NiI/RuII model for the Ni-L state of the [NiFe]hydrogenases: Synthesis, spectroscopy, and reactivity

Geoffrey M. Chambers, Joyee Mitra, Thomas B. Rauchfuss, Matthias Stein

Research output: Contribution to journalArticlepeer-review


This study describes the characterization of a mixed-valence Ru II/NiI complex, a structural model for the Ni-L state of the [NiFe]hydrogenases. One-electron oxidation of (cymene)Ru(μ-pdt)Ni(diphos) ([1]0, diphos = dppe, C2H4(PPh 2)2; [2]0, diphos = dcpe, C2H 4(P(C6H11)2)2] affords the mixed-valence cations [(cymene)Ru(pdt)Ni(diphos)]+ ([1] + and [2]+). Crystallographic and spectroscopic measurements indicate that these cations are described as RuII/ NiI. Although [1]0 and [1]+ are very similar structurally, the following changes are notable: the Ni-P distances elongate upon oxidation, and the Ru-Ni distance changes insignificantly. The molecular and electronic structures of the Ni center in [1]+ approaches that observed in the [NiFe]hydrogenases. Density functional theory calculations indicate that [1]0 is best described as RuII/Ni 0, consistent with its oxidation to RuII/NiI in [1]+. The fast electron self-exchange rate of 107 M -1 s-1 between [1]0 and [1]+ suggests minor reorganization, more consistent with a Ni0/Ni I oxidation state change than a NiI/NiII couple. In solution, [1]+ slowly converts to [H1]+ and [1-H]+, with the latter being a complex of the thioaldehyde SCHCH2CH2S arising from C-H activation of the pdt backbone. Treatment of [1]+ with the H-atom abstracting reagent 2,2,6,6-tetramethylpiperidine-1-oxy also gives [1-H]+.

Original languageEnglish (US)
Pages (from-to)4243-4249
Number of pages7
JournalInorganic Chemistry
Issue number8
StatePublished - Apr 21 2014

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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