[Au 9 Ag 6 (CCR) 10 (DPPM) 2 Cl 2 ](PPh 4 ): a four-electron cluster with a bi-decahedral twisted metal core.

The assembly of cluster units in a distinct manner can give rise to nanoclusters exhibiting unique geometrical structures and properties. Herein, we present a one-pot synthesis and structural characterization of a AuAg alloy cluster, [Au 9 Ag 6 (CCR) 10 (DPPM) 2 Cl 2 ](PPh 4 ), denoted as Au9Ag6 (where HCCR is 3,5-bis(trifluoromethyl)phenylacetylene, and DPPM is bis(diphenylphosphino)methane). Single-crystal X-ray diffraction data analysis reveals that Au9Ag6 features a distinctive Au 7 Ag 6 bi-decahedral core, formed by a twisted assembly of two Au 4 Ag 3 decahedra sharing one vertex. The Au 4 Ag 3 building blocks are bridged by two gold atoms on opposite sides of the bi-decahedral core. The Au9Ag6 cluster is monoanionic and it is stabilized by two chloride, two DPPM and ten alkynyl ligands. This cluster represents the first instance of a cluster of clusters built upon decahedral units.