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Author Schrock, R. R. ♦ Luo, S. ♦ Lee, J. C. (Jr.) ♦ Zanetti, N. C. ♦ Davis, W. M.
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword CHEMISTRY ♦ ALKENES ♦ POLYMERIZATION ♦ MOLYBDENUM COMPLEXES ♦ STRUCTURAL CHEMICAL ANALYSIS ♦ EXPERIMENTAL DATA ♦ ACETYLENE ♦ CHEMICAL REACTION KINETICS ♦ NMR SPECTRA ♦ CATALYSTS ♦ BOND ANGLE ♦ BOND LENGTHS
Abstract syn-Mo(CHCMe{sub 2}Ph)(NAd) [OCH(CF{sub 3}){sub 2}]{sub 2}(2,4-lutidine) (2a; Ad = 1-adamantyl) reacts with (o-(trimethylsilyl) phenyl)acetylene(o-TMSPA) solely via formation of an {alpha}-substituted metallacyclobutene intermediate ({alpha} addition) that opens to give a single rotamer of a disubstituted alkylidene complex. o-TMSPA is smoothly polymerized at a rate k{sub 2a}[2a]{sub 0}[o-TMSPA] when [2a] < 1 mM with a propagation rate constant k{sub 2a} = 0.30 s{sup -1} M{sup -1}. Additional studies confirmed that the disubstituted alkylidene propagating species is essentially base-free and that the propagating species is stable under catalytic conditions (25{degree}C). Other versions of the Mo(CHCMe{sub 2}Ph)(NAd)[OCH(CF{sub 3}){sub 2}]{sub 2}(base) catalyst are either inactive (base = pyridine) or unstable (base = 2-(3-pentyl)pyridine). Low-polydispersity polyenes containing up to 150 equiv of o-TMSPA can be obtained readily using either catalyst. The thermodynamically most stable form of poly(o-TMSPA), which contains nearly 25 double bonds, is air-sensitive and has a significantly red-shifted {lambda}{sub max}. o-t-BuPA also can be polymerized to give highly conjugated polyenes, but o-i-PrPa, o-MePA, and phenylacetylene itself add to initiator 2a with decreasing {alpha} regiospecificity (73%, 60%, and 56%, respectively). 35 refs., 6 figs., 10 tabs.
ISSN 00027863
Educational Use Research
Learning Resource Type Article
Publisher Date 1996-04-24
Publisher Place United States
Journal Journal of the American Chemical Society
Volume Number 118
Issue Number 16


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