Abstract
[Fe(β-BPMCN)(CH(3)CN)(2)](2+) (1, BPMCN = N,N' -bis(pyridyl-2-methyl)- N,N' -dimethyl- trans-1,2-diaminocyclo-hexane) is a relatively poor catalyst for cyclohexane oxidation by H(2)O(2) and cannot perform benzene hydroxylation. However, addition of Sc(3+) activates the 1/H(2)O(2) reaction mixture to be able to hydroxylate cyclohexane and benzene within seconds at -40 °C. A metastable S = 1/2 Fe(III)-(η(1)-OOH) intermediate 2 is trapped at -40 °C, which undergoes rapid decay upon addition of Sc(3+) at rates independent of [substrate] but linearly dependent on [Sc(3+)]. HClO(4) elicits comparable reactivity as Sc(3+) at the same concentration. We thus postulate that these additives both facilitate O-O bond heterolysis of 2 to form a common highly electrophilic Fe(V)═O oxidant that is comparably reactive to the fastest nonheme high-valent iron-oxo oxidants found to date.