poss monomer and reagent chemistry chemistry
TRANSCRIPT
POSS Monomer and Reagent ChemistryChemistry
Frank J. Feher, Raquel Terroba, Ren-Zhi Jin,
Sabine Lücke, Frank Nguyen,
Richard Brutchey and Kevin D. Wyndham
Department of Chemistry – UCI
Irvine, CA 92697-2025
Acknowledgements
Coworkers (recent past)
Daravong Soulivong
Richard Baldwin
Collaborators
Joseph Lichtenhan (Hybrid Plastics LLC)
Joseph Schwab (Hybrid Plastics LLC)
Shawn Phillips (AFRL - Edwards AFB)
Joseph Ziller (UCI Crystallography)
John Greaves (UCI Mass Spec Facility)
Andre Lee (Michigan State)
Funding
National Science FoundationAir Force Research Laboratory (Edwards AFB)Los Alamos National LaboratoryHybrid Plastics LLCNational Institute of Standards & Technology – Advanced Technology Program
Outline for this Presentation
• Introduction– Polyhedral oligosilsesquioxanes (POSS) as precursors to hybrid
hybrid inorganic/organic polymers
– Overview of advances in POSS synthesis to date
• New methods for synthesizing POSS monomers
– Selective cleavage of Si-O-Si in fully condensed [RSiO3/2]n
frameworks
– Manipulation of functional groups
– General synthetic methods
• Conclusions
– Overview of POSS synthesis - past, present and future
Polyhedral Oligosilsesquioxanes
Scott (1946), Barry & Gilkey (50’s), Sprung & Guenther (50’s), Brown & Vogt (60’s), Olsson (60’s), Olsson (60’s), Frye (70’s), Voronkov & Lavrentyev (70’s-80’s), Klemperer (1985), Feher Feher (1986), Agaskar (1989), Calzaferri (1987), Weidner (1989), Bassindale (1993), Marsmann Marsmann (1995), Laine (1996), Others ...
R = H, Me, vinyl, small alkyls, aryls, (CH2)3X, OSiR3
RSiX3H2O
solvent[RSiO3/2]n
SiO O
Si
OSi
Si
O
Si
SiR
OO
O
O
O
R
R
R R
RSiR
Si
O
O
Si OO
Si
O Si
Si
O
Si O Si
O
O O
OO
RR
R
RR
RR
O
Si
Si
O
R
O
O
Si
Si
Si
O
O
R
R
SiR
R
O
O
O
R
O
O
RR
R
RSi
O Si
O OSi
O
Si
Si
SiO
OSi
R
R
R
O
O
Si
OSi
SiO
O
R
R
SiR
R
O
O
O
R
RR
Cy
O
OO
O
Si
OSi R
Si
OSi
O SiO
R6Si6O9 R8Si8O12 R10Si10O15 R12Si12O18
Synthesis of Silsesquioxanes
Brown, Vogt J. Am. Chem. Soc. 1965, 87, 4313.
Feher, Newman, Walzer J. Am. Chem. Soc. 1989, 111, 1741.
Feher, Budzichowski, Blanski, Weller, Ziller Organometallics 1991, 10, 2526.
15%
H2O
acetone3 - 36 months~ 70% yield
60% 25%
SiR
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
R
R
RR
RR
RSi
Si O Si
OORSi
R
O
Si
R
Si
R
Si
RSi
R
R
O
O O
HO
OH
O
O
O
OSi
O OSi
OSi
SiO
Si
SiR
OO
O
O
O
R
R
R R
RSiCl3
Silsesquioxanes as Precursors to Inorganic/Organic Hybrid Materials
Lichtenhan (Edwards Air Force Base) & Feher (UCI)Hybrid Plastics LLC (Fountain Valley, CA)Phillips (Edwards AFB), Lee (MSU), Mather (UConn), Hsiao (SUNY), Coughlin
Coughlin (UMass)
XX
R
Si
Si O Si
OORSi
R
O
Si
R
Si
R
Si
RSi
R
R
O
O O
HO
OH
O
O
O
OSiR
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
R
R
RR
RR
X
X
Si O
SiR
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
R
R
RR
RRSi O
R
Highly Desirable Transformations
Any reaction that selectively introduces functionality !!!
