Determination of the gas-phase molecular structure of bis(trimethylsilyl)sulphide by electron diffraction and molecular mechanics calculations

Abstract

The molecular structure of S(SiMe 3) 2 in the gas phase has been determined by electron diffraction, aided by molecular mechanics (MM2) calculations. The results of two refinements are reported. In the first, the SiMe 3 groups were assumed to have local C 3 symmetry, while in the second all the SSi distances, SiC distances, and SSiC and CSiC angles were allowed to differ from one another, with the differences fixed at the values calculated by molecular mechanics. Allowing for the asymmetry of the SiMe 3 groups had a significant effect on some of the refined parameters, most notably the mean SSiC angle, which increased from 105.6(7) to 109.2(3)°, and the angle SiSSi, which increased from 104.0(5)° to 105.8(7)°. Other major parameters ( r a) obtained in the refinement with asymmetric SiMe 3 groups are r(SiS)=215.4(1) pm and r(SiC) (mean)=187.1(1) pm. The two SiMe 3 groups are twisted by 17.1(13) and 29.6(14)° from the position in which one SiC bond of each group lies anti with respect to the further SSi bond.