Spin state tuning of non-heme iron-catalyzed hydrocarbon oxidations: participation of Fe~III-OOH and Fe~V=O intermediates

摘要

We have found a family of non-heme iron complexes [Fe~II(L)(CH_3CN)_2] (L=tetradentate pyridine containing ligand) with cis labile sites that catalyze highly stereo-selective hydrocarbon oxidations using H_2O_2 as oxidant. The hydrocarbon oxidation reactivity patterns of this family of catalysts divide them into two subgroups: Category A catalysts which carry out highly stereoselective alkane hydroxylation, olefin epoxidation, and olefin cis-dihydrox-ylation via low-spin Fe~III-OOH, Fe~V=O intermediates and category B catalysts which form high-spin Fe~III-OOH inter-mediates and strongly favor olefin cis-dihydroxylation in which both diol oxygen atoms derive from H_2O_2. 6-Methyl substituents on the ligands play an important role in tuning the spin states of the iron centers to afford a family of non-heme iron complexes that catalyze a remarkable array of hydrocarbon oxidation reactions.