Vibrational Spectra of SPCl3, SPCl2F, SPClF2, and SPF3

Abstract

The infrared spectra of thiophosphoryl trichloride and thiophosphoryl dichlorofluoride in both the liquid and gaseous states, and thiophosphoryl chlorodifluoride and thiophosphoryl trifluoride in only the gaseous state have been recorded from 4000 to 100 cm⁻¹. The Raman spectra have also been recorded for the four thiophosphoryl trihalides in the liquid state and depolarization values measured. Complete vibrational assignments based on band contours, positions, and depolarization values are given. The spectra are interpreted in detail assuming C_s symmetry for thiophosphoryl dichlorofluoride and thiophosphoryl chlorodifluoride, and C_3v symmetry for the other two molecules. The vibrational assignment proposed for the SPF₃ molecule is in marked contrast to that currently accepted. The P–S stretching vibration is found to decrease in frequency with the increased number of fluoride atoms attached to the phosphorous atom. Possible reasons for the decrease in frequency are discussed.