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. (C) 2010 Elsevier Inc. All rights reserved.