Microwave, r0 structural parameters, conformational stability and vibrational assignment of cyclopropylcyanosilane

Abstract

The FT-microwave spectrum (6000–19,800MHz) of cyclopropylcyanosilane, c-C3H5SiH2CN has been recorded and 773 transitions for the 28Si, 29Si, 30Si, 13C and 15N isotopomers have been assigned for cis and gauche conformers. Infrared spectra (3200–220cm−1) of gas and Raman spectra (3200–40cm−1) of the liquid have been recorded as well as the variable temperature (−60 to −100°C) studies of the infrared spectra of the sample dissolved in liquid xenon. The enthalpy difference between the conformers in xenon solutions has been determined to be 123±13cm−1 (1.47±0.16kJmol−1) with the cis conformer as the more stable form. Approximately 48±2% of the cis form is present at ambient temperature. By utilizing the microwave rotational constants of six isotopomers for cis and seven isotopomers for gauche combined with the structural parameters predicted from MP2(full)/6-311+G(d,p) calculations, adjusted r0 parameters have been obtained for both conformers.