Superatomic Aromaticity in Cyclic Superatomic Molecules: Ligand-Protected Penta-Icosahedral [M@Au₁₁]₅ (M = Au, Pt) Clusters

Abstract

Pure or doped gold icosahedra, which can be generally viewed as superatoms, are promising candidates for cluster-assembled structures. As the first largescale ring-like gold cluster, the report of [Au 60 Se 2 (Ph 3 P) 10 (SeR) 15 ] + has arisen much interest, where its Au 60 core is composed of five vertex-sharing gold icosahedra in a cyclic way. From electronic characters, this Au 60 core is a 40e cyclic penta-superatom network formed by five 8e closed-shell superatoms (S 2 P 6 ). When more valence electrons are introduced into the penta-superatom network by atomic doping, global delocalized bonds are induced in its bonding framework. In the 42e Au 60 core of the [Au 60 Se 2 Cl 15 ] − cluster, two extra electrons occupy one delocalized π-bonding orbital formed by super D orbitals of five superatoms, resulting in superatomic π aromaticity. In the 46e [Pt@Au 11 ] 5 core of [(Pt@Au 11 ) 5 Ga 2 Cl 15 ] cluster, three delocalized super-π bonds are formed, which are organized in the similar way as the aromatic C 5 H 5 − molecule. The unveiling of superatomic aromaticity promotes our understanding of the stability of cyclic superatom assemblies and extends the family of superatomic bonding patterns.