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Bimetallic Iridium-Carbene Complexes with Mesoionic Triazolylidene Ligands for Water Oxidation Catalysis
Petronilho, Ana; Woods, James A.; Bernhard, Stefan; Albrecht, Martin
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 mm catalyst concentration. Under dilute conditions (0.03 mm), 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. European Research Council Science Foundation Ireland National Science Foundation
Keyword(s): Water chemistry; Oxidation; Iridium; Carbenes; Bimetallic complexes; N-heterocyclic carbene; Triazolylidene; Water oxidation; Bimetallic
Publication Date:
2015
Type: Journal article
Peer-Reviewed: Unknown
Language(s): English
Institution: University College Dublin
Publisher(s): Wiley
First Indexed: 2015-05-16 05:30:17 Last Updated: 2018-10-11 15:33:11