Kinetic Analysis Of H2o2 Activation By An Iron(Iii) Complex In Water Reveals A Nonhomolytic Generation Pathway To An Iron(Iv)Oxo Complex

[Fe-III(OH)(tpena)](+) (tpena(-) = N,N,N'-tris(2-pyridylmethyl)ethylenediamine-N'-acetate) catalytically activates H2O2 with the concomitant formation of the active oxidants [Fe-IV(O)(tpena)](+) and HO center dot in aqueous solutions at pH 8. A kinetic model is used to demonstrate that the activation of [Fe-III(OH)(tpena)](+) by H2O2 proceeds by the formation of [Fe-III(OOH)(tpena)](+). Two previously unreported reactions of [Fe-III(OOH)(tpena)](+), the first with another H2O2 molecule to afford [Fe-III(OH)(tpena)](+), O-2(center dot-), and HO center dot and the second, and dominant, with [Fe w (OH)(tpena)](+) to yield 2 equiv of [Fe-IV(O)(tpena)](+) and H2O, are found to be the major pathways for the formation of HO center dot and [Fe-IV(O)(tpena)](+), respectively. The production of HO center dot was quantified by a chemiluminescence method showing that [Fe-IV(O)(tpena)](+) is produced in much larger yields than HO'. The generation of HO center dot compromises the stability of [Fe-III(OH)(tpena)](+) unless an external substrate is present that can outcompete [Fe-III(OH)(tpena)](+) for HO center dot. Significantly, we demonstrate that the reaction commonly assumed to occur in the decay of nonheme iron(III)hydroperoxides, homolytic O-O bond cleavage, is of minor significance for the generation of HO center dot and the iron(IV)oxo complex. The production of both a reactive high-valent iron-oxo species and HO center dot under mild, aqueous ambient conditions represents a significant contribution to the current state of the art for biomimetic nonheme chemistry in water.