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

We have found a family of non-heme iron complexes [Fe^II(L)(CH₃CN)₂](L = tetradentate pyridine containing ligand) with cis labile sites that catalyze highly stereo-selective hydrocarbon oxidations using H₂O₂ 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 olefincis-dihydroxylationvia low-spin Fe^III-OOH, Fe^V=O intermediates and category B catalysts which form high-spin Fe^III-OOH intermediates and strongly favor olefin cis-dihydroxylation in (which both diol oxygen atoms derive from H₂O₂. 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.