Spectra and structure of silicon containing compounds. XXVI. Raman and infrared spectra, r(o) structural parameters, conformational stability, vibrational assignment, and ab initio calculations of vinyl silyl chloride

Variable temperature (-55 to -150 degrees C) studies of the infrared spectr a between 4000 and 400 cm(-1) of vinyl silyl chloride, CH2CHSiH2Cl, dissolv ed in liquid xenon and krypton have been recorded. From the xenon 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. However, in the krypton solution the conformational stability could not be determined. The Raman spectra (3500-20 cm(-1)) of liquid and solid, as well as the infrare d spectra of the gaseous and solid vinyl silyl-d(2) chloride, have been rec orded. Utilizing the isolated silicon-hydrogen stretching frequencies from the CH2CNSiHDCl molecule the Si-H distances of 1.479 Angstrom were obtained for both conformers. Vibrational assignments are provided for the CH2CHSiD 2Cl molecule for both conformers. Complete equilibrium geometrics have been determined for both rotamers using ab initio calculations employing the 6- 31 G(d), 6-311 + G(d,p) and 6-311 + G(2d,2p) basis sets at. the levels of r estricted Hartree-Fock and/or with full electron correlation by the perturb ation method, Moller-Plesset, to the second order, irrespective of the size of the basis set used, the gauche conformer is predicted to be the more st able conformer, which is in agreement with the experimental results. Utiliz ing previously reported microwave rotational constants for both conformers along with the ab initio predicted structural values, r(0) parameters have been obtained for both the cis and gauche conformers. The spectroscopic and theoretical results are discussed and compared to the corresponding quanti ties for some similar molecules. (C) 2000 Elsevier Science B.V. All rights reserved.