Conjugated Cu-Ni bimetallic complex supported on Fe 3 O 4 @SiO 2 : An efficient nanocatalyst with synergistic performance for the solvent-free Sonogashira, and C-N cross-couplings

Abstract

Synthesis of a novel Cu-Ni bimetallic system comprising magnetic nanoparticles as the core and 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (4-ABPT) as a conjugated bridge between nickel and copper species is described. With low Cu and Ni loading (0.06 mol% Ni, 0.08 mol% Cu), the resulting Fe3O4@SiO2@4-ABPT/Cu-Ni is discovered to be a highly efficient catalyst for the Sonogashira and C-N cross-coupling reactions. It is well characterized by FT-IR, XRD, EDX, FE-SEM, TEM, ICP, VSM, TGA/DTG/DTA, and XPS techniques. Fe3O4@SiO2@4-ABPT/Cu-Ni as a nanocatalyst in the Sonogashira and C-N cross-coupling reactions is compatible with a wide range of amines and aryl halides and gives desired coupling products in high to excellent yields under palladium- and solvent-free conditions. The XPS results show that the 4-ABPT as a ligand can adjust electron transfer between Ni and Cu in Fe3O4@SiO2@4-ABPT/Cu-Ni, which promotes the formation and stabilization of Cu+ and Ni3+ species. Electronic interactions and the synergistic effect between these metals increase the selectivity and activity of Fe3O4@SiO2@4-ABPT/Cu-Ni as a catalyst in the Sonogashira and C-N cross-coupling reactions in comparison with its monometallic counterparts. Additionally, the magnetic properties of the Fe3O4@SiO2@4-ABPT/Cu-Ni make it easy to separate from the reaction mixture, and it can be reused several times without a significant loss in its catalytic activity or performance.