Phosphinium Radical Cations

The phosphinium radical cation is the parent ion in the mass spectra of phosphines, phosphinites, phosphonites and phosphites. The triphenylphosphinium radical cation, PhjP+j is produced by y-ray irradiation of PhjP in dichloromethane or in sulphuric acid at 77 K. It has also been observed by oxidation of phosphines at a mercury anode, after which it combines with mercury as in Equation 13.209. Recent studies include radical cations of type PhEPHJ (E = N, P, As) [36]. 

Phosphite and hypophosphite radicals are produced initially by y-ray bombardment of solid phosphites and hypophosphites, respectively. 

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The reaction of ( )-bis-(2,4,6-tri-t-butylphenyl)diphosphane (16) with a four equivalent excess of tetrachloro-o-benzoquinone (17) gave (19). Evidence was presented to suggest that the reaction occurred via (18) with cleavage of the P=P bond and indeed, with two equivalents of (17) a low yield of (18) was isolated. The structures of the products were determined by X-ray crystallography and it was also suggested that the formation of (18) involved an electron transfer mechanism (Route A or Route B, Scheme 1) via a phosphinium radical cation and the radical anion of (17). ... 

The ability of phosphines to act as either one-electron acceptors or one-electron donors may be crucial in the mechanism of their cytotoxicity and allow them to interfere with electron transport processes. Phosphinium radical cations have been generated by oxidation of phosphines at a mercury anode or by y-irradiation of tertiary phosphines on silica and in sulphuric acid The oxidation potentials appear to be within the range accessible to biological systems Aryl phosphines are more easily oxidised than alkyl phosphines Ejq (polarography in CH3CN, anodic oxidation) PPha -H 50 mV, PEt3 - 415 Phosphine dimer cation radicals (R3PPR3) have been identified by... 

ESR spectroscopy as products generated during electrochemical oxidation of PR3 compounds in solution the initially-formed phosphinium radical cation reacts rapidly with a further molecule of phosphine Phosphonium radical anions are the least well characterised of all phosphorus radicals. Electrolytic reduction of PPh3 in CH3CN, at a dropping mercury cathode, produced biphenyl and diphenylphosphonic add. The radical anion was presumed to be an intermediate ... 

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