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

Abstract

Mononuclear Mn(III) -peroxo and dinuclear bis(μ-oxo)Mn(III) 2 complexes that bear a common macrocyclic ligand were synthesized by controlling the concentration of the starting Mn(II) complex in the reaction of H2 O2 (i.e., a Mn(III) -peroxo complex at a low concentration (≤1 mM) and a bis(μ-oxo)Mn(III) 2 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 Mn2 O2 diamond core is in the bis(μ-oxo)Mn(III) 2 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.