Cs[Er6C]I12 und Cs2Lu[Lu6C]Cl18: Beispiele für quaternäre reduzierte Halogenide der Lanthanide mit isolierten „Clustern”︁

CS[Er₆C]I₁₂ and cs₂Lu[Lu₆C]CI₁₈: Examples for Quaternary Reduced Halides of the Lanthanides with Isolated “Clusters” Cs[Er₆C]I₁₂ and Cs₂Lu[Lu₆C]Cl₁₈ were obtained as byproducts through metallothermic reductions of ErI₃ and LuCl, with cesium in the presence of carbon in sealed tantalum containers at temperatures ranging from 700 to 940 °C. Cs₂Lu[Lu₆C]Cl₁₈ (isostructural with Cs₂Zr[Zr₆H]Cl₁₈, R 3 , a = 981.7 pm, c = 2723.2 pm, Z = 3, R = 0.082, R, = 0.053) contains octahedral [Lu₆C] clusters which are slightly compressed along the threefold axis and edge-bridged by twelve chloride anions to form [Lu₆C]Cl₁₂ units. Six additional Cl in exo positions of the cluster provide octahedral coordination for the seventh Lu³⁺. Cs⁺ occupies anticuboctahedral interstices within the Cl⁺ layers as a part of the (hexagonal) closest packed arrangement. Cs[Er₆C]I₁₂ (trigonal, R 3, a = 1112.0pm, c = 2063.8pm, Z = 3, R = 0.094, R, = 0.068) exhibits [Er₆C]I₁₂ units as well and shows the structural framework of Sc[Sc₆N]Cl₁₂. Instead of Sc³⁺ in octahedral holes, cesium occupies a regular iodide position within the ccp sheets forming [CsI₃] layers. Both halides are compared with other compounds of the lanthanides containing isolated [M₆X₁₂] clusters. The extreme electron deficiency is discussed.