Abstract
A new series of water soluble Ir(iii) catalysts has been designed and synthesized to determine the catalyst ligand's role in activating CO2 through electronic and second-coordination-sphere effects for the homogeneous catalytic hydrogenation of CO2. We report high catalytic hydrogenation activity of [Cp*Ir(6,6′-R2-bpy)(OH 2)]SO4 (bpy = 2,2′-bipyridine, R = OH) at ambient temperatures and pressures. Good correlation between the ligand substituents' Hammett parameters, which we varied by synthesizing ligands and catalysts substituted with R = H, Me, OMe and OH, and catalytic hydrogenation rates clearly illustrates the importance of electronic effects. Remarkably, additional rate enhancements are consistently observed when substituents are moved from 4,4′ positions to 6,6′ positions on 2,2′-bipyridine. Combined DFT calculations and NMR experiments suggest that the origin of these effects lies in the pendent base-aided heterolysis of H2, which significantly lowers the transition state energy. These studies are significant in elucidating new design principles for CO2 hydrogenation that lead to superior catalytic activity.
| Original language | English |
|---|---|
| Pages (from-to) | 7923-7926 |
| Number of pages | 4 |
| Journal | Energy and Environmental Science |
| Volume | 5 |
| Issue number | 7 |
| DOIs | |
| Publication status | Published - Jul 2012 |
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ASJC Scopus subject areas
- Renewable Energy, Sustainability and the Environment
- Environmental Chemistry
- Pollution
- Nuclear Energy and Engineering
Cite this
Second-coordination-sphere and electronic effects enhance iridium(iii)-catalyzed homogeneous hydrogenation of carbon dioxide in water near ambient temperature and pressure. / Wang, Wan Hui; Hull, Jonathan F.; Muckerman, James; Fujita, Etsuko; Himeda, Yuichiro.
In: Energy and Environmental Science, Vol. 5, No. 7, 07.2012, p. 7923-7926.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Second-coordination-sphere and electronic effects enhance iridium(iii)-catalyzed homogeneous hydrogenation of carbon dioxide in water near ambient temperature and pressure
AU - Wang, Wan Hui
AU - Hull, Jonathan F.
AU - Muckerman, James
AU - Fujita, Etsuko
AU - Himeda, Yuichiro
PY - 2012/7
Y1 - 2012/7
N2 - A new series of water soluble Ir(iii) catalysts has been designed and synthesized to determine the catalyst ligand's role in activating CO2 through electronic and second-coordination-sphere effects for the homogeneous catalytic hydrogenation of CO2. We report high catalytic hydrogenation activity of [Cp*Ir(6,6′-R2-bpy)(OH 2)]SO4 (bpy = 2,2′-bipyridine, R = OH) at ambient temperatures and pressures. Good correlation between the ligand substituents' Hammett parameters, which we varied by synthesizing ligands and catalysts substituted with R = H, Me, OMe and OH, and catalytic hydrogenation rates clearly illustrates the importance of electronic effects. Remarkably, additional rate enhancements are consistently observed when substituents are moved from 4,4′ positions to 6,6′ positions on 2,2′-bipyridine. Combined DFT calculations and NMR experiments suggest that the origin of these effects lies in the pendent base-aided heterolysis of H2, which significantly lowers the transition state energy. These studies are significant in elucidating new design principles for CO2 hydrogenation that lead to superior catalytic activity.
AB - A new series of water soluble Ir(iii) catalysts has been designed and synthesized to determine the catalyst ligand's role in activating CO2 through electronic and second-coordination-sphere effects for the homogeneous catalytic hydrogenation of CO2. We report high catalytic hydrogenation activity of [Cp*Ir(6,6′-R2-bpy)(OH 2)]SO4 (bpy = 2,2′-bipyridine, R = OH) at ambient temperatures and pressures. Good correlation between the ligand substituents' Hammett parameters, which we varied by synthesizing ligands and catalysts substituted with R = H, Me, OMe and OH, and catalytic hydrogenation rates clearly illustrates the importance of electronic effects. Remarkably, additional rate enhancements are consistently observed when substituents are moved from 4,4′ positions to 6,6′ positions on 2,2′-bipyridine. Combined DFT calculations and NMR experiments suggest that the origin of these effects lies in the pendent base-aided heterolysis of H2, which significantly lowers the transition state energy. These studies are significant in elucidating new design principles for CO2 hydrogenation that lead to superior catalytic activity.
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U2 - 10.1039/c2ee21888g
DO - 10.1039/c2ee21888g
M3 - Article
VL - 5
SP - 7923
EP - 7926
JO - Energy and Environmental Science
JF - Energy and Environmental Science
SN - 1754-5692
IS - 7
ER -