The formation of [(N4Py)Fe =O] species was accomplished by the reaction of [Fe (N4Py)] with 20 equivalents of tBuO H (TBHP, 70 % in H O). The temperature, [Fe (N4Py)] -concentration and H O-concentration in anhydrous TBHP (5.5 m in decane) dependences of its yields and rates were analyzed to indicate that the proton migration from [(N4Py)Fe -HOOtBu] to [(N4Py)Fe -OO HtBu] is the rate-determining step followed by rapid heterolytic O-O bond cleavage of Fe -OO HtBu to Fe =O complex. The formation of [(TPA)Fe =O] is thus revealed to be greatly enhanced by the similar oxidation of [Fe (TPA)] (40 mm) with 10 equivalents of tBuO H at -45 °C. These results demonstrate the heterolytic O-O bond cleavage of Fe -alkylperoxo species to form Fe =O originating from the direct reaction of iron(II) complexes/TBHP. The observation of concentration and temperature effects leads to the hypothesis that O-O bond homolysis is a kinetic control pathway and O-O bond heterolysis is a thermodynamic control pathway.
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