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

• Ni complexes of the 1,2,4-triazole based NHC ligands were synthesized.
• The Ni–NHC interaction was probed by DFT studies.
• The Ni–NHC complexes exhibited moderate activity in borylation of arylbromides.

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]2Ni [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 NiCl2·6H2O in presence of K2CO3 as a base. The density functional theory studies performed on these complexes reveal highly polar character of the NHC–Ni σ-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 (B2pin2) in the presence of Cs2CO3 as a base at 70 °C.

A series of nickel complexes of 1,2,4-triazole derived amido-functionalized N-heterocyclic carbene ligands were prepared, characterized and explored for their activity in the borylation reaction of arylbromides.Figure optionsDownload as PowerPoint slide