η-Mo4O11 und Mg2Mo3O8: eine neue Synthese und Verfeinerung ihrer Kristallstrukturen

η-Mo₄O₁₁ and Mg₂Mo₃O₈: a New Way of Synthesis and Refinement of their Crystal Structures Mg₂Mo₃O₈ was obtained by solid state reaction of MgI₂ and MoO₃ (1:1) at 200°C and subsequent crystallization at 800°C. Under the same conditions, ZnI₂ and MoO₃ only yielded rather impure Zn₂Mo₃O₈; however, when ZnI₂ or CdI₂ and MoO₃ were taken in a molar ratio of 1:2, well crystallized η-Mo₄O₁₁ was obtained. The known crystal structures of Mg₂Mo₃O₈ and η-Mo₄O₁₁ were refined with new X-ray diffraction data (R = 0.030 and 0.059, respectively). The kind of twinning of monoclinic η-Mo₄O₁₁ is discussed.