Spectra and structure of organosphosphorus molecules. Part LX—Raman and infrared spectra, conformational stability, ab initio calculations and vibrational assignment of fluoromethyldichlorophosphine

✍ Scribed by J. R. Durig; T. R. Honeycutt; F. F. D. Daeyaert; J. B. Robb II

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 176 KB
• Volume: 30
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/(sici)1097-4555(199903)30:3<155::aid-jrs364>3.0.co;2-4

✦ Synopsis

The Raman spectra (3500-30 cm-1) of gaseous, liquid and solid and the infrared spectra (3500-400 cm-1) of gaseous and solid Ñuoromethyldichlorophosphine, were recorded. The data indicate that two con-FCH 2 PCl 2 , formers are present in the Ñuid states where the gauche conformer is the predominant species but only the trans rotamer (the F atom on the methyl group is trans to the phosphorus lone pair of non-bonded electrons) remains in the crystalline solid. The enthalpy, DH, was determined to be 165 » 8 cm-1 (472 » 24 cal mol-1); 1 cal = 4.184 J with the gauche conformer more stable from the sample dissolved in liquiÐed xenon utilizing the bands assigned to the rocks for the two conformers. Additionally, utilizing six Raman lines in the spectrum of the liquid and CH 2 adjusting for their ab initio-predicted relative intensities, the enthalpy di †erence was determined to be 156 » 67 cm-1 (447 » 193 cal mol-1), again with the gauche conformer the more stable form. These values are in agreement with the 273 cm-1 energy di †erence obtained from ab initio MP2/6-311+ + G** calculations. Complete vibrational assignments are proposed for both conformers based on infrared band contours, Raman and infrared relative intensities and group wavenumbers, which are supported by normal coordinate calculations utilizing the force constants from ab initio MP2/6-31G* calculations. The optimized geometries, conformational stabilities, harmonic force Ðelds, infrared intensities, Raman activities, depolarization ratios and vibrational wavenumbers are reported for both conformers from RHF/6-31G* and/or MP2/6-31G* ab initio calculations. The calculated quantities are compared with the experimentally determined values where applicable and also with some corresponding results for some similar molecules.