Hydrothermal Synthesis, Structure And Characteration Of Novel Tungsten-Oxo Clusters

The research work of this thesis is based on the synthesis method of the reactionsystems containing lacunary fragments precursors by means of the hydrothermal techniqueand the synthetic consideration of lacunary sites of lacunary tungsten-oxo clusters asstructure-directing agents to induce the formation of cluster aggregation, resulting in theformation of novel metal substitued-ed POMs which were initiated by our group. In thiswork, we have successfully extent the reaction systems containing kacunary fragments forKeggin-type to Preyssler-type under hydrothermal conditions. Moreover, we introduce thestrategy to lther metal like Ln3+and Cr3+. After numerous experiments, we almost masteredthe law of transformation of different precursors unnder hydrothermal conditions, andsuccessfully synthesized twelve novel metal-substituted POMs, and characterized bysingle-crystal X-ray diffraction, Infrared spectra, elements analysis and powder X-raydiffraction, also their thermal stabilities have been investigated. The successful syntheses ofthese twelve novel compounds not only enruch the structural type of POMs chemistry, butalso provide new routes for the development of tungsten-oxo cluster chemistry.{P5W30}-based tungsten-oxo cluster: KNa7[{Sm6Mn(μ-H2O)2(OCH2COO)7(H2O)18}{Na(H2O)P5W30O110}]·22H2O (3-1), K4[{Sm4Cu2(gly)2(ox)(H2O)24}-{NaP5W30O110}]Cl2·25H2O (3-2), Na7[Ce2(H2O)14{Na(H2O)HP5W30O110}]·22H2O (3-3),Na5[Ce4(H2O)21(2-pca)3{Na(H2O)P5W30O110}]·10H2O (3-4), Na2[Tb4(H2O)28{Na(H2O)P5-W30O110}]·19H2O (3-5) and Na2K2[Cu4(en)4(μ3-O)3(μ-H2O)][Cu(en)2]4{Na(H2O)P5W30-O110}·16H2O (3-6). Compound3-1and3-2not only represent the first {P5W30}-basedTM–Ln heterometllic polyoxometalates, but also the first3-D frameworks consisting of{P5W30} subunits and TM/Ln–carboxylate–Ln connectors. Moreover, for3-1, the drum-shapedPreysseler {P5W30} anion acts as a13-dentate inorganic ligand here reported represents thehighest coordinated polyanion to date. Compound3-3and3-4are1D chain built by {P5W30}anion and Ce3+cations. Compound3-5displays2D layer built by {P5W30} anion and Tb3+cations. Compound3-6is2D layer built by {P5W30} anion and Cu complex bridges butalso the rarely saturated POT connected by {Cu4} clusters.Co-substituted tungsten-oxo cluster:(H2TED)2Cs4[Co4(H2O)2(B-α-HPW9O34)2]·28H2O (4-1),(H2en)9[Co4(H2O)2(PW9O34)2]- {[Co(H2O)4][Co4(H2O)2(PW9O34)2]}·20H2O (4-2) and (H2en)5[Co4(H2O)2(H3GeW9O34)2]-{[Co(H2O)4]2[Co4(H2O)2(H2GeW9O34)2]}·16H2O (4-3). Compound4-1reveals that thetetra-CoII substituted sandwich-type phosphotungstate units [Co4(H2O)2(B-a-PW9O34)2]10-are combined together by Cs+cations giving rise to the3D framework with the ‘‘sqc876’’3D net. Compound4-2and4-3contatin two Co4-substituted sandwich-type polyoxoanions.This type of a molecular unit containing double polyoxoanions is very rare. From theviewpoint of supramolecular chemistry, the sandwich-type polyoxoanions in4-2and4-3can bi further extended to3D frameworks via extensive hydrogen-bonding interactions.Cu-/Cr-substitued tungsten-oxo cluster:[Cu(en)2]{[Cu2(en)2(μ-1,1-N3)2(H2O)]2[Cu6(en)2(H2O)2(B-α-PW9O34)2]}·6H2O (5-1),Na0.5(C6N4H16)2[Cr4.5W1.5(OH)3(SiW9O34)2]·6H2O (5-2) and (C6N4H18)[Cr2(H2O)2(SiW10-O36)]·2H2O (5-3). Compound5-1displays a beautiful1D chain architecture constructedfrom sandwich-type[Cu2(en)2(μ-1,1-N3)2(H2O)]2[Cu6(en)2(H2O)2(B-α-PW9O34)2]2unitsand [Cu(en)2]2+linkers. To our knowledge,5-1represents the first hexa-CuIIsandwichedphosphotungstate with supporting Cu-azido complexes. Compound5-2is hexa-CrWsandwiched polyoxotungstate. Compound5-3is binuclear CrIIIsandiwiched Keggin-typepolyoxotungstate.