(769a) The Nature of Heterogeneous Palladium Catalyzed Cross-Coupling Reactions on Novel Carbon Support Systems

Palladium-catalyzed carbon-carbon bond forming reactions have emerged as one of the most important chemical transformations in the preparation of complex organic molecules. The Suzuki-Miyaura cross-coupling reaction has gained particular prominence in pharmaceutical applications due to its mild reaction conditions and broad application across a wide range of functionalized substituents. These reactions are most often carried out under homogeneous conditions that can lead to product contamination, extensive purifications and loss of expensive metals and ligands. Pdn clusters supported on graphene (Pd/G) present an attractive alternative to homogeneous catalysis. These materials offer excellent catalytic activity with extremely high turnover frequencies, minimal leaching and remarkable recyclability opening a new paradigm in cross coupling reactions. Here we demonstrate that unlike previously reported examples of solid-supported metal catalysts, Pd/G operates as a heterogeneous catalyst where the enhanced binding to defect sites precludes leaching of the metal nanoparticles. In addition, the conductive nature of the support allows charge exchange that lowers the reaction barriers offering a highly effective catalyst with exceptional recyclability.