[V@Ge8As4]3- and [Nb@Ge8As6]3-: encapsulation of electron-poor transition metal atoms.

[K([2.2.2]crypt)](+) salts of [V@Ge8As4](3-) and [Nb@Ge8As6](3-) were obtained by extraction of quaternary phases with en/[2.2.2]crypt. The V-Ge-As anion is the first Zintl anion incorporating a (formal) V(5+) cation, thus the smallest cation ever embedded within a main group (semi-)metal cage. It represents the second example of a novel 12-vertex cluster architecture. The bonding situation was elucidated by quantum chemistry, also allowing for a precise assignment of Ge vs. As atoms, being indistinguishable by X-ray diffraction.