Radical ions in the reactions of p-chloranil with triphenylphosphine and with triethyl phosphite : Electron spin resonance and ultraviolet absorption spectra

Abstract

The colour and the ESR spectrum which develop during the reaction of triphenylphosphine with p-chloranil are due to a phenoxy-O-phosphonium radical cation and to a semiquinone radical anion. These are formed by oxidation of the phosphine, or of a phosphine-quinone complex, by quinone. The radical ions are not formed by oxidation of the final product of the reaction (a phenoxide-O-phosphonium dipolar ion) by p-chloranil in solution. The reaction of triethyl phosphite with p-chloranil produces analogous coloured species with unpaired electrons. The g-factors and the hyperfine constants (ΔH) for the radical cations from triphenylphosphine and triethyl phosphite, are, respectively: 2·0050, 2·42 gauss and 2·0051, 1·83 gauss.