THE STRUCTURE OF HEXAAQUAALUMINIUM(III) BROMATE TRIHYDRATE, [AL(H2O)6](BRO3)3-BULLET-3H2O

Hexaaquaaluminium(III) bromate trihydrate, [Al(H2O)6](BrO3)3.3H2O, M(r) = 572.84, triclinic, P1BAR, a = 9.536 (2), b = 11.095 (4), c = 9.291 (2) angstrom, alpha = 106.58 (2), beta = 100.42 (2), gamma = 113.01 (2)-degrees, V = 818.1 (4) angstrom3, Z = 2, D(x) = 2.33 g cm-3, lambda(Mo K-alphaBAR) = 0.71073 angstrom, mu = 74.58 cm-1, F(000) = 560, T = 296 K, R = 0.050 for 3777 unique reflections having I > sigma(I). The single type of Al ion is coordinated by six inequivalent water O atoms which form a slightly distorted octahedron. The average Al-O distance within the octahedron is 1.872 (11) angstrom. Each of the three inequivalent bromate groups has three inequivalent 0 atoms. The average Br-O distances and O-Br-O angles for these ions are: 1.652 (25) angstrom and 104.1 (17)-degrees for Br(1)O3; 1.650 (9) angstrom and 104.4 (18)-degrees for Br(2)O3: 1.643 (9) angstrom and 103.6 (14)-degrees for Br(3)O3. The aluminium-oxygen complex conformed to rigid-body behavior but the bromate groups did not. Corrected for rigid-body motion, the average Al-O distance becomes 1.880 (10) angstrom. Least-squares refinement of the positional parameters of the 18 inequivalent H atoms permitted a detailed analysis of the hydrogen bonding.