Maria Michela Dell’Anna
Polythecnic University of Bari, Italy
Title: Catalytic activity and recyclability of polymer supported palladium or nickel nanoparticles in organic reactions in water
Biography
Biography: Maria Michela Dell’Anna
Abstract
An insoluble palladium catalyst (Pd-pol) was obtained by copolymerization of the metal containing monomer Pd(AAEMA)2 [AAEMA− = deprotonated form of 2-(acetoacetoxy)ethyl methacrylate] with ethyl methacrylate (co-monomer) and ethylene glycol dimethacrylate (cross-linker), followed by in situ reduction of Pd(II) to Pd(0), to give polymer stabilized metal nanoparticles. The good swellability in water exhibited by Pd-pol rendered it an ideal potential catalyst for reactions carried out in a green solvent, such as water, since the migration of the reagents to the active sites would not be hampered by the solid support. With the aim to develop innovative catalytic processes that enable chemical transformations to be performed under mild and sustainable conditions with high efficiency, we decided to evaluate the catalytic activity of Pd-pol for several important organic reactions using water as solvent. Pd-pol resulted highly active and selective in catalyzing (figure 1): the Suzuki-Miyaura coupling between aryl bromides or activated aryl chlorides and phenylboronic acid; the oxidation of benzyl alcohols to aldehydes; the reduction of quinolines and nitroarenes by H2 or NaBH4. Pd-pol was recyclable for several consecutive runs (for example, at least 12 times in the nitroarene reduction). TEM analyses carried out on the catalyst showed that the active species were supported palladium nanoparticles having a mean size of 4 nm, which did not aggregate with the recycles. Recently, due to their low cost, Ni catalysts have been employed in several organic reactions (mainly hydrogenations). In this context, we synthetized a Ni catalyst similar to Pd-pol, starting from Ni(AAEMA)2 and we employed it as active and recyclable, insoluble catalyst for the reduction of different nitroarenes to give the corresponding anilines, under sustainable conditions. All these results proved that the proposed Pd or Ni based composite materials are excellent hybrid structures as efficient and reusable catalysts.