Agostic Interactions in Nickel(II) Complexes: Trans Influence of Ancillary Ligands on the Strength of the Bond

The selectivity of transition-metal-catalyzed alkyl cross-coupling is significantly affected by agostic interactions. We report a systematic computational study of how ligand trans influence affects the strength of beta-agostic interactions in Ni(II)-ethyl complexes selected to model cross-coupling intermediates. The roles of pi back-donation and in-plane pi coupling are highlighted. Calculations with carbene ligands illustrate the relevance of these ideas for ligand design.