X-Ray structural analysis of a new barium aluminate glycolate (BaA108C6.75H14.75) has revealed a novel aluminate anion, formed from two distorted trigonal bipyramids sharing an edge to give a dimer.
Abstract. Mr=431.51 , orthorhombic, Ccc2, a= 13.774 (15), b = 10.828 (10), c = 9.105 (12) A, V--1358(9)A 3, Z=4, Dx=2.111 , Dm=2.17Mgm -3, 2(Mo Ka) = 0.71069 A, ~ = 3.166 mm -I, F(000) = 840.0, T= 298 K, R =0.0436 for 620 independent reflections. The A1 coordination is unusual, being a distorted trigonal bipyramid (i.e. five coordinate) rather than tetrahedral or octahedral; two polyhedra share edges to form a dimer. A1-O bond lengths [apical 1.924 (7), 1.884 (7) A; equatorial 1.863 (7), 1.80 (1), 1.72 (1)A] and angles are compared with those in other structures containing five-coordinated A1 atoms.
BaAIsHO9, M r = 417.2, hexagonal, P63/mmc, a = 5.635 (3), c = 13.489 (8) A, V= 371.0 (3) A 3, Z = 2, D m = 3.93, D x = 3.733 Mg m -3, MoKa, 2=0.71069A, p=5.967mm -~, F(000)= 388, T= 298 K, R = 0.0693 for 225 independent reflections. This novel compound (obtained by the hydrothermal reaction of barium hydroxide and hydrated alumina, A1203: BaO ratio 2.5, at temperatures >528 K) exhibits a structure related to the well known fl-alumina (Na20.11A1203) structure. The main difference is the absence of two of the oxygen layers from the spinel blocks.
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