Ligand Influence on Structural Properties and Reactivity of Bis(μ‐oxo)dimanganese(III,IV) Species and Comparison of Reactivity with Terminal Mn IV ‐oxo Complexes

The ligand influence on structure and reactivity of a pair of bis(μ‐oxo)dimanganese(III,IV) complexes was investigated. The pentadentate N4py and DMM N4py ligands were employed to assemble the [Mn III Mn IV (μ‐O) 2 (N4py) 2 ] 3+ ( 1 ) and [Mn III Mn IV (μ‐O) 2 ( DMM N4py) 2 ] 3+ ( 2 ) species by H 2 O 2 oxidation of the corresponding Mn II complexes. The electronic absorption and EPR properties of 1 and 2 are nearly identical. Analysis of the EXAFS region of the Mn K‐edge XAS spectra of 1 and 2 reveals comparable Mn‐ligand and Mn−Mn distances. Molecular structures of 1 and 2 from DFT calculations showed only minor variations in Mn‐ligand bond lengths between these complexes. Despite these structural similarities, a ligand influence was observed on the Mn III Mn IV to Mn III Mn III reduction potential. Nonetheless, the oxidation of 2,4‐di‐ tert ‐butylphenol by 1 and 2 proceeded at essentially identical rates. In contrast, reactivity comparison between 2 and the corresponding monomeric Mn IV ‐oxo species, [Mn IV (O)( DMM N4py)] 2+ , showed that the latter complex is a vastly superior oxidant for O−H bond oxidation, showing a rate enhancement of 10 5 at parity of substrate and temperature.