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

Pentamethylcyclopentadienyl iridium (Cp*Ir) complexes with bidentate ligands consisting of a pyridine ring and an electron-rich diazole ring were prepared. Their catalytic activity towards 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 TOF values of 1300 h -1, 1550 h -1 and 2000 h -1, respectively. Here, 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 the high catalytic performance in basic media.
Authors:
 [1] ;  [2] ;  [2] ;  [1] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan)
Publication Date:
Report Number(s):
BNL-114435-2017-JA
Journal ID: ISSN 1864-5631; R&D Project: CO026; KC0304030; TRN: US1702901
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
ChemSusChem
Additional Journal Information:
Journal Volume: 10; Journal Issue: 22; Journal ID: ISSN 1864-5631
Publisher:
ChemPubSoc Europe
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; CO2 hydrogenation formic acid catalysis iridium DFT
OSTI Identifier:
1405934
Alternate Identifier(s):
OSTI ID: 1407830