Nanomagnetic nickel complex based on salicylamide and l-proline ligands as an efficient heterogeneous catalyst for synthesis of tetrazoles

A novel salicylamide–L-proline–nickel(II) complex, supported on magnetic iron oxide [Fe₃O₄@salicylamide–L-proline–Ni(II)], was synthesized through a three-step procedure. This included the functionalization of Fe₃O₄ with amine groups using glycine as a linker, followed by direct amidation of salicylic acid and its subsequent coordination with Ni(II) and L-proline as a co-ligand to form the nanomagnetic Ni(II) complex. The resulting catalyst was comprehensively characterized by several techniques. The catalyst exhibited outstanding catalytic performance in the homoselective synthesis of 5-substituted-1H-tetrazoles from benzonitriles. Notably, it demonstrated excellent recyclability, maintaining high efficiency over eight reaction cycles. The use of a low-cost linker, ligand, and complex catalyst, combined with easy magnetic separation, minimal leaching, and scalability, renders this approach both environmentally sustainable and economically advantageous compared to traditional Ni-based methods.