FACILE SYNTHESIS OF Pd NANOPARTICLES ON SILICA SUPPORTS AS RECYCLABLE CATALYSTS FOR SUZUKI-MIYAURA REACTION IN WATER: EFFECT OF DONOR LIGANDS

Silica supported palladium nanoparticles (PdNPs) were prepared by a convenient one-step method, without taking assistance from any external reductant or stabilizer. The ligands (-NMe2, -NH2 and –SH) anchored to silica gel play the dual role of reducing and stabilizing agent. The materials were characterized by techniques such as N2 adsorption-desorption, HR-TEM, ICP and XRD analyses and applied as catalysts for Suzuki-Miyaura coupling of aryl bromides in water. With the catalysts (PdNP-NMe2@SiO2 and PdNP-NH2@SiO2)coupling reactions aryl bromides were performed without using any phase transfer additive. Under similar experimental conditions, catalyst PdNP-NMe2@SiO2 shows better activity than other systems. The catalysts could be reused at least six cycles without significant loss in their activity. TEM images show no aggregation of NPs even after reusing the catalysts for six times