SPECTRA AND STRUCTURE OF ORGANOPHOSPHORUS COMPOUNDS .52. RAMAN AND INFRARED-SPECTRA, CONFORMATIONAL STABILITY, AND AB-INITIO CALCULATIONS FOR METHOXYDICHLOROPHOSPHINE

The Raman (3500 to 30 cm(-1)) and infrared spectra (3500 to 50 cm(-1)) of gaseous and solid methoxydichlorophosphine, CH3OPCl2, have been re corded. An infrared study of CH3OPCl2 dissolved in xenon as a function of temperature, as well as a temperature study of the Raman spectra o f all phases, definitively shows that only the trans conformer (methyl group trans to the phosphorus lone pair) is present in all phases. Th e far-infrared spectrum of the gas has been recorded from 350 to 30 cm (-1) at a resolution of 0.10 cm(-1). The fundamental asymmetric torsio nal mode has been observed at 120 cm(-1), and the frequency of the met hyl torsional mode is estimated to be 58 cm(-1) from a combination ban d. A complete vibrational assignment is given for both the normal and d(3)-isotopomer which is supported by ab initio calculations employing the RHF/3-21G basis set. The structural parameters and relative conf ormer stabilities have been obtained with the RHF/6-31G and MP2/6-31G basis sets. From these calculations, the gauche conformer is estimat ed to be more than 3.6 kcalmol(-1) less stable than the trans conforme r which is consistent with the observation of only the trans conformer in the Raman spectrum of the gas at ambient temperature. All of these results are discussed and compared with the corresponding quantities obtained for some similar molecules.