Search for: All records

Nickel-palladium bimetallic nanoparticles supported on multi-walled carbon nanotubes (Ni-Pd/MWCNTs) were prepared by dry mixing of the nickel and palladium salts using the mechanical energy of a ball-mill. These nanoparticles demonstrated remarkable catalytic activity in Sonogashira cross-coupling reactions with a wide range of functionalized aryl halides and terminal alkynes under ligand and copper free conditions using Monowave 50 heating reactor. The catalyst is air-stable and can be easily removed from the reaction mixture by centrifugation and reused several times with minimal loss of catalytic activity. Furthermore, the concentration of catalyst in Sonogashira reactions can be lowered to a minimum amount of 0.01 mol%while still providing a high conversion of the Sonogashira product with an excellent turnover number (TON) of 7200 and turnover frequency (TOF) of 21600 h. The Ni-Pd/MWCNTs nanoparticles were fully characterized by a variety of spectroscopic techniques including X-ray diffraction (XRD), transmission electron microscopy(TEM) and X-ray photoelectron spectroscopy (XPS). The remarkable reactivity of the Ni-Pd/MWCNTs catalyst toward Sonogashira cross-coupling reactions is attributed to the high degree of the dispersion of Ni-Pdnanoparticles with small particle size of 5-10 nm due to an efficient grinding method. This work provides a facile, solventless and inexpensive method for large-scale preparation of Ni-Pd/MWCNTs to accomplish often-challenging Sonogashira cross-coupling reactions. 

Sonogashira cross coupling reactions have a wide range of applications in pharmaceutical industry for drug discovery and organic synthesis of natural products and pharmaceutical compounds. These reactions typically involve the coupling of aryl halides with terminal alkynes in the presence of palladium catalyst under appropriate reaction conditions. Most Sonogashira reactions have been carried out with homogeneous Pd catalysis, in which the catalyst is soluble in the reaction mixture. There are many disadvantages to this method including the difficulty to remove the catalyst from the sample and recyclability. Heterogeneous catalysis is an alternative approach to address the issues associated with homogeneous system mainly due to facile and clean removal of the catalyst and minimum metal residual contamination. Herein, we report the preparation of nickel-palladium nanoparticles supported on multi-walled carbon nanotubes (Ni-Pd/MWCNTs) as an effective heterogeneous catalyst for Sonogashira coupling reactions. The catalyst was prepared by mixing the appropriate ratio of nickel-palladium salts with multi-walled carbon nanotubes using a mechanical power of a ball mill. The nanoparticles prepared by this method were successfully used to catalyze Sonogashira coupling reactions of various substituted aryl halides and terminal alkynes using an equal amount of water and ethanol as an environmentally benign solvent system. This project provides a facile and effective method for largescale preparation of Ni-Pd/MWCNTs to catalyze Sonogashira cross-coupling reactions. The recyclability of the catalyst makes this an affordable and clean option for pharmaceutical and industrial applications.