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

Pure or doped gold icosahedra, which can be generally viewed as superatoms, are promising candidates for cluster-assembled structures. As the first large-scale ring-like gold cluster, the report of [Au₆₀Se₂(Ph₃P)₁₀(SeR)₁₅]⁺ has arisen much interest, where its Au₆₀ core is composed of five vertex-sharing gold icosahedra in a cyclic way. From electronic characters, this Au₆₀ core is a 40e cyclic penta-superatom network formed by five 8e closed-shell superatoms (S²P⁶). 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 Au₆₀ core of the [Au₆₀Se₂Cl₁₅]^- 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@Au₁₁]₅ core of [(Pt@Au₁₁)₅Ga₂Cl₁₅] cluster, three delocalized super-π bonds are formed, which are organized in the similar way as the aromatic C₅H₅^- molecule. The unveiling of superatomic aromaticity promotes our understanding of the stability of cyclic superatom assemblies and extends the family of superatomic bonding patterns.