Issue 20, 2013

Iridium(i) N-heterocyclic carbene complexes of benzimidazol-2-ylidene: effect of electron donating groups on the catalytic transfer hydrogenation reaction

Abstract

Two new [Ir(NHC)(COD)Cl] (NHC = N-heterocyclic carbene; COD = 1,5-cyclooctadiene) iridium complexes (2a,b) have been prepared by the reaction of [Ir(COD)Cl]2 with in situ prepared NHC–Ag carbene transfer agents in dichloromethane at ambient temperature. They have been fully characterized by 1H, 13C NMR, and elemental analysis. X-ray diffraction studies on single crystals of 2a and 2b confirm the square planar geometry. Complexes of type [Ir(NHC)(CO)2Cl] [NHC = 1,3-diisopropyl(5,6-dimethyl)benzimidazol-2-ylidene] 3 were also synthesized to compare σ-donor/π-acceptor strength of NHC ligands. Transfer hydrogenation (TH) reactions of various aldehydes and ketones have been studied using complexes 2a and 2b as catalysts. The 5,6-dimethyl substituted iridium complex (2b) showed the highest catalytic activity for the TH reaction.

Graphical abstract: Iridium(i) N-heterocyclic carbene complexes of benzimidazol-2-ylidene: effect of electron donating groups on the catalytic transfer hydrogenation reaction

Supplementary files

Article information

Article type
Paper
Submitted
17 Oct 2012
Accepted
21 Nov 2012
First published
22 Nov 2012

Dalton Trans., 2013,42, 7305-7311

Iridium(I) N-heterocyclic carbene complexes of benzimidazol-2-ylidene: effect of electron donating groups on the catalytic transfer hydrogenation reaction

S. Gülcemal, A. G. Gökçe and B. Çetinkaya, Dalton Trans., 2013, 42, 7305 DOI: 10.1039/C2DT32482B

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