Three-fold rotational barrier in CH2=CH-MX3 (M=C, Si, and Ge, and X=F and Cl) and analysis of vibrational spectra of the germanes

Abstract

The structure of CH 2=CH-MCl 3 and CH 2=CH-MF 3 (where, M is C, Si, and Ge) series of molecules was investigated by DFT-B3LYP/6-311++G** and ab initio MP2/6-311++G** calculations. The symmetric potential functions for the internal rotation of the MX 3 rotors were calculated and determined to be in the order: CX 3>SiX 3>GeX 3 for the molecules. The vibrational frequencies were computed. The decrease in the MX 3 rotational barrier is attributed to the decrease in the C–M covalent bond character as going from C, Si, to Ge. The potential energy distributions PED among symmetry coordinates of the normal modes of vinyl trihalogermanes were calculated from normal coordinate calculations.