Mixed halogen complexes of phosphorus. Part I. Preparation and Raman spectra of the chlorobromophosphonium ions, [PClnBr4–n]+(0 ⩽n⩽ 4)

Abstract

The preparation of some complexes and mixtures containing the PCl₃Br⁺, PCl₂Br₂⁺ and PClBr₃⁺ ions is described. A vibrational assignment for each species has been made based on data from Raman spectra of the complexes in the solid state. Some characteristic shifts occur in the fundamental frequencies of the phosphonium ions where single halide or polyhalide anions are present in the crystal lattice. It is suggested that such vibrational frequencies can be used to infer (a) the structures of complexes involving phosphonium ions and (b) the presence or absence of single halide or trihalide ions in the lattice.