Structures of Copper Complexes of the Hybrid [SNS] Ligand of Bis(2-(benzylthio)ethyl)amine and Facile Catalytic Formation of 1-Benzyl-4-phenyl-1H-1,2,3-triazole through Click Reaction

A hybrid ligand, bis(2-(benzylthio)ethyl)amine (SNS), with an amine and two thioether donors reacts with Cu(II) to give mononuclear [CuCl2(SNS)] (1), [CuBr2(SNS)] (2), [Cu(OTf)(2)(SNS)(OH2)] (3), and an one-dimensional Cu(I) coordination polymer [Cu2I2(SNS)](n) (4). All complexes have been characterized by single-crystal X-ray diffraction analysis, and 1-3 were studied by EPR analysis at room temperature. Complexes 1 and 2 are penta-coordinated with a distorted square pyramidal metal supported by a tridentate SNS ligand on the basal plane. Complex 3 shows a tetragonally distorted octahedral sphere with two trans and weakly bonding monodentate triflates. A 12-membered ring in the solid lattice is formed by intermolecular H-bonding among the coordinated triflate and aqua ligands from four neighboring molecules. Complex 4, the only Cu(I) in this series, shows a coordination polymer chain [CU4I4](n) comprising tetrahedral Cu(I) centers stitched by the SNS ligand in a unique bridge-chelate mode in the form of a helix. All four complexes are catalytically active at room temperature in a copper-catalyzed azide-alkyne cycloaddition (CuAAA) three-component click reaction of benzyl chloride, sodium azide, and phenylacetylene in an aqueous MeCN mixture to give good isolated yields of 1-benzyl-4-phenyl-1H-1,2,3-triazole, without the use of a base or reducing agent.