A Synthetic Model for the Possible FeIV2(μ-O)2 Core of Methane Monooxygenase Intermediate Q Derived from a Structurally Characterized FeIIIFeIV(μ-O)2 Complex.

A bis(μ-oxo)diiron(IV,IV) complex as a model for intermediate Q in the methane monooxygenase reaction cycle has been prepared. The precursor complex with a [FeIIIFeIV(μ-O)2] core was fully characterized by X-ray crystallography and other spectroscopic analyses and was converted to the [FeIV2(μ-O)2] complex via electrochemical oxidation at 1000 mV (vs Ag/Ag+) in acetone at 193 K. The UV-vis spectral features, Mössbauer parameters (ΔEQ = 2.079 mm/s and δ = -0.027 mm/s), and EXAFS analysis (Fe-O/N = 1.73/1.96 Å and Fe···Fe = 2.76 Å) support the structure of the low-spin (S = 1, for each Fe) [FeIV2(μ-O)2] core. The rate constants of the hydrogen abstraction reaction from 9,10-dihydroanthracene at 243 K suggest the high reactivity of these synthetic bis(μ-oxo)diiron complexes supported by simple N4 tripodal ligand.