Heterolytic cleavage of hydrogen by an iron hydrogenase model: an Fe-H⋅⋅⋅H-N dihydrogen bond characterized by neutron diffraction.
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) Å between the protic N-H(δ+) and hydridic Fe-H(δ-) part. The structural data for [Cp(C5F4N)FeH(P(tBu)2N(tBu)2H)](+) 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 a functional model of the active site of the [FeFe] hydrogenase enzyme.
Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (USA). Tianbiao.Liu@pnnl.gov.
Tianbiao
T
Liu
Xiaoping
X
Wang
Christina
C
Hoffmann
Daniel L
DL
DuBois
R Morris
RM
Bullock
D055162:Biocatalysis; D056831:Coordination Complexes / Q000737:chemistry; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D006859:Hydrogen / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D033363:Neutron Diffraction; D009584:Nitrogen / Q000737:chemistry; D010084:Oxidation-Reduction
D056831:Coordination Complexes; D007506:Iron-Sulfur Proteins; D006859:Hydrogen; D007501:Iron; C118830:iron hydrogenase; D006864:Hydrogenase; D009584:Nitrogen
enzyme models; hydrogen; hydrogenases; iron; neutron diffraction