A Dichalcogenide-Protected Pt@Au12@Ag8 Nanocluster

Precise control over the location of heterometal atoms in alloy nanoclusters is essential for understanding how metal distribution governs superatomic structure and properties. Herein we show that PtAg20[S2P(OPr)2]12 (PtAg20) can serve as a structurally defined precursor for constructing a PtAu12 superatom copassivated by ligands and Ag atoms through redox-mediated Au-for-Ag exchange. Treatment of PtAg20 with an excess of Au(I) affords PtAu12Ag8[S2P(OPr)2]12 (PtAu12Ag8), in which substitution of Ag by Au occurs exclusively on the PtAg20 icosahedral core. Single-crystal X-ray diffraction reveals a compact PtAu12 core encapsulated by two Ag4(dtp)6 (dtp = dithiophosphate) units. Unlike all the known silver-rich isoelectronic nanoclusters featuring a centered icosahedron protected by a Ag8(dtp)12 outer shell that adopt C3-type or C3-derived shell arrangements, PtAu12Ag8 displays a C2 geometry. Spectroscopic and mass-spectrometric measurements support the formation of the Au-rich cluster, while DFT calculations identify the [PtAu12]4+ core as an eight-electron superatom with a closed-shell 1S21P61D0 electronic configuration. This work demonstrates that selective replacement of the icosahedral cage can generate not only a new trimetallic superatomic core but also an unusual reconstruction of the surrounding Ag-ligand passivating layer.