Characterized cis-Fe(V)(O)(OH) intermediate mimics enzymatic oxidations in the gas phase

Fe(V)(O)(OH) species have long been proposed to play a key role in a wide range of biomimetic and enzymatic oxidations, including as intermediates in arene dihydroxylation catalyzed by Rieske oxygenases. However, the inability to accumulate these intermediates in solution has thus far prevented their spectroscopic and chemical characterization. Thus, we use gas-phase ion spectroscopy and reactivity analysis to characterize the highly reactive [Fe(V)(O)(OH)((5tips3)tpa)](2+) (3(2+)) complex. The results show that 3(2+) hydroxylates C–H bonds via a rebound mechanism involving two different ligands at the Fe center and dihydroxylates olefins and arenes. Hence, this study provides a direct evidence of Fe(V)(O)(OH) species in non-heme iron catalysis. Furthermore, the reactivity of 3(2+) accounts for the unique behavior of Rieske oxygenases. The use of gas-phase ion characterization allows us to address issues related to highly reactive intermediates that other methods are unable to solve in the context of catalysis and enzymology.