Palladium Nanoparticles Supported on Porous Silica Materials as Heterogeneous Catalysts of C-C Coupling and Cross-Coupling Reactions

Noble metal nanoparticles supported on porous silica materials represent an important class of heterogeneous catalysts. Recently, a remarkable progress has been made concerning the synthesis, characterization, and catalytic application of noble metal nanoparticles immobilized on zeolites and mesoporous silica-based materials. Various synthesis strategies have been developed, including the application of ligand-assisted metal precursors, multistep synthesis procedures, post-synthetic modifications, and magnetic mesoporous silica particles. Emphasis has been laid on the introduction of green procedures, based on the utilization of environmentally friendly solvents, efficient stabilizing agents, non-toxic reagents, and mild reaction conditions. Palladium nanoparticles have long been recognized as the most efficient catalysts in a wide range of organic transformations, including the Heck, Suzuki, Stille, and Sonogashira reactions. Although these transformations have been extensively investigated in homogeneous catalytic systems, the application of heterogeneous catalysts, including silica-supported Pd0 nanoparticles, has gained in increasing importance. This may be due to the easy handling and recovery of the latter catalysts, which facilitates their repeated applications. The aim of this review is to provide an outlook on the current research progress achieved on the development of novel synthetic procedures, affording highly dispersed Pd0 nanoparticles immobilized on porous silica materials, which proved to be efficient and recyclable catalysts in C-C coupling and cross-coupling reactions. The focus of this review is on results published in the last six years with a handful of examples in previous years. Palladium nanoparticles immobilized on porous silica materials have been demonstrated to be efficient heterogeneous catalysts in various coupling and cross-coupling reactions. Utilized in combination with suitable ligands or under ligand-free conditions, these catalysts exhibit high activities and selectivities under mild conditions. Their further advantages include easy handling and recovery, and the possibility of repeated applications.image