Superparamagnetic nanoparticles-supported phosphine-free palladium catalyst for the Sonogashira coupling reaction

Superparamagnetic nanoparticles were synthesized following a microemulsion method, and functionalized with Schiff-base groups on the surface to form immobilized bidentate ligands. The functionalized nanoparticles were complexed with palladium acetate, affording the immobilized palladium complex catalyst with a palladium loading of 0.24 mmol/g. The catalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), atomic absorption spectrophotometry (AAS), and nitrogen physisorption measurements. The immobilized palladium complex was used as an efficient catalyst for the Sonogashira reaction of iodobenzene and phenylacetylene to form diphenylacetylene as the principal product without added phosphine ligands. Recovery of catalyst was facilely achieved by simple magnetic decantation. The immobilized palladium complex catalyst could be reused several times without significant degradation in catalytic activity. No contribution from homogeneous catalysis of active palladium species leaching into reaction solution was detected. (C) 2010 Elsevier B.V. All rights reserved.