Tl5SnF9 und Tl5TiF9: die ersten [Tl5F3]2+‐Schichten in neuartigen Thallium(I)‐fluoridfluorometallaten(IV)

Tl₅SnF₉ and Tl₅TiF₉: The First [Tl₅F₃]²⁺ Layers in Novel Thallium(I) Fluoridefluorometallates(IV) Tl₅TiF₉ and Tl₅SnF₉ were prepared via solid state reactions from mixed powders of the TlF and SnF₄ or TiF₄, respectively, in platinum crucibles under Ar (573 K). Both fluorides are colourless, transparent and extremely hygroscopic. The compounds Tl₅MF₉ (M = Sn, Ti) crystallize in a new structure type in Pbam (Nr. 55) with a = 1117.6 pm, b = 684.8 pm, c = 799.2 pm for Tl₅SnF₉ and a = 1111.4 pm, b = 674.7 pm, c = 783.2 pm for Tl₅TiF₉. Characteristic building units in the new Thallium(I) fluoridefluorometallates(IV) are [Tl₅F₃]²⁺ sheets found for the first time, which are connected via [MF₆]^2– octahedra (M = Ti, Sn) to a threedimensional network (d_Sn–F = 194–197 pm, d_Ti–F = 186–187 pm). The monovalent Tl are coordinated by 8 F with distances Tl–F between 264 and 334 pm. The chemical bonding is discussed on the basis of Extended‐Hückel band structure calculations.