Spectra and structure of silicon-containing compounds. XXV. Raman and infrared spectra, r(0) structural parameters, vibrational assignment, and ab initio calculations of ethyl Chlorosirane-Si-d(2)

The infrared (3200 to 400 cm(-1)) spectra of gaseous and solid and Raman (3 200 to 20 cm(-1) spectra of liquid and solid ethyl chlorosilane-Si-d(2), CH 3CH2SiD2Cl, have been recorded. Both the gauche and trans conformers have b een identified in the fluid phases, but only the gauche conformer remains i n the solid phase. Variable temperature (-105 to -150 degrees C) studies of the infrared spectra of CH3CH2SiH2Cl dissolved in liquid krypton have been carried out. From these data, the enthalpy difference has been determined to be 78 +/-11 cm(-1) (0.93 +/- 0.13 kJ/mol), with the gauche conformer the more stable form. Utilizing the frequencies of the silicon-hydrogen stretc hes, from the chlorosilane-Si-d isotopomer, Si-H bond distances of 1.481 an d 1.480 Angstrom have been obtained for the gauche conformer and 1.481 Angs trom for the trans conformer. Complete vibrational assignments are proposed for both isotopomers which are consistent with the predicted frequencies u tilizing the force constants from ab initio MP2/6-31G(d) calculations. Both the infrared intensities and the Raman activities and depolarization value s have been obtained from the ab initio calculations. Complete equilibrium geometries have been determined by ab initio calculations employing the 6-3 1(d), 6-311++G(d,p), and 6-311+G(2d,2p) basis sets with full electron corre lation by the Moller-Plesset CMP) perturbation method to second order. Cont inuing the previously reported rotational constants from five different iso topomers and the ab initio predicted structural parameters, adjusted r(0) p arameters have been calculated, which are compared to the corresponding r(s ), parameters. The results are discussed and the theoretical values are com pared to the experimental values when appropriate.