Some remarks on the Raman spectrum of solid phosphorus pentachloride

Powell c.s. deduced from an X‐ray study that solid PCl5 has to be considered as [PCl4+] [PCl6−]. From the distances between P and Cl in PCl4+ and in PCl6− given by the authors, force constants fPCl4+ and fPCl6− have been calculated using Badger's rule. From these f values and by a comparison with the results of a similar calculation for SiCl4 it follows that the strongest lines of the Raman spectrum of PCl5, namely 358(15) and 451 (7), belong to v1(PCl6−) and v1(PCl4+) respectively. With these frequencies known, it is possible to make an estimate of the frequencies to be expected for the other Raman‐active vibrations of both ions. A probable assignment of Raman shifts to vibrations of PCl4+ and PCl6− is given. Force constants have been calculated for both ions, using formulae based on Nath's force field and on the orbital valence force field introduced by Heath and Linnett, Probable frequency values: PCl4+ 173, 244, 451, 627; PCl6− 244, 285, 358.