Preparation and properties of the pentachlorovanadate(IV) ion and related species

Abstract

The compound previously believed to be vanadium(V) chloride has been shown to be the tetrachlorophosphonium salt of the five-co-ordinate VCl₅^– anion. This salt arises in the reactions of phosphorus pentachloride with vanadium(V) oxide trichloride in hot phosphoryl chloride or dichloroethane and of vanadium(IV) chloride with phosphorus pentachloride in arsenic trichloride or phosphoryl chloride. The novel compounds [PCl₄⁺][VOCl₄^–] and VBr₃,POBr₃ have also been characterised. Contrary to previous reports no evidence has been found to support the existence of solid salts of [PCl₄⁺] with chlorovanadate(IV) anions of higher co-ordination number than five.