Recyclable hollow Pd-Fe nanospheric catalyst for Sonogashira-, Heck-, and Ullmann-type coupling reactions of aryl halide in aqueous media.

Hollow Pd-Fe nanospheres were fabricated through a vesicle-assisted chemical reduction method. With the characterization of X-ray diffraction, selected area electron diffraction, X-ray photoelectron spectroscopy, scanning electron micrography, transmission electron micrography, and N(2) physisorption experiment, the resulting Pd-Fe material was identified to be hollow spherical with mesoporous shell. During aqueous Sonogashira-, Heck-, and Ullmann-type coupling reactions of aryl halide, the as-prepared hollow Pd-Fe nanospheres exhibited much higher activity than the dense counterpart nanoparticles. The enhanced reactivity was attributed to both the hollow chamber structure and the promotional effect of Fe-dopants, which provided more Pd active sites for the reactants. Moreover, this hollow material displayed other advantages such as low-cost, recyclability and easy experimental handling.