Activation of dioxygen by a mononuclear non-heme iron complex: characterization of a Fe(III)(OOH) intermediate.

The reaction of the iron(ii) complex supported by the ligand L(5)(2)aH (2,2-dimethyl-N-[6-({[2-(methyl-pyridin-2-ylmethyl-amino)-ethyl]-pyridin-2-ylmethyl-amino}-methyl)-pyridin-2-yl]-propionamide) with dioxygen, in the presence of HClO(4) and NaBPh(4) yields the corresponding low spin (S = 1/2) Fe(III)(OOH) complex. This reaction, where the anion BPh(4)(-) acts as an electron donor, is reminiscent of the reductive activation of O(2) by enzymatic systems. Under these specific experimental conditions, the hydroperoxoiron(iii) complex evolves in an unexpected way to yield a high spin (S = 5/2) green species. This transformation is shown to arise from the reaction between the hydroperoxoiron(iii) intermediate and BPh(3), a side product of BPh(4)(-).