. M. Science 1997,

278, 252.

(87) Schumm, J. S.; Pearson, D. L.; Tour, J. M. Angew. Chem., Int. Ed. Engl. 1994,

33, 1360.

(88) Iijima, S. Nature 1991, 354, 56.

(89) Tans, S. J.; Devoret, M. H.; Dai, H.; Thess, A.; Smalley, R. E.; Geerligs, L. J.;

Dekker, C. Nature 1997, 386, 474.

(90) Yang, X. Carbon Nanotubes: Synthesis, Applications and Some New Aspects;

State University of New York, 2006.

(91) Guldi, D. M.; Aminur Rahman, G. M.; Sgobba, V.; Ehli, C. Chem. Soc. Rev.

2006, 35, 471.

(92) Coat, F.; Lapinte, C. Organometallics 1996, 15, 477.

(93) Robin, M. B.; Day, P. Adv. Inorg. Chem. Radiochem. 1967, 10, 247.

(94) Demadis, K. D.; Hartshorn, C. M.; Meyer, T. J. Chem. Rev. 2001, 101, 2655.

(95) Evans, D. H.; O’Connell, K. M.; Petersen, R. A.; Kelly, M. J. J. Chem. Educ.

1983, 60, 290.

(96) Kissinger, P. T.; Heineman, W. R. J. Chem. Educ. 1983, 60, 702.

(97) Vaswani, H.; Watkins, J. Cyclic Voltammetry: a Tutorial; Rice University:

Texas, 2000.

(98) Astruc, D. Electron Transfer and Radical Processes in Transition-Metal

Chemistry; VCH Pub. Inc.: New York, 1995.

(99) Barriére, F.; Camire, N.; Geiger, W. E.; Müller-Westerhoff, U. T.; Sanders, R.

J. Am. Chem. Soc. 2002, 124, 7262.

227

(100) Reichert, J.; Ochs, R.; Beckmann, D.; Weber, H. B.; Mayor, M.; von

Löhneysen, H. Phys. Rev. Lett. 2002, 88, 176804.

(101) McCleverty, J. A.; Ward, M. D. Acc. Chem. Res. 1998, 31, 842.

(102) Bruce, M. I.; Ellis, B. G.; Skelton, B. W.; White, A. H. J. Organomet. Chem.

2005, 690, 792.

(103) Rigaut, S.; Costuas, K.; Touchard, D.; Saillard, J.-Y.; Golhen, S.; Dixneuf, P.

H. J. Am. Chem. Soc. 2004, 126, 4072.

(104) Zhu, Y.; Clot, O.; Wolf, M. O.; Yap, P. A. J. Am. Chem. Soc. 1998, 120, 1812.

(105) Polam, J. R.; Porter, L. C. J. Coord. Chem. 1993, 29, 109.

(106) Rigaut, S.; Perruchon, J.; Guesmi, S.; Fave, C.; Touchard, D.; Dixneuf, P. H.

Eur. J. Inorg. Chem. 2005, 447.

(107) Burgun, A., Honours Thesis, Université de Rennes 1, 2006.

(108) Uson, R.; Laguna, A.; Laguna, M.; Fernandez, E. J. Chem. Soc., Dalton Trans.

1982, 1971.

(109) Uson, R.; Laguna, A.; Vicenti, J. J. Organomet. Chem. 1977, 131, 471.

(110) Schmidbaur, H.; Wohlleben, A.; Wagner, F.; Orama, O.; Huttner, G. Chem.

Ber. 1977, 110, 1748.

(111) Vicente, J.; Chicote, M. T. Coord. Chem. Rev. 1999, 193-195, 1143.

(112) Antonova, A. B.; Bruce, M. I.; Ellis, B. G.; Gaudio, M.; Humphrey, P. A.;

Jevric, M.; Melino, G.; Nicholson, B. K.; Perkins, G. J.; Skelton, B. W.;

Stapleton, B.; White, A. H.; Zaitseva, N. N. Chem. Commun. 2004, 960.

(113) Sonogashira, K. Handbook of Organo-Palladium Chemistry for Organic

Synthesis; Wiley-Interscience: New-York, 2002.

(114) Sonogashira, K. J. Organomet. Chem. 2002, 653, 46.

(115) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett. 1975, 4467.

(116) Bruce, M. I.; Duffy, D. N.; Liddell, M. J.; Snow, M. R.; Tiekink, E. R. T. J.


(117) Bruce, M. I.; Humphrey, P. A.; Snow, M. R.; Tiekink, E. R. T. J. Organomet.

Chem. 1986, 303, 417.

(118) Diez, J.; Pilar Gamasa, M.; Gimeno, J.; Lastra, E.; Aguirre, A.; García-

Granda, S. Organometallics 1993, 12, 2213.

