K2Br(OH) und Rb2Br(OH): Zwei neue ternäre Alkalimetallhalogenidhydroxide mit ausgeprägter Strukturverwandtschaft zu KOH bzw. RbOH

K₂Br(OH) and Rb₂Br(OH): Two New Ternary Alkali Metal Halide Hydroxides with a Pronounced Structural Relationship to KOH resp. RbOH Two isotypic compounds K₂Br(OH) and Rb₂Br(OH) were prepared in the systems KOH/KBr and RbOH/RbBr. Their structures were determined by single crystal X-ray methods: K₂Br(OH): P2₁/m, Z = 2, a = 6.724(1) Å, b = 4.272(4) Å, c = 8.442(2) Å, β = 108.14(2)°, Z(F_o) = 651 with (F_o)² ≥ 3σ(F_o)², Z(parameter) = 28, R/R_w = 0.041/0.047 Rb₂Br(OH): P2₁/m, Z = 2, a = 6.918(3) Å, b = 4.483(2) Å, c = 8.850(5) Å, β = 108.08(6)°, Z(F_o) = 326 mit (F_o)² ≥ 3σ(F_o)², Z(parameter) = 27, R/R_w = 0.074/0.082. The compounds are built up by chains of [M₂(OH)⁺] connected via Br^?. The structure of the chains as well as their orientation to one another show a pronounced relationship to the structures of the room temperature modifications of the isotypic binary hydroxides KOH and RbOH.