Coordination preferences of the alkali cations sodium and caesium in the mixed-cationic Zintl ammoniate Cs3.2Na0.8Ge9·5.3NH3

Abstract

The involvement of two different alkali cations in the nonagermanide ammoniate Cs3.2Na0.8Ge9·5.3NH3[tricaesium sodium nonagermanide–ammonia (1/5.3)] provides insights into the coordination behaviour of ammonia towards sodium and caesium cations within one compound and represents the first mixed-cationic solvate structure of nonagermanide tetraanions. The compound crystallizes in the monoclinic space groupP21/mand, with the presence of pseudomerohedral twinning, mixed-cation sites and disordering of the nonagermanide cage anions, features a combination of crystallographic challenges which could all be resolved during the refinement.