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

Abstract

Pd-PVP colloid (stabilized with polyvinylpyrrolidone) with a diameter of 19.8 nm in [Bu 4N]Br medium catalyzes Heck coupling of bromobenzene with butyl acrylate and methoxycarbonylation of iodobenzene reactions. Oxidative addition of PhI 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 = I, Br) and [Bu 4N]X (X = Cl, Br, I). The biggest shift of the center of nanoparticle size distribution, from 19.8 nm to 7.6 nm, was found when Pd-PVP reacted with PhI and [Bu 4N]Br. The formation of [Bu 4N] 2[Pd(Ph)Br 3]- and [Bu 4N] 2[PdBr 4]-type complexes in that system was evidenced by XPS and UV–vis spectra.