咪唑配位的夹心型杂多化合物Na_9[{Na(H_2O)}_3{Co(C_3H_4N_2)}_3(BiW_9O_(33))_2]·33H_2O的合成，结构和磁性质研究

在pH=7.5的水溶液中，咪唑与Na_2WO_4,Bi(NO_3)_3及Co(NO_3)_2反应，得到 了咪唑配位的新型杂多钨酸盐Na_9[{Na(H_2O)}_3{Co(C_3H_4N_2)}_3(BiW_9O_(33) )_2]·33H_2O，用X射线单晶衍射法及元素分析确定了其结构，晶胞参数为：空间 群P3，a=1.3904(4)nm, b=1.3904(4)nm, c=3.3169(13)nm, γ=120 °,V=5.553(3) nm~3, Z=2, R_1=0.0361，wR_2=0.0507(I>2σ)。杂多阴离子[{Na(H_2O)_3}{Co (C_3H_4N_2)}_3(BiW_9O_(33))_2]~(9-)为夹心式结构，两个三空缺Keggin离子α- B-BiW_9O_(33)~(9-)夹层中的中心离子为交替排列的三个Na(H_2O)~+和三个Co (C_3H_4N_2)~(2+)，中心离子钴的配位数为5，该杂多阴离子具有C_(3v)对称性。 对标题化合物进行了磁性质表征，拟合结果为J=6.90cm~(-1),g=2.10,θ=0.25K， 表明该化合物中的Co(II)三核簇存在着铁磁偶合。

Synthesis,Structure and Magnetic Properties of Imidazole Coordinated Sandwich-type Bismuth Tungstate Na9[{Na(H2O)}3{Co(C3H4N2)}3-(BiW9O33)2]·33H2O

The imidazole coordinated novel heteropolyoxometalate Na_9[{Na (H_2O}_3{Co(C_3H_4N_2)}_3(BiW_9O_(33)_2]·33H_2O was synthesized by the reaction of Na_2WO_4·2H_2O with Bi(NO_3)_3 and Co(NO_3)_2 in pH = 7.5 aqueous solution. The single crystal X-ray diffraction study shows that the ciystal belongs to trigonal system, space group P3 , with a = 1.3904(4) nm, b = 1.3904(4) nm, c = 3.3169(13) nm, γ = 120°, V = 5. 553(3) nm~3, Z = 2, R_1 = 0.0361, wR_2 = 0.0507 (I>2σ). The structure of anion [{Na(H_2O)}_3{Co(C_3H_4N_2)}_3(BiW_9O_(33))_2]~(9-) reveals a sandwich-like arrangement of two {α-B-AsW_9} moieties enclosing three Co(C_3H_4N_2)~(2+) and three Na(H_2O)~+ . The coordination number of Co~(2+) and Na~+ in the sandwich anion are all five, and the polyanion has C_(3v) symmetry. Magnetic data have been fitted assuming that the only exchange-coupled centers are the cobalts, the compound exhibits ferromagnetic coupling with J = 6.90 cm~(-1), g = 2.10, and θ = 0.25 K.