(119) Yam, V. W.-W. Chem. Commun. 2001, 789.

(120) Yam, V. W.-W.; Fung, W. K.-M.; Cheung, K. K. Organometallics 1997, 16,

2032.

228

(121) Yam, V. W.-W.; Fung, W. K.-M.; Cheung, K. K. Organometallics 1998, 17,

3293.

(122) Yam, V. W.-W.; Fung, W. K.-M.; Wong, K. M.-C.; Lau, V. C.-Y.; Cheung, K.

K. J. Chem. Soc., Chem. Commun. 1998, 777.

(123) Yam, V. W.-W.; Fung, W. K.-M.; Wong, M.-T. Organometallics 1997, 16,

1772.

(124) Yam, V. W.-W.; Lo, K. K.-W. Chem. Soc. Rev. 1998, 323.

(125) Yip, J. H. K.; Wu, J.; Wong, K.-Y.; Yeung, K.-W.; Vittal, J. J.


(126) Yam, V. W.-W.; Lo, W. K. K.-W.; Wong, K. M.-C. J. Organomet. Chem.

1999, 578, 3.

(127) Yam, V. W.-W.; Lo, W.-Y.; Lam, C.-H.; Fung, W. K.-M.; Wong, K. M.-C.;

Lau, V. C.-Y.; Zhu, N. Coord. Chem. Rev. 2003, 245, 39.

(128) Liu, H.; Calhorda, M. J.; Drew, M. G. B.; Felix, V.; Novosad, J.; Veiros, L. F.;

de Biani, F. F.; Zanello, P. Dalton Trans. 2002, 4365.

(129) Halet, J.-F.; LeGuinnec, B. Personal communication.

(130) Le Guennic, B., Ph.D. Thesis, Université de Rennes 1, 2002.

(131) Rigaut, S.; Perruchon, J.; Le Pichon, L.; Touchard, D.; Dixneuf, P. H. J.


(132) Morandini, F.; Dondana, A.; Murani, I.; Pilloni, G.; Consiglio, G.; Sironi, A.;

Moret, M. Inorg. Chim. Acta 1998, 282, 163.

(133) Bruce, M. I.; Hameister, C.; Swincer, A. G.; Wallis, R. C. Inorg. Synth. 1982,

21, 78.

(134) Gutiérrez Alonso, A.; Ballester Reventés, C. J. Organomet. Chem. 1998, 338,

249.

(135) Bruce, M. I.; Kramaczuk, K. A.; Perkins, G. J.; Skelton, B. W.; White, A. H.;

Zaitseva, N. N. J. Cluster Sci. 2004, 15, 119.

(136) Bruce, M. I.; Nicholson, B. K.; bin Shawkataly, O. Inorg. Synth. 1989, 26,

325.

(137) Diez, J.; Gamasa, M. P.; Gimeno, J. J. Chem. Soc., Dalton Trans. 1987, 1275.

(138) Ramsden, J. A.; Weng, W.; Arif, A. M.; Gladysz, J. A. J. Am. Chem. Soc.

1992, 114, 5890.

(139) Ramsden, J. A.; Weng, W.; Gladysz, J. A. Organometallics 1992, 11, 3635.

(140) Dahlenburg, L.; Weib, A.; Moll, M. J. Organomet. Chem. 1997, 535, 195.

229

(141) Melino, G., Honours Thesis, The University of Adelaide, 2002.

(142) Li, D.; Hong, X.; Che, C.-M.; Lo, W. C.; Peng, S.-M. J. Chem. Soc., Dalton

Trans. 1993, 2929.

(143) Payne, N. C.; Ramachandran, R.; Puddephatt, R. J. Can. J. Chem. 1995, 73, 6.

(144) Costa, G.; Reisenhofer, E.; Stefani, L. J. Inorg. Nucl. Chem. 1965, 27, 2581.

(145) Evans, D.; Osborn, J. A.; Wilkinson, G. Inorg. Synth. 1990, 28, 79.

(146) Tayim, H. A.; Bouldoukian, A.; Awad, F. J. Inorg. Nucl. Chem. 1970, 32,

3799.

(147) Enriquez, A. E.; White, P. S.; Templeton, J. L. J. Am. Chem. Soc. 2001, 123,

4992.

(148) Chambers, R. D.; Mobbs, R. H. Adv. Fluorine Chem. 1965, 4, 50.

(149) Wiles, M. R.; Massey, A. G. Tetrahedron Lett. 1967, 51, 5137.

(150) Parker, C., Personal communication.

(151) Armit, D. J.; Bruce, M. I.; Gaudio, M.; Zaitseva, N. N.; Skelton, B. W.; White,

A. H.; Le Guennic, B.; Halet, J.-F.; Fox, M. A.; Low, P. J. In Submission

2008.

