K2BR(OH) AND RB2BR(OH) - 2 NEW TERNARY AL KALI-METAL HALIDE HYDROXIDES WITH A PRONOUNCED STRUCTURAL RELATIONSHIP TO KOH RESP RBOH

Two isotypic compounds K2Br(OH) and Rb2Br(OH) were prepared in the sys tems KOH/KBr and RbOH/RbBr. Their structures were determined by single crystal X-ray methods: K2Br(OH): P2(1)/m, Z = 2, a = 6.724(1) Angstro m, b = 4.272(4) Angstrom, c = 8.442(2) Angstrom, beta = 108.14(2)degre es, Z(F-o) = 651 with (F-o)(2) greater than or equal to 3 sigma(F-o)(2 ), Z(parameter) = 28, R/R(w) = 0.041/0.047 Rb2Br(OH): P2(1)/m, Z = 2, a = 6.918(3) Angstrom, b = 4.483(2) Angstrom, c = 8.850(5) Angstrom, b eta = 108.08(6)degrees, Z(F-o) = 326 mit (F-o)(2) greater than or equa l to The compounds are built up by chains of (1) infinity[M(2)(OH)(+)] connected via Br-. The structure of the chains as well as their orien tation to one another show a pronounced relationship to the structures of the room temperature modifications of the isotypic binary hydroxid es KOH and RbOH.