(Fe3O4@SiO2/GO–NH2–CoII NPs): A Novel and Efficient Nanomagnetic Heterogeneous Cobalt Catalysis in the Sonogashira and Heck–Mizoroki Coupling Reactions

A Co(II) complex (Fe 3 O 4 @SiO 2 /GO–NH 2 –Co II NPs) immobilized on a magnetic graphene oxide nanocomposite was efficiently synthesized and characterized by a variety of techniques, including XRD, FT-IR, SEM/EDX, TEM, VSM, TGA and AAS. Then, the catalytic activity of this new Fe 3 O 4 @SiO 2 /GO–NH 2 –Co II complex was examined in the Sonogashira cross-coupling reaction and Heck–Mizoroki coupling reaction. The Pd/Cu-free Sonogashira cross-coupling reaction of different aryl halides and terminal alkynes was achieved in the presence of Fe 3 O 4 @SiO 2 /GO–NH 2 –Co II NPs under reflux in ethanol, and the corresponding products were obtained successfully in good to high yields. In addition, Heck–Mizoroki cross-coupling reactions of various aryl halides by using Fe 3 O 4 @SiO 2 /GO–NH 2 –Co II and Et 3 N under reflux in DMSO afforded the desired products in good to high yields. This heterogeneous catalyst can be recovered using a magnet and reused several times without obvious loss of catalytic activity.