(152) Fischer, H.; Leroux, F.; Roth, G.; Stumpf, R. Organometallics 1996, 15, 3723.

(153) Kolb, C.; Finn, M. G.; Sharpless, K. B. Angew. Chem., Int. Ed. Engl. 2001, 40,

2004.

(154) Beatty, K.; Xie, F.; Wang, Q.; Tirrell, D. A. J. Am. Chem. Soc. 2005, 127,

14150.

(155) Collman, J. P.; Devaraj, N. K.; Chidsey, C. E. D. Langmuir 2004, 20, 1051.

(156) Lee, J. K.; Chi, Y. S.; Choi, I. S. Langmuir 2004, 20, 3844.

(157) Lummerstorfer, T.; Hoffmann, H. J. Phys. Chem. 2004, 108, 3963.

(158) Bettinetti, L.; Löber, S.; Hübner, H.; Gmeiner, P. J. Comb. Chem. 2005, 7,

309.

(159) Mocharla, V. P.; Colasson, B.; Lee, L. V.; Röper, S.; Sharpless, K. B.; Wong,

C.-H.; Kolb, H. C. Angew. Chem., Int. Ed. Engl. 2005, 44, 116.

(160) Speers, A. E.; Cravatt, B. F. Chem. Biol. 2004, 11, 535.

(161) Li, H.; Cheng, F.; Druft, A. M.; Andronov, A. J. Am. Chem. Soc. 2005, 127,

14518.

(162) Joremelon, M. J.; O’ Reilly, R. K.; Matson, J. B.; Nugent, A. K.; Hawker, C.

J.; Wooley, K. L. Macromolecules 2005, 38, 5436.

230

(163) Malkoch, M.; Thibault, R. J.; Drockenmuller, E.; Messerschmidt, M.; Voit, B.;

Russell, T. P.; Hawker, C. J. J. Am. Chem. Soc. 2005, 127, 7404.

(164) Helms, B.; Mynar, J. L.; Hawker, C. J.; Fréchet, J. M. J. J. Am. Chem. Soc.

2004, 126, 15020.

(165) Tsarevsky, N. V.; Bernaerts, K. V.; Dufour, B.; Du Prez, F. E.; Matyjaszrewki,

K. Macromolecules 2004, 37, 9308.

(166) Evans, R. A. Aust. J. Chem. 2007, 60, 384.

(167) Wu, P.; Fokin, V. V. AldrichimicaActa 2007, 40, 7.

(168) Lwowski, L. 1,3-Dipolar Cycloaddition Chemistry,; Wiley: New York, 1984;

Vol. 1.

(169) Tornøe, C. W.; Christensen, C.; Meldal M., J. Org. Chem. 2002, 67, 3057.

(170) Speers, A. E.; Adam, G. C.; Cravatt, B. F. J. Am. Chem. Soc. 2003, 125, 4686.

(171) Díaz, D. D.; Punna, S.; Holzer, P.; McPherson, A. K.; Sharpless, K. B.; Fokin,

V. V.; Finn, M. G. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 4392.

(172) Wu, P.; Feldman, A. K.; Nugent, A. K.; Hawker, C. J.; Scheel, A.; Voit, B.;

Pyun, J.; Fréchet, J. M. J.; Sharpless, K. B.; Fokin, V. V. Angew. Chem., Int.

Ed. Engl. 2004, 43, 3928.

(173) Hawker, C. J.; Fokin, V. V.; Finn, M. G.; Sharpless, K. B. Aust. J. Chem.

2007, 60, 381.

(174) Lee, L. V.; Mitchell, M. L.; Huang, S.-J.; Fokin, V. V.; Sharpless, K. B.;

Wong, C.-H. J. Am. Chem. Soc. 2003, 125, 9588.

(175) Himo, F.; Lovell, T.; Hilgraf, R.; Rostovtsev, V. V.; Noodleman, L.;

Sharpless, K. B.; Fokin, V. V. J. Am. Chem. Soc. 2005, 127, 210.

(176) Partyka, D. V.; Updegraff, J. B.; Zeller, M.; Hunter, A. D.; Gray, T. G.


(177) Chang, C.-W.; Lee, G.-H. Organometallics 2003, 22, 3107.

(178) Bruce, M. I.; Ellis, B. G.; Skelton, B. W.; White, A. H. J. Organomet. Chem.

2004, 689, 698.

(179) Vicente, J.; Chicote, M. T.; Abrisqueta, M. Organometallics 1997, 16, 5628.

