Round-Trip Oxidative Addition, Ligand Metathesis, and Reductive Elimination in a PIII/PV Synthetic Cycle

A synthetic cycle for aryl C–F substitution comprising oxidative addition, ligand metathesis, and reductive elimination at a Cs-symmetric phosphorus triamide (1, P­{N­[o-NMe-C6H4]2}) is reported. Reaction of 1 with perfluoro­arenes (ArF–F) results in C–F oxidative addition, yielding fluoro­phosphoranes 1·[F]­[ArF]. The P-fluoro substituent is exchanged for hydride by treatment with DIBAL-H, generating hydrido­phosphoranes 1·[H]­[ArF]. Heating of 1·[H]­[ArF] regenerates 1 by C–H reductive elimination of ArF–H, where experimental and computational studies establish a concerted but highly asynchronous mechanism. The results provide well-characterized examples of the full triad of elementary mechanistic aryl C–X substitution steps at a single main-group site.