PI and PIII Ions Supported by BZIMPY Ligands.

We report a class of compounds in which both PIII−X and PI forms featuring the same ligand are stable and readily cycled with each other. A series of PIII−X (X=Cl, Br, I) dicationic triflate salts supported by benzyl‐ and allyl‐substituted 2,6‐bis(benzimidazole‐2‐yl)pyridine (BZIMPY) ligands is synthesized. Surprisingly, treatment of these with R3PO (R=Et, Oct) results in reduction to BZIMPY‐ligated PI monocationic triflate salts while treatment with Ph3P reduces but also substitutes the compound to produce Ph3P‐BZIMPY‐ligated PI dicationic triflate salts. The mechanisms of these surprising reductions are probed experimentally and rationalized computationally. The PIII−X dications are shown to be strong Lewis acids both experimentally and computationally and to readily behave as X+, PX, and P+ transfer agents in reactions with phosphines, NHCs, and diazabutadienes. The PI mono‐ and dications are shown to be very effective P+ transfer agents when treated similarly. Oxidation from a monocationic PI salt back to the dicationic PIII−X (X=Cl, Br) salt was achieved by treatment with N‐chlorosuccinimide (NCS) or N‐bromosuccinimide (NBS). Full characterization is reported using multinuclear nuclear magnetic resonance spectroscopy, elemental analysis, and single‐crystal X‐ray diffractometry where suitable crystals were isolated. [ABSTRACT FROM AUTHOR]