Vibrational spectra of fluorocarbon–Group V derivatives. Part II. The compounds CF₃·PX₂where X = halogen or hydrogen

Abstract

The gas-phase i.r. and liquid-phase Raman spectra of the phosphines CF,-PX, (X = H, F, CI. Br. or I) have been recorded. The observed bands have been assigned on the basis of C, symmetry. However, there is substantial mixing of the internal co-ordinates of vibration, and so simple group-frequency correlations cannot be made for all of the bands. The coupling of vibrations is less severe in the case of CF,PH,.

Vibrational spectra, force constants and conformations of molecules of trivalent tricoordinate phosphorus compounds

“…2 & 700 cm 71 . These changes in the n(P7C) frequencies on going from molecule 1 to the molecule 2 are mainly due to the coupling of two individual oscillators sharing the phosphorus atom.…”

“…2 ) can differ appreciably from the frequencies of the `old' vibrations; as a rule, n 0 1 < n 1 & n 2 < n 0 2 . Thus in the molecule of methylphosphine (1), vibrations with a predominant contribution of the P7C bond occur at a frequency of about 670 cm 71 . Vibrations of two P7C bonds in the molecule of dimethylphosphine (2) give rise to two new vibrations, viz., a symmetric stretch of both bonds at a frequency n 0…”

“…Vibrations of the PCl 2 group in the molecule of methyl phosphorodichloridite, CH 3 OPCl 2 (3), are characterised by strong IR absorption bands at * 460 and * 500 cm 71 . The frequencies of bending vibrations of the butyl group lie in the same spectral region.…”

“…This makes it possible to judge the changes in the electronic structure of the molecules if analysis of their force fields reveals large and systematic deviations. The notations are given according to monograph 6 and the values of force constants are given in 10 2 N m 71 .…”

“…All frequencies are given in cm 71 . The intensities (I ) and shapes of spectral bands, as well as the degree of depolarisation of the Raman lines (r), are qualitatively described using the following notations: w for weak, m for medium, s for strong, ms for medium strong, br for broad, v for very, sh for shoulder, p for polarised and dp for depolarised.…”