Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignments for 2-chloroethyl silane

The infrared (3500-30 cm(-1)) spectra of gaseous and solid and the Raman (3500-10 cm(-1)) spectra of liquid with quantitative depolarization ratios and solid 2-chloroethyl silane, ClCH2CH2SiH3, have been recorded. Similar data have been recorded for the Si-d(3) isotopomer. These data indicate that two conformers, trans and gauche, are present in the fluid states bur only one conformer, trans, is present in the solid. The mid-infrared spectra of the sample dissolved in Liquified xenon as a function of temperature (-55 to -100 degrees C) has been recorded. The enthalpy difference between the conformers has been determined to be 181 +/- 12 cm(-1) (2.17 +/- 0.14 kJ/mol) with the trans rotamer the more stable form. From the isolated Si-H frequencies from the Si-d(2) isotopomer the r(o) Si-H distances of 1.484 and 1.483 Angstrom for the trans and 1.481 for the gauche conformers have been obtained. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311+G** from which structural parameters and conformational stabilities have been determined. With all the basis sets the trans form is predicted to be the more stable conformer which is consistent with the experimental results. These results are compared to the corresponding quantities for the carbon analogue. (C) 1999 Elsevier Science B.V. All rights reserved.