Lu2Te3O9: The First Example of the Triclinic C-Type Lanthanoid(III) Oxotellurates(IV) with the Composition M2Te3O9.

By fusing Lu2O3 and TeO2 in a molar ratio of 1:3 in a CsCl flux, colorless single crystals of the lutetium(III) oxotellurate(IV) Lu2Te3O9 could be obtained as first representative of the structurally so far unknown C-type for the composition M2Te3O9. The title compound crystallizes triclinically in space group P $\bar{1}$ with a = 689.67(4) pm, b = 1320.91(8) pm, c = 1450.06(9) pm, α = 110.057(3)°, β = 90.606(3)°, γ = 100.125(3)°, and Z = 6. The crystal structure contains six different Lu3+ cations in eightfold (Lu1 and Lu2: trigonal dodecahedra) and sevenfold (Lu3 and Lu6: monocapped trigonal prisms; Lu4 and Lu5: pentagonal bipyramids) oxygen coordination. These lutetium-oxygen polyhedra ( d(Lu-O) = 214-274 pm) are condensed to serrated layers according to 2∞{[Lu6O26]34-} that are stacked along [100]. The oxotellurate(IV) partial structure consists of basically nine crystallographically independent [TeO3]2- ( d(Te-O) = 184-196 pm) units connecting the above-mentioned layers to a three-dimensional framework. Strong secondary Te4+ ···O2- interactions between adjacent [TeO3]2- entities as common feature in the crystal structures of all known ternary lanthanoid(III) oxotellurates(IV) are also present in the crystal structure of Lu2Te3O9. Depending upon the range of these secondary contacts taken into account, the [TeO3]2- units are linked to form one-dimensional strands ( d(Te ···O) = 237-272 pm) like in B-type Dy2Te3O9 or even two-dimensional layers emerge ( d(Te ···O) = 237-285 pm). [ABSTRACT FROM AUTHOR]