MU-OXO-BRIDGED DIIRON(III) COMPLEXES AND H2O2 - MONOOXYGENASE-LIKE AND CATALASE-LIKE ACTIVITIES

The mu-oxo-bridged diiron (III) complex [Fe2O(bipy)4(OH2)2][ClO4]4 1 ( bipy = 2,2'-bipyridine) was found to exhibit monooxygenase-like activi ty, using H2O2 as the oxidant. The system oxidizes alkanes to alcohols and ketones quite efficiently (46 mmol of cyclohexanol + cyclohexanon e per mmol complex in 10 min). In the case of adamantane, selectivity for the tertiary hydrogen was indicated by a high normalized C3:C2 rat io of 9:1. The same reaction yields and rates were obtained whether ar gon or dioxygen was bubbled through the solution. Dimethyl sulfide was transformed into dimethyl sulfoxide and dimethylsulfone and benzene i nto phenol. These results exclude O2, as a key reactant in this system and suggest that high-valent oxoiron intermediates and hydroxyl radic als are the active species. The potential of this system is strongly l imited by the instability of the catalyst and by its strong catalase-l ike activity. Complex 1 is actually a very efficient catalyst for hydr ogen peroxide dismutation, thus transforming 50% of the excess of H2O, into O2 in 10 min.