A 19 F Nuclear Magnetic Resonance and Raman Spectroscopic Study of Complex Formation between Antimony Pentafluoride and the Pentafluorides of Niobium and Tantalum

Abstract

The low temperature 19 F nuclear magnetic resonance (n.m.r.) spectra of NbF 5 –SbF 5 –SO 2 ClF and TaF 5 –SbF 5 –SO 2 ClF systems appear to indicate ionization of the pentafluorides to form niobium (tantalum) fluorocations and antimony polyfluoroanions, but the solutions show an unusual distribution of species and have very low conductivities. It is concluded that neutral "fluxional" MF 4 –Sb n F 5n+1 molecules are formed. The 19 F n.m.r. spectra and conductivities of the liquid systems NbF 5 –SbF 5 and TaF 5 –SbF 5 are consistent with the formation of neutral fluorine-bridged polymers with mixed transition metal and antimony units. These polymers may be "fluxional" on the n.m.r. time scale. The Raman spectra of the liquid systems and the crystalline pentafluoride mixtures show that both contain mixed cis fluorine-bridged units. The Raman spectrum of crystalline SbF 5 and the 19 F n.m.r. spectrum of the NbSbF 11 − ion are reported.