Mononuclear manganese-peroxo and bis(m-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 (≥30mM)). 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 demon-strated 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.