Catalysts of Suzuki Cross-Coupling Based on Functionalized Hyper-cross-linked Polystyrene: Influence of Precursor Nature

Abstract

This paper describes synthesis of Pd-containing catalysts of Suzuki cross-coupling based on amino-functionalized hyper-cross-linked polystyrene at variation of Pd precursor nature (PdCl2, PdCl2(CH3CN)2, or PdCl2(PhCN)2). The investigation of the influence of palladium oxidation state (Pd(II) or Pd(0)) and form (Pdn clusters or Pd nanoparticles) on the rate of Suzuki cross-coupling of 4-bromoanisole and phenylboronic acid is discussed. Developed catalysts are shown to allow achieving conversion of 4-bromoanisole higher than 98% under mild reaction conditions. Independently of the precursor nature, Pd(II) is mainly responsible for observed catalytic activity. However, preliminary reduction of catalysts with H2 results in formation of a large number of Pdn clusters, the contribution of which in the Suzuki reaction becomes predominant.