Binary alkali metal compounds with the zintl anions [Ge₉]⁴⁻ and [Sn₉]⁴⁻

Abstract

Abstract The binary germanides M 12 Ge 17 and M 4 Ge 9 (M  Na, K, Rb, Cs) and the stannides M 12 Sn 17 and M 4 Sn 9 (M  K, Rb, Cs) were identified by a combination of direct synthesis, thermogravimetric analysis, vibrational spectroscopy, X‐ray powder data and single crystal structure analysis. The M 12 E 17 phases contain the cluster anions [E 9 ] 4− and [E 4 ] 4− in the ratio 1:2, forming a hierarchical structure with the cluster anions at the atomic positions of the hexagonal Laves phase MgZn 2 . Like the M 4 E 4 phases, the M 4 Ge 9 compounds are hierarchical derivatives of the cubic Cr 3 Si structure but with [Ge 9 ] 4− anions. The thermogravimetric analyses give strong evidence for the existence of at least one more phase with [E 9 ] 4− and [E 4 ] 4− clusters and of the clathrate phases M 6 E 136 in addition to the well‐known M 8 E 44 □ 2 chlathrates.