Heterothiometallic clusters as robust and efficient copper(I) catalysts for azide–alkyne [3 + 2] cycloadditions

We investigated heterothiometallic W(Mo)/S/Cu clusters [NH 4 ] 2 [MS 4 Cu n X n ] (M = W, Mo; X = Br, I; n = 2, 4, 6) as novel copper(I) catalysts for Huisgen 1,3-dipolar cycloadditions. The experiments indicate that the thiometallic ligands can stabilize copper(I) ions and improve their solubility. Interestingly, these cluster compounds have very different catalytic performances in copper(I)-catalyzed azide–alkyne cycloadditions (CuAACs), which may correlate to their different redox potentials. Cluster [NH 4 ] 2 [MS 4 Cu 4 I 4 ] was found to be a very robust and efficient catalyst of CuAACs, and was utilized to synthesize a variety of 1,4-disubstituted 1,2,3-triazoles in excellent yields at room temperature under polar solvent or solvent-free conditions.