Catalytic Activation of H_2 under Mild Conditions by an [FeFe]-Hydrogenase Model via an Active /μ-Hydride Species

摘要

A [FeFe]-hydrogenase model (1) containing a chelating diphosphine ligand with a pendant amine was readily oxidized by Fc~+ (Fc = Cp_2Fe) to a Fe~ⅡFe~Ⅰ complex ([1]~+), which was isolated at room temperature. The structure of [1]~+ with a semibridging CO and a vacant apical site was determined by X-ray crystallography. Complex [1]~+ catalytically activates H_2 at 1 atm at 25 ℃ in the presence of excess Fc~+ and P(o-tol)_3. More interestingly, the catalytic activity of [1]~+ for H_2 oxidation remains unchanged in the presence of ca. 2% CO. A computational study of the reaction mechanism showed that the most favorable activation free energy involves a rotation of the bridging CO to an apical position followed by activation of H_2 with the help of the internal amine to give a bridging hydride intermediate.