H2 Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex

Demyan E. Prokopchuk, Geoffrey M. Chambers, Eric D. Walter, Michael T. Mock, R Morris Bullock

Research output: Contribution to journalArticle

Abstract

While diamagnetic transition metal complexes that bind and split H2 have been extensively studied, paramagnetic complexes that exhibit this behavior remain rare. The square planar S = 1/2 FeI(P4N2)+ cation (FeI+) reversibly binds H2/D2 in solution, exhibiting an inverse equilibrium isotope effect of KH2/KD2 = 0.58(4) at -5.0 °C. In the presence of excess H2, the dihydrogen complex FeI(H2)+ cleaves H2 at 25 °C in a net hydrogen atom transfer reaction, producing the dihydrogen-hydride trans-FeII(H)(H2)+. The proposed mechanism of H2 splitting involves both intra- and intermolecular steps, resulting in a mixed first- and second-order rate law with respect to initial [FeI+]. The key intermediate is a paramagnetic dihydride complex, trans-FeIII(H)2 +, whose weak FeIII-H bond dissociation free energy (calculated BDFE = 44 kcal/mol) leads to bimetallic H-H homolysis, generating trans-FeII(H)(H2)+. Reaction kinetics, thermodynamics, electrochemistry, EPR spectroscopy, and DFT calculations support the proposed mechanism.

Original languageEnglish
Pages (from-to)1871-1876
Number of pages6
JournalJournal of the American Chemical Society
Volume141
Issue number5
DOIs
Publication statusPublished - Feb 6 2019

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Electrochemistry
Coordination Complexes
Thermodynamics
Discrete Fourier transforms
Hydrides
Reaction kinetics
Isotopes
Free energy
Transition metals
Paramagnetic resonance
Cations
Hydrogen
Spectrum Analysis
Iron
Spectroscopy
Atoms
Metal complexes
Positive ions

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

H2 Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex. / Prokopchuk, Demyan E.; Chambers, Geoffrey M.; Walter, Eric D.; Mock, Michael T.; Bullock, R Morris.

In: Journal of the American Chemical Society, Vol. 141, No. 5, 06.02.2019, p. 1871-1876.

Research output: Contribution to journalArticle

Prokopchuk, Demyan E. ; Chambers, Geoffrey M. ; Walter, Eric D. ; Mock, Michael T. ; Bullock, R Morris. / H2 Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex. In: Journal of the American Chemical Society. 2019 ; Vol. 141, No. 5. pp. 1871-1876.
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