New Lanthanum Stannide/Germanides: La3Sn4.4Ge0.6, La3Sn3.1Ge0.9 and La9Sn6.7Ge3.3 (In German)

The new complex lanthanum tetrelide La55Sn36.6Ge24.4

“…The main reflections of the powder diagrams of these samples could be indexed by La2SnGe2 (Mo2FeB2 structure type), but in addition, minor amounts of LaGe2−x (˛-GdSi2 type, [18,19]) and La3Sn3Ge2 (Th3Pd5 structure type [17]) are visible in the powder diffractogram. With the knowledge of the composition of the title compound from the X-ray single crystal structure analysis, phase pure samples of La55Sn36.6Ge24.4 (La:Sn:Ge = 1:0.66:0.44) could be prepared in several directed syntheses from melts in the vicinity of this stoichiometry.…”

“…With lanthanum as a countercation, the crystal structures of the stannides La 5 Sn 3 (W 5 Si 3 and Mn 5 Si 3 structure type), La 11 Sn 10 and l.t.-LaSn [5] exhibit isolated tin anions. Examples among the germanides are La 4 Ge 3 (Th 3 P 4 type [12]) and La 3 Sn 4.4 Ge 0.6 [17] (La 3 In 4 Ge type [23]). For the stannides, a nine-fold coordination by La cations, which form monocapped square antiprisms or tricapped trigonal prisms, is characteristic.…”

“…For example, the somewhat La-richer sample composed of 121 mg (0.87 mmol) La, 56 mg (0.47 mmol) Sn and 23 mg (0.32 mmol) Ge and prepared in the arc-melter as described above contains the title compound in pure phase. Furnace and arcmelted samples with only slightly decreased lanthanum and increased tin contents like LaSn0.77Ge0.46 or LaSnGe0.25 yielded two further new mixed Ge/Sn tetrelides La3Sn3.1Ge0.9 (Er3Ge4 structure type) and La9Sn6.7Ge3.3 (new structure type) [17].…”

“…Ca7Ge6 [24] Ca7Sn6 [33] --0.909 ---La11Sn10 (Ho11Ge10) [5] 1 AGe (CrB) ASn (CrB) ht-LaGe (FeB) [4] ht-LaSn (CrB) [5] lt-LaGe (lt-LaSi) [10] lt-LaSn [11,5] CaGe2 (EuGe2 [37,38]) BaSn2 [39] LaGe2−x (˛-GdSi2) [18,19] LaSn2 (ZrGa2) [40] 2.33 -…”

“…Both border phases, LaGe and LaSn, are dimorphic exhibiting the simple FeB (LaGe [1][2][3][4]) and CrB (LaSn [5]) structure types at higher temperatures. Despite their simple crystal structures, which exhibit planar all-trans zig-zag chains in different orientations to each other, the chemical bonding in these compounds is still puzzling and has therefore been the topic of several recent experimental and theoretical studies [4,[6][7][8][9]. The low-temperature (l.t.)…”