Atmosphere-controlled Dual Reactivity of Triarylphosphine in the Photoexcited State: P–C Bond Cleavage vs. Electron Transfer

Steady-state photolysis of an acetonitrile solution of triarylphosphine (Ar3P) was carried out using a xenon lamp. The major products resulting from photolysis under deoxygenated conditions and under air were diaryl(cyanomethyl)phosphine Ar2PCH2CN and triarylphosphine oxide Ar3P=O, respectively. Intrinsically, Ar3P in the excited state undergoes homolytic cleavage of a P–C bond; however, electron transfer to O2 is predominant under air. Reactivity of Ar3P in the excited state is readily controlled by the choice of atmosphere used in the reaction.