Mechanistic studies on oxidation of hydrogen peroxide by an oxo-bridged diiron complex in aqueous acidic media.

A novel Raman spectroscopic model for the dinuclear iron site in ribonucleotide reductase and met-hemerythrin, [Fe2(micro-O)(phen)4(H2O)2]4+, 1, (phen = 1,10-phenanthroline) quantitatively oxidizes hydrogen peroxide to dioxygen via an inner-sphere electron transfer pathway. Although 1 deprotonates to form [Fe2(micro-O)(phen)4(H2O)(OH)]3+ (2) and [Fe2(micro-O)(phen)4(OH)2]2+ (3) in aqueous media, neither 2 nor 3 is reactive in oxidising H2O2. In the presence of excess phen, no phen-releasing equilibria from , and exist. Kinetic evidence of the generation of a (micro-1,2 peroxo)diiron(III,III) intermediate, prior to electron transfer, were obtained. Significant rate retardation in D2O media suggests proton coupled electron transfer (PCET) in the rate determining step of the title redox reaction.