二聚结构[(CH3)4N]4[PW11O39)H2La(H2O)4]2·3H2O的合成、结构及性质

Syntheses, crystal structure and properties of the dimeric [(CH_3)_4N]_4[PW_(11)O_(39)H_2La(H_2O)_4]_2 · 3H_2O

以α-Na7PW11O39·nH2O,LaCl3·7H2O和(CH3)4NCl为原料,利用常规水溶液方法合成了2:2型二聚的单缺位Keggin结构稀土衍生物[(CH3)4N]4[PW11O39H2La(H2O)4]2·3H2O(1).X射线单晶衍射结果表明,该晶体属三斜晶系,P-1空间群,晶胞参数:a=1.35383(10)nm,b=1.60687(12)nm,c=1.86958(13)nm,α=65.9630(10)°,β=83.1650(10)°,γ=83.6780(10)°,Z=1,R1=0.0589,wR2=0.1447.二聚阴离子{[(α-PW11O39H2)La(H2O)4]2}4-由2个[α-PW11O39]7-缺位阴离子通过2个[La(H2O)4]3+配离子连接形成,La3+离子占据[α-PW11O39]7-阴离子的缺位位置,采用九配位单加冠四方反棱柱构型,相邻的2个单取代阴离子[α-PW11LaO39]4-通过2个La–Ot–W桥连成二聚物.热重分析结果表明,化合物1在25～600℃范围内表现为两步失重;循环伏安行为表明,化合物1阴离子在pH4.3的水溶液中存在两步可逆的单电子还原过程.

2：2-type dimeric [（CH3）4N]4[PW11O39H2La（H2O）4]2·3H2O was successfully synthesized by reaction of the monovacant Keggin structure α-Na7PW11O39·nH2O with LaCl3·7H2O and （CH3）4NCl in aqueous solution. Single crystals of this compound were analyzed by X-ray crystallography and found to be in the triclinic space group P1 with the following parameters： a = 1.35383（10） nm, b = 1.60687（12） nm, c = 1.86958（13） nm, α = 65.9630（10）°, γ = 83.1650（10）°, γ = 83.6780（10）°, Z = 1, R1 = 0.0589, wR2 = 0.1447. The dimeric polyoxoanion [{（α-PW11O39H2）La（H2O）4}2]4– consisted of two [α-PW11O39]7- subunits linked together by two [La（H2O）4]3＋ cations. The nine-coordinate La3＋ cation was incorporated in the vacant site of the [α-PW11O39]7- subunit, which adopted monocapped square antiprismatic coordination geometry. Thermogravimetric analysis exhibited two weight loss steps between 25 and 600°C; cyclic voltammetry indicated that two reversible single-electron reductions of the synthesized compound occurred in aqueous solution at pH 4.3.