Palladium complexes of amido-functionalized N-heterocyclic carbenes as effective precatalysts for the Suzuki-Miyaura C-C cross-coupling reactions of aryl bromides and iodides |
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Authors: | Sachin Kumar Prasenjit Ghosh |
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Institution: | a Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India b National Single Crystal X-ray Diffraction Facility, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India |
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Abstract: | A series of air-stable, robust and highly active palladium based precatalysts of amido-functionalized N-heterocyclic carbenes for the Suzuki-Miyaura C-C cross-coupling reaction has been designed. In particular, the 1-R-3-{N-(benzylacetamido)imidazol-2-ylidene]2PdCl2 R = i-Pr (1c) and CH2Ph (2c)] complexes efficiently carried out the Suzuki-Miyaura coupling of the aryl bromide and iodide substrates with phenyl boronic acid in good to excellent yields in air at 90 °C in 12 h. Quite interestingly, of these palladium precatalysts, the i-propyl derivative (1c) exhibited superior activity as compared to the benzyl derivative (2c). The density functional theory (DFT) studies carried out on the 1c and 2c complexes revealed the strong σ-donating nature of the NHC ligand as reflected in their high d/b ratio i.e. forward σ-donation (d) to backward π-donation (b)] of these complexes and, thus, point towards greater stability of the Pd-NHC interaction in these complexes. |
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Keywords: | Carbenes Functionalized NHC Suzuki-Miyaura coupling Organometallic catalysis Palladium-NHC complex |
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