Synthesis and Crystal Structure of the Rubidium Scandium Telluride RbSc 5 Te 8

During attempts to synthesize the rubidium dicopper triscandium hexatelluride RbCu 2 Sc 3 Te 6 in analogy to CsCu 2 Sc 3 Te 6 from 2:3:6‐molar mixtures of the elements (Cu, Sc and Te) with an excess of RbBr as flux and rubidium source, after 14 days at 900 °C in torch‐sealed evacuated silica tubes brown lath‐shaped crystals of RbSc 5 Te 8 did form instead. This new compound crystallizes monoclinically in space group C 2/ m (no. 12) with two formula units in a unit cell of the dimensions a = 2130.61(9) pm, b = 413.94(2) pm, c = 1022.03(5) pm and β = 104.392(4)°. The crystal structure of RbSc 5 Te 8 consists of a three‐dimensional anionic framework $^{3}_{\infty}\rm \{[Sc_{5}Te_{8}]^{-}\}$ of face‐, edge‐ and vertex‐sharing [ScTe 6 ] 9− octahedra that provides one‐dimensional tunnels with a distorted square shape. For charge compensation they are occupied with Rb + cations (CN = 10) coordinated in a trans ‐face bicapped cubic fashion by Te 2− anions.