Palladium Immobilized Catalyst:an Efficient And Recyclable Catalyst For Suzuki Coupling Reaction And Hydrogenation Reaction

To our best of knowledge, numerous catalysts using a variety of metals including Cu、Ru、Au、 Fe、Pd、Pt and Rh have been investigated for various reactions. Palladium-catalyzed reactions has been used in various reactions such as Heck, hydrogenation and Suzuki, and provides high reaction rate or high turnover numbers (TON). While traditional catalysts have the problem of being costly and less green, researchers pay more attention to the designing of a catalyst that can be efficient and recoverable. We have already developed a facile and expediently approach of immobilizing palladium on a solid support to solve the difficulty in the separation of a homogeneous Pd-loaded catalyst from mixture. Considerable efforts have been made to immobilize palladium on varieties of solid supports such as microporous polymers, mesoporous silica, magnetic nanoparticles and carbon nanofiber, which made the catalysts easy to be separated from the reaction mixture by filtration steps.In this study, we report on the simple co-precipitation synthesis of nano-magnetite-supported, magnetically recyclable, and highly active Pd catalyst and its application in hydrogenation. Here, successful immobilization of the Pd nanoparticles onto the surface of the superparamagnetic nanoparticles via thiol bonding was achieved. In order to predict the behaviour of the Pd catalyst under mild conditions, the present paper provides a systematic study of the performance of Pd immobilized on thiol-modified magnetic nanoparticles (Fe3O4-SH-Pd). Particularly, we are interested in using alcohol as a medium for the hydrogenation reactions because using alcohol as solvent represents a green, safe and cost-effective process.The turn-over frequency (TOF) can be66.46h-1in ethanol under a H2atmosphere at room temperature. Another advantage is that the magnetite nanoparticles modified by thiol group can be separated just though the external magnetic force and can be reused at least ten times without any significant loss in activity.A novel solid catalyst for Suzuki coupling reaction has been successfully prepared by immobilizing palladium in the nanocages of the ethylenediamine-functionalized mesoporous material SBA-16. The structure and composition of the solid catalyst were characterized by N2 adsorption-desorption, XRD, TEM, FT-IR and TGA. These results revealed that Pd (Ⅱ) was successfully embedded inside the nanocages of SBA-16. This catalyst afforded the higher activity (over91%conversion) for the Suzuki coupling of various aryl bromides and phenyiboronic acids in ethanol solvent at60℃even at the loading of0.5mol%Pd. More importantly, the SBA-16-2N-Pd (Ⅱ) catalyst could be separated easily from reaction mixture and reused for ten times without obvious loss of catalytic activity, showing the superiority over the homogeneous catalysts in industrial applications.