A Spectroscopic and Crystallographic Study of the Polymorphism of [SF3][SbF6], and Structural Characterization of [SF3][AsF6]

Abstract

The [SF3][AsF6] and [SF3][SbF6] salts are structurally characterized by X-ray crystallography. Variable-temperature Raman and 19F MAS NMR spectroscopy reveal three different polymorphes for [SF3][SbF6] between −25 and −145 °C, while the AsF6– salt does not exhibit polymorphism in this temperature range. The high- and low-temperature modifications of [SF3][SbF6], i.e., α- and γ-[SF3][SbF6], could be structurally characterized by X-ray crystallography. The β-[SF3][SbF6] phase shows a distinctly different 19F MAS NMR spectrum with resolved couplings to the 121,123Sb nuclei. In the entire temperature range, the exchange of the environments within the cations and within the anions is rapid on the NMR time scale.