K3FeSe3 und K3Fe2Se4, zwei neue Verbindungen im System K/Fe/Se

Abstract

Die ternären Selenide K3FeSe3 und K3Fe2Se4 konnten über Schmelzreaktionen aus Kaliumcarbonat, Eisen und Selen in einem mit Selen beladenen Wasserstoffstrom bei 695 °C beziehungsweise bei 710–730 °C dargestellt werden. Röntgenographische Untersuchungen an Einkristallen führten zur Aufklärung der Kristallstrukturen. Die Atomanordnung der Verbindung K3FeSe3 ist durch [Fe2Se6]‐Doppeltetraeder charakterisiert, die durch die Kaliumionen isoliert werden (Raumgruppe P21/c, Z = 4). In der gemischtvalenten Verbindung K3Fe2Se4 bilden kantenverknüpfte durch Eisenatome zentrierte Selentetraeder Zick‐Zack‐Ketten, die wiederum durch Kaliumionen separiert werden (Raumgruppe Pnma, Z = 4).

Synthesis and Structure of the Sodium Phosphidosilicate Na2SiP2

“…Due to the chain orientation with respect to the ab ‐plane there are two differently oriented, but topologically identical chains in K 2 SiP 2 whereas in Na 2 SiP 2 three types occur (symmetrically inequivalent due to shift in the z parameter, Figure ) leading to nearly the same c ‐ and almost doubled a and b cell parameters involving quadruplicating of respective Wyckoff sites. The majority of representatives of the K 2 ZnO 2 ‐type structure are sulfides or selenides with relatively big cations separating the tetrahedra chains like in A 2 Co X 2 or A 2 Mn X 2 or in the compounds A 3 Fe 2 X 4 ( A = K, Rb, Cs; X = S, Se) with the Tl 3 Fe 2 S 4 ‐type structure. There are fewer examples of tetrahedra chains surrounded by cations smaller than potassium like in Na 2 ZnS 2 , Na 2 Co(S;Se) 2 or Na 3 Fe 2 (S;Se) 4 , .…”

K6In2Q6 (Q = S, Se, Te): Missing Links in the Series of Alkali Chalcogenido Ditrielates(III)

“…Cs 6 Fe 2 O 6 exceptionally form dimetallate anions of two edge‐shared tetrahedra, resulting in very short Fe–Fe distances. These dimers, as well as all sulfido and selenido diferrates(III), show an antiferromagnetic (AFM) spin coupling, whereas the recently obtained mixed‐valent phase Na 7 Fe 2 S 6 exhibits a very uncommon ferromagnetic (FM) spin coupling . As model systems of such mixed‐valent metallates, where the amount of M II and M III can easily be adjusted, we recently obtained (among other mixed Mn/In metallates) a salt containing the heterobimetallic dimer [Mn II In III S 6 ] 5–…”

Crystal Growth, Structure, Resistivity, Magnetic, and Photoelectric Properties of One‐Dimensional Selenometallate Ba2BiFeSe5

“…These values are comparable to those of BaGa 4 Se 7 (3.429(2) to 3.861(2) Å) and BaGa 2 MQ 6 (M=Si, Ge; Q=S, Se) (3.474(1) to 3.774(1) Å) . Fe atoms feature a slight distorted tetrahedral coordination geometry with Fe−Se bond lengths ranging from 2.335 to 2.404 Å, which are close to those for tetrahedrally coordinated Fe in FeSe (2.300(2) Å), K 3 Fe 2 Se 4 (2.402(4) to 2.465(3) Å), and BaFe 2 Se 3 (2.428(5) Å), whereas Bi atoms are coordinated to distorted quadrangular pyramids of five Se atoms with three short Bi−Se bonds (2.671(1) to 2.779(9) Å) and two longer ones (3.207 (1) Å), thus proving the stereochemical activity of the 6s 2 lone‐pair electrons. These values are close to those of Pb 7 Bi 4 Se 13 (2.789(6) to 3.189(6) Å) and Ba 3 Bi 6.67 Se 13 (2.725(4) to 3.165(3) Å) .…”