“Excess” electrons in LuGe

Abstract

The monogermanide LuGe is obtained via high‐pressure high‐temperature synthesis (5–15 GPa, 1023–1423 K). The crystal structure is solved from single‐crystal X‐ray diffraction data (structure type FeB, space group Pnma, a=7.660(2) Å, b=3.875(1) Å, and c=5.715(2) Å, RF=0.036 for 206 symmetry independent reflections). The analysis of chemical bonding applying quantum‐chemical techniques in position space was performed. It revealed—beside the expected 2c‐Ge‐Ge bonds in the germanium polyanion—rather unexpected four‐atomic bonds between lutetium atoms indicating the formation of a polycation by the excess electrons in the system Lu3+(2b)Ge2−×1 e−. Despite the reduced VEC of 3.5, lutetium monogermanide is following the extended 8‐N rule with the trend to form lutetium‐lutetium bonds utilizing the electrons left after satisfying the bonding needs in the anionic Ge‐Ge zigzag chain.

Polycation–Polyanion Architecture of the Intermetallic Compound Mg3−xGa1+xIr

“…Using this technique and under ELSA deficiency conditions, it was shown that the formation of polyanions can be observed in Zintl phases (e.g., [3][4][5]) and in compounds with lower ELSA and multi-atomic bonding (e.g., [6]). Moreover, the "excess" electrons not consumed in the anionic substructure can be used for the formation of polycations, such as in LuGe with Zintl-like electron counting [7] or in Sr 3 Li 5 Ga 5 , representing a polycation requiring less electrons for its stabilization compared with a Zintl count [8]. While the polyanionic entities in these materials are either infinite (chain-like 1 ∞ [Ge]) or island-like (bell-like [Ga 5 ]), the observed size of the polycations is limited to either four-atom tetrahedral [Lu 4 ] or six-atom octahedral [Sr 6 ] entities.…”

Flux Growth, Crystal Structure, and Chemical Bonding of Yb2PdGe3, an AlB2Superstructure within the Rare-Earth Series

“…The described ELI-D topology composed of two lone pairs and two bonds per germanium is quite characteristic for two-bonded (2 b ) species and has been recently reported for both binary and ternary germanides within Ge zigzag chains (e.g., RE 2 M Ge 6 , CaGe, 58 and LuGe 71 ). Nonetheless, interesting differences may be detected when focusing on the average electronic populations.…”

“…This is in contrast with the expected overpopulation of lone pairs, along with a consequent bonds underpopulation, with respect to the ideal 2.00 electrons (e – ). 58 , 71 , 72 A comparative analysis with related intermetallic germanides is helpful; RE 2 M Ge 6 ( M = another metal) compounds are particularly suitable for this purpose due to similar Ge coordination environments (see Figure S7 ). In Y 2 PdGe 6 , 58 the population of 1.68 e – , found in the bonding basin associated to Ge–Ge contacts at 2.45 Å, is significantly lower than the 2.40 e – for the same basin in the title phase.…”

Bell–like [Ga5] clusters in Sr3Li5Ga5: synthesis, crystal structure and bonding analysis.

“…This would also explain the formation of the polycation [Sr 6 ] (1.22 e À per 6atomic bond, upper region of Figure 4, middle right) using the 'excess' electrons (cf. the polycation [Lu 4 ] in LuGe [30] ). Whilst in case of LuGa the'excess' electrons are recognizable already on the conceptual level, in Sr 3 Li 5 Ga 5 the leftover electrons can be understood based on the consideration of the real bonding situation.…”