Synthese, Struktur und Eigenschaften der Nonachloroditellur(IV)- und Tetrachlorohydroxotellur(IV)säure-Hydrate. Kristallstrukturen der Oxonium-Salze [H₉O₄]_n[Te₂Cl₉]_n und [H₉O₄][TeCl₄OH ] · H₂O/Synthesis, Structure and Properties of Nonachloroditellurous and Tetrachlorohydroxotellurous Acid Hydrates. Crystal Structures of the Oxonium Salts [H₉O₄]_n[Te₂Cl₉]_n und [H₉O₄][TeCl₄OH ] · H₂O

Light yellow needles of crystalline nonachloroditellurous acid with the formal composition HTe₂Cl₉ · 4H₂O (1) (space group C2/c, a = 11.642(6), b = 13.012(4), c = 12.663(5) Å, β = 119.64(3)° at 140 K) were isolated from a saturated solution of TeCl₄ in conc. HCl. From a solution of more diluted HCl the acid HTeCl₄OH · 5H₂O (2) could be prepared (space group P2₁2₁2₁, a = 7.065(3), b = 8.551(2), c = 18.192(6)Å at 140 K). 1 is the first acid isolated from the system TeCl₄ /HCl/H₂O with a polymeric anion. The novel polynuclear [Te₂Cl₉]_n^n- chains are built from alternately corner-sharing and edge-sharing distorted octahedral TeCl₆ units. The mean bond distances are 2.356 Å for terminal Te-Cl and 2.805 Å for Te-μ₂Cl. 2 contains square-pyramidal [TeCl₄OH]^- anions with oxygen in the apical position (Te-Cl: 2.447-2.552 Å; Te-O: 1.926 Å). The cations in both structures are [H₉O₄]⁺ hydroxonium ions (O···O (1): 2.47(3), 2.55(2) and 2.57(1) Å; O···O (2): 2.550(4), 2.584(4) and 2.588(5) Å). Thus the formulae of the acids have to be written as [H₉O₄]_n[Te₂Cl₉]_n and [H₉O₄][TeCl₄OH] · H₂O. Raman spectra of both compounds are reported.