SiR
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
RR
R
RR
RR
SiR
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
R
R
RR
RR
Si O Si
OORSi
R
R
Si
OHSi
R
Si
RSi
R
R
O
O O
O
O
O
O
O
SiHO R
SiR
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
OHR
R
RR
RR
or
Si O Si
OORSi
R
R
Si
RSi
R
Si
RSi
HO
R
O
O O
O
O
O
O
O
SiR OH
oror
SiR
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
R1R
R
RR
RR
or
Si O Si O Si O
Cleavage of Cy8Si8O12 by Strong Acid
XX
Net Result:
SiCy
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
CyCy
Cy
CyCy
CyCy
SiCy
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
CyCy
Cy
CyCy
CyCy
X X
excess HX
HX = HBF4·OMe2or CF3SO3H
Si O Si O
High yield at high conversion!
Four Disilanols from R8Si8O12 and CF3SO3H
SiCy
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
CyCy
Cy
CyCy
CyCy
SiCy
Si
OSiO
O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOCy
Cy
CyCy
OH Cy
Cy
Cy
SiCy
Si
OSiO
O
Si
O Si
Si
O
Si O Si
O
O O
OO
CyCy
Cy
CyCy
Cy Cy
OH
HO
SiCy
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
CyCy
Cy
CyCy
CyCy
HO OH
SiCy
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
Cy
CyCy
CyCy
Cy Cy
Si O
Si O
Si O
Feher, Soulivong, Nguyen Chem. Commun. 1998, 1279.
Methodology is not general and reactions do not scale up well.
Potential Routes to Cy8Si8O12
• PhSi(OMe)3 is readily available.
• Hydrogenation of PhSi to to CySi is known.
• Ph8Si8O12 can be prepared prepared in ~100% yield.yield.
• Cy8Si8O12 can be prepared prepared in >85% yield.yield.
• Basic Ru catalysts available for arene hydrogenation
• One pot synthesis of Cy8Si8O12 from PhSi(OMe)3?
SiCy
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
CyCy
Cy
CyCy
CyCySi O
Si(OMe)3
SiO3/2
<H>
SiO3/2
OH–OH–
n n
SiPh
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
PhPh
Ph
PhPh
PhPhSi O
<H>
OH–OH–
Si(OMe)3<H>
Base-Mediated Cleavage of Si-O-Si
High Yield to Disilanol, High Conversion and General
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
R
RR
RR
R R
35% aq Et4NOH
THFSiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
RR
R R
SiR
Si
O
OH
O
Si
O Si
Si
O
Si O Si OH
O O
OO
RR
R
RR
R
R
HO
OHSiR
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
R
R
RR
RR
Si OSi O
Si O
Proposed Mechanism
• Cleavage with retention of stereochemistry at Si (strong nucleophile and poor poor leaving group)
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
R
RR
RR
R R
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
RR
R R
OH–
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
R
RR
RR
R ROH –
H+ from H2O
Si O Si O
Si O
Proposed Mechanism
–
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
RR
R R
SiR
Si
O
OH
O
Si
O Si
Si
O
Si O Si OH
O O
OO
RR
R
RR
R
R
HO
OHSiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
ROH
R RR
SiR
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
R
R
RR
RR
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O OH
OO
OHOH
R
RR
R
R
R
R
HO
RSi(OH)3
SiR
Si
O
O
O SiO Si
O
Si O Si
O
SiOO
OO
O
R
R
RR
RR
HH
–
Si O Si O Si O
Si O
OH– H+
H+
H2O –H+
Current State of the Art
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
R
RR
RR
R R
aq Et4NOH
THF0 °C
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
RR
R R
SiR
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
R
R
RR
RR
R = i-Bu
Si O Si Oaq Et4NOH
THFreflux
i-BuSi(OMe)3
>95% yield
>95% yield>80% yield
>95% yield
(< $3.50 per pound)
Outlook for the future: The cost of POSS monomers should become comparable to the cost of bulk silanes (RSiX3).
