Iridium Complexes with Proton-Responsive Azole-Type Ligands as Effective Catalysts for CO 2 Hydrogenation.

Autor: Suna Y; Research Institute of Energy Frontier, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan., Himeda Y; Research Institute of Energy Frontier, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan., Fujita E; Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA., Muckerman JT; Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA., Ertem MZ; Chemistry Division, Brookhaven National Laboratory, Upton, NY, 11973-5000, USA.
Jazyk: angličtina
Zdroj: ChemSusChem [ChemSusChem] 2017 Nov 23; Vol. 10 (22), pp. 4535-4543. Date of Electronic Publication: 2017 Nov 07.
DOI: 10.1002/cssc.201701676
Abstrakt: Pentamethylcyclopentadienyl iridium (Cp*Ir) complexes with bidentate ligands consisting of a pyridine ring and an electron-rich diazole ring were prepared. Their catalytic activity toward CO 2 hydrogenation in 2.0 m KHCO 3 aqueous solutions (pH 8.5) at 50 °C, under 1.0 MPa CO 2 /H 2 (1:1) have been reported as an alternative to photo- and electrochemical CO 2 reduction. Bidentate ligands incorporating an electron-rich diazole ring improved the catalytic performance of the Ir complexes compared to the bipyridine ligand. Complexes 2, 4, and 6, possessing both a hydroxy group and an uncoordinated NH group, which are proton-responsive and capable of generating pendent bases in basic media, recorded high initial turnover frequency values of 1300, 1550, and 2000 h -1 , respectively. Spectroscopic and computational investigations revealed that the reversible deprotonation changes the electronic properties of the complexes and causes interactions between pendent base and substrate and/or solvent water molecules, resulting in high catalytic performance in basic media.
(© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)
Databáze: MEDLINE
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