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.