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 language | English |
|---|---|
| Pages (from-to) | 1871-1876 |
| Number of pages | 6 |
| Journal | Journal of the American Chemical Society |
| Volume | 141 |
| Issue number | 5 |
| DOIs | |
| Publication status | Published - Feb 6 2019 |
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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 journal › Article
}
TY - JOUR
T1 - H2 Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex
AU - Prokopchuk, Demyan E.
AU - Chambers, Geoffrey M.
AU - Walter, Eric D.
AU - Mock, Michael T.
AU - Bullock, R Morris
PY - 2019/2/6
Y1 - 2019/2/6
N2 - 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.
AB - 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.
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U2 - 10.1021/jacs.8b12823
DO - 10.1021/jacs.8b12823
M3 - Article
VL - 141
SP - 1871
EP - 1876
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 5
ER -