Methanolothermale Synthese von Rb3AsSe4 · 2Se6 und Cs3AsSe4 · 2Cs2As2Se4 · 6Te4Se2, zwei Selenidoarsenate mit sechsgliedrigen Chalkogenringen/ Methanolothermal Synthesis of Rb3AsSe4 · 2Se6 and Cs3AsSe4 · 2Cs2As2Se4 · 6Te4Se2. Two Selenidoarsenates with Six-Membered Chalcogen Rings

Abstract

Abstract The methanolothermal reaction of Rb2CO3 with As2Se3 and black selenium leads to the formation of Rb3AsSe4 and the new selenidoarsenate(V) Rb3AsSe4 · 2Se6 (1), which crystallizes in the cubic space group Fd3̄ (No. 203) with a = 16.660(2) Å, V = 4624.1(1) Å , Z = 8. The structural features are isolated tetrahedral AsSe4 3- anions and Se6 rings in a chair conformation. Whereas the similar reaction with Cs2CO3 only affords the known selenides Cs3AsSe4 and Cs4Se16, replacement of As2Se3 by As2Te3 leads to a compound with similar lattice constants to 1 (Fd3̄, a = 17.275(2) A), containing disordered AsSe4 3- and As2Se4 2- anions, the latter of which exhibit a four-membered As2Se2 ring with m-positioned terminal selenium atoms. The six-membered chalcogen ring is likewise disordered with Se and Te site occupation factors of respectively 0.333 and 0.667 with the result that 2 can be formulated as Cs3AsSe4 · 2Cs2As2Se4 · 6Te4Se2. 2 provides the first example of a TexSe6-x ring to be characterized in the solid state.