In this work, we report the synthesis and characterization of two novel Ru-containing Zintl clusters: [Sn₁₉{Ru(COD)(en)}₂]⁴⁻ and [Sn₂₀{Ru(COD)}₂]⁶⁻. The synthesized compounds not only expand the family of Ru-Sn cluster systems but also shed light on the structure of heterometallic complexes in a previously unknown range of tin atoms. The single-crystal X-ray diffraction (XRD) analysis reveals the dimeric nature of the clusters. Two different assembly patterns of the formal [Sn(η³-Sn₉)] monomer were observed: the dimerization through the vertex fusion process and the direct dimerization through the formation of 2c–2e Sn–Sn σ-bond. For both clusters, the density functional theory calculations reveal the locally σ-aromatic nature of the [Sn(η³-Sn₉)] monomer resulting in two independent magnetic shielding cones. We believe that our findings will help the community to further explore the fascinating chemistry of polystannide clusters.

We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene.