CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand

Naoya Onishi, Shaoan Xu, Yuichi Manaka, Yuki Suna, Wan Hui Wang, James Muckerman, Etsuko Fujita, Yuichiro Himeda

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

The catalytic cycle for the production of formic acid by CO2 hydrogenation and the reverse reaction have 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 sophisticated N^N-bidentate ligands is reported. We describe how a ligand containing hydroxy groups as proton-responsive substituents enhances the catalytic performance by an electronic effect of the oxyanions and a pendent-base effect through secondary coordination sphere interactions. In particular, [(Cp∗IrCl)2(TH2BPM)]Cl2 (Cp∗ = pentamethylcyclopentadienyl; TH2BPM = 4,4′,6,6′-tetrahydroxy-2,2′-bipyrimidine) enormously promotes the catalytic hydrogenation of CO2 in basic water by these synergistic effects under atmospheric pressure and at room temperature. Additionally, newly designed complexes with azole-type ligands were applied to CO2 hydrogenation. The catalytic efficiencies of the azole-type complexes were much higher than that of the unsubstituted bipyridine complex [Cp∗Ir(bpy)(OH2)]SO4. Furthermore, the introduction of one or more hydroxy groups into ligands such as 2-pyrazolyl-6-hydroxypyridine, 2-pyrazolyl-4,6-dihydroxypyrimidine, and 4-pyrazolyl-2,6-dihydroxypyrimidine enhanced the catalytic activity. It is clear that the incorporation of additional electron-donating functionalities into proton-responsive azole-type ligands is effective for promoting further enhanced hydrogenation of CO2.

Original languageEnglish
Pages (from-to)5114-5123
Number of pages10
JournalInorganic Chemistry
Volume54
Issue number11
DOIs
Publication statusPublished - Jun 1 2015

Fingerprint

Iridium
iridium
Hydrogenation
hydrogenation
Protons
azoles
Azoles
Ligands
ligands
protons
formic acid
Bearings (structural)
Hydrogen storage
Atmospheric pressure
catalytic activity
Catalyst activity
atmospheric pressure
cycles
Electrons
Water

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

Cite this

Onishi, N., Xu, S., Manaka, Y., Suna, Y., Wang, W. H., Muckerman, J., ... Himeda, Y. (2015). CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand. Inorganic Chemistry, 54(11), 5114-5123. https://doi.org/10.1021/ic502904q

CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand. / Onishi, Naoya; Xu, Shaoan; Manaka, Yuichi; Suna, Yuki; Wang, Wan Hui; Muckerman, James; Fujita, Etsuko; Himeda, Yuichiro.

In: Inorganic Chemistry, Vol. 54, No. 11, 01.06.2015, p. 5114-5123.

Research output: Contribution to journalArticle

Onishi, Naoya ; Xu, Shaoan ; Manaka, Yuichi ; Suna, Yuki ; Wang, Wan Hui ; Muckerman, James ; Fujita, Etsuko ; Himeda, Yuichiro. / CO2 hydrogenation catalyzed by iridium complexes with a proton-responsive ligand. In: Inorganic Chemistry. 2015 ; Vol. 54, No. 11. pp. 5114-5123.
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