一个新的铈砷钨酸盐大阴离子[As4W40O140Ce(H2O)5]^25-

合成了一新的铈砷钨酸盐As4W40C140Ce(H2O)5]Na25·63H2O,用X射线单晶衍射法及元素分析确定了其结构。其晶胞参数为：a=3.1252(8)nm,b=2.2656(6)nm,c=1.3973(9)nm,α=β=γ90°,V=9.893(7)nm^3,空间群P21/m21/m2/n。在聚阴离子As4W40O140Ce(H2O)5]^25-中，四个桥连WO6八面体通过相互共享两个顺式氧串联四个B-α-(AsW9O33)^9-形成环配体(As4W40O140)^28-的基本框架，四个B-α-(AsW9O33)^9-并不处在一个平面上，而是上下交错分布的。中心离子Ce(Ⅲ)未完全填充在(As4W40O140)^28-中具有八齿配位能力的S1洞穴中，而是四个桥连的WO6八面体各提供一个端基氧向Ce(Ⅲ)配位，另有五个水分子向Ce(Ⅲ)配位，Ce(Ⅲ)离子的配位数为9,该离具有C2v对称性。

A new large heteropolyanion [As4W40O140Ce(H2O)5]^25-

The heteropolytungstate As4W40O140Ce(H2O)5]Na25· 63H2O is prepared by the reaction of NaWO4·2H2O with NaAsO2 and Ce(NO3)3·6H2O. Its structure is determined by X-ray diffraction and element analysis. The cell parameters of As4W40O140Ce(H2O)5]Na25·63H2O are as follows:a=3.1252(8)nm, b=2.2656(6)nm, c=1.3973(9)nm, α=β=γ90°,V=9. 893(7)nm^3 , space group P21/m21/m2/n.In the anion As4W40O140Ce(H2O)5 ]^25-, the ring-type ligand (As4W40O140)^28- consists of four bridging WO6 octahedras that connect four B-α-(AsW9O33)^9- subunits yb sharing two cis oxygen atoms with each one. The four B-α-(AsW9O33) ^9- subunits in the anion do not lie in the same plane but in a up- down-up arrangement. The center ion Ce^3+ does not completely fit into the cavity of eigher S1 or S2. There are nine oxygen atoms coordinating to Ce(Ⅲ), with four oxygen atoms coming from four extra WO6 octahedras respectively and five oxygen atoms from five water molecules. The anion has a C2v symmetry.