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Bimetallic Iridium–Carbene Complexes with Mesoionic Triazolylidene Ligands for Water Oxidation Catalysis
Author(s) -
Petronilho Ana,
Woods James A.,
Bernhard Stefan,
Albrecht Martin
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201300843
Subject(s) - bimetallic strip , chemistry , catalysis , mesoionic , iridium , turnover number , cerium , inorganic chemistry , carbene , ligand (biochemistry) , photochemistry , medicinal chemistry , organic chemistry , biochemistry , receptor
Two new diiridium–triazolylidene complexes were prepared as bimetallic analogues of established mononuclear water oxidation catalysts. Both complexes are efficient catalyst precursors in the presence of cerium ammonium nitrate (CAN) as sacrificial oxidant. Up to 20000:1 ratios of CAN/complex, the turnover limitation is the availability of CAN and not the catalyst stability. The water oxidation activity of the bimetallic complexes is not better than the monometallic species at 0.6 m M catalyst concentration. Under dilute conditions (0.03 m M ), the bimetallic complexes double their activity, whereas the monometallic complexes show an opposite trend and display markedly reduced rates, thereby suggesting a benefit of the close proximity of two metal centers in this low concentration regime. The high dependence of catalyst activity on reaction conditions indicates that caution is required when catalysts are compared by their turnover frequencies only.