Palladium nanoparticles on noncovalently functionalized graphene-based heterogeneous catalyst for the Suzuki-Miyaura and Heck-Mizoroki reactions in water

We describe here a methodology to synthesize a reusable heterogeneous catalyst based on palladium nanoparticles (Pd NPs) supported on noncovalently functionalized graphene using 1-pyrene carboxylic acid. This can be used efficiently for Suzuki-Miyaura and Heck-Mizoroki reactions in water up to five cycles, providing excellent yields with high selectivity of cross coupled products. It is also useful for more challenging substrates like electron-rich and electron-poor bromoarenes and chloroarenes which resulted in good isolated yields (alkenes and biphenyls) in pure water. Use of functionalized graphene in the catalyst preparation improved the dispersion of it in water medium and also acted as a stabilizing agent for the Pd NPs. The percentage of metal loading in the catalyst and its thermal stability were determined by inductively coupled plasma atomic emission spectroscopy and thermo gravimetric analysis respectively. The composite formation was confirmed by X-ray diffraction patterns, Fourier transform infrared spectroscopy and Raman spectroscopy. The surface elemental composition with oxidation state was determined by UV-visible and X-ray photoelectron spectroscopy. The size and morphology of the Pd NPs on the functionalized graphene sheets were directly observed by Transmission Electron Microscopy.