Formation of dispersed palladium-nickel bimetallic nanoparticles in microemulsions: synthesis, characterization, and their use as efficient heterogeneous recyclable catalysts for the amination reactions of aryl chlorides under mild conditions

A simple method for preparing spherical palladium-nickel bimetallic nanoparticles with a molar ratio of 1.0 (Pd-0.5-Ni-0.5 B-NPs) has been adopted using a water-in-oil microemulsion system of water/aerosol-OT/isooctane at room temperature. The morphology, size, structure, and elemental composition of these particles as the superior catalyst were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive analysis using X-rays (EDAX), and X-ray fluorescence (XRF) analyses. The effects of the reaction parameters on the Buchwald-Hartwig amination reaction yield in the presence of these NPs as catalyst have been screened and the results are evaluated by using chlorobenzene and morpholine as a model reaction. Initially, differences in the catalytic properties of some synthesized NPs have been compared. In this context, Pd-Ni B-NPs with the molar ratio of 1 : 1 (Pd/Ni = 1) showed the highest catalytic activity for this reaction. The Pd-0.5-Ni-0.5 B-NPs are stable and the leaching of catalyst in solution is very low. Therefore, they has been employed as efficient catalysts in the C-N coupling reaction. Finally, a mechanism for an amination reaction on the Pd/Ni catalyst surface was proposed.