The i.r. and Raman spectra of sodium hexafluorophosphate monohydrate, NaPF 6·H 2O

Abstract

The i.r. and Raman spectra of NaPF 6·H 2O and partially deuterated NaPF 6·H 2O have been obtained. All of the fundamental modes of the PF − 6-ion have been located and the rule of mutual exclusion applies for these modes. In the Raman spectra, the number of components observed for each fundamental PF − 6-mode is consistent with the number of site group components predicted. The hydrogen bonds in NaPF 6·H 2O are very weak and the hydrogen bond energy is of the order of 1.7 kcal/mole. The frequencies of the nine fundamental modes of the H 2O, D 2O and HDO molecules have been converted to harmonic values. It is shown that if the HOH valence angle is varied, and the effective harmonic force field of the water molecules calculated for each assumed value, an estimated value of this angle in NaPF 6·H 2O can be obtained. The librational modes of the water molecules have been located and are assigned to rocking and wagging modes.