Phosphonium Salt - Phosphonium Halides

Phosphines (R₃P) react with halogens (X₂) to phosphonium halides of the type R₃PX₂. The compound Ph₃PBr₂ (high melting solid) formed by reaction of triphenylphosphine and bromine is called bromotriphenylphosphonium bromide or dibromotriphenylphosphorane (now defined as a phosphorane) or simply triphenylphosphine dibromide. The dibromide and dichloride are commercially available as halogenation reagents for instance in halogenation of alcohols and phenols.

The compound triphenylphosphine dichloride, Ph₃PCl₂, is reported as being an ionic compound (PPh₃Cl)+Cl− in polar solutions and a molecular species with trigonal bipyramidal molecular geometry in apolar solution and in the solid state.