Crystal Structure of [Al4(OH)6(H2O)12][Al(H2O)6]2Br12: A New Polyaluminum Compound

A vertex-shared tetrahedral [Al-4(OH)(6)(H2O)(12)](6+) (Al-4) and a disordered [Al(H2O)(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)(H2O)(12)][Al(H2O)(6)](2)Br-12, which crystallized in a cubic Fd (3) over barm space group from a spontaneously hydrolyzed solution of AlBr3. The former is composed of four AlO6 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 Al3+ ion of the latter is coordinated by 6 disordered OH2 molecules, that form a core-shell structure with ideal D-3d symmetry.