Functional modeling of the MnCAT active site with a dimanganese(III) complex of an unsymmetrical polydentate N 3 O 3 ligand

Abstract

A new diMn III complex, [Mn 2 L(OAc) 2 (H 2 O)](BPh 4 )·3H 2 O (1), obtained with the unsymmetrical N 3 O 3 -ligand H 3 L = 1-[N-(2-pyridylmethyl),N-(2-hydroxybenzyl)amino]-3-[N′-(2-hydroxybenzyl),N′-(benzyl)amino]propan-2-ol, has been prepared and characterized. The unsymmetrical hexadentate ligand L 3− leads to coordination dissymmetry (dissimilar donor atoms) around each Mn ion (N 2 O 4 and NO 4 (solvent), respectively) leaving one labile site on one of the two Mn ions that facilitates interaction of the metal center with H 2 O 2 , as in Mn catalase. 1 is able to catalyze H 2 O 2 disproportionation in acetonitrile, with second-order rate constant k cat = 23.9(2) M −1 s −1 . The accessibility of the Mn II 2 state and the closeness of the two one-electron reduction processes suggest 1 employs Mn III 2 /Mn II 2 oxidation states for catalysis.