Chalcogenides by Reduction of their Dioxides in Ultra‐Alkaline Media

The reaction of chalcogen dioxides ChO(2) (Ch=Se, Te) with As(2)O(3) in a 30 molar KOH hydroflux at about 200 °C yielded crystals of potassium trichalcogenides K(2) Ch (3) with dimensions up to 2 cm. Arsenic trioxide acts as electron donor and is oxidized to arsenate(V). The new heterochalcogenide anion (TeSe(2))(2−) formed when starting from SeO(2) and TeO(2) simultaneously. The compound K(2)TeSe(2) crystallizes isostructural to K(2)S(3) and K(2)Se(3). The unexpected redox reaction as well as the precipitation of hygroscopic compounds from an aqueous solution are attributed to a strongly reduced activity of water. The reactions were studied by Raman and UV/Vis spectroscopy. Depending on the concentration of As(2)O(3), colorless monochalcogenide Ch (2−) or orange Se(2) (2−) and purple Te(2) (2−) anions are dominating the solutions.