| The development of green, sustainable and economical chemical processes is one of the major challenges in chemistry. Besides the traditional need for efficient and pelective catalytic reactions that will transform raw materials into valuable chemicals, Pharmaceuticals and fuels, green chemistry also strives for waste reduction, atomic efficiency and high rates of catalyst recovery.Magnetic nanostructured materials are attractive candidates for various organic transformations, especially because they meet the goals of green chemistry. The ease of isolation and separation from the desired organic product and the recovery and reuse of these magnetic nanostructured materials further enhance their attractiveness as green and sustainable catalysts.The use of N-heterocyclic carbenes as ligands in palladium-catalyzed cross-coupling reactions is rapidly gaining in popularity. These two-electron donor ligands combine strong σ-donating properties with a shielding steric pattern that allows for both stabilization of the metal center and enhancement of its catalytic activity. As a result, the number of well-defined NHC-containing palladium complexes is growing, and their use in coupling reactions is witnessing increasing interest.In this work, Fe3O4@SiO2 was chosen as the support. The catalyst was prepared by grafting NHC-Pd on the surface of Fe3O4@SiO2, which was characterized by TEM, XPS, XRD, FT-IR, VSM. etc. The results illustrated that Fe3O4@SiO2@Pd-NHC had an ordered core-shell structure like the support Fe3O4@SiO2, and NHC-Pd was successfully grafted on the surface of Fe3O4@SiO2.We established a fast and efficient strategy for Suzuki coupling reactions. At 40 ℃, using 0.1 mol% palladium catalyst, the Suzuki coupling reactions of iodobenzene and bromobenzene was complete within 15 minutes and 30 minutes, respectively. The catalyst could be recovered using a simple magnetic separation and washing sequence, and a good yield was still achieved even after running ten times. |
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