Bio-inspired non-heme iron catalysts are capable of carrying out a variety of hydrocarbon functionalization reactions using H2O2 as the terminal oxidant. Previously, we have systematically studied the series of nonheme iron catalysts supported by nitrogen-rich tripodal ligand TPA (TPA = tris(pyridyl-2-methyl)amine) and its 6-methylpyridyl derivatives, which shows high selectivity in the epoxidation and cis-dihydroxylation of olefins. In Fe(TPA)-catalyzed reactions, much evidence supports a water-assisted mechanism, where a proton from the iron-bound water facilitates the heterolytic O–O bond cleavage of the FeIII–OOH species, generating a high-valent FeV(O)(OH) species as the active oxidant. However, much less is known about the mechanism for Fe(6Me3TPA) (6Me3TPA = tris(6-methylpyridyl-2-methyl)amine) catalysis, as no intermediate has yet been identified. In this study, we employ the Fe(TQA) complex (TQA = tris(quinolinyl-2-methyl)amine) to investigate the mechanism of its catalytic oxidation of olefins. The TQA framework imposes similar geometric constraints on the metal center as 6Me3TPA but does not possess the 6-methyl substituents that could be susceptible to attack by the high-valent iron-oxo intermediate that may form during catalysis. Furthermore, Fe(TQA) has been already been shown to support an FeIV=O species with an S = 2 ground spin state, which resembles the iron centers found in the active diferryl species Q of the enzyme methane monooxygenase (MMO) that oxidizes methane to methanol. Experiments will be described aimed at the determing the outcome of catalytic reactions and the spectroscopic characterization of reaction intermediates. Furthermore, the effect of various additives such as water and acids will be investigated to gain insight into the important role of the proton is likely to play in the overall reaction mechanism.

Mechanism of olefin cis-dihydroxylation catalyzed by a bio-inspired non-heme iron complex

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.