Syntheses And Structures Of Two Transition-metal-cluster-containing Polyoxotungstate Sandwich Compounds

Polyoxometalates (POMs) are a remarkable class of inorganic compounds which possessenormous size and compositional diversity as well as potential applications in various fields,such as catalysis, magnetism, nanotechnology, and medicine. In particular lacunarypolyoxotungstates of the Keggin and Wells–Dawson type acting as inorganic, polydentateligands can react with various transition metal ions, such as Co2+, Ni2+, Cu2+, Fe2+and so on.And then obtain a series of transition-metal-substituted polyoxometalates derivatives,inwhich the sandwich species are especially common.In this paper, we chose two kinds of lacunary polyoxometalates of the Keggin type asprecursors to react with Co2+and Ni2+respectively. By using conventional synthesis methods,we have succeeded in preparing two sandwich-type compounds. Also, the two compoundswere characterized by single-crystal X-ray diffraction (XRD), powder X-ray diffraction(PXRD), FT-IR spectroscopy, as well as thermogravimetric (TG).1、Selecting [A-α-GeW9O34]10-as precursor, using conventional synthesis methods, wesuccessfully synthesized a {Co4}-containing Weakley-Type POMs:Na12[Co4(H2O)2(B-α-GeW9O34)2]·27H2O (1)In the sandwich structure, the four Co atoms are in a common plane and form a regularrhombus. Furthermore, as the polyanion was forming, a configuration transformation of thePOM from A-type to B-type occurred. The polyanions are linked to a3-D structure viasodium cations.2、Selecting [A-α-PW9O34]9-as precursor, in conventional synthesis conditions, wesuccessfully synthesized a sandwich-type phosphotungstate with nonequivalent Kegginfragments in alkalescent condition:Na16[Na6(H2O)24{Ni3(H2O)(B-α-PW9O33(OH))(B-β-PW8O31)}2]·31H2O (2)Polyanion of compound2is composed of two{Ni3(H2O)(B-α-PW9O33(OH))(B-β-PW8O31)}11-subunits linked by six Na+ions. And eachsubunit consists of two asymmetric Keggin fragments,[B-α-PW9O33(OH)]8-and[B-β-PW8O31]9-held together via three Ni2+ions. The adjacent sandwich polyanions arelinked to a1-D chain architecture via sodium cations.