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(CCC6H4CH3)(28)](SbF6)(6)(1), are reported. The metallic core of this cluster can be viewed as a concentric three-shell Russian doll comprising Pt@Ag-12@Ag-30, in which the missing icosidodecahedral Ag-30 shell and a new structural unit, M-43, have been observed. On the surface of 1, 28alkynyl groups and 4SbF(6)(-) anions were found co-protecting it. The protective role of SbF6- in nanoclusters is unprecedented. Moreover, of the 28alkynyl ligands, 12 are connected not only with the outermost Ag-30 shell, but also the inner Ag-12 shell through the twelve pentagonal faces of the outermost icosidodecahedral Ag-30 shell. Overall, by determining the crystal structure of 1, we discovered the missing icosidodecahedral Ag-30 shell and the protective effect of SbF6- anions and demonstrated a novel M-43 structural unit and the unique penetrability of pentagonal faces.