Immobilized Cu complex on modified Fe3O4 nanoparticles as a magnetically separable catalyst for the oxidative homocoupling of terminal alkynes

Fe3O4 nanoparticles were prepared by the co-precipitation method, and silica was then coated on the magnetic nanoparticles followed by modification with (3-aminopropyl)trimethoxysilane (APTMS) and complexation with CuI, Cu(bpy)2I and Cu(en)2I and designated as Fe3O4@SiO2@APTMS@Cu Complex. The prepared catalysts were characterized by FTIR, XRD, SEM, and VSCM techniques. It was found that Fe3O4@APTMS@Cu(en)2 successfully mediates the oxidative homocoupling of phenylacetylene, 4-tert-butylphenylacetylene, 1-ethynyl-4-fluorobenzene and pent-1-yn-3-ol with 67–100 % conversion and 95–100 % selectivity. The prepared Fe3O4@APTMS@Cu(en)2 nanoparticles were magnetically recovered and recycled without significant decrease in activity.