Pd-containing Mono- and Bimetallic Nanoparticles Incorporated in Highly Porous Hypercrosslinked Polystyrene as Effective Catalysts of Suzuki Cross-coupling

Abstract

This paper describes synthesis of Pd-containing catalysts of Suzuki cross-coupling based on non-functionalized hyper-crosslinked polystyrene (HPS) at variation of Pd precursor nature (PdCl₂, PdCl₂(CH₃CN)₂ or PdCl₂(PhCN)₂). Relatively low affinity of Pd species to the chosen polymeric support was shown to be responsible for in situ formation of Pd nanoparticles and their aggregates. During the investigation of aryl halide nature, catalytic activity was shown to decrease in the following order: Br > I > Cl. Best results were obtained for the preliminarily reduced HPS-based sample synthesized while using PdCl₂ in the reaction between phenylboronic acid and 4-bromoanisole: more than 93% yield of cross-coupling product was achieved at mild reaction conditions (NaOH, 60^oC, solvent ethanol-water mixture) using 0.8 mol.% of Pd.