B. Beagley, R. Pritchard
Sep 1, 1982
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Influential Citations
20
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Journal
Journal of Molecular Structure
Abstract
Abstract The molecular structure of the sterically overcrowded molecule tris(trimethylsilyl)-methane has been studied using gas-phase electron diffraction data collected on the Balzers KDG2 instrument at UMEST. The diffraction data are compatible with a single conformer of point group C 3 and local three-fold symmetry at the -CH 3 and -SiMe 3 groups. The three-fold axes of the —SLMe 3 groups are inclined at 99.3(3)° to the molecular three-fold axis. The molecular overcrowding also leads to a slight lengthening of the central Si-C bonds (1.888(6)A) compared with the Si-Me bonds (1.873(2)A), and a deviation of the torsional angles from the values typifying staggered conformations. The torsional angle for H * CSiMe is 80.5(3)° (where H* denotes the unique H atom) and that for the methyl groups is −23(4)° (mean from preferred refinements). The three-fold axes of the -SiMe 3 groups may deviate slightly (1.9(6)° ) from the line of the H*C-SiMe 3 bonds. Other structural parameters are C-H = 1.114(2)A, ∠CSiMe = 112.8° (average), and within SiMe 3 groups: ∠MeSiMe = 105.8(3)°, ∠SiCH = 112.1(3)° and ∠HCH = 106.7(3)°.