Sulfide Oxidation by Hydrogen Peroxide Catalyzed by Iron Complexes: Two Metal Centers Are Better Than One

Peroxoiron species have been proposed to be involved in catalytic cycles of iron‐dependent oxygenases and in some cases as the active intermediates during oxygen‐transfer reactions. The catalytic properties of a mononuclear iron complex, [FeII(pb)2(CH3CN)2] (pb=(−)4,5‐pinene‐2,2′‐bipyridine), have been compared to those of its related dinuclear analogue. Each system generates specific peroxo adducts, which are responsible for the oxidation of sulfides to sulfoxides. The dinuclear catalyst was found to be more reactive and (enantio)selective than its mononuclear counterpart, suggesting that a second metal site affords specific advantages for stereoselective catalysis. These results might help for the design of future enantioselective iron catalysts. Enantioselective sulfoxidation by H2O2 is used as a probe for a comparison of mono‐ and dinuclear iron catalysts. Whereas both systems form peroxoiron intermediates as active species, the dinuclear one proved to be more efficient and selective.