Atom-efficient catalytic coupling of imidazolium salts with ethylene involving Ni-NHC complexes as intermediates: a combined experimental and DFT study

Abstract

The coupling reaction between azolium salts (N-heterocyclic carbene precursors) and ethylene, catalyzed by zerovalent nickel complexes, has been investigated using a combination of experiment and density functional theory (DFT). The reaction proceeds via a redox mechanism involving the generation of Nicarbene intermediates. The experimental studies employed an in situ catalyst system, derived from Ni- (COD)2 and a variety of phosphine and N-heterocyclic carbene spectator ligands, to couple 1-propyl-3- methylimidazolium bromide (ionic liquid) and other azolium salts with ethylene. The DFT studies employed the simpler dimethylimidazolium salt to model the reaction.