Abstract: | Ho2Te4O11 and Ho2Te5O13: Two Telluriumdioxide‐rich Oxotellurates(IV) of Trivalent Holmium Ho2Te4O11 (monoclinic, C2/c; a = 1240.73(8), b = 511.21(3), c = 1605.84(9) pm, β = 106.142(7)°; Z = 4) and Ho2Te5O13 (triclinic, P1; a = 695.67(5), b = 862.64(6), c = 1057.52(7) pm, α = 89.057(6), β = 86.825(6), γ = 75.056(6)°; Z = 2) are obtained by the reaction of holmium sesquioxide with tellurium dioxide in appropriate molar ratios (Ho2O3 : TeO2 = 1 : 4 and 1 : 5, respectively) in evacuated silica tubes within eight days at 800 °C. The application of cesium chloride (CsCl) as flux in about five times molar excess secures fast and complete reactions to the single‐crystalline products aimed at. In the crystal structure of Ho2Te4O11 HoO8] polyhedra are connected via oxygen edges thereby building up a network {Ho2O10]14–} (001). On the other hand, the crystal structure of Ho2Te5O13 exhibits oxygen‐linked (Ho1)O8] and (Ho2)O7] polyhedra, which form ribbons {(Ho1)2(Ho2)2O20]28–} running along 100]. Common to both structures, however, is the stereochemical activity of the non‐bonding electron pairs (“lone pairs”) of all the of the Te4+ cations (Te1 and Te2 in Ho2Te4O11, Te1–Te5 in Ho2Te5O13) causing ψ1‐polyhedral figures of coordination with 3 + 1, 4 and 3 + 2 oxygen atoms, respectively, around the central atoms. |