Crystal structure of [Al4(OH)6(H2O)12][Al(H2O)6]2Br12: a new polyaluminum compound

A vertex-shared tetrahedral Al(4)(OH)(6)(H(2)O)(12)](6+) (Al(4)) and a disordered Al(H(2)O)(6)](3+) (Al(1)) that coexist in a 1:2 ratio within each unit cell were observed in the structure of Al(4)(OH)(6)(H(2)O)(12)]Al(H(2)O)(6)](2)Br(12), which crystallized in a cubic Fd3m space group from a spontaneously hydrolyzed solution of AlBr(3). The former is composed of four AlO(6) octahedra that are connected to each other by sharing three vertexes of each octahedron and form a large regular tetrahedron with ideal T(d) symmetry. The central Al(3+) ion of the latter is coordinated by 6 disordered OH(2) molecules, that form a core-shell structure with ideal D(3d) symmetry.