DETERMINATION BY ELECTRON-DIFFRACTION OF THE MOLECULAR-STRUCTURES OF CHLORO-TRIS(TRIMETHYLSILYL)METHANE AND BROMO-TRIS(TRIMETHYLSILYL)METHANE IN THE GAS-PHASE

The molecular structures of chloro- and bromo-tris(Trimethylsilyl)meth ane in the gas phase have been determined by electron diffraction. Bot h molecules have inner SI-C bonds which are longer than normal and wid e Si-C-Si angles. Principal parameters (r(a)) for CCI(SiMe(3))(3), wit h estimated standard deviations in parentheses, are r(C-CI) 182.3(15) pm, r(Si-C-inner) 193.9(6) pm, r(Si-C-outer) 188.2(2) pm, and angles C I-C-Si 102.7(5)degrees and C-outer-SI-C-outer 109.6(4)degrees. The thr ee trimethylsilyl groups are twisted 14.6(7)degrees from the staggered positions, and tilted 1.3(6)degrees away from the molecular three-fol d axis. For CBr(SiMe(3))(3) the major parameters are r(C-Br) 191.1(35) pm. r(Si-C-inner) 195.4(15) pm, r(Si-C-outer) 187.7(3) pm. Br-C-Si 10 6.5(6)degrees and C-outer-SI-C-outer 109.3(5)degrees. The trimethylsil yl groups are twisted 13.5(7)degrees from the staggered positions, but the tilt angle of these groups could not be determined.