Syntheses, Crystal Structures And Properties Of Transition-metal Substituted Sandwich-type Tungstoarsenates

Polyoxometalates constitute a large subclass, and here the so called “transition-metalsubstituted POMs （TMSPs）” are rather prominent. They have a wide varity and application inthe fields of mangnetism, catalysis and electrochemistry. In this paper, on the basis ofmolecular design and assembly conceptions, we adopted simple materials such asNa2WO₄·2H₂O, NaAsO2and transition metal salts under the conventional aqueous methods,three of novel sandwich-type transition metal substituted polyoxometalates derivatives basedon arsenic heteroatom were obtained by controlling reaction conditions such as pH value,temperature, time, concentration and reactant stoichiometry. These complexes werecharactered by X-ray crystallography, IR, UV spectroscopy, thermal properties, XPRD, XPS,magnetic analyses, antumer activity and catalysis research.1. Two novel high nuclearity transition-metal substituted sandwich-type POMsNa₈[H₄Cu₉As₆O₁₅（H₂O）₆(α-AsW₉O₃₃)₂]·41H₂O （1） and Na₄[H₅Na₃（H₂O）₆Cu3（H₂O）3(α-AsW₉O₃₃)₂]·35H₂O （2） have been prepared by the reaction ofNa2WO₄·2H₂O, NaAsO2and CuCl2in aqueous solution. To the best of our knowledge,compound1is regarded as the highest nuclear sandwich-type Cu-substitutedpolyoxometalate which has never been seen in the provious reports and represents thefirst example of {As₂O₅} acting as SSAs in sandwich-type TMSPs. Compounds1and2exhibit remarkable biological activity.2. One tri-Ag^I cluster substituted sandwich-type tungstoarsenatesNa₁₄[HAg₃（H₂O）₂(α-AsW₉O₃₃)₂]·38H₂O （3） has been synthesized by the reaction of Na2WO₄·2H₂O, NaAsO2and AgNO3. Compound3shows a1-D chains structure. Thereaction results indicate that compound3has a remarkable catalytic activity on theepoxidation of alkenes.