Peculiar All‐Metal σ‐Aromaticity of the [Au₂Sb₁₆]⁴⁻ Anion in the Solid State

Abstract

Gas-phase clusters are deemed to be σ-aromatic when they satisfy the 4n+2 rule of aromaticity for delocalized σ electrons and fulfill other requirements known for aromatic systems. While the range of n values was shown to be quite broad when applied to short-lived clusters found in molecular-beam experiments, stability 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 a unique example of a storable compound, which was isolated as a stable [K([2.2.2]crypt)] salt, featuring a [Au Sb ] cluster core possessing two all-metal aromatic AuSb fragments with six delocalized σ electrons each (n=1). This discovery pushes the boundaries of the original idea of Kekulé and firmly establishes the usefulness of the σ-aromaticity concept as a general idea for both small clusters and solid-state compounds.

Expansion of Magnetic Aromaticity Criteria to Multilayer Structures: Magnetic Response and Spherical Aromaticity of Matryoshka‐Like Cluster [Sn@Cu12@Sn20]12−

“…In recent years, research on Zintl clusters has been encouraged by their potential to form versatile novel derivatives, such as organo‐Zintl, organometallic‐Zintl, and heterometallic species . Moreover, among all‐metal species, Zintl clusters are promising candidates to host aromaticity, which provides their remarkable stability …”

Chemical Bonding and σ-Aromaticity in Charged Molecular Alloys: [Pd2As14]4− and [Au2Sb14]4− Clusters

“…We have recently described a synthetic [Au 2 Sb 16 ] 4− compound 38 , which is highly distorted with quasi- C 2 point group symmetry, also featuring two σ sextets. In carefully designed and controlled syntheses, we anticipate the D 2 h σ-aromatic [Au 2 Sb 14 ] 4− ( 2 ) complex to be made as bulk materials in laboratory.…”

“…In the past years, we have been interested in exploring the structural, electronic, and bonding properties of gas-phase clusters 23–27 and synthetic cluster compounds 36–38 . In the present contribution, we shall report on a quantum chemical study on the structure and bonding of a “charged molecular alloy” cluster: D 2 h [Pd 2 As 14 ] 4− ( 1 ).…”

“…It is stressed that 1 and 2 are relatively large cluster systems and bonding analyses are rather challenging; the current level of understanding for 1 and 2 is largely attributed to the powerful AdNDP tool 41 for chemical bonding analyses, which was not possible even a couple of years ago. The concept of σ-aromaticity, in particular σ sextets, was discussed recently in a synthetic [Au 2 Sb 16 ] 4− compound 38 .…”

Aromaticity and Antiaromaticity in Zintl Clusters

“…However, Sun and co‐workers have recently synthesized an all‐metal cluster [Au 2 Sb 16 ] 4− (Figure ), which contains two AuSb 4 fragments with six σ‐delocalized electrons each, rendering these fragments σ‐aromatic. The [Au 2 Sb 16 ] 4− anion was crystallized in the form of [K([2.2.2]crypt)] 4 [Au 2 Sb 16 ]⋅4 en from en solution of K 3 Sb 7 , Au(PPh 3 )Ph, and [2.2.2]‐crypt . In the [Au 2 Sb 16 ] 4− cluster, each Au atom is located at the center of slightly distorted Sb 4 squares with the Au−Sb bond lengths spanning a very narrow range.…”