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

Authors

  • Dr. Tianbiao Liu,

    Corresponding author
    1. Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (USA)
    • Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (USA)===

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  • Dr. Xiaoping Wang,

    1. Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (USA)
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  • Dr. Christina Hoffmann,

    1. Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (USA)
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  • Dr. Daniel L. DuBois,

    1. Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (USA)
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  • Dr. R. Morris Bullock

    Corresponding author
    1. Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (USA)
    • Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352 (USA)===

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  • This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy. We thank Dr. Molly O’Hagan for assistance with HSQC NMR experiments and Dr. John A. S. Roberts for assistance with the electrochemical studies. Research conducted at ORNL’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. ORNL is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract No. DE-AC05-00OR22725.

Abstract

Hydrogenase enzymes in nature use hydrogen as a fuel, but the heterolytic cleavage of H[BOND]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-Hδ+ and hydridic Fe-Hδ− part. The structural data for [Cpinline imageFeH(PtBu2NtBu2H)]+ provide a glimpse of how the H[BOND]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.

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