Living Polymerization of (o-(Trimethylsilyl)phenyl)acetylene by Molybdenum Imido Alkylidene Complexes
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- 作者：Richard R. Schrock ; Shifang Luo ; Jesse C. Lee ; Jr. ; Nadia C. Zanetti ; and William M. Davis
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：April 24, 1996
- 年：1996
- 卷：118
- 期：16
- 页码：3883 - 3895
- 全文大小：392K
- 年卷期：v.118,no.16(April 24, 1996)
- ISSN：1520-5126
文摘
syn-Mo(CHCMe2Ph)(NAd)[OCH(CF3)2]2(2,4-lutidine)(2a; Ad = 1-adamantyl) is a distortedtrigonalbipyramid in which 2,4-lutidine occupies an axial position, a structurethat results from addition of 2,4-lutidine tothe CNO face of unstable pseudotetrahedralsyn-Mo(CHCMe2Ph)(NAd)[OCH(CF3)2]2.2a reacts with (o-(trimethylsilyl)phenyl)acetylene (o-TMSPA) solelyvia formation of an 
-substituted metallacyclobuteneintermediate( addition) that opens to give a single rotamer of a disubstitutedalkylidene complex. o-TMSPA is smoothlypolymerized at a ratek2a[2a]0[o-TMSPA]when [2a] < 1 mM with a propagation rate constantk2a = 0.30s-1M-1.Additional studies confirmed that the disubstituted alkylidenepropagating species is essentially base-free(K2a = 62M-1) and that the propagating species isstable under catalytic conditions (25 
C). Other versions of theMo(CHCMe2Ph)(NAd)[OCH(CF3)2]2(base)catalyst are either inactive (base = pyridine) or unstable (base =2-(3-pentyl)pyridine).Mo(CHCMe2Ph)(NAr')(OC6F5)2(quinuclidine)(7; Ar' = 2,6-Me2C6H3)will also react smoothlywith (o-(trimethylsilyl)phenyl)acetylene to givepoly(o-TMSPA) with K7= 1380 M-1 andk7 = 0.23s-1 M-1.Low-polydispersity polyenes containing up to 150 equiv of o-TMSPAcan be obtained readily using either catalyst. Thethermodynamically most stable form of poly(o-TMSPA),which contains ~25 double bonds, is air-sensitive andhasa significantly red-shifted 
max.o-t-BuPA also can be polymerized to givehighly conjugated polyenes, but o-i-PrPA, o-MePA, and phenylacetylene itself add to initiator2a with decreasing regiospecificity (73%, 60%,and56%, respectively). A lack of regiospecificity we propose leadsto polymers that do not have a pure head-to-tailstructure, have a lower degree of conjugation, and have a progressivelymore blue-shifted max.
-substituted metallacyclobuteneintermediate( addition) that opens to give a single rotamer of a disubstitutedalkylidene complex. o-TMSPA is smoothlypolymerized at a ratek2a[2a]0[o-TMSPA]when [2a] < 1 mM with a propagation rate constantk2a = 0.30s-1M-1.Additional studies confirmed that the disubstituted alkylidenepropagating species is essentially base-free(K2a = 62M-1) and that the propagating species isstable under catalytic conditions (25 C). Other versions of theMo(CHCMe2Ph)(NAd)[OCH(CF3)2]2(base)catalyst are either inactive (base = pyridine) or unstable (base =2-(3-pentyl)pyridine).Mo(CHCMe2Ph)(NAr')(OC6F5)2(quinuclidine)(7; Ar' = 2,6-Me2C6H3)will also react smoothlywith (o-(trimethylsilyl)phenyl)acetylene to givepoly(o-TMSPA) with K7= 1380 M-1 andk7 = 0.23s-1 M-1.Low-polydispersity polyenes containing up to 150 equiv of o-TMSPAcan be obtained readily using either catalyst. Thethermodynamically most stable form of poly(o-TMSPA),which contains ~25 double bonds, is air-sensitive andhasa significantly red-shifted max.o-t-BuPA also can be polymerized to givehighly conjugated polyenes, but o-i-PrPA, o-MePA, and phenylacetylene itself add to initiator2a with decreasing regiospecificity (73%, 60%,and56%, respectively). A lack of regiospecificity we propose leadsto polymers that do not have a pure head-to-tailstructure, have a lower degree of conjugation, and have a progressivelymore blue-shifted max.