Ab initio calculation of the conformational stability, vibrational wavenumbers, Raman and infrared intensities and structural parameters of chloromethyldichlorophosphine

The structural parameters acid conformational stabilities of the trans (the C-Cl bond is trans to the phosphorus lone pair) and gauche rotamers of chloromethyldichlorophosphine, ClCH2PCl2, were obtained from ab initio calculations up to the MP2/6-311 + G** level. In each case the gauche form was determined to be more stable than the tuans conformer and the energy difference was calculated to be in the region of 400 cm(-1) (4.79 kJ mol(-1)). Utilizing four pairs of conformer bands in the Raman spectrum of the liquid, the enthalpy difference was determined to be 240 +/- 40 cm(-1) (2.87 +/- 0.48 kJ mol(-1)). Full optimization was also performed at the gauche/trans and gauche/gauche transitional states and the gauche to gauche barrier was calculated to be 1119 cm(-1) and the gauche to trans barrier to be 2188 cm(-1) from the MP2/6-31G* calculation. The ab initio-calculated vibrational wavenumbers and the Raman and infrared intensities were compared with the corresponding experimental quantities. Similar ab initio calculations were carried out for methyldichlorophosphine, CH3PCl2, for comparison with the results for ClCH2PCl2, and with the corresponding experimental data when appropriate. (C) 1998 John Wiley & Sons, Ltd.