Formation of a Reactive [Mn(III)−O−Ce(IV)] Species and its Facile Equilibrium with Related Mn(IV)(OX) (X = Sc or H) Complexes

Abstract Lewis acid‐bound high valent Mn‐oxo species are of great importance due to their relevance to photosystem II. Here, we report the synthesis of a unique [(BnTPEN)Mn(III)−O−Ce(IV)(NO 3 ) 4 ] + adduct ( 2 ) by the reaction of (BnTPEN)Mn(II) ( 1 ) with 4 eq. ceric ammonium nitrate. 2 has been characterized using UV/Vis, NMR, resonance Raman spectroscopy, as well as by mass spectrometry. Treatment of 2 with Sc(III)(OTf) 3 results in the formation of (BnTPEN)Mn(IV)−O−Sc(III) ( 3 ), while HClO 4 addition to 2 forms (BnTPEN)Mn(IV)−OH ( 4 ), reverting to 2 upon Ce(III)(NO 3 ) 3 addition. 2 can also be prepared by the oxidation of 1 eq. Ce(III)(NO 3 ) 3 with [(BnTPEN)Mn(IV)=O] 2+ ( 5 ). In addition, the EPR spectroscopy revealed the elegant temperature‐dependent equilibria between 2 and Mn(IV) species. The binding of redox‐active Ce(IV) boosts electron transfer efficiency of 2 towards ferrocenes. Remarkably, the newly characterized Mn(III)−O−Ce(IV) species can carry out O‐atom and H‐atom transfer reactions.