MU-OXO BRIDGED DIIRON(III) COMPLEXES AND HYDROGEN-PEROXIDE - OXYGENATION AND CATALASE-LIKE ACTIVITIES

The crystal structures of two dinuclear iron(III) compounds with a ben t mu-oxo bridge, [Fe2O(CH3CO2)(tpa)(2)][ClO4](3).2H(2)O and [Fe2O(CH3C O2)(mep)(2)][ClO4](3), were determined, where tpa and mep represent tr is(2-pyridylmethyl)-amine and ethyl-N,N'-bis(2-pyridylmethyl)ethane-1, 2-diamine, respectively Their structural features which include a (mu- oxo)(mu-acetato)diiron(III) core are very similar. In spite of this, t hese two complexes exhibit very different reactivity towards hydrogen peroxide in solution; the tpa complex showed high catalase-like activi ty, whereas that of the mep complex was negligible. In the oxygenation of cyclohexane the mep complex-H2O2 system exhibited high activity gi ving cyclohexanol and cyclohexanone, but formation of oxygenated produ cts was negligible with the tpa complex-H2O2. The absorption spectrum of the tpa complex shows no change in the presence of H2O2; however a drastic change was observed in the spectrum of the mep complex on addi tion of H2O2. Based on the structural and spectroscopic data, the stru ctures of the active species for catalase-and oxygenase-like functions and the origin of the differences in reactivity observed for these tw o compounds are discussed.