Superatomic Three-Center Bond in a Tri-Icosahedral Au 36 Ag 2 (SR) 18 Cluster: Analogue of 3c-2e Bond in Molecules.

Probing the nature of electronic stability for ligand-protected gold clusters is important in gold chemistry. A thermally stable Au 36 Ag 2 (SR) 18 nanocluster was synthesized recently. It has a D 3 h tri-icosahedral [Au 30 Ag 2 ] 12+ core with 20 valence electrons, which does not follow the magic number of gold superatoms. Herein, we propose a superatomic three-center bond to unveil its electronic stability. The [Au 30 Ag 2 ] 12+ core is viewed as a union of three face-fused superatoms, and chemical bonding analysis suggests a three-superatom-center two-electron (3sc-2e) bond for the octet rule of each superatom, which mimics the bonding framework of the D 3 h O 3 2- molecule. Moreover, a liganded tri-icosahedral [Au 27 Pt 3 Ag 2 ] 11+ core with 18 valence electrons is predicted, and three 2sc-2e bonds are formed between each of two superatoms to satisfy the octet rule (analogue of D 3 h O 3 ), indicating the flexibility of superatomic bonding. Such a superatomic three-center bond extends the community of superatomic bonding and gives a new perspective for superatom assembling.