DFT-Based Insights into Pd-Zn Cooperative Effects in Oxidative Addition and Reductive Elimination Processes Relevant to Negishi Cross-Couplings

The individual steps of a model Pd-catalyzed Negishi coupling between vinyl bromide and MeZnClS2 (S = THF), using Pd(PMe3)(2) as catalyst, have been examined with the aid of DFT computations in THF solution with the B97D functional to gain further insight into the role of Pd-Zn interactions on the oxidative addition and reductive elimination steps. Comparisons between such processes taking place on monometallic Pd complexes and on bimetallic Pd-Zn complexes reveal a detrimental effect of Pd-Zn interactions in oxidative addition, whereas reductive elimination is favored by Pd-Zn cooperativity. Additionally, a cis transmetalation pathway has been characterized that complements previous studies involving trans complexes.