[Co@Ge10]3-: an intermetalloid cluster with archimedean pentagonal prismatic structure

Area of Science:

• Inorganic Chemistry
• Materials Science
• Computational Chemistry

Background:

• Zintl ions are polyatomic anions typically featuring main group elements.
• Metal-encapsulated Zintl clusters are rare, with limited understanding of their electronic structure and bonding.
• Pentaprismane structures are uncommon in inorganic chemistry, especially in ligand-free clusters.

Purpose of the Study:

• To synthesize and characterize the novel inorganic pentaprismane anion [Co@Ge(10)](3-).
• To investigate the unusual structure and chemical bonding within this ligand-free Zintl ion cluster.
• To explore the electronic properties and symmetry of the [Co@Ge(10)](3-) cluster.

Main Methods:

• Reaction of K(4)Ge(9) with [Co(C(8)H(12))(C(8)H(13))] in ethylenediamine.
• X-ray crystallography for structural determination.
• Computational chemistry methods (e.g., DFT) for analyzing bonding and electronic structure.

Main Results:

• Successful synthesis of the [Co@Ge(10)](3-) anion, featuring a pentaprismane cage structure.
• The cluster exhibits virtual D(5h) symmetry, a rare symmetry point group for inorganic clusters.
• Analysis revealed delocalized chemical bonding within the cluster, deviating from simple localized models.
• The [Co@Ge(10)](3-) cluster is a unique example of a ligand-free cluster that is not a deltahedron.

Conclusions:

• The [Co@Ge(10)](3-) anion represents a novel class of inorganic clusters with unique structural and bonding characteristics.
• The study provides insights into the chemical bonding of ligand-free, non-deltahedral Zintl ion clusters.
• This discovery expands the scope of known inorganic cluster architectures and bonding paradigms.