Syntheses, Crystal Structure And Properties Of Polyoxometalate Clusters With Dawson And Anderson Structures As Building Blocks

The polyoxometalate compounds supported by Dawson-type and Anderson polyanions as building blocks were successfully synthesized by the ambient-temperature aqueous solution (or mixed solvent) and water-bath refluxing methods by virtue of metal coordination ions as bridging ligands, and characterized by X-ray crystallography, spectroscopic, thermal, electrochemical properties.(1) Two new polyoxometalate compounds based on saturated Wells-Dawson polyoxoanions and alkaline earth metal derivatives, H2[Ca2(α-P2W18O62)(H2O)5]·7.5H2O (1) and H2[Ca2(α-P2W18O62)(H2O)5]·9H2O(2), have been successfully synthesized in aqueous solution. Both of them consist of one saturated Dawson unit [α-P2W18O62]6-. This unit connects with other adjacent units via W-O-Ca-O-W bridges constructing an infinite 3D framework.(2) A new polyoxometalate dimer based on lacunary Wells-Dawson anion and lanthanide cation, Na14[{Nd(H2O)3(α2-P2W17O61)}2]·17H2O(3), was isolated as a sodium salt under ambient conditions and characterized by IR, TG, X?ray single crystal structure analysis and electrochemistry. The Nd3+ ion is substituted for a [W=O]4+ unit in the"cap"site of the tungsten-oxygen framework of the parent Wells-Dawson ion.(3) [Nd(H2O)7Cr(OH)6Mo6O18]n·4nH2O(4), a new one-dimensional chainlike polyoxometalate, has been synthesized under ambient conditions and characterized by IR, TG and single crystal X-ray diffraction. Compound possesses a 1D polymer chain structure composed of [Cr(OH)6Mo6O18]3- as bidentate ligands, neodyminm cation linkers and crystal lattice water molecules.