CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand
In this study, the catalytic cycle for the production of formic acid by CO₂ hydrogenation and the reverse reaction has received renewed attention because they are viewed as offering a viable scheme for hydrogen storage and release. In this Forum Article, CO₂ hydrogenation catalyzed by iridium complexes bearing N^N-bidentate ligands is reported. We describe how a ligand containing hydroxyl groups as proton-responsive substituents enhances catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interaction. In particular, [(Cp*IrCl)₂(TH2BPM)]Cl₂ (Cp* = pentamethyl cyclopentadienyl, TH2BPM = 4,4',6,6'-tetrahydroxy-2,2'-bipyrimidine) promotes enormously the catalytic hydrogenation of CO₂ by these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands are applied to CO₂ hydrogenation. The catalytic efficiencies of the azole-type complexes are much higher than that of the unsubstituted bipyridine complex [Cp*Ir(bpy)(OH₂)]SO₄. Furthermore, the introduction of one or more hydroxyl groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxyl pyrimidine, and 4-pyrazolyl-2,6-dihydroxyl pyrimidine enhanced catalytic activity. It is clear that the incorporation of electron-donating hydroxyl groups into proton-responsive ligands is effective for promoting the hydrogenation of CO₂.
- Authors:
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[1]
; [1]
; [2]
; [2]
; [2]
; [3]
; [3]
; [1]
- National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan); Japan Science and Technology Agency, Saitama (Japan)
- National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan)
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- Publication Date:
- Report Number(s):
- BNL-107637-2015-JA
Journal ID: ISSN 0020-1669; R&D Project: CO026; KC0304030
- Grant/Contract Number:
- SC00112704
- Type:
- Accepted Manuscript
- Journal Name:
- Inorganic Chemistry
- Additional Journal Information:
- Journal Volume: 54; Journal Issue: 11; Journal ID: ISSN 0020-1669
- Publisher:
- American Chemical Society (ACS)
- Research Org:
- Brookhaven National Laboratory (BNL), Upton, NY (United States)
- Sponsoring Org:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; proton-responsive ligand; iridium complexes; CO₂ hydrogenation
- OSTI Identifier:
- 1182536
- Free Publicly Accessible Full Text
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Accepted Manuscript (DOE)
- Publisher's Version of Record
- https://doi.org/10.1021/ic502904q