一个新的夹心型杂多钨酸盐Na_6(C_5N_2H_7){[Na(H_2O)_2]_3Co(H_2O)_5-[Co(H_2O)]_3(AsW_9O_(33))_2}·27H_2O的晶体结构及性质

Crystal Structure and Properties of a New Sandwich Heteropolytungstate Na_6(C_5N_2H_7){[Na(H_2O)_2]_-Co(H_2O)_5[Co(H_2O)]_3(AsW_9O_(33))_2}·27H_2O

在pH=7.5的水溶液中,Na_2WO_4·2H_2O,NaAsO_2,CoCI_2·6H_2O与对氨基吡啶反应,得到了一种新的夹心型杂多钨酸盐Na_6(C_5H_7N_2){[Na(H_2O)_2]_3Co(H_2O)_5[Co(H_2O)]_3(AsW_9O_(33))_2}·27H_2O单晶,用X射线单晶衍射法及元素分析确定了结构,晶体属三斜晶系,p1^-空间群,其晶胞参数为:a=1.3276(8)nm,b=1.7581(10)nm,c=2.4381(14)nm,a= 70.954(9)°,β=86.663(9)°,γ=72.885(9)°,V=5.136(5)nm^3,Z=2,R_1=0.0608,wR_2=0.0848[I>2σ(I)].在{[Na(H_2O)_2]_3Co(H_2O)_5[Co(H_2O)]_3(AsW_9O_(33))2}^(7-)阴离子中,一个Co^(2+)与聚阴离了{[Na(H_2O)_2]_3[Co(H_2O)]_3(AsW_9O_(33))_2}^(9-)的一个端基氧共价连接,Co^(2+)呈现出5和6两种配位数,质子化的氨基吡啶正离子作为抗衡离子存在于晶体之中.对标题化合物进行了IR,UV-Vis,TG-DSC表征.对该化合物、Na_2WO_4·2H_2O及COCl_2·6H_2O催化H_2O_2氧化乙醛的活性进行了比较研究,该化合物的催化活性远优于简单化合物Na_2WO_4·2H_2O和CoCl_2·6H_2O.

A new sandwich heteropolytungstate Na6（CsN2H7）{[Na（H2）2]3Co（H2O）5[Co（H2O）]3-（AsW9O33）2}·27H2O was synthesized by the reaction of Na2WO4·2H2O, NaAsO2, CoCl2·6H2O and p-aminopyridine （C5H7N2） in pH=7.5 aqueous solution. The single crystal X-ray diffraction study shows that the crystal belongs to triclinic system, space group P-↑1, with α= 1.3276（8） nm, b= 1.7581（10） nm, c=2.4381（14） nm, α=70.954（9）°, β= 86.663（9）°, γ=72.885（9）°, V=5.136（5） nm^3, Z=2, R1 =0.0608, ωR2= 0.0848 [I〉2σ（I）]. The structure of anion {[Na（H2O）2]3Co（H2O）5[Co（H2O）]3（AsW9O33）2}^7- reveals a sand-wich arrangement of two {α-B-AsW9} moieties enclosing three Co（H2O）^2＋ and three Na（H2O）2^＋, and another Co（H2O）5^2＋ connects with one terminal oxygen of {[Na（H2O）2]3[Co（H2O）]3（AsW9O33）2}^9-. There are two kinds of coordination numbers of Co^2＋ in the polyanion, 5 and 6. The title compound was also characterized by IR, UV-Vis and TG-DSC. The formation condition of the the title compound was discussed. It was shown that the title compound was much more effective than Na2WO4·2H2O or CoCl2·6H2O for the catalytic oxidation of acetaldehyde with hydrogen peroxide in an aqueous solution.