Supported Palladium on Magnetic Nanoparticles-Starch Substrate (Pd-MNPSS): Highly Efficient Magnetic Reusable Catalyst for C-C Coupling Reactions in Water

A novel heterogeneous Pd-catalyst system (Pd-MNPSS) was developed using immobilization of Pd species (Pd-II and Pd) on starch-functionalized magnetic nanoparticles. For the synthesis of Pd-MNPSS catalyst, first, magnetic nanoparticles (MNPs) were prepared and coated with a silica layer (Fe3O4@SiO2) to increase their stability and functionalization capability. The Fe3O4@SiO2 particles were reacted with thionyl chloride (SOCl2) to generate chlorosilyl groups on the surface of MNPs. Reaction of starch with chloro-functionalized MNPs leads to a magnetic reusable polyhydroxy-functionalized substrate (MNPSS), which is highly suitable for immobilization of Pd metal on its surface. This catalyst system was designed to be applied in Pd-catalyzed organic coupling reactions in water. Finally, the Pd-MNPSS catalyst was prepared via reaction of MNPSS and Pd(OAc)(2). After characterization of the Pd-MNPSS catalyst it was applied in the Heck and Sonogashira coupling reactions in water solvent, and excellent results were obtained. The catalyst system was separated from the reaction mixture employing an outside magnetic field. In these processes the catalyst was reusable for 5 times without remarkable decrease in its activity. The Pd-MNPSS catalyst has many advantages especially in the workup process related to our previously reported catalyst systems, Pd supported on silica starch substrate (PNP-SSS) and Pd supported on silica cyclodextrin substrate (PNP-SCD).