Mechanistic Insights and Synthetic Explorations of the Photoredox-Catalyzed Activation of Halophosphines.

The light-driven activation of halophosphines RPX (R = alkyl- or aryl, X = Cl, Br) by an Ir-based photocatalyst is described. It is shown that initially formed secondary phosphines RPH react readily with the remaining RPX in a parent-child reaction to form diphosphines RP-PR. Aryl-containing diphosphines can be further reduced to secondary phosphines RPH under identical photoredox conditions.