Vibrational Spectra of OsF6 and PtF6

Abstract

Infrared absorption spectra of gaseous OsF6 and PtF6 from 6–50μ and the Raman spectrum of liquid OsF6 are reported. These are interpreted in terms of the octahedral point group Oh, and the six fundamental frequencies are determined. Their values and symmetry species are for OsF6 733 (a1g), 632 (eg), 720 (f1u), 268 (f1u), 252 (f2g), and 230 (f2u); for PtF6 655 (a1g), 601 (eg), 705 (f1u), 273 (f1u), 242 (f2g), and 211 (f2u). Thermodynamic functions, including electronic contributions, are calculated for the ideal gaseous state of both compounds. A comparison of the details of the vibrational spectra of eleven hexafluorides reveals certain characteristic features for OsF6 and ReF6. Since only these two molecules have appropriately degenerate electronic ground states these differences are interpreted as evidence of a Jahn-Teller effect.