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

• Heterothiometallic W(Mo)/S/Cu clusters were developed as novel copper(I) catalysts.
• W(Mo)/S/Cu clusters can stabilize copper(I) ions and improve their solubility.
• [NH4]2[WS4Cu4I4] is a robust and efficient catalyst for CuAAC reactions.
• CuAAC reactions were performed under polar solvent or solvent-free conditions.

We investigated heterothiometallic W(Mo)/S/Cu clusters [NH4]2[MS4CunXn] (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 [NH4]2[MS4Cu4I4] 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.

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