title: Resin-Immobilized Palladium Nanoparticle Catalysts for Organic Reactions in Aqueous Media: Morphological Aspects.
abstract: An insight into the nano- and micro-structural morphology of a polymer supported Pd catalyst employed in different catalytic reactions under green conditions is reported. The pre-catalyst was obtained by copolymerization of the metal-containing monomer Pd(AAEMA)₂ [AAEMA-=deprotonated form of 2-(acetoacetoxy) ethyl methacrylate] with ethyl methacrylate as co-monomer, and ethylene glycol dimethacrylate as cross-linker. This material was used in water for the Suzuki-Miyaura cross-coupling of aryl bromides, and for the reduction of nitroarenes and quinolines using NaBH₄ or H₂, as reductants. TEM analyses showed that in all cases the pristine Pd(II) species were reduced in situ to Pd(0), which formed metal nanoparticles (NPs, the real active species). The dependence of their average size (2-10 nm) and morphology on different parameters (temperature, reducing agent, presence of a phase transfer agent) is discussed. TEM and micro-IR analyses showed that the polymeric support retained its porosity and stability for several catalytic cycles in all reactions and Pd NPs did not aggregate after reuse. The metal nanoparticle distribution throughout the polymer matrix after several recycles provided precious information about the catalytic mechanism, which was truly heterogeneous in the hydrogenation reactions and of the so-called "release and catch" type in the Suzuki coupling.
authors.affiliation: Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica (DICATECh), Politecnico di Bari, via Orabona 4, Bari 70125, Italy. p.mastrorilli@poliba.it.
authors.forename: Piero
authors.initials: P
authors.lastname: Mastrorilli
authors.affiliation: Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica (DICATECh), Politecnico di Bari, via Orabona 4, Bari 70125, Italy. mariamichela.dellanna@poliba.it.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Dell'Anna
authors.affiliation: Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica (DICATECh), Politecnico di Bari, via Orabona 4, Bari 70125, Italy. antonio.rizzuti@poliba.it.
authors.forename: Antonino
authors.initials: A
authors.lastname: Rizzuti
authors.affiliation: Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica (DICATECh), Politecnico di Bari, via Orabona 4, Bari 70125, Italy. matilda.mali@poliba.it.
authors.forename: Matilda
authors.initials: M
authors.lastname: Mali
authors.affiliation: Centro Interdipartimentale Grandi Strumenti (C.I.G.S.), Università di Modena e Reggio Emilia, via Campi 213\A, Modena 41125, Italy. mauro.zapparoli@unimore.it.
authors.forename: Mauro
authors.initials: M
authors.lastname: Zapparoli
authors.affiliation: Dipartimento di Ingegneria "Enzo Ferrari", Università di Modena e Reggio Emilia, via Pietro Vivarelli 10, Modena 41125, Italy. cristina.leonelli@unimore.it.
authors.forename: Cristina
authors.initials: C
authors.lastname: Leonelli
mesh_terms: D001894:Borohydrides / Q000737:chemistry; D002384:Catalysis; D017743:Equipment Reuse; D006859:Hydrogen / Q000737:chemistry; D006865:Hydrogenation; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D009578:Nitrobenzenes / Q000737:chemistry; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry*; D011804:Quinolines / Q000737:chemistry*; D012117:Resins, Synthetic / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D001894:Borohydrides; D009578:Nitrobenzenes; D011109:Polymethacrylic Acids; D011804:Quinolines; D012117:Resins, Synthetic; C535266:poly(2-(acetoacetoxy)ethyl methacrylate); D014867:Water; D010165:Palladium; D006859:Hydrogen; C025364:sodium borohydride
keywords: Suzuki-Miyaura coupling; TEM; micro-IR spectroscopy; morphological analysis; nitrobenzene reduction; polymer supported Pd nanoparticles; quinoline hydrogenation; quinoline transfer hydrogenation; recyclable catalyst; water solvent