Two Faces of a Biomimetic Non-Heme HO-FeV=O Oxidant: Olefin Epoxidation versus cis-Dihydroxylation

摘要

The family of non-heme iron complexes - exemplified by [FeII(tpa)(CH3CN)2]2+, where tpa is the tetradentate tripodal tris(2-pyridylmethyl)amine ligand - efficiently utilizes H2O2 to carry out stereospecific olefin epoxidation and cis-dihydroxylation.[1]-[4] The latter reaction was not previously known to be catalyzed by a synthetic iron complex and is precedented only in the chemistry of Rieske dioxygenases,[5] non-heme iron enzymes responsible for cis-dihydroxylation in the biodegradation of arenes by soil bacteria. Isotope-labeling experiments on the biomimetic reaction show the involvement of a highly selective metal-based oxidant capable of introducing water into the product.[1], [2] This oxidant is proposed to result from the low-spin complex [FeIII(tpa)(H2)(OOH)]2+ (1) and be a formally HFeVO species (2; indicates an oxygen atom with isotope labeling), both shown in Figure 1.