Gas-phase clusters are deemed to be s-aromatic when they satisfy the 4n + 2rule of aromaticity for delocalized s electrons and fulfill other requirements knownf or aromatic systems.W hile the range of nvalues was shown to be quite broad when applied to short-lived clusters found in molecularbeam experiments,s tability of all-metal cluster-like fragments isolated in condensed phase was previously shown to be mainly ascribed to two electrons (n = 0). In this work, the applicability of this concept is extended towards solid-state compounds by demonstrating au nique example of as torable compound, which was isolated as astable [K([2.2.2]crypt)] + salt, featuring a[ Au 2 Sb 16 ] 4À cluster core possessing two all-metal aromatic AuSb 4 fragments with six delocalized s electrons each (n = 1). This discovery pushes the boundaries of the original idea of KekulØ and firmly establishes the usefulness of the s-aromaticity concept as ag eneral idea for both small clusters and solid-state compounds.Although the original concept of aromaticity in chemistry was put forward by August KekulØ [1] more than 150 years ago, it currently occupies am assive niche in modern chemistry. [2] Theconcepts of p aromaticity/antiaromaticity were primarily used to explain chemical bonding in organic compounds. Today,t hese terms are well used for av ariety of molecules, including inorganic compounds.A longside,t hese concepts have also gained huge popularity as more and more chemical species are being discovered, where delocalized bonding is used to describe the structures.I n1 995, Robinson and coworkers reported [3] thes ynthesis of Na 2 [[(2,4,6-Me 3 C 6 H 2 ) 2 C 6 H 3 ]Ga] 3 with two p electrons delocalized over the three gallium atoms that make the system p-aromatic according to the Hückel rule.Recently,the first solid-state allmetal p-antiaromatic compounds [Ln(h 4 -Sb 4 ) 3 ] 3À (Ln = La, Y, Ho,E r, Lu) were synthesized and characterized. [4] The [U@Bi 12 ] 3À anion with similar geometry was reported very recently by Dehnen and co-workers. [5] Thea romaticity/ antiaromaticity concept was also extended to bare metal clusters found in the gas phase. [6] Fort he first time,t he saromaticity concept was shown to be applicable to small alkali metal and alkaline earth metal clusters. [7] Modern developments on aromaticity in various aromatic/antiaromatic chemical species composed of main-group elements and transition metals have been extensively reviewed elsewhere. [8][9][10][11] Fora ll all-metal aromatic fragments that have been synthesized in the solid state up to date,t here were only two delocalized electrons responsible for the s-aromaticity of the compounds,asexemplified by the cases of Pd 3 + ,Au 3 + ,and TiSn 2 clusters. [12][13][14] Thus far,w ea re not aware of any solidstate compounds containing two all-metal s-aromatic fragments involving six delocalized electrons each. Hence,the 6s-electron aromatic fragments found in the [Au 2 Sb 16 ] 4À cluster in this study expand the family of storable aromatic metal clusters thus solidifying ...
