A Functional [NiFe]-Hydrogenase Model Compound That Undergoes Biologically Relevant Reversible Thiolate Protonation

Katharina Weber, Tobias Kraemer, Hannah S. Shafaat, Thomas Weyhermueller, Eckhard Bill, Maurice van Gastel, Frank Neese, Wolfgang Lubitz

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Abstract

Two model compounds of the active site of [NiFe]-hydrogenases with an unusual {S2Ni(mu-S)(mu-CO)Fe-(CO)(2)S}-coordination environment around the metals are reported. The neutral compound [Ni(xbsms)(mu-CO)(mu-S)Fe-(CO)(2)('S')], (1) (H(2)xbsms = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene) is converted to [1H][BF4] by reversible protonation using HBF4 center dot Et2O. The protonation takes place at the terminal thiolate sulfur atom that is coordinated to nickel. Catalytic intermediates with a protonated terminal cysteinate were suggested for the native protein but have not yet been confirmed experimentally. [1H][BF4] is the first dinuclear [NiFe] model compound for such a species. Both complexes have been synthesized and characterized by X-ray crystallography, NMR-, FTIR-, and Fe-57-Mossbauer spectroscopy as well as by electronic absorption and resonance Raman spectroscopy. The experimental results clearly show that the protonation has a significant impact on the electronic structure of the iron center, although it takes place at the nickel site. DFT calculations support the interpretation of the spectroscopic data and indicate the presence of a bonding interaction between the metal ions, which is relevant for the enzyme as well. Electrochemical experiments show that both 1 and [1H][BF4] are active for electrocatalytic proton reduction in aprotic solvents.

Original languageEnglish
Pages (from-to)20745-20755
Number of pages11
JournalJournal of the American Chemical Society
Volume134
Issue number51
DOIs
Publication statusPublished - 26 Dec 2012

Keywords

  • VULGARIS MIYAZAKI-F
  • APPROXIMATE COULOMB POTENTIALS
  • NICKEL-IRON HYDROGENASES
  • AUXILIARY BASIS-SETS
  • ACTIVE-SITE MODELS
  • INTERMEDIATE NI-C
  • DESULFOVIBRIO-GIGAS
  • ELECTRONIC-STRUCTURE
  • MOLECULAR ELECTROCATALYSTS
  • ENZYMATIC MECHANISM

Cite this

Weber, K., Kraemer, T., Shafaat, H. S., Weyhermueller, T., Bill, E., van Gastel, M., Neese, F., & Lubitz, W. (2012). A Functional [NiFe]-Hydrogenase Model Compound That Undergoes Biologically Relevant Reversible Thiolate Protonation. Journal of the American Chemical Society, 134(51), 20745-20755. https://doi.org/10.1021/ja309563p