Palladium Nanoparticles Immobilized on Chemically Modified Silica Gel: Efficient Heterogeneous Catalyst for Suzuki, Stille and Sonogashira Cross-Coupling Reactions

Nanoparticulate palladium (Pd-np-2) supported on polyethylene glycol-functionalized silica gel is an excellent heterogeneous catalytic system for Suzuki, Sonogashira and Stille cross-coupling reactions that afford products in high yield. The immobilized palladium nanoparticles were readily prepared by reaction of modified silica gel (1) with potassium tetrachloropalladate(II) in the presence of an acyl metal salt of a Fischer carbene complex. The nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The catalyst (Pd-np-2) is thermally stable, insensitive to oxygen, and recyclable. The catalyst has been used for five cycles without noticeable loss of catalytic activity.