Unstable intermediates. Part 173. Triphenyl-phosphonium and -arsonium cations and various phosphoranyl and arsoranyl radicals derived from triphenylphosphine and its oxide, sulphide, and selenide and triphenylarsine and its oxide by the action of ionizing radiation

Abstract

Exposure of solutions of triphenyl-phosphine and -arsine in sulphuric acid at 77 K to ⁶⁰Co γ-rays gave the corresponding cations, characterised by their e.s.r. spectra. Triphenylphosphine oxide, sulphide, and selenide also gave Ph₃P˙⁺ radicals together with species thought to be Ph₃ṖSH and Ph₃ṖSeH from the sulphide and selenide. These species are thought to have a near tetrahedral, σ*, structure rather than the ‘normal’ trigonal bipyramidal structure. Diphenylmethyl- and phenyldimethyl-phosphine gave cations with e.s.r. parameters between the extremes for Ph₃P˙⁺ and Me₃P˙⁺. Triphenylarsine oxide in sulphuric acid also gave Ph₃ As˙⁺, but in methanol either Ph₃ȦsO^– or Ph₃ȦsOR was formed. Tetraphenylarsonium cations in methanolic solution at 77 K gave Ph₄ As˙ but no such species was obtained from tetraphenylphosphinium cations. From these results various modes of electron addition to the parent compounds are deduced and discussed.