Composite Fe3O4/Si/Poly(N-Isopropyl Acrylamide)/Au Catalyst for Heck, Suzuki, and Sonogashira Cross-Coupling Reactions

Abstract

In this research, a magnetic catalyst with immobilized gold nanoparticles (Au NPs) for C─C cross-coupling reactions has been introduced. The catalyst consists of Au NPs immobilized on functionalized poly(N-isopropyl acrylamide) (PNIPAM) grafted to Fe₃O₄ magnetic nanoparticles (MNPs) modified with silica. For the catalyst synthesis, firstly, the Fe₃O₄ MNP core is prepared, modified with silica, coated with PNIPAM, and subsequently functionalized with amino functional group and EDTA. Finally, it is decorated with Au NPs to create the desired catalyst (Fe₃O₄/Si/modified PNIPAM-Au). TEM images of the catalyst confirmed the presence of spherical gold NPs with an approximate size of 13 nm on the catalyst matrix. Also, XPS analysis well proves the presence of zero metallic gold. The catalytic performance of the Au catalyst was evaluated through the C─C coupling transformations, for example, Suzuki–Miyaura, Mizoroki–Heck, and Sonogashira–Hagihara reactions. The results demonstrated significant catalytic activity of the as-synthesized Au catalyst. Using a magnet, the catalyst could be isolated from the reaction mixture and employed again in eight consecutive coupling reactions. During these reactions, some reduction in catalytic efficiency and gold leaching is observed. Overall, this catalyst shows excellent potential for efficient catalytic reactions, offering the advantages of easy separation, recyclability, and high catalytic activity.