Oxo-bridged dimanganese complexes have been proposed as an intermediate of the metal center found in Class Ib Ribonucleotide reductase. In this enzyme, a Mn(III)Mn(IV) or Mn(IV)Mn(IV) intermediate is generated from Mn(II)Mn(II) by a reduced form of O2 (H2O2, HO2- or O2●-) to make a tyrosyl radical. Model complexes can serve as a valuable tool to broaden insights of the reactivity of this dinuclear bis(μ-oxo) manganese species. A recent study by our group on a series of oxomanganese(IV) complexes supported by the neutral pentadentate N4py ligand and its derivatives showed that the difference of equatorial ligand fields brings significant changes in the hydrogen atom transfer (HAT) reactivity. In this study, we synthesized two different Mn(III,IV) bis(μ-O) species utilizing N4py and one of its derivatives, DMMN4py. The oxo-bridged dimanganese complexes were prepared by adding 5 equivalents of H2O2 in water, which is the similar condition used in Ribonucleotide reductase. The reactivities of these dinuclear manganese species towards a range of O-H bonds was investigated, which shows the reaction rates of bis(μ-O) dimanganese species with N4py ligand are faster than those of the complexes with DMMN4py ligand. However, the ligand field perturbations appear to have less influence on the reactivities of the oxo-bridged dimanganese complexes than that reported for the oxomanganese(IV) complexes.

Structural and reactivity investigation of oxomanganese(IV) and bis(μ-oxo)dimanganese(III,IV) complexes

255th National Meeting (2018)

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