Dioxygen oxidation of hydrocarbons by a methane monooxygenase-like system: diiron complex-O 2 -Zn/HOAc-MV 2+

Abstract

The activation of dioxygen and incorporation into hydrocarbons have been achieved under mild conditions by a methane monooxygenase (MMO)-like system using a dinuclear iron complex [Fe2 Dhist (OAc)2]BPh4.3H2O as the model complex, zinc powder as the electron donor, HOAc as the proton source and methylviologen as the electron transfer agent. The results show that styrene is oxygenated predominantly to styrcne oxide (1 396 mol/100 mol of the Fe2 complex), benzaldehyde (16160) and acetophenone (986), and cyclohexane to cyclohexanol (9370) and cyclohexanone (2670). EPR studies indicate that the hypervalent ironoxo spices FeIVFeIV=O, derived from FeIII FeIII core via reduction, O2-binding and protonation, is the active intermediate which inserts the activated oxygen atom into C—C or C—H bond giving each product. The system closely resembles MMO and its close relative hemerythrin in the aspects of reaction phenomena, EPR characteristics and product distributions. The Mn2 analog cmplex, Fe-Zn heterodinuclear complex and mononuclear iron complex show no catalytic activity, indicating that dinuclear iron core is indespansable to catalytic activity.