Practical Route to POSS Monomers
SiR
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
R
R
RR
RR SiCl3X
Et3N
SiR
Si
O
O
Si OO
Si
O Si
Si
O
Si O Si
O
O O
OO
R
R
RR
RR
X
pre-1999: R = cyclopentyl or cyclohexyl
cyclopentyl, cyclohexyl, isobutyl (all work well on large scale)p-tolyl (very promising)
now:
Manufacturing costs have dropped by 2 orders of magnitude.
Practical Route to POSSMonomers
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO R
RR
RR
RR
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
RR
RR
Z–SiMeCl2
Et3N / CDCl325 °C
OSi
O
Me
Si O
R = i-Buethylvinyl
c-C5H9
c-C6H11
p-tolylC3H6NHBoc
R = = i-Buvinyl
c-C5H9
O
O
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO R
RR
RR
RR
OSi
O
Me
H
Si O
Si O R = i-Buc-C5H9
c-C6H11
Z–SiMeCl2
Et3N / CDCl325 °C
Practical Route to POSS Monomers
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO R
RR
RR
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
HOOH
R
RR
RR
RR
HBF4 · OMe2
BF3 · OEt2
R R
Si O
R = i-Bu, ethyl, vinyl,c-C5H9, c-C6H11, p-tolyl
R = = i-Buc-C5H9
c-C6H11
Si O
NH2
H2N
NLi1.
2. workup
Si
Si
SiR
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
RR
R
RR
RR
FF
Si O
Methyl-Substituted POSS
SiMe
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
Me
MeMe
MeMe
Me Me
aq Et4NOH
THFmodest yield
SiMe
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
Me
Me
MeMe
MeMeSi O
O
O
SiMe
Si
O O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
Me
MeMe
MeMe
Me
Si O• Modest quantities available.
• Properties can be evaluated.
• The potential of methyl-substituted substituted POSS can assessed.
Spherosilicates as Feedstocks?
Si
O O
Si
O
Si
Si
O
Si
SiTMSO
OO
O
O
O
TMSO
TMSO
TMSO OTMS
OTMS
TEOS or SiO2R4NOH
spherosilicatesolutions
TMSCl[(TMSO)SiO3/2]n
n = 6,8,10
SiTMSO
Si
OSi O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
O
OTMS
OTMSTMSO
TMSOOTMS
TMSO OTMS
O
Si
Si
O
OTMS
O
O
Si
Si
Si
O
O
TMSO
TMSO
SiTMSO
OTMS
O
O
O
OTMS
O
O
OTMS
OTMSTMSO
Si
O Si
O OSi
O
Si
D. Hoebbel, I. Hasegawa, P. A. Agaskar, P. G. Harrison, R. M. Laine, & others…Weidner, Zeller, Deubzer, Frey USP 5,047,492 (1991 to Wacker Chemie)
Spherosilicates as Feedstocks
Si
O O
Si
O
Si
Si
O
Si
Si
TMSO
OO
O
O
O
TMSO
TMSO
TMSO OTMS
OTMS OH–/H2O
SiTMSO
SiTMSO
Si
TMSO
SiOTMS
SiTMSO
SiOTMS
O
O
HO
HOO
O
O
O
OH
O
OH
low T
(vinyl)Me2SiCl
SiTMSO
SiTMSO
Si
TMSO
SiOTMS
SiTMSO
SiOTMS
O
O
RO
ROO
O
O
O
OR
O
OR
R = SiMe2(vinyl)
Yields for both reactions are quantitative. Both products are extremely soluble in organic solvents, and both have resisted crystallization.
