[Ag(Sn₉-Sn₉)]⁵⁻ and [(η⁴-Sn₉)Ag(η¹-Sn₉)]⁷⁻, as aggregates of spherical aromatic building blocks. Persistence of aromaticity upon cluster gathering

Formation of cluster-based materials requires a fundamental understanding of the resulting cluster aggregation processes. The Sn₉⁴⁻ Zintl-ion structure can be viewed as a building block featuring a spherical aromatic species, leading to a cluster gathering upon oxidative coupling and/or mediated by transition metals. Here, we evaluate the spherical aromatic properties of [Sn₉-Sn₉]⁶⁻, [Ag(Sn₉-Sn₉)]⁵⁻ and [(η⁴-Sn₉)Ag(η¹-Sn₉)]⁷⁻, as aggregates of two Sn₉ building units held together via oxidative coupling and mediated by a Ag(i) transition metal center. Our results from magnetic criteria of aromaticity show that the inherent spherical aromatic characteristics of the parent Sn₉⁴⁻ cluster are persistent in the overall aggregate where the enabled shielding cones ascribed to each Sn₉ unit are able to interplay between them, leading to an overlap of the shielding regions. Hence, the two approaches for bringing cluster units together are able to retain the inherent spherical aromatic features for each Sn₉ unit, leading to a cluster-based dimer where the parent properties remain. Thus, further cluster-based materials can be envisaged from aggregation upon oxidative coupling and/or mediated by transition metals, where the constituent building blocks retain their initial features, useful to guide the formation of more complex cluster-based aggregates.