New monodispersed palladium nanoparticles stabilized by poly-(N-vinyl-2-pyrrolidone): Preparation, structural study and catalytic properties

Mesitylene/1-hexene solvated palladium nanoparticles, obtained by metal vapour synthesis (MVS) technique, were stabilized in solution at room temperature with poly-(N-vinyl-2-pyrrolidone) (PVP) and isolated by precipitation with a diethyl ether or THF as brown powder. HRTEM and FT-IR analyses on samples with different Pd/PVP ratio (1%, 5%, 10%, 15%, 20 w/w%) showed palladium nanoparticles with mean diameters limited in the range 1.5–2.5 nm and the presence of competitive intermolecular interactions between C@O groups and palladium atoms on nanoparticle surface. The Pd–PVP systems, dissolved in EtOH solvent, showed excellent catalytic activity and selectivity in the hydrogenation of aliphatic alkynes (1-hexyne, 2-hexyne, 3-hexyne, 3-hexyne-1-ol) to the corresponding (Z)-alkenes. The catalytic activity of Pd–PVP samples, dissolved in 1-methyl-2-pyrrolidinone (NMP), has been also evaluated in the Mizoroki–Heck C–C coupling reaction of iodobenzene and bromo-arenes with butyl acrylate showing high efficiency. Moreover, the catalyst can be quantitatively recovered at the end of the reaction by precipitation with diethyl ether and reused without significant loss of catalytic activity

Nanostructured gold/conjugated polymer hybrids: Preparation, chemical structure and morphology

Conjugated micro and nanostructured Pd containing polymers, derived from a monosubstituted acetylene, namely 3-dimethylamino-l-propyne (DMPA), has been synthesized and used as matrix for the preparation of hybrid systems containing Au(0) nanoparticles, obtained by means of Metal Vapor Synthesis (MVS) technique. By this way the formation of a new heterobimetallic Au/Pd polymeric material was achieved. The novel hybrid was characterized by means of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and high resolution transmission microscopy (HRTEM) showing the Au/polymer interaction and the particle dispersion in the nanostructured polymer matrix. The morphology of the pristine polymer shows dendritic structures or compact enamels and upon formation of the hybrid a high surface extension was observed. HRTEM measurements showed in the Au/Pd-PDMPA hybrid system an almost homogeneously distributed population of gold particles with a main size value of 3.4 +/- 1.4 nm. (c) 2006 Elsevier B.V. All rights reserved

Palladium nanoparticles supported on polyvinylpyridine: Catalyticactivity in Heck-type reactions and XPS structural studies

Palladium nanoparticles, obtained by metal vapour synthesis (MVS), weredeposited on cross-linked polyvinylpyridine. The Pd/PVPy system showedhigh catalytic activity in the Heck C-C coupling reaction of iodo- andbromo-arenes (iodobenzene, bromobenzene, p-nitrobromobenzene,p-bromoacetophenone, p-(methoxy)bromobenzene) with alkyl acrylates(methyl acrylate, n-butyl acrylate, ethylhexyltrans-3-(4-methoxyphenyl)acrylate) at 100 degrees C-175 degrees Cworking under nitrogen atmosphere as well as in air. The catalyst isstable and the leaching of metal in solution is very low. When reused,the recovered Pd/PVPy maintains the catalytic activity of the pristinematerial. XPS structural studies performed on the starting catalyst aswell as on the recovered one indicate the presence of a interactionbetween the basic nitrogen of the pyridine present in the polymer andthe metal. (C) 2009 Elsevier Inc. All rights reserved

Preparation of nanostructured organometallic polymer/palladium hybrids by metal vapour synthesis: structure and morphology

Pd(0) nanoclusters were dispersed by using the metal vapour synthesis technique in organometallic polymers of chemical structure [-M(PBu3)(2)-C&3bond; C-C6H4-C6H4-C&3bond; C-](n) (M = Pd, Pt), namely Pd-DEBP and Pt-DEBP. The hybrids were characterized by means of solid state C-13 and 31 P nuclear magnetic resonance, which highlighted the chain organization and the plasticizing effect of the nanoparticles on the polymers. Scanning electron microscopy images of the pristine organometallic polymers, and of their hybrids containing Pd(0), exhibited a growth of nanosized fibrils on glass substrates. High resolution transmission electron microscopy measurements showed a narrow distribution of Pd(0) nanoparticles which have dimensions in the range 1.0-5.0 nm in the case of Pd/Pd-DEBP hybrids and 0.5-2.0 nm in the case of Pd/Pt-DEBP hybrids