Theoretical studies on the reaction mechanism of alcohol oxidation by high-valent iron-oxo complex of non-heme ligand

Abstract

The catalytic mechanism for the oxidation of methanol to formaldehyde and water catalyzed by the biomimetic non-heme iron complex, [(tpa)Fe(IV)O](2+) (tpa = tris(2-pyridylmethyl)amine), is presented by the density functional method B3LYP. Experimentally, acetate and CH(3)CN could be coordinated to the Fe center as the sixth ligand to form the catalyst [(tpa)Fe(IV)=O](2+). To investigate the detailed reaction mechanisms for the two possible ligands, two models (acetate-bound ferryl model A and CH(3)CN-bound ferryl model B) are chosen. In total, six routes have been presented for two models. Our calculations show that both acetate and CH(3)CN could provide reasonable pathways. The calculated energy barriers for these routes are between 19.0 and 23.7 kcal mol(-1) in solution, within the error limits of B3LYP. It is also found that the CH(3)CN molecule acts only as a ligand throughout the reaction cycle. By contrast, the acetate ligand acts as a proton sink to assist the product formation. In addition, the less polarized solvent is more suitable for the alcohol oxidation catalyzed by non-heme model complexes.