Nickel nanoparticles supported on reduced graphene oxide sheets: a phosphine free, magnetically recoverable and cost effective catalyst for Sonogashira cross-coupling reactions

In this study, we have developed a cost effective and one-pot strategy for the synthesis of a heterogeneous catalyst consisting of a Ni nanoparticle-reduced graphene oxide composite for Sonogashira cross-coupling reactions. Several characterization tools were employed to characterize the Ni nanoparticle-reduced graphene oxide composite, which indicated that magnetic Ni nanoparticles of a size range of 1-4 nm were uniformly anchored on the reduced graphene oxide nanosheets without using any surfactant or stabilizing agent. Different types of aryl halides and phenylacetylenes were coupled under the optimized reaction conditions with excellent yields to give biphenylacetylenes. The ferromagnetic behaviour of the Ni nanoparticle-graphene composite resulted in it being easily separable from the reaction mixture and the composite was reusable, up to six times, without losing its catalytic activity. The fresh as well as the reused catalyst for the Sonogashira cross-coupling reaction was well characterized using analytical techniques which showed that the Ni nanoparticles were well dispersed on the reduced graphene oxide nanosheets without agglomeration, and the size and morphology of the catalyst remained unchanged after use in the catalytic reaction.