Electron spin resonance study of phosphoranyl radicals. Part II. intramolecular electron transfer in phosphoranyl radicals : an E.S.R. study on the stereoisomerization of phenylphosphoranyl radicals in solution

An electron spin resonance study on a series of phenylphosphoranyl radicals generated either by u.v. irradiation of solutions containing the corresponding P(III) or P(V) compounds and a dialkylperoxide, or by electrochemical reduction of the phosphonium salts, is reported. It is demonstrated, by careful examination of the phenylphosphoranyl radicals formed, that the initial precursor structure strongly defines the ultimate structure of the radicals detected. Furthermore, the transformation of a trigonal bipyramidal phenylphosphoranyl radical into its tetrahedral counterpart could actually be observed for the first time. This study therefore provides the prerequisites necessary for the isomerization process to take place