Preparation Of Magnetic Hollow Pd Catalyst And Its Application In Suzuki Cross-coupling Reactions

Noble metal Pd is a good catalyst for Suzuki cross-coupling reactions. When using the presence of homogeneous, it is difficult to be separated. When it is used as a heterogeneous catalyst, the problem is poor dispersion、loss of the active ingredient easily and difficult to separate from the reaction system. This paper is focus on hollow magnetic noble metal palladium catalyst system. On the basis of previous work, through synthesizing Pd-Fe bimetallic magnetic sphere or introducing the magnetic substance to the carrier, we can easily separate the catalyst from the reaction system with the help of external magnetic field. Therefore, on the basis of previous literature, we use different methods to develop the following two hollow magnetic nanoparticles heterogeneous palladium catalyst and conduct in-depth study of its catalytic activity and chemical stability.The [PdX4]2-(X=Cl or Br) and Fe3+ surround the outer shell of the vesicles template of tetrabutylphosphonium bromide(Bu4PBr) due to electrostatic interactions. Subsequently, Pd(II) ions and Fe(III) ions can be reduced into metallic Pd nanoparticles and Fe nanoparticles by adding BH4-, which forms hollow palladium–ferrum bimetallic magnetic sphere catalyst. The catalyst characterized by TEM, BET, XRD, XPS and VSM. The catalyst shows high activity for Suzuki coupling reaction in water which makes catalytic process become more green. The newly developed catalyst is easy to be recovered and recycled by magnetic separation from liquid phase reactions. More importantly, the catalyst revealed high efficiency and high stability under the reaction conditions and during recycling stages.Using the copolymers of acrylic acid and styrene(polystyrene spheres having abundant carboxyl group) as the template, in an aqueous solution, we immobilized Fe3O4 on the template with the electrostatic adsorption. The surface was coated with SiO2 and the template was burned off. And then modifying the surface with 3-mercaptopropyl trimethoxysilane. The last, under the action of coordination and in-situ reduction of PdCl2, the hollow magnetic mesoporous spheres(HMMS) catalyst was synthesized. The catalyst characterized by TEM, XRD, XPS and VSM. The catalyst shows high activity for the carbonylative cross-coupling reaction of aryl iodides with arylboronic acids and Suzuki coupling reaction. The newly developed catalyst is easy to be recovered and recycled by magnetic separation from liquid phase reactions. More importantly, the catalyst revealed high efficiency and high stability under the reaction conditions and during recycling stages.