A computational study of the effects of ancillary ligands on copper(I)–ethylene interaction

A set of [Cu(I)Ln(C2H4)]q (q = −1, 0, or 1) complex modelling systems of experimental interest were studied by DFT calculations to analyze the Cu(I)–ethylene bonding using NBO and CDA analyses. All complexes are better viewed as donor–acceptor complexes between a d10 Cu(I) center and ethylene. Back-donation depends significantly on the nature and number of ancillary ligands, and hence on the coordination sphere at copper. Back-donation is shown to vary more with the nature of the ligands than donation and to increase significantly with the number of ancillary ligands. However, even with strongly donating ligands such as alkyl (modelled by CH3), there is no tendency of forming a metallacyclopropane. This can lead to revisiting the mechanisms of alkylation of olefin catalyzed by copper complexes.