Mononuclear Manganese–Peroxo and Bis(μ‐oxo)dimanganese Complexes Bearing a Common N‐Methylated Macrocyclic Ligand

Mononuclear Mn^III–peroxo and dinuclear bis(μ‐oxo)Mn^III₂ complexes that bear a common macrocyclic ligand were synthesized by controlling the concentration of the starting Mn^II complex in the reaction of H₂O₂ (i.e., a Mn^III–peroxo complex at a low concentration (≤1 mM ) and a bis(μ‐oxo)Mn^III₂ complex at a high concentration (≥30 mM )). These intermediates were successfully characterized by various physicochemical methods such as UV–visible spectroscopy, ESI‐MS, resonance Raman, and X‐ray analysis. The structural and spectroscopic characterization combined with density functional theory (DFT) calculations demonstrated unambiguously that the peroxo ligand is bound in a side‐on fashion in the Mn^III–peroxo complex and the Mn₂O₂ diamond core is in the bis(μ‐oxo)Mn^III₂ complex. The reactivity of these intermediates was investigated in electrophilic and nucleophilic reactions, in which only the Mn^III–peroxo complex showed a nucleophilic reactivity in the deformylation of aldehydes.