An All-Alkynyl Protected 74-Nuclei Silver(I)-Copper(I)-Oxo Nanocluster: Oxo-Induced Hierarchical Bimetal Aggregation and Anisotropic Surface Ligand Orientation.

The hardness of oxo ions (O2- ) means that coinage-metal (Cu, Ag, Au) clusters supported by oxo ions (O2- ) are rare. Herein, a novel μ4 -oxo supported all-alkynyl-protected silver(I)-copper(I) nanocluster [Ag74-x Cux O12 (PhC≡C)50 ] (NC-1, avg. x=37.9) is characterized. NC-1 is the highest nuclearity silver-copper heterometallic cluster and contains an unprecedented twelve interstitial μ4 -oxo ions. The oxo ions originate from the reduction of nitrate ions by NaBH4 . The oxo ions induce the hierarchical aggregation of CuI and AgI ions in the cluster, forming the unique regioselective distribution of two different metal ions. The anisotropic ligand coverage on the surface is caused by the jigsaw-puzzle-like cluster packing incorporating rare intermolecular C-H⋅⋅⋅metal agostic interactions and solvent molecules. This work not only reveals a new category of high-nuclearity coinage-metal clusters but shows the special clustering effect of oxo ions in the assembly of coinage-metal clusters.