Photocatalytic Arylation of P₄ and PH₃: Reaction Development Through Mechanistic Insight

Abstract

Detailed ³¹ P{¹ H} NMR spectroscopic investigations provide deeper insight into the complex, multi-step mechanisms involved in the recently reported photocatalytic arylation of white phosphorus (P₄ ). Specifically, these studies have identified a number of previously unrecognized side products, which arise from an unexpected non-innocent behavior of the commonly employed terminal reductant Et₃ N. The different rate of formation of these products explains discrepancies in the performance of the two most effective catalysts, [Ir(dtbbpy)(ppy)₂ ][PF₆ ] (dtbbpy=4,4'-di-tert-butyl-2,2'-bipyridine) and 3DPAFIPN. Inspired by the observation of PH₃ as a minor intermediate, we have developed the first catalytic procedure for the arylation of this key industrial compound. Similar to P₄ arylation, this method affords valuable triarylphosphines or tetraarylphosphonium salts depending on the steric profile of the aryl substituents.