Spherosilicates as Feedstocks
SiTMSO
Si
O
OH
O SiO Si
O
Si O Si
O
SiOHO
OO
OH
Ph
OTMS
OTMSTMSO
TMSOOTMS
SiTMSO
SiTMSO
Si
TMSO
Si
OTMS
SiTMSO
SiOTMS
O
O
HO
HOO
O
O
O
OH
O
OH
PhSi(OH)3
THF–20 °C
Si
TMSOSi
O O
O
Si
O
Si
OSi
O
SiO
Si
O
O
O
O O
Ph
OTMSOTMS
TMSO
TMSO
OTMS
Z-SiCl3
Si O
O
• Modest quantities available.
• Properties can be evaluated.
• Potential can assessed.
Three Approaches to Polyfunctional POSS
Direct Synthesis From Monomers
ZSiX3 Z8Si8O12 (Z = polymerizable group)
RSiX3 + ZSiZ3 ZnR(8-n)Si8O12
Partial Functionalization of Highly Functionalized POSSR8Si8O12 ZnR(8-n)Si8O12
Stoichiometric Reactions of Lightly Functionalized POSS
XnR(8-n)Si8O12 ZnR(8-n)Si8O12
R7Si7O9(OH)3 + 3 ClSiMe2Z R7Si7O9(OSiMe2Z)3
SiR
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
RR
R
RR
RRSi O
R8Si8O12
Pendant Group Modifications
X8T8 Y8T8There are 21 possible species!There are 22 possible species!
Simulation of X8Si8O12 to Y8Si8O12
(assuming that all sites are equally reactive)reactive)
0
10
20
30
40
50
60
70
80
90
100
Time
012345678
1 eq 2 eq 3 eq 4 eq
NOTE: The same product distributions can be produced by random co-condensation of X–SiCl3 and Y–SiCl3.
POSS with an Average of Three Epoxides
• Vinyl8Si8O12 is readily available in pure state
• Extent of epoxidation evaluated by 1H NMR spectroscopy
• Product distribution is believed to be random statistical mixture
(~25% tetra, 10-15% tri, 10-15% penta, 5-10% di, 5-10% hexa)
Vinyl–SiCl3 Si
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
Si O
Si
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
Si O
OO
O
(+ other isomers & homologs)
POSS with an Average of Three EpoxidesSiCl3
+
SiCl3H2O
mixed T-resincat. OH–
Cy*nCy(8-n)Si8O12
CySiCl3Cy*SiCl3(8-n)n
random statisticalmixture
peraceticacid
SiCy
Si
O
O
O
Si
O Si
Si
O
Si O Si
O
O O
OO
Cy
Cy
CyCySi O
O
O
O
(+ other isomers/homologs)
• Excellent overall yield
• Product distribution set by ratio of CySiCl3
CySiCl3 to Cy*SiCl3 (0–100%)
• Isomorphous substitution of Cy*/Cy ?
