Silicon-Carbon Double Bond: Theory Takes a Round

H. S. Gutowsky, Jane Chen, P. J. Hajduk, J. D. Keen, C. Chuang, T. Emilsson

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Abstract

Six b-dipole rotational transitions have been observed between 8 and 9.2 GHz for the transient species 1,1-dimethylsilaethylene (DMSE) produced by thermal decomposition of 1,1-dimethylsilacyclobutane at ~1000 °C. The Si=C and C-C bond lengths determined from these observations are in excellent agreement with theoretical predictions [Acc. Chem. Res. 1982, 15, 283]. Analysis of the quartet fine structure from internal rotation gives a barrier V3 = 1004 (17) cal/mol, a methyl top moment of inertia Iα = 3.18 (5) µÅ2, and a top axis to b-axis angle θ = 55.6 (1)°. The fit of the line centers with a rigid-rotor model finds A, B, and C rotational constants to be 6037.93, 5896.78, and 3093.70 MHz, respectively. The heavy-atom effective structure determined from these parameters is ro(Si=C) = 1.692 (3) Å, ro(C-Si) = 1.868 (3) Å, and ∠(C-Si-C) = 111.4 (2)°. The methyl groups do not appear to be tilted appreciably; however, the observed ∠(C-Si-C) is 2.3° smaller than predicted. The furnaces and procedures developed for the formation and observation of DMSE are described. They are applicable to other transient and reactive species.

Original languageEnglish (US)
Pages (from-to)4747-4751
Number of pages5
JournalJournal of the American Chemical Society
Volume113
Issue number13
DOIs
StatePublished - Jun 1 1991

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