Cyclometalated Phosphinine–Iridium(III) Complexes: Synthesis, Reactivity, and Application as Phosphorus-Containing Water-Oxidation Catalysts

The novel phosphinine-based coordination compound [Cp*Ir­(P∧C)­(CH3CN)]­CF3SO3 (P∧C = cyclometalated 2,4,6-triphenylphosphinine) could be synthesized by chloride abstraction from [Cp*Ir­(P∧C)­Cl] with AgOSO2CF3 and crystallographically characterized. It turned out that this species is the first phosphorus-containing Ir­(III) complex which shows a remarkable activity in the cerium ammonium nitrate driven water oxidation reaction. In situ NMR spectroscopic investigations further reveal that water is added selectively to one of the PC double bonds with formation of four stereoisomers. Moreover, [Cp*Ir­(P∧C)] species, possibly OH-functionalized but still having Cp* and P∧C-ligands contemporary bound to iridium, are present in solution, even under catalytic conditions.