Ruthenium-mediated assembly and enhanced stability of heterometallic polystannides [Ru₂Sn₁₉]⁴⁻ and [Ru₂Sn₂₀]⁶⁻

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.