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.