DETERMINATION OF THE GAS-PHASE MOLECULAR-STRUCTURES OF DI-TERT-BUTYLDICHLOROSILANE AND DI-TERT-BUTYLCHLOROSILANE BY ELECTRON-DIFFRACTION AND MOLECULAR MECHANICS CALCULATIONS

The molecular structures of SiBut2Cl2 and SiBut2ClH in the gas phase have been determined by a combination of electron diffraction and molecular mechanics. The advantage of using molecular mechanics as a guide to the structures is shown. In both structures the butyl groups adopt nearly staggered conformations with respect to opposite SiC bonds. In SiBut2Cl2, assuming C2 symmetry, the parameters (ra) are: r(SiCl)=206.9(1), r(SiC)=189.1(4), r[C(1)-C(2)]=154.8(2), r(CH)=113.5(2) pm, ∠ SiC(1)C(2)=108.7(2), ∠ CCH=112.6(9), ∠ CSiC=125.3(6), ∠ ClSiCl=102.7(5), ø[C(14)SiC(1)C(2)]=167.1(1), ø[SiC(1)C(2)H(3)]=145.9(18)°. In SiBut2ClH, the geometric parameters are: r(SiCl)=208.7(2), r(SiC)=190.3(4), r[C(1)-C(2)]=154.1(1), r(CH)=113.1(3), r(SiH)=148.7 pm, ∠ SiC(1)C(2)=106.5(2), ∠ CCH=113.2(11), ∠ CSiC=125.2(5), ∠ ClSiH= 102.7(13), ø[C(14)SiC(1)C(2)]=167.8(8), ø[SiC(1)C(2)H(3)]=157.4(17)°. © 1990.