Organophosphorus intermediates. Part IV. Formation of phenylphosphinidene in the decomposition of phenylphosphinic anhydride: mechanism for the thermal decomposition of monosubstituted phosphinic acids

Abstract

Phenylphosphinidene, formed in the decomposition of phenylphosphinic anhydride, has been trapped by reaction with benzil to give a spirophosphole (4).

Phenylphosphinic acid and pentaphenylcyclopentaphosphine react readily by an ionic mechanism to give phenylphosphine and phenylphosphonic anhydride. The two reactions provide an explanation of the thermal decomposition of monosubstituted phosphinic acids to give phosphines and phosphonic acids.

Phosphorous and hypophosphorous acid also react with pentaphenylcyclopentaphosphine to give phosphine and phenylphosphine together with a complex mixture of other products.

Free-radical abstraction of hydrogen from phenylphosphinic acid converts it into pentaphenylcyclopentaphosphine and polymeric phenylphosphonic anhydride. Phenylphosphine is similarly converted into the polyphosphine in good yield.