Tl ₂ [Te ₂ O ₆ ]: The First Mixed‐Valent Oxidotellurate(IV/VI) of Thallium(I)

Single crystals of Tl 2 [Te 2 O 6 ] were grown hydrothermally at 220 °C starting from telluric acid and elemental thallium, whereas single‐phase microcrystalline material was obtained from solid‐state reactions between Tl 2 CO 3 , Tl 2 O 3 , and TeO 2 in evacuated silica ampoules at 450 °C. The crystal structure ( P 2 1 / c , Z = 4, a = 7.6071(15), b = 7.1018(14), c = 13.458(2) Å, β = 114.926(9)° at room temperature; R 1 = 0.0279, wR 2 = 0.0565 for all data) consists of 2 ∞ {Tl 2 } 2+ and 2 ∞ {Te 2 O 6 } 2− layers alternately stacked along [100] and is topologically related to that of one of the Ag 2 [Te 2 O 6 ] polymorphs. Vibrational spectra (Raman and infrared) show characteristic bands for the Te−O vibrations. On heating, Tl 2 [Te 2 O 6 ] is stable up to ≈540 °C.