Generation of an Isolable, Monomeric Manganese(V)–Oxo Complex from O₂ and Visible Light

The direct conversion of a Mn^III complex [(TBP₈Cz)­Mn^III (1)] to a Mn^V–oxo complex [(TBP₈Cz)­Mn^V(O) (2)] with O₂ and visible light is reported. Complex 1 is also shown to function as an active photocatalyst for the oxidation of PPh₃ to OPPh₃. Mechanistic studies indicate that the photogeneration of 2 does not involve singlet oxygen but rather likely occurs via a free-radical mechanism upon photoactivation of 1.