Hydrothermal Synthesis And Characterization Of The Substituted Oxo-tungsten Clusters

According to the literature, we prepared a series of tri-vacant tungsten-oxo clustes,such as: K8Na₂[A-α-GeW₉O₃₄]·25H₂O, Na9[A-PW₉O₃₄]·7H₂O, Na10[A-α-SiW₉O₃₄]·24H₂O,etc. Using these lacunary tungsten-oxo clusters as precursors, we succeeded in exploringfour classes of tungsten-oxo clustes that were substituted by Fe-Ln （Ln=Sm, Ce）3d-4fheterometallic systems, Fe, Ni and Cu. The formulas of these compounds are as follows:1、（enH₂）₁₃HK₉[Fe₆Sm₆（H₂O）₁₂(GeW₁₀O₃₈)₆]·42H₂O （en=1,2-ethylenediamine）2、（enH₂）₁₃H₃K₇[Fe₆Ce₆（H₂O）₁₂(GeW₁₀O₃₈)₆]·42H₂O3、（enH₂）₆K[HFe₆(B-α-GeW₉O₃₄)₂（α-GeW6O26）（H₂O）₂]·11H₂O4、（enH₂）₅[（enH₂）₂Fe4(FeW₉O₃₄)₂][（enH）₂Fe4(FeW₉O₃₄)₂]·9H₂O5、（enH₂）₁₁[{(B-a-PW₉O₃₄)-Fe₃（OH）₃}4（PO₄）₄Fe]·38H₂O6、[Ni₆（μ₃-OH）₃（H₂O）₂（dien）₃(B-α-PW₉O₃₄)]·4H₂O （dien=diethylenetriamine）7、（enH₂）₂[（en）₄Cu₈（H₂O）₂(B-α-SiW₉O₃₄)₂]·8H₂OAmong them, compound1was synthesized by using the K8Na₂[A-α-GeW₉O₃₄]·25H₂Oprecursor. It has [Sm–（μ₃-O）₃–Fe] bridges and a trimeric cryptand-type[KFe₃Sm3（H₂O）₆(α-GeW₁₀O₃₈)₃]17-aggregate that contains three divacant Keggin[α-GeW₁₀O₃₈]12-subunits. A K⁺embedded in the central. What’s more, under the couplingeffect of K⁺, two trimmers aggregated into hexamers and the hexamers aggregated into a1-D chain. The structure of the compound2is similar to compound1. It’s a trimericcryptand-type structure that include the [Sm–（μ₃-O）₃–Fe] bridges and the Keggin type[α-GeW₁₀O₃₈]12-subunits. It also presented a1-D chain-like structure. Compound3is anexample of double sandwich structure which was substituted by two Fe₃clusters. Thepolyoxometalates it contains are two [B-α-GeW₉O₃₄]10-fragments and one [α-GeW6O26]12-.Two double sandwich structural units are interconnected with each other via two K⁺cations,giving rise to a ring-like assembly. The common futures of compounds1-3are as follows:（a） they all made by using the same precursor, K8Na₂[A-α-GeW₉O₃₄]·25H₂O.（b） they allsubmitted by transition metal, Fe.（c） the K⁺embedded in these three structures, and thestructures of them became more stable. The compounds4and5are both synthesized basedon the Na9[A-PW₉O₃₄]·7H₂O precoursor and substituted by irons clusters. The compound4is contained the [B-α-FeW₉O₃₄]11-fragment with the1-D chain-like assembly. The ironclusters in the central belt have the mixed valence. The compound5is a tetra-polymeric structure containing Fe13clusters. A Fe4disordered in four sites of the central cube. Thecompounds6is a Ni substituted polymer synthesized by using the Na9[A-PW₉O₃₄]·7H₂O.The compound7is a Cu substituted fragment. However, the precursor used in it isNa10[A-α-SiW₉O₃₄]·24H₂O. In the structures of compounds6and7, they both belongs tothe organic-inorganic hybrid structures with the coordination of the organic amines. In thefollowing works, these seven compounds were structurally characterized by usingsingle-srystal X-ray diffraction, powder X-ray diffraction （PXRD）, thermogravimetric （TG）analyses and elemental analyses. The magnetic susceptibility measurements demonstratethe presence of antiferromagnetic interactions in compounds1and3.