SPECTRA AND STRUCTURE OF PHOSPHORUS-BORON COMPOUNDS .27. LOW-RESOLUTION MICROWAVE, IR AND RAMAN-SPECTRA, CONFORMATIONAL STABILITY, AB-INITIO CALCULATIONS, VIBRATIONAL ASSIGNMENT AND NORMAL-COORDINATE CALCULATIONS FOR (CHLOROMETHYL)DIFLUOROPHOSPHINE BORANE
Bj. Vanderveken et al., SPECTRA AND STRUCTURE OF PHOSPHORUS-BORON COMPOUNDS .27. LOW-RESOLUTION MICROWAVE, IR AND RAMAN-SPECTRA, CONFORMATIONAL STABILITY, AB-INITIO CALCULATIONS, VIBRATIONAL ASSIGNMENT AND NORMAL-COORDINATE CALCULATIONS FOR (CHLOROMETHYL)DIFLUOROPHOSPHINE BORANE, Spectrochimica acta. Part A: Molecular spectroscopy, 49(13-14), 1993, pp. 1833-1871
The low-resolution microwave spectrum of (chloromethyl)difluorophosphi
ne borane, ClCH2PF2.BH3, has been investigated from 26.5 to 39 GHz. Ba
sed on the calculated dipole moments and the fact that the microwave s
pectrum is an a-type spectrum along with the spacing of the central tr
ansitions for the near-prolate top, it is concluded that the predomina
nt spectrum is that for the conformer with the CCl bond trans to the P
B bond. The IR (4000-40 cm(-1)) and Raman (3500-20 cm(-1)) spectra of
the gas and solid of five isotopic species have been recorded. Additio
nally, the Raman spectra of the liquids have been recorded and qualita
tive depolarization values have been obtained. Both the trans and gauc
he conformers have been identified in the vibrational spectra of the f
luid phases. From a temperature study of the Raman spectrum of the liq
uid, the enthalpy difference between the trans and gauche conformers w
as determined to be 162 +/- 9 cm(-1) (463 +/- 26 cal mol(-1)) with the
gauche conformer being the more stable rotamer. Depending on experime
ntal circumstances upon crystallization, either a solid containing onl
y the gauche conformer or a solid containing both the gauche and trans
conformers can be obtained. All of the normal modes have been assigne
d based on IR band contours, depolarization values and group frequenci
es. Additionally, ab initio calculations have been carried out utilizi
ng both 3-21G and 6-31G* basis sets to obtain the stabilties, barrier
s to internal rotation, and optimized structural parameters. A normal
coordinate analysis has also been performed with a force field determi
ned from the 3-21G basis set for both conformers. These results are c
ompared with the corresponding quantities, of some similar compounds.