Palladium Nanoparticles Immobilized with Polymer Containing Nitrogen-Based Ligand: A Highly Efficient Catalyst for Suzuki-Miyaura and Mizoroki-Heck Coupling Reactions

An outstanding heterogeneous catalyst was successfully prepared by immobilization of palladium nanoparticles (Pd NPs) with polymer containing 4 '-(4-hydroxyphenyl)-2,2 ':6 ',2 ''-terpyridine (HPTPy) ligand. The polymer cross-linked with trimethylolpropane triacrylate (TMPTA) units was synthesized by polymerization of itaconic acid-HPTPy (ITC-HPTPy) monomer (so-called cross-linked poly (ITC- HPTPy)). The cross-linked poly (ITC-HPTPy) can stabilize the Pd NPs effectively against aggregation, thereby improving the catalytic efficiency of Pd NPs. The presence of Pd NPs on the polymer was confirmed by various physicochemical techniques. The resulting cross-linked poly (ITC-HPTPy)-Pd was applied as a highly effective recyclable catalyst in Suzuki-Miyaura and Mizoroki-Heck coupling reactions under low Pd-loading conditions and straightforward methods, and provided the corresponding products with excellent yields (up to 98%), high catalytic activities (TOF up to 213 h(-1)). The catalyst can be separated from the reaction mixture by centrifugation and can be reused consecutive six times with slight reduction in catalytic activity. Graphic Pd NPs immobilized with polymer containing terpyridine ligand are highly active heterogeneous catalysts for Suzuki-Miyaura and Mizoroki-Heck coupling reactions.