(180) Djukic, J.; Michon, C.; Heiser, D.; Kyritsakas-Gruber, N.; de Cian, A.; Dotz,

K. H.; Pfeffer, M. Eur. J. Inorg. Chem. 2004, 2107.

231

Complexes Index

1. trans-Ru(C4H)(dppe)2

2. trans-Ru{C4[Ru(dppe)Cp*]}2(dppe)2

3. trans-Ru{C4[Ru(dppe)Cp]}2(dppe)2

4. trans-Ru{C4[Ru(PPh3)2Cp]}2(dppe)2

5. trans-Ru{C4[Ru(dppe)Cp*]}{C4H}(dppe)2

6. trans-Ru{C4[Ru(dppe)Cp]}{C4H}(dppe)2

7. trans-Ru{C4[Ru(PPh3)2Cp]}{C4H}(dppe)2

8. trans-Ru{C4[Ru(dppe)Cp*]}{C4[Ru(dppe)Cp]}(dppe)2

9. trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Ru(dppe)Cp]}(dppe)2

10. trans-RuCl{C4[Ru(dppe)Cp*]}(dppe)2

11. trans-Ru{C4[Ru(dppe)Cp*]}{C4[Au(PPh3)]}(dppe)2

12. trans-Ru{C4[Ru(dppe)Cp]}{C4[Au(PPh3)]}(dppe)2

13. trans-Ru{C4[Ru(PPh3)2Cp]}{C4[Au(PPh3)]}(dppe)2

14. trans-Ru{C4[Ru(dppe)Cp*]}{C5[Co3(µ-dppm)(CO)7]}(dppe)2

15. trans-Ru{C4[Au(PPh3)]}2(dppe)2

16. trans-Ru{C5[Co3(µ-dppm)(CO)7]}2(dppe)2

17. Ru{C≡CC[=C(CN)2]CH[=C(CN)2]}2(dppe)2

18. [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6]

19. [{Cp*(dppe)Ru}(C≡C)2{Cu3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4]

20. [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][PF6]

21. [{Cp*(dppe)Ru}(C≡C)2{Ag3(µ-dppm)3}(C≡C)2{Ru(dppe)Cp*}][BF4]

22. Ru(C≡CC≡CTMS)(dppe)Cp*

23. Ru(C≡CC≡CTMS)(PPh3)2Cp

24. Ru{C≡CC≡C[Au(PPh3)]}(dppe)Cp*

25. Ru{C≡CC≡C[Au(PPh3)]}(PPh3)2Cp

26. {Au(C≡CC≡C[Ru(dppe)Cp*])}2(µ-dppm)

27. Ru{C≡CC≡C[PtCl(PPh3)2]}(dppe)Cp*

28. Ru(C≡CC≡CGePh3)(dppe)Cp*

29. Ru(C≡CC≡CSnPh3)(dppe)Cp*

232

30. {Cp*(dppe)Ru}(C≡CC≡CC≡CC≡C){Ru(dppe)Cp*}

31. {Cp(Ph3P)2Ru}(C≡CC≡C){Cu(PPh3)}

32. {Cp(Ph3P)2Ru}(C≡CC≡C){Rh(CO)(PPh3)2}

33. Ru(C≡CC≡CMe)(dppe)Cp*

34. Ru{C≡CC≡CC(O)Ph}(dppe)Cp*

35. Ru{C≡CC≡CC(O)Me}(dppe)Cp*

36. Ru{C≡CC≡CC(O)OCH3}(dppe)Cp*

37. {Ru(C≡CC≡C)(dppe)Cp*}2(CO)2

38. Ru{C≡CC≡CCHPh(OH)}(dppe)Cp*

39. {Ru(dppe)Cp*}2{µ-C≡CC[=C(CN)2]C[=C(CN)2]C≡C}

40. Ru{C≡CC3NH(CN)(CO)=C(CN)2}(dppe)Cp*

41. Ru{C≡CC4N(NH)H(Me)=C(CN)2}(dppe)Cp*

42. Ru(C≡CC≡CC6F5)(dppe)Cp*

43. Ru(C≡CC≡CC6F4NO2-4)(dppe)Cp*

44. Ru(C≡CC≡CC6F4CN-4)(dppe)Cp*

45. Ru(C≡CC≡CC6F4OMe-4)(dppe)Cp*

46. Ru(C≡CC≡CC10F7-2)(dppe)Cp*

47. [{Cp*(dppe)Ru(C≡C)2}{C4(C6F5)2H}]BF4

48. Ru{C≡CC[=C(CN)2]C[=C(CN)2]C6F5}(dppe)Cp*

49. Ru{C2N3(CN)(CH3)}(dppe)Cp*

50. Ru{C2N3(CH3)H}(dppe)Cp*

51. Ru{NC[C3N2H(NTs)(Ts)]}(dppe)Cp*

52. Ru(N3)(PPh3)2Cp

53. Ru(N3)(dppe)Cp*

university of adelaide · contents abstract i declaration iii acknowledgements iv abbreviations v...

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