Fe_3O_4@Sio2 Nanoparticles Decorated with Schiff base Complex of Pd(II) as a Magnetically Phosphine-free Catalyst for Heck-Mizoroki Coupling Reactions

摘要

Background: The palladium-catalyzed couplings of alkenes with aryl halides is considered as one of the most important methods for carbon-carbon bond formation and have been utilized in the areas of natural products, high performance materials, bioactive compounds, new drugs and many industrially useful chemicals. Although the homogeneous palladium catalysts offer several advantages concerning higher selectivity and yields, better tuning of chemoselectivity and high efficiency but commercializing most of homogeneous has not been possible because of recycling problem of the catalyst from the mixture of reaction. Therefore, for resolving this problem, immobilization of homogeneous Pd complexes via grafting to solid supports such as activated carbon, zeolites, silica or modified silica, polymers, nanoparticles, and magnetic core shells have been subject of great challenges. Methods: Fe_3O_4 nanoparticles was coated by silica gel and then decorated by Schiff base Pd complex to provide Fe_3O_4@SiO_2/Schiff base/Pd(II) nanoparticles. After optimization of reaction parameters, Heck-Mizoroki coupling reaction of aryl halides with olefins was studied. Results: The magnetic Schiff base complex of Pd, as a phosphine free nanocatalyst, catalyzed efficiently Heck-Mizoroki carbon-carbon coupling reaction between aryl halides and alkenes and provided the desired products in high yields. The magnetic Pd complex was easily removed from the reaction mixture and reused for eight runs. Conclusion: A new efficient, simple and cost effective protocol was introduced for carbon-carbon bond formation via Heck-Mizoroki coupling reaction of aryl halides with olefins in high to excellent yields in short reaction times. These valuable advantages were achieved because of employing Fe_3O_4@SiO_2/Schiff base/Pd(II) complex as a dispersible, phosphine free ligand, highly active, magnetically recoverable and reusable several times.