Palladium nanoparticles immobilized on amphiphilic and hyperbranched polymer‐functionalized magnetic nanoparticles: An efficient semi‐heterogeneous catalyst for Heck reaction

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Abstract
To address the obstacles facing the use of palladium‐based homogeneous and heterogeneous catalysts in C─C cross‐coupling reactions, a novel semi‐heterogeneous support was developed based on hyperbranched poly(ethylene glycol)‐block‐poly(citric acid)‐functionalized Fe3O4 magnetic nanoparticles (Fe3O4@PCA‐b‐PEG). Because of the surface modification of the Fe3O4 nanoparticles with amphiphilic and hyperbranched polymers (PCA‐b‐PEG), these hybrid materials are not only soluble in a wide range of solvents (e.g. water, ethanol and dimethylformamide) but also are able to trap Pd2+ ions via complex formation of free carboxyl groups of the PCA dendrimer with metal ions. The reduction of trapped palladium ions in the dendritic shell of Fe3O4@PCA‐b‐PEG leads to immobilized palladium nanoparticles. The morphology and structural features of the catalyst were characterized using various microscopic and spectroscopic techniques. The catalyst was effectively used in the palladium‐catalysed Mizoroki–Heck coupling reaction in water as a green solvent. In addition, the catalyst can be easily recovered from the reaction mixture by applying an external magnetic field and reused for more than ten consecutive cycles without much loss in activity, exhibiting an example of a sustainable and green methodology.

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