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合成了新型杂多阴离子二聚体K_(12)(SiMW_(11)O_(39))_2O·29H_2O(简写为(SiMW_(11))_2O,M=Fe~Ⅱ,Cr~Ⅱ,Al~Ⅲ),并用元素分析、红外及电子光谱等进行了表征。其中(SiCrW_(11))_2O及(SiAlW_(11))_2O未见文献报导。用XPS测定了M_(2p)的结合能,结果表明:与SiMW_(11)相比,(SiMW_(11))_2O中M_(2p)结合能偏低0.7～0.9ev,结合红外及紫外光谱,可以推测,二聚体中两个杂多阴离子以M-O-M桥氧相连。其中氧的2p轨道与M的3d轨道重叠形成了d-pπ键。二聚体(SiFeW_(11))_2O及(SiCrW_(11))_2O中Fe~Ⅱ,Cr~Ⅱ的有效磁矩比单体明显偏低,表明铁、铬桥氧键中两个金属原子M~Ⅱ的d电子通过桥氧发生了反磁性交换。
A new heteropolyanion dimer K_ (12) (SiMW_ (11) O_ (39)) _ 2O · 29H_2O (SiMW_ (11)) _2O, M = Fe ~ Ⅱ, Cr ~ Ⅱ, Al ~ Ⅲ ), And characterized by elemental analysis, infrared and electron spectroscopy. Among them, (SiCrW_ (11)) _2O and (SiAlW_ (11)) _ 2O have not been reported in the literature. The binding energy of M_ (2p) was determined by XPS. The results showed that the binding energy of M_ (2p) in SiMW_ (11) __2O was 0.7 ~ 0.9ev lower than that of SiMW_ (11) Presumably, two heteropolyanions in the dimer are linked by MOM bridging oxygen. Where the oxygen 2p orbit overlaps with the 3d orbit of M to form the d-pπ bond. The effective magnetic moments of Fe ~ Ⅱ and Cr ~ Ⅱ in the dimer (SiFeW_ (11)) _2O and (SiCrW_ (11)) _2O are obviously lower than those of the monomer, indicating that the two metal atoms M The d electrons of ~ Ⅱ have diamagnetic exchange through the bridge oxygen.