Cis-Thiolate Bridged Heterobimetallic Complexes as Efficient Catalysts for Glycosyl Triazole Synthesis

Abstract

Ni(II) and Zn(II) complexes with an N,N,S tridentate ligand were synthesized and structurally characterized, revealing distorted octahedral geometries with cis-arranged thiolate sulfur atoms. Subsequent reactions with Cu(PPh3)2NO2 and Ag(PPh3)2NO₃ afforded heterobimetallic complexes in which the thiolates bridge between M(II) (Ni/Zn) and M(I) (Cu/Ag) centers, as confirmed by single-crystal X-ray diffraction. These complexes were evaluated as catalysts for azide-alkyne cycloaddition (AAC) reactions. Among them, the Ni-Cu complex exhibited exceptional catalytic efficiency, promoting the synthesis of glycosyl and aryl triazoles in up to 95% yield within 10 minutes at room temperature under optimized conditions. The catalyst retained activity over multiple cycles and enabled access to diverse triazole libraries, including sialylated conjugates and sugar-fused heterocycles. These results highlight cis-thiolate-bridged heterobimetallic complexes as robust and versatile catalysts for rapid and high-yielding AAC “click” chemistry with applications in glycoconjugate synthesis.