Iron complexes for the electrocatalytic oxidation of hydrogen: Tuning primary and secondary coordination spheres

Jonathan M. Darmon, Simone Raugei, Tianbiao Liu, Elliott B. Hulley, Charles J. Weiss, R. Morris Bullock, Monte L. Helm

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

A series of iron hydride complexes featuring PRN ROPR (PRNR′ PR = R2PCH2N(R′)CH2PR 2 where R = Ph, R′ = Me; R = Et, R′ = Ph, Bn, Me, tBu) and cyclopentadienide (CpX = C5H 4X where X = H, C5F4N) ligands has been synthesized; characterized by NMR spectroscopy, X-ray diffraction, and cyclic voltammetry; and examined by quantum chemistry calculations. Each compound was tested for the electrocatalytic oxidation of H2, and the most active complex, (CpC5F4N)Fe(PEtNMeP Et)(H), exhibited a turnover frequency of 8.6 s-1 at 1 atm of H2 with an overpotential of 0.41 V, as measured at the potential at half of the catalytic current and using N-methylpyrrolidine as the exogenous base to remove protons. Control complexes that do not contain pendant amine groups were also prepared and characterized, but no catalysis was observed. The rate-limiting steps during catalysis are identified through combined experimental and computational studies as the intramolecular deprotonation of the FeIII hydride by the pendant amine and the subsequent deprotonation by an exogenous base.

Original languageEnglish
Pages (from-to)1246-1260
Number of pages15
JournalACS Catalysis
Volume4
Issue number4
DOIs
Publication statusPublished - Apr 4 2014

Keywords

  • diphosphine
  • electrocatalyst
  • hydrogen oxidation
  • iron
  • piano-stool
  • proton relay

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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