• Product distribution can be analyzed by ultra-high resolution 29Si NMR
Simulated vs Experimental 29Si NMR Spectra
Random statistical Cy/Cy*
Simple additivity rules are valid
Refs: Cy8Si8O12, Cy*8Si8O12, Cy*Cy7Si8O12
“edge” effect: ~8 Hz“face diagonal” effect: 1.5 Hz“body diagonal” effect: 0 Hz
Simulation assumes:
δ1 + 3e1 + 2f1
δ2 + 2e2
δ2 + e2δ2 + 2f2
ab
cd
Polyaminosilsesquioxanes
• Wacker-Chemie (‘91 US Patent) claims free amine, but no details provided
• Independently rediscovered by R. M. Laine (Michigan)
• Starting materials are inexpensive
• Readily available in LARGE quantities
NMR, MALDI-TOF
SiClH 3NCH 2CH 2CH2
Si
O
O
Si OO
Si
O Si
Si
O
Si O Si
O
O O
OO
CH 2CH2CH2NH 3ClClH3NCH2CH 2CH2
CH 2CH2CH2NH 3Cl
CH2CH 2CH 2NH3ClClH 3NCH 2CH 2CH2
ClH 3NCH 2CH2CH2CH 2CH2CH2NH 3Cl
H2NCH2CH2CH2Si(OMe)3HCl
MeOH
Reactions with Electrophilic Reagents
Reagent X IsolatedYield (%)
ε-caprolactone HN
OOH 23
benzoyl chloride HN
O49
maleic anhydride HN
O
OH
O64
allyl isocyanate HN
O
NH 90
phosgene N=C=O 11-47
CH2O/HPPh2 NPPh2
PPh2 37
SiR
Si
O
O
Si OO
Si
O Si
Si
O
Si O Si
O
O O
OO
RR
R
RR
RR
R = CH2CH2CH2NH2
R = CH2CH2CH2X
Silsesquioxane “Sugarballs”
O
HO OH
OHO
OHO
HO OH
OH
O
lactonolactone
O
HO OH
OHO
OHO
HO OH
OH
O
maltonolactone
galactose residue
O
HO OH
OHO
OHHO
OHOH
OH
O
glucose residue
RNH2 RNH2
NH
RO
HO OH
OHO
OHHO
OHOH
OH
O
NH
R
Si
Si
O
O
OO
Si
O Si
Si
Si O Si
O
O O
OO
NH2 H2N
H2N
NH2NH2
NH2
Si
O
H2N
NH2
I ) Concanavalin A (Con A)Turbidity Experiment
ll Octa-glucosyl POSS
¡¡ Octa-galactosyl POSS
∆∆ Octa-aminopropyl POSS
0.00
0.04
0.08
0.12
0.16
0 25 50 75 100 125 150 175
Time (minutes)
-20
0
20
40
60
80
0 1000 2000 3000
Inhibitor (µM)
Selective Binding to Lectins
Glucose Specific(reversed by addition of D-maltose)
Galactose Specific
II ) Competitive Inhibition of HepG2 (ASGPR)/125I-ASOM
Site-Specific Drug Delivery
Si
Si
O
O
O
Si
O Si
Si
Si O Si
O
O O
OO
NHHN
HN
HNNH
NH
O
NH
HN
Si
Si
O
O
O
Si
O Si
Si
Si O Si
O
O O
OO
NHHN
HN
NH
NH
ONH
HN
HN
OSiOSi
OSi
Targeting Groups
Bioactive Groupor Tag
Summary
• Fully-condensed POSS frameworks are attractive precursors to precursors to useful compounds.
– Cleavage of many frameworks is both favorable and remarkably selective.selective.
– Intermediates are versatile precursors to POSS monomers.
– Many highly functionalized frameworks are now available.
• Efforts to develop fundamental chemistry of POSS have paid big paid big dividends.
– Many fundamental chemical problems have been solved.
– Many reactions are amenable to scale up.
– Prospects for continued development are excellent.
Where is the Market for Polyhedral Silsesquioxanes (POSS)?
Considering that…
• Si and O are nearly 3/4 of the Earth’s crust.
• Starting materials are readily available: RSiX3
• Many POSS frameworks (e.g., R8Si8O12) can be prepared in high yield.yield.
• Physical characteristics should be useful:
optically transparent good UV/thermal stability
hydrolytically stable good insulators
desirable chemical and mechanical properties
• Silicones (i.e., [R2SiO]n) and silicates (i.e., [SiO2]n) are each multibillion multibillion dollar businesses.
There are Markets Everywhere!
The potential of POSS has been
unrealized because the chemistry of
POSS has been relatively undeveloped.
Recent developments in POSS chemistry provide provide ways to capture this potential.