Dinuclear Pd II Bis-MIC/PCy 3 Pre-Catalyst for Cooperative Catalysis: Suzuki–Miyaura Coupling of Aryl Chlorides and α-Arylation of Cyclic Amide

Mixed carbene-phosphine complexes are known to be beneficial in many catalytic reactions. However, synergistic catalysis employing such complexes utilizing two metal centers, each possessing a combination of mesoionic carbene (MIC) and phosphine ligands, is very rare. This report describes the synthesis of the first dinuclear palladium(II) complex utilizing a combination of MIC and PCy 3 ligands, and the same has been characterized by using standard spectroscopic techniques. The aforementioned complex appeared to be an efficient precatalyst, working at a very low catalyst loading for the Suzuki–Miyaura coupling of aryl chlorides and copper-free intermolecular α-arylation reactions. In addition, the catalytic outcomes of the dinuclear MIC/PCy 3 complex are superior when compared to the catalytic outcomes of the corresponding mononuclear MIC/PCy 3 complex under identical reaction conditions, indicating potential metal–metal cooperativity during catalysis. The Pd•••Pd separation is crucial in synergistic catalysis, and the same in the dinuclear MIC/PCy 3 complex has been compared with the distances reported for dinuclear Pd II –NHC complexes.