Light-Driven, Proton-Controlled, Catalytic Aerobic C–H Oxidation Mediated by a Mn(III) Porphyrinoid Complex

The visible light-driven, catalytic aerobic oxidation of benzylic C–H bonds was mediated by a Mn^III corrolazine complex. To achieve catalytic turnovers, a strict selective requirement for the addition of protons was established. The resting state of the catalyst was unambiguously characterized by X-ray diffraction as [Mn^III(H₂O)­(TBP₈Cz­(H))]⁺, in which a single, remote site on the ligand is protonated. If two remote sites are protonated, however, reactivity with O₂ is shut down. Spectroscopic methods revealed that the related Mn^V(O) complex is also protonated at the same remote site at −60 °C, but undergoes valence tautomerization upon warming.