Horizontal expansion of biicosahedral M-based nanoclusters: resolving decades-long questions.

For metal nanoclusters with the "cluster of clusters" intramolecular evolution pattern, most efforts have been made towards the vertical superposition of icosahedral nanobuilding blocks (, from mono-icosahedral Au to bi-icosahedral Au and tri-icosahedral Au), while the horizontal expansion of these rod-shaped multi-icosahedral aggregates was largely neglected. We herein report the horizontal expansion of the biicosahedral M cluster framework, yielding an [AuAg(S-Adm)(DPPM)Cl] nanocluster that contains an AuAg kernel and six Au(DPPM)(S-Adm) peripheral wings. The structural determination of [AuAg(S-Adm)(DPPM)Cl] resolved a decades-long question towards rod-shaped multi-icosahedral aggregates: how to load bidentate phosphine and bulky thiol ligands onto the nanocluster framework? The structural comparison between [AuAg(S-Adm)(DPPM)Cl] and previously reported [AuAg(PPh)Cl] or [AuAg(SR)(PPh)Cl] rationalized the unique packing of Au(DPPM)(S-Adm) motif structures on the surface of the former nanocluster. Overall, this work presents the horizontal expansion of rod-shaped multi-icosahedral nanoclusters, which provides new insights into the preparation of novel icosahedron-based aggregates with both vertically and horizontally growing extensions.