Steric effects determine the mechanisms of reactions between bis(N-heterocyclic carbene)-nickel(0) complexes and aryl halides

Computational investigations of the reactions of [Ni(NHC) 2 ] complexes with aryl halides show that the outcomes are governed by the steric impact of the ligand (NHC = N-heterocyclic carbene). Small ligands permit facile oxidative addition, leading to Ni II complexes, while larger NHC ligands prevent coordination of the aryl halide and favour the halide abstraction to form Ni I . DFT studies show that [Ni(NHC) 2 ] complexes with large ligands disfavour oxidative addition and instead react with aryl halides via halide abstraction.