High Turnover Catalase Activity of a Mixed-Valence (MnMnIII)-Mn-II Complex with Terminal Carboxylate Donors

The neutral dimanganese(II,III) complex [Mn-2(BCPMP)-(OAc)(2)] [1; BCPMP3- = 2,6-bis({(carboxymethyl)[(1-pyridyl)-methyl] amino} methyl)-4-methylphenolato] has been synthesized and characterized. The complex contains two terminal carboxylate donors. Complex 1 was found to be an effective catalyst for the disproportionation of H2O2 with high catalytic rate and a turnover number of 7500, the highest turnover reported to date for a catalase mimic. The rates and TON were significantly higher than recorded for a dicationic dimanganese( II,III) counterpart ([Mn-2(BPBP)(OAc)(2)]center dot(ClO4)(2), 2; BPBP- = 2,6-bis{[bis(2-pyridylmethyl)amino]methyl}-4-butylphen-olato), which lacks the terminal carboxylate donors, suggesting that introduction of a terminal carboxylate donor improves activity. A well-resolved 16-line pattern obtained upon addition of H2O2 to complex 1 suggests involvement of an (MnMnIV)-Mn-III species in the catalytic cycle.