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 Li3 Al4 (-) 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(η(4) -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(η(4) -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.

A new complex comprising [Co@Ge12]3– cluster core was synthesized through the reaction of CoMe(PMe3)4 and K4Ge9 in ethylenediamine solution. The pseudo‐D5d geometry of this cluster can be viewed as structurally derived from an icosahedral cage via Jahn‐Teller effect, leading to notable bonding differences from Ih‐[M@E12]q− clusters (E = Sn, Pb with q = 2, 3). The [Co@Ge12]3– cluster represents a structural conundrum. On the basis of the geometric considerations it could be viewed as a sandwich complex. However, chemical bonding analysis revealed that there is a direct covalent multicenter bonding between the two pentagons, thus indicating that the structure should be viewed as an elongated icosahedron. Further theoretical calculations on [M@Ge12]3− (M = Rh, Ir, Mt) indicate that similar compounds of larger‐size metal atoms can drive the complete transformation of [M@Ge12]3− clusters from icosahedron structure to a sandwich one.

We report the successful isolation and structural elucidation of two bimetallic doped [Co @Ge ] clusters (α and β form), which were synthesized through the reaction of [{(ArN) CtBu}Co(η -toluene)] (Ar=2,6-diisopropylphenyl) and K Ge in ethylenediamine (en) solution and co-crystallized together in [K(2,2,2-crypt)] [Co @Ge ]⋅en. The α-[Co @Ge ] isomer prefers a distinct D 3-connected architecture, whereas the deltahedral isomeric β-[Co @Ge ] isomer adopts a quasi-C geometry and can be seen as coupling of two distorted arachno-[Co@Ge ] units. Chemical bonding analyses indicate that the skeleton of the α isomer is mainly composed of localized bonds, whereas only multicenter bonding interactions govern the geometry of the β isomer, which was further found to exhibit a fluxional behavior. The coexistence of both isomers within one unit cell links the 3-connected clusters with their deltahedral congeners, thus highlighting the structural and electronic flexibility of such discreet cluster systems.