A computational mapping of the R-NHC coupling pathway - the key process in the evolution of Pd/NHC catalytic systems

摘要

C-C coupling reactions are of great importance in metal-catalyzed synthetic transformations. Reductive elimination of two carbon centers is the key stage, which takes place in the metal coordination sphere. In the present study, we provide a detailed analysis of nonclassical R-NHC coupling in the model (NHC)Pdii(Ph)(X)(Solv) complex, which is a representative intermediate of the Mizoroki-Heck and cross-coupling reactions. This C-C bond formation stage proceeds as Ph ligand movement and insertion into the Pd-NHC bond, rather than classical C-C coupling. Based on the analysis by the quantum theory of atoms in molecules (QTAIM) of the reaction path structures, the atomic rearrangements and alterations in the electronic system during the R-NHC coupling process were characterized in detail.