Synthesis, Structures And Characterization Of Several New Iso- And Hetero-polyoxotungstates

Polyoxometalates have attracted great attention not only stems from their intriguing variety of architectures,but also from their potential applications in the fields as diverse as catalysis,medicine,molecular magnetism and material science.In recent years,the synthesis of second transition metal-containing polyoxotungstates has become an important research area of the synthesis of polyoxometalates.In this paper, the four new polyoxo tungstates have been synthesized and characterized by elemental analysis,IR,UV and X-ray single-crystal analysis,and the electrochemical behaviors of compound 1,2 and 3 were also studied.The four new polyoxo tungstates are as follows:Paradodecatungstate-B coordinated manganictungstate polyoxometalates: K₈H₈ {[Ni(H₂O)₅]₂[H₂W₁₂O₄₂]}[H₂W₁₂O₄₂]·15H₂O(1)Paradodecatungstate-B coordinated falcialtungstate polyoxometalates: Na₁₀{[Mn(H₂O)₃]₂[H₂W₁₂O₄₂]}{[Mn(H₂O)₃]₂[Mn(H₂O)₄][H₂W₁₂O₄₂]}·56H₂O(2)Double 1:11 series germanotungstates compound: K_8.5Na₃H_0.5[Ce(α-GeW₁₁O₃₉)₂]·17H₂O(3)Open Wells-Dawson structure compound: H₄K₃Na₁₆[K(H₂O)(μ₂-H₂O)(μ₃-H₂O)Co(μ₂-H₂O)Na₂(H2O)₂(Si₂W₁₈O₆₆)] [K(μ₂ -H₂O)₂Co(H₂O)(μ_a-H₂O)Na(H₂O)(Si₂W₁₈O₆₆)]·59H₂O(4)Compound 1 and 2 are the compound that paratungstate[H₂W₁₂O₄₂]¹⁰- clusters act as multidentate ligands coordinating to different transition metal(TM)complex.In compound 1 there are two crystallographic unsymmetrical of polyanions,one is not coordinated to TM ions and another acts as 2-dentate ligand coordinating to two nickel (â…¡)ions.Both of the two nickel ions are six-coordinate.The neighboring polyoxoanions are linked by salt bonds(K⁺—O)and strong hydrogen bonds into 3D structure.Compound 2 also has two crystallographic unsymmetrical of polyanions, {[Mn(H₂O)₃]₂[H₂W₁₂O₄₂]}^6-and {[Mn(H₂O)₃]₂[Mn(H₂O)₄][H₂W₁₂O₄₂]}^4-,the 1D chains {[Mn(H₂O)₃]₂[H₂W₁₂O₄₂]}_n^6n-are connected by 6-coordinated Mn²⁺to form two- dimensional layer structure,and furthermore these layers are connected by salt bonds (Na⁺—O)and strong hydrogen bonds into 3D structure.Compound 3 is a sandwich type polyoxometalates in which the Ce^â…£is binded to two mono-lacunary Keggin-type [α-GeW₁₁O₃₉]^8-anions.Each[α-GeW₁₁O₃₉]^8-anion acts as a tetra-dentate ligand by its four unsaturated oxygen atoms coordinating with the Ce^â…£metal center,and the coordination number of Ce^â…£is eight.The four unsaturated oxygen atoms from the same[α-GeW₁₁O₃₉]^8-units are practically in a plane.The two planes are not exactly parallel and form an angle of 3.5°.The structure of compound 4 derives formally from the Wells-Da wson structure by the breaking of the four of the six W—O—W junctions. Between the two subunits there exsit an open angle of about 40°and can be referred to as an "open Wells-Da wson" structure.A potassium cation,a sodium cation and a cobalt cation are included in the pocket.