Heterolytic Cleavage of Hydrogen by an Iron Hydrogenase Model: An Fe-H···H-N Dihydrogen Bond Characterized by Neutron Diffraction

摘要

Hydrogenase enzymes in nature use hydrogen as a fuel, but the heterolytic cleavage of H-H bonds cannot be readily observed in enzymes. Here we show that an iron complex with pendant amines in the diphosphine ligand cleaves hydrogen heterolytically. The product has a strong Fe-H-H-N dihydrogen bond. The structure was determined by single-crystal neutron diffraction, and has a remarkably short H-H distance of 1.489(10) A between the protic N-H~(δ+) and hydridic Fe-H~(δ-) part. The structural data for [Cp~(C5F4N)FeH(P~(tBu)2N2~(tBu)H)]~+ provide a glimpse of how the H-H bond is oxidized or generated in hydrogenase enzymes. These results now provide a full picture for the first time, illustrating structures and reactivity of the dihydrogen complex and the product of the heterolytic cleavage of H2 in afunctional model of the active site of the [FeFe] hydrogenase enzyme.