Raman spectra and isomerism of some bromophenylphosphoranes PhnPBr5–n(1 ⩽n⩽ 3) and their salts
Abstract
A synthetic and Raman investigation of isomerism in the bromophenylphosphoranes has shown no evidence for ionic–covalent isomerism analogous to that in the chlorophenylphosphoranes. Two ionic modifications of PhPBr4 have been identified by Raman spectroscopy, whereas Ph2PBr3 was found to exist in only one ionic form, Ph2PBr2+Br–. A recent proposal that Ph3PBr2 is a molecular four-co-ordinate species is disputed and evidence supporting an ionic formulation Ph3PBr+Br– is presented. Vibrational Raman assignments for the bromophenylphosphoranes and some of their tetrabromoborate and tetrabromoaluminate salts are given.