Lutetium(III) oxotellurate(IV), Lu₂Te₄O₁₁

Rare-earth(III) oxotellurates(IV) with the composition M₂Te₄O₁₁ are known for yttrium and all lanthanides except promethium and lutetium from single-crystal X-ray structure determinations. Single crystals of the last missing non-radioactive isostructural compound, Lu₂Te₄O₁₁, can now be obtained by modifying the common method of synthesis from the binary oxides (Lu₂O₃ and TeO₂; 1:4 molar ratio) using torch-sealed non-evacuated silica ampoules as reaction containers. The structure contains layers of edge-sharing [LuO₈] polyhedra connected by oxotellurate(IV) chains. These consist of [TeO₃]²⁻ and [Te₂O₅]²⁻ anions (with ψ¹-tetra­hedral oxygen coordination for all central Te⁴⁺ cations) linked by strong secondary Te—O inter­actions.

Xenotime-type Yb[AsO₄]

Yb[AsO₄], ytterbium(III) oxoarsenate(V), adopts the xenotime structure type. Single crystals were obtained in an attempt to synthesize a compound with nominal composition Yb₃OCl[AsO₃]₂ by fusing a mixture of Yb₂O₃, YbCl₃ and As₂O₃ in a 4:1:3 molar ratio at 1123 K, owing to air-intrusion during the reaction. The structure is built up by chains of edge-sharing [YbO₈] trigonal dodeca­hedra and [AsO₄] tetra­hedra in a primitive rod packing. Yb and As are situated on positions with m2 symmetry, whereas O atoms are located on a mirror plane.