Zinc is usually found in its stable +II oxidation state. Low-valent zinc compounds and clusters are rare, but can have interesting properties and reactivities. Metals such as zinc do not form metal–metal bonds and low-valent-metalloid clusters easily.

Florian Weigend, University of Marburg, Germany, and Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany, Stefanie Dehnen, University of Marburg, and colleagues have synthesized the heterometallic cluster anion [K₂Zn₂₀Bi₁₆]^6–, which contains a rare metalloid Zn₁₂ unit at its core. The team reacted K₅Ga₂Bi₄ with ZnPh₂ in ethane-1,2-diamine in the presence of [2.2.2]-cryptand at room temperature and obtained [K(crypt-222)]₆[K₂Zn₂₀Bi₁₆] as a black, crystalline product.

The structure of the cluster anion was studied using X-ray crystallography. It contains a cluster of twelve zinc atoms in its center, surrounded by a cycle consisting of eight Zn atoms and 16 Bi atoms. Quantum-chemical calculations show that the Zn₁₂ cluster has a metalloid character, with four-center bonding connecting the Zn atoms. According to the researchers, the cluster could potentially be useful in catalysis.

• Stabilizing a metalloid {Zn₁₂} unit within a polymetallide environment in [K₂Zn₂₀Bi₁₆]⁶⁻,
  Armin R. Eulenstein, Yannick J. Franzke, Patrick Bügel, Werner Massa, Florian Weigend, Stefanie Dehnen,
  Nat. Commun. 2020.
  https://doi.org/10.1038/s41467-020-18799-6