Endohedral [Au@In₁₀]^9- Cluster: Synthesis and Characterization of Na_3+xA_6-xIn₁₀Au (x = 0, 0.25; A = Rb, Cs)

The synthesis and characterization of two new compounds Na₃Rb₆In₁₀Au and Na_3.25Cs_5.75In₁₀Au are reported, which contain [Au@In₁₀]^9- clusters as anionic entities. Single-crystal X-ray structure analysis shows that the alkali metal composition is the key factor for structure formation, while the anionic entity remains unchanged. The chemical composition was confirmed by SEM/EDS measurements, and the given compositions of both compounds are fixed according to the line compounds. Quantum chemical calculations for the compound Na₃Rb₆In₁₀Au were performed and show a band gap at the Fermi level, classifying the materials as salt-like, including endohedral [Au@In₁₀]^9- Zintl-type clusters. Dissolution experiments in liquid ammonia were carried out, revealing In₂Au as the reaction product.