Crystal structure of a novel hydrated tridecameric polyaluminium chloride, [Al13（μ3-OH）6（μ2-OH）6（μ2-OH）12（H2O）24] Cl15·13H2O, has been determined by X-ray structure analysis, obtaining the detailed structural parameters and structure features. Moreover, the formation course was also discussed. The crystal belongs to monoclinic system, space group P21/c, with a = 1.3912（2）, b = 2.3529（3）, c = 2.2395（2） nm, β= 90.407（2）°, V = 7.3307（14） nm^3, Z = 4, Dc = 1.773 g/cm^3, F（000） = 4040, GOOF = 1.050,μ（MoKα）= 0.829 mm^-1, the final R = 0.0506 and wR = 0.1453 for 10553 observed reflections with I〉 2σ（I）. The structure of polycation of the title compound is different from either Keggin-type Al13 consisting of a central tetrahedral AlO4 core surrounded by twelve octahedral AlO6 units through corner-sharing or the ＂three hexameric rings juxtaposed＂ side by side predicted by ＂Core-Links＂ model linked by thirteen octahedral AlO6 units through edge-sharing. It has a ＂tortoise-like＂ structure with turnup ＂forefeet＂ and ＂tail＂, that is, an octahedral AlO6 core is surrounded by a ＂hexameric ring＂ through edge-sharing, then six octahedral AlO6 units are suspended onto the periphery of the ring upper and lower alternately by sharing two neighboring corners with an average turn angle of 21° entad. This kind of hydrated tridecameric polyaluminium chloride with such form is very important to further understand the existing forms and transformation rules of aluminium ion in hydrolysis system of its salts, speculate the process and mechanism of various hydrolysis and polymerization forms from Al（H2O）6^3＋ to Al（OH）3, and establish the relationship between structure and properties.
SUN ZhongZHAO Hai-DongTONG Hong-Ge-ErWANG Rui-FenZHU Fan-Zhu
