[Au₁₆Ag₄₃H₁₂(SPhCl₂)₃₄]^5–: An Au–Ag Alloy Nanocluster with 12 Hydrides and Its Enlightenment on Nanocluster Structural Evolution

The structural determination of alloy hydride nanoclusters with high nuclearity remains challenging. We herein report the synthetic procedure and the structural elucidation of an Au–Ag alloy nanocluster with 12 hydride ligands―[Au₁₆­Ag₄₃­H₁₂­(SPhCl₂)₃₄]^5–. The structure of [Au₁₆­Ag₄₃­H₁₂­(SPhCl₂)₃₄]^5– comprises an Au₁₆Ag₃ kernel that is stabilized by 12 hydride ligands, 8 thiol bridges, and 6 Ag_m(SR)_n motif units. The 12 hydride ligands in Au₁₆Ag₄₃ have been confirmed by both ²H NMR and ESI-MS measurements, and their positions have been theoretically evaluated, located at the interlayer between the Au₁₆Ag₃ kernel and the Ag-SR shell. The metastable [Au₁₆­Ag₄₃­H₁₂­(SPhCl₂)₃₄]^5– can convert to [Au₁₂­Ag₃₂­(SPhCl₂)₃₀]^4– spontaneously. Structurally, the Au₁₆Ag₃ kernel of [Au₁₆­Ag₄₃­H₁₂­(SPhCl₂)₃₄]^5– could be regarded as the overlapping of two hollow Au₈Ag₃ cages via sharing an Ag₃ line, which is in contrast to the solely icosahedral Au₁₂ kernel of [Au₁₂­Ag₃₂­(SPhCl₂)₃₀]^4–. Besides, the overall construction of Au₁₆Ag₄₃ or Au₁₂Ag₃₂ follows a complementing or overlapping assembly mode, respectively. Overall, the structural anatomy of Au₁₆­Ag₄₃­H₁₂­(SPhCl₂)₃₄ sheds some new insight into the structural evolution of metal nanoclusters.