Yet Another Case of Lithium Metal Atoms and Germanium Atoms Sharing Chemistry in the Solid State: Synthesis and Structural Characterization of Ba₂LiGe₃.

Several Ba−Li−Ge ternary phases are known and structurally characterized, including the title compound Ba2LiGe3. Its structure is reported to contain [Ge6]10− anions that exhibit delocalized bonding with a Hückel‐like aromatic character. The Ge atoms are in the same plane with the Li atoms, and if both types of atoms are considered as covalently bonded, [LiGe3]4− honeycomb‐like layers will result. The latter are separated by slabs of Ba2+ cations. However, based on the systematic work detailed herein, it is necessary to re‐evaluate the phase as Ba2Li1−xGe3+x (x<0.05). Although small, the homogeneity range is clearly demonstrated in the gradual change of the unit cell for four independent samples. Subsequent characterization by single‐crystal X‐ray diffraction methods shows that the Ba2Li1−xGe3+x structure, responds to the varied number of valence electrons and the changes are most pronounced for the refined lengths of the Li−Ge and Ge−Ge bonds. Indirectly, the changes in the Ge−Li/Ge distances within layers affect the stacking too, and these changes can be correlated to the variation of the c‐cell parameter. Chemical bonding analysis based on TB‐LMTO‐ASA level calculations affirms the notion for covalent character of the Ge−Ge bonds; the Ba−Ge and Li−Ge interactions also show some degree of covalency. [ABSTRACT FROM AUTHOR]