Easy-separable magnetic nanoparticle-supported Pd catalysts: Kinetics, stability and catalyst re-use

A series of novel palladium-based catalysts supported on magnetic nanoparticles with diameters of 7–17 nm have been prepared and evaluated in C–C coupling, hydrogenation and amination reactions. One type of catalyst used palladium complexes containing phosphine and/or acetate ligands for applications in Suzuki and Heck reactions. The second type consisted of Pd(0)-functionalised magnetic cores for use in hydrogenation and C–C coupling. Each type was effective for a range of reactions and was easily recoverable from the reaction mixture due to the superparamagnetic behaviour of the support. Detailed rate studies, found to correspond to pseudo-first-order kinetics, were conducted to assist in determining the mechanism of the reactions and showed that, during Heck reactions, Pd leaching is critically dependent on the presence of the aryl halide. The catalysts were found to retain their activity for several cycles although the rate of reaction was markedly reduced on re-use.