Diferrate [Fe2(CO)6(μ-CO){μ-P(aryl)2}] as Self-Assembling Iron/Phosphor-Based Catalyst for the Hydrogen Evolution Reaction in Photocatalytic Proton Reduction—Spectroscopic Insights

Steffen Fischer, Arend Rösel, Anja Kammer, Enrico Barsch, Roland Schoch, Henrik Junge, Matthias Bauer, Matthias Beller, Ralf Ludwig

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11 Scopus citations

Abstract

This work is focused on the identification and investigation of the catalytically relevant key iron species in a photocatalytic proton reduction system described by Beller and co-workers. The system is driven by visible light and consists of the low-cost [Fe3(CO)12] as catalyst precursor, electron-poor phosphines P(R)3 as co-catalysts, and a standard iridium-based photosensitizer dissolved in a mixture of THF, water, and the sacrificial reagent triethylamine. The catalytic reaction system was investigated by operando continuous-flow FTIR spectroscopy coupled with H2 gas volumetry, as well as by X-ray absorption spectroscopy, NMR spectroscopy, DFT calculations, and cyclic voltammetry. Several iron carbonyl species were identified, all of which emerge throughout the catalytic process. Depending on the applied P(R)3, the iron carbonyl species were finally converted into [Fe2(CO)6(μ-CO){μ-P(R)2}]. This involves a P−C cleavage reaction. The requirements of P(R)3 and the necessary reaction conditions are specified. [Fe2(CO)6(μ-CO){μ-P(R)2}] represents a self-assembling, sulfur-free [FeFe]-hydrogenase active-site mimic and shows good catalytic activity if the substituent R is electron poor. Deactivation mechanisms have also been investigated, for example, the decomposition of the photosensitizer or processes observed in the case of excessive amounts of P(R)3. [Fe2(CO)6(μ-CO){μ-P(R)2}] has potential for future applications.

Original languageEnglish
Pages (from-to)16052-16065
Number of pages14
JournalChemistry - A European Journal
Volume24
Issue number60
DOIs
StatePublished - 26 Oct 2018
Externally publishedYes

Keywords

  • enzyme mimics
  • EXAFS spectroscopy
  • hydrogen
  • IR spectroscopy
  • photocatalysis
  • proton reduction

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