[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.
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