Dy3OF5S: Das erste Oxidfluoridsulfid eines Lanthanoids

Dy₃OF₅S: The First Oxyfluoride Sulfide of the Lanthanides While trying to synthesize DyFS with the PbFCl‐type crystal structure by the reaction of DyF₃ with dysprosium and sulfur in 1:2:3‐molar ratios at 850 °C in gas‐tight sealed tantalum ampoules, oxygen contaminated educts (e.g. DyOF‐containing DyF₃) were also applied occasionally. Consequently a small quantity of almost colourless, rod‐shaped single crystals of Dy₃OF₅S, the first oxyfluoride sulfide of the lanthanides, were formed in small quantities on adding equimolar amounts of NaCl as flux. Almost phase‐pure samples are obtained under otherwise analogous reaction conditions according to 2 Dy + 5 DyF₃ + Dy₂O₃ + 3 S = 3 Dy₃OF₅S by deliberate addition of Dy₂O₃. In the hexagonal crystal structure (space group: P6₃/m; a = 942.58(8), c = 368.12(4) pm; c/a = 0.391, V_m = 85.285 cm³/mol, Z = 2) Dy³⁺ resides in nine‐fold anionic coordination (tricapped trigonal prism comprising 1.333 O^2—, 5.667 F^— and 2 S^2—). The fractional numerical values for the “light anions” are due to two six‐fold point positions with the exclusive existence of F^— in trigonal non‐planar coordination (CN = 3, d(F1—Dy) = 232 (1×) and 241 pm, 2×) on the one hand, but F^— and O^2— simultaneously in the ratio 2 : 1 in tetrahedral coordination of Dy³⁺ (CN = 4, d(F2/O—Dy) = 234 (2×), 236 and 241 pm, 1× each) on the other. Finally, a trigonal prismatic Dy³⁺ coordination (d(S—Dy) = 290 pm, 6×) is attributed to the S^2— anions. From the data of the single crystal X‐ray structure analysis, no indication of an ordering of O^2— and F^— is obtained, its true nature as an oxyfluoride sulfide, however, is unambiguously confirmed by electron‐beam microanalysis on Dy₃OF₅S.