All‐Metal Antiaromaticity in Sb₄‐Type Lanthanocene Anions

Abstract

Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4n π electrons. This concept was extended to all‐metal molecules after the observation of Li3Al4− in the gas phase. However, the solid‐phase counterparts have not been documented to date. Herein, we describe a series of all‐metal antiaromatic anions, [Ln(η4‐Sb4)3]3−(Ln=La, Y, Ho, Er, Lu), which were isolated as the K([2.2.2]crypt) salts and identified by single‐crystal X‐ray diffraction. Based on the results obtained from the chemical bonding analysis, multicenter indices, and the electron‐counting rule, we conclude that the core [Ln(η4‐Sb4)3]3− fragment of the crystal has three locally π‐antiaromatic Sb4 fragments. This complex represents the first locally π‐antiaromatic all‐metal system in the solid state, which is stabilized by interactions of the three π‐antiaromatic units with the central metal atom.

Contrasting Bonding Extremes in Two [Ge6]n−Complexes: A Wadian Polyhedron (n= 2) versus a Hydrocarbon-like 2c–2e Polygermanide (n= 12)

“…41 (n = 4, 5) ions. 42 Recently, a series of mixed-group (14 and 15) Zintl anions that incorporate early transition-metal, 43,44 lanthanoid, 45 or actinoid 46 cations have been reported by Dehnen's and Sun's groups. The multivertex cluster ion [M@ Ge 8 As 4/6 ] 3− (M = V, Nb) 43 as well as [Ta@Ge 6 As 4 ] 3− , [Ta@ Ge 8 As 4 ] 3− , and [Ta@Ge 8 As 6 ] 3− 44 emphasized the uniqueness of the early transition metal incorporation into this field of Zintl cluster research and differentiated this chemistry from the late transition metal analogues.…”

Aromaticity and Antiaromaticity in Zintl Clusters

“…[19] Along this line, Sun and co-workerss ynthesized as eries of isostructurala ll-metala nions[ Ln(h 4 -Sb 4 ) 3 ] 3À (Ln = La, Y, Ho, Er,L u; Figure 6). [38] Specifically,A dNDP analysis of the [La(h 4 -Sb 4 ) 3 ] 3À clusterr evealed twelves -type lone pairs on twelve Sb atoms, twelve classical2c-2 eS b ÀSb s bonds (4 on each Sb 4 unit), three 3c-2e s bonds responsible for the interaction between the three separate cyclo-Sb 4 units in the equatorial plane, as well as for the bonding of La with the equatorial Sb atoms, and six 5c-2 e p bonds on the three LnSb 4 units (Figure 7). The two 5c-2 e p bonds on each Sb 4 units are analogous to the two 4c-2 e pbonds in the distorted rectangular structure of an eutralS b 4 cluster,r endering the compound p-antiaromatic according to Breslow's 4n rule.…”