Reactivity of Triarylphosphine Peroxyl Radical Cations Generated through the Reaction of Triarylphosphine Radical Cations with Oxygen

摘要

One-electron oxidation of triarylphosphines (Ar_3P,Ar - phenyl and substituted phenyl) in benzonitrile (PhCN) has been studied using pulse radiolysis technique.One-electron oxidation of Ar_3P occurred to yield the radical cation (Ar_3P~(centre dot+)) which showed an intense absorption with a peak at 360-370 nm together with a broad band at 500-600 nm.The addition of molecular oxygen (O_2) to the phosphorus atom of Ar_3P~(centre dot+) took place at the second-order rate constant of 10~7-10~9 dm~3 mol~(-1) s~(-1) to yield the peroxyl triarylphosphinyl radical cation (Ar_3P~+OO~(centre dot)).It is found that the electron-releasing substituents on the para position of the phenyl ring of Ar_3P influence the rate constants of the reaction of Ar_3P~(centre dot+) with O_2 and that o-methyl substituents on the phenyl ring influence the reactivity of Ar_3P~+OO~(centre dot).