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Research describing the mechanism of aerobic oxidation of alcohols using the catalytic system of Ruthenium/TEMPO is presented. Particular attention is given to the process of alcohol oxidation into ketones and aldehydes and to the transfer mediating properties of TEMPO.

Several experiments are conducted to examine the kinetics of the conversion of the nonheme (alkylperoxo)iron(III) species to the iron(IV) complexes by the homolysis of the peroxide O-O bond. The analysis reveals that the kinetic model is in good agreement with the geometric isomerism in the low-spin intermediates, as the alkylperoxo ligand in the compounds is in one of the inequivalent cis sites afforded by the nonheme ligands.

Low-spin mononuclear (alkylperoxo)iron(III) complexes decompose by peroxide O-O bond homolysis to form iron-(IV) species. We examined the kinetics of previously reported homolysis reactions for (alkylperoxo)iron(III) intermediates supported by IPA (tris(2-pyridylmethyl)amine) in CH3CN solution and promoted by pyridine N-oxide, and by BPMCN (N,N-bis(2-pyridylmethyl)-N,N-dimethyl-trans-1,2-diaminocyclohexane) in its cis-β configuration in CH3CN and CH2-Cl2, as well as for the previously unreported chemistry of TPA and 5-Me3TPA intermediates in acetone. Each of these reactions forms an oxoiron(IV) complex, except for the β-BPMCN reaction in CH2Cl2 that yields a novel (hydroxo)(alkylperoxo)iron(IV) product. Temperature-dependent rate measurements suggest a common reaction trajectory for each of these reactions and verify previous theoretical estimates of a ca. 60 kJ/mol enthalpic barrier to homolysis. However, both the tetradentate supporting ligand and exogenous ligands in the sixth octahedral coordination site significantly perturb the homolyses, such that observed rates can vary over 2 orders of magnitude at a given temperature. This is manifested as a compensation effect in which increasing activation enthalpy is offset by increasingly favorable activation entropy. Moreover, the applied kinetic model is consistent with geometric isomerism in the low-spin (alkylperoxo)iron(III) intermediates, wherein the alkylperoxo ligand is coordinated in either of the inequivalent cis sites afforded by the nonheme ligands. [ABSTRACT FROM AUTHOR]