Nickel complexes of 1,2,4-triazole derived amido-functionalized N-heterocyclic carbene ligands: Synthesis, theoretical studies and catalytic application

A series of nickel complexes (1-3)b of 1,2,4-triazole derived amido-functionalized N-heterocyclic carbene ligands were synthesized and structurally characterized. In particular, the [1-(R)-4-N-(furan-2-ylmethyl) acetamido-1,2,4-triazol-5-ylidene](2)Ni [R = Et (1b), i-Pr (2b) and Bn (3b)] complexes were obtained by the direct reaction of the corresponding triazolium chloride salts (1-3) a by the treatment with NiCl2 center dot 6H(2)O in presence of K2CO3 as a base. The density functional theory studies performed on these complexes reveal highly polar character of the NHC-Ni sigma-bonding interaction with corresponding molecular orbital having a maximum contribution (59-69%) from the NHC ligand fragments while that of a minimum contribution (4%) from the central nickel atom. The (1-3)b complexes were found to be moderately active for the catalytic borylation reactions of bromoaryl derivatives by bis(pinacolato) diboron reagent (B(2)pin(2)) in the presence of Cs2CO3 as a base at 70 degrees C. (C) 2015 Elsevier B.V. All rights reserved.