An Atomically Precise Alkynyl-Protected PtAg₄₂ Superatom Nanocluster and Its Structural Implications

The synthesis and structure determination of an alkynyl-protected Pt-doped Ag superatom nanocluster, [PtAg₄₂ (C≡CC₆ H₄ CH₃ )₂₈ ](SbF₆ )₆  (1), are reported. The metallic core of this cluster can be viewed as a concentric three-shell Russian doll comprising Pt@Ag₁₂ @Ag₃₀ , in which the missing icosidodecahedral Ag₃₀ shell and a new structural unit, M₄₃ , have been observed. On the surface of 1, 28 alkynyl groups and 4 SbF₆^- anions were found co-protecting it. The protective role of SbF₆^- in nanoclusters is unprecedented. Moreover, of the 28 alkynyl ligands, 12 are connected not only with the outermost Ag₃₀ shell, but also the inner Ag₁₂ shell through the twelve pentagonal faces of the outermost icosidodecahedral Ag₃₀ shell. Overall, by determining the crystal structure of 1, we discovered the missing icosidodecahedral Ag₃₀ shell and the protective effect of SbF₆^- anions and demonstrated a novel M₄₃ structural unit and the unique penetrability of pentagonal faces.