Synthesis of efficient and reusable palladium catalyst supported on pH-responsive colloid and its application to Suzuki and Heck reactions in water

An efficient and reusable pH-responsive colloid supported palladium catalyst was synthesized by loading 3-nm Pd nanoparticles into the pH-responsive colloid of core–shell microspheres of poly[styrene-co-2-(acetoacetoxy)ethyl methacrylate-co-methyl acrylic acid] (PS-co-PAEMA-co-PMAA). The colloidal scaffold of the core–shell microspheres, which contained a pH-responsive shell of PMAA segment and a coordinative core of PAEMA and PS segments, was synthesized by one-stage soap-free emulsion polymerization in water. The pH-responsive colloid supported palladium catalyst was dispersed in basic aqueous medium like a homogeneous catalyst, and also could be simply separated and recovered like a heterogeneous one just by adjusting pH of the aqueous medium. The pH-responsive colloid-supported palladium catalyst proved to be efficient and reusable for the Suzuki and Heck reactions performed in water.