Vibrational spectra and normal coordinate analysis of CF3 compounds Part XLVII. Vibrational spectra, normal coordinate analysis and electron diffraction investigation of CF3SiH3 and its deuterated varieties

The molecular structure of CF₃SiH₃ in the gas phase has been determined by electron diffraction analysis. Combined with a B₀ value derived from high resolution infrared spectra, this yielded r(SiC), 1.923(3) Å, r(SiH) 1.482(5) Å, r(CF) 1.348(1) Å, FCF 106.7(5)° and HSiH 110.3(10)° (r° values). The gas phase infrared and liquid phase Raman spectra of CF₃SiH₃, CF₃SiH₂D, CF₃SiD₃ have been measured and assigned, and force constants have been calculated by means of a normal coordinate analysis based on 52 experimental frequencies. The weakness of the SiC bond is confirmed by the low f(SiC) value of 2.54 N cm⁻¹. Infrared spectra recorded with a resolution of 0.04 cm⁻¹ at 240 K revealed rotational structure of vibrational bands. Rotational analyses of most parallel and a few perpendicular bands of CF₃SiH₃ and CF₃SiD₃ have been performed. Ground and excited state vibrational parameters have been obtained and used as supplementary data for the determination of the harmonic force field. Strong blending of all bands due to hot band cascades was noted.