Pd-PVP colloid as catalyst for Heck and carbonylation reactions:: TEM and XPS studies

Pd-PVP colloid (stabilized with polyvinylpyrrolidone) with a diameter of 19.8 nm in [Bu4N]Br medium catalyzes Heck coupling of bromobenzene with butyl acrylate and methoxycarbonylation of iodobenzene reactions. Oxidative addition of Phl or PhBr to Pd-PVP as the first step of a catalytic reaction was confirmed by TEM and XPS measurements. TEM studies showed significant reduction of Pd nanoparticle size after their reaction with PhX (X = 1, Br) and [Bu4N]X (X = Cl, Br, 1). The biggest shift of the center of nanoparticle size distribution, from 19.8 run to 7.6 nm, was found when Pd-PVP reacted with Phl and [Bu4N]Br. The formation of [Bu4N](2)[Pd(Ph)Br-3]- and [Bu4N](2)[PdBr4]-type complexes in that system was evidenced by XPS and UV-vis spectra. (C) 2004 Elsevier Inc. All rights reserved.