ABSTRACT
An acetate-bridged Ru-substituted arsenotungstate [H2 N(CH3 )2 ]14 [As4 W40 O140 {Ru2 (CH3 COO)}2 ]â 22 H2 O (1) has been synthesized and structurally characterized. Four Ru atoms occupy the respective lacunary S2 sites of the crown-shaped polyanion [As4 W40 O140 ]28- , and each Ru atom is coordinated by one As atom and five µ2 -O atoms, comprising four from the S2 site and one from the acetate ligand. To the best of our knowledge, this coordination of the Ru atom, with an Ru-As bond length of 2.377(3)-2.387(3)â Å, is unprecedented in polyoxometalate (POM) chemistry. Notably, 1 exhibits high efficiency, excellent selectivity, and good recyclability for the oxidation of sulfides with hydrogen peroxide (H2 O2 ). Catalytic oxidation of various sulfides in the presence of 1 gives superior conversion and selectivity for sulfones in acetonitrile, whereas sulfoxides are obtained in methanol.
ABSTRACT
A novel class of organophosphonate-based polyoxomolybdate derivatives, K4H5[Ln3(H2O)14{(Mo8O24)(O3PCH2COO)3}2]·23H2O (Ln = Gd (1Gd), Tb (2Tb), Dy (3Dy)), have been fully investigated by a few characterization methods such as single-crystal X-ray crystallography, XRPD, elemental analysis, TGA, and IR spectra. The magnetic properties of 1Gd, 2Tb, and 3Dy were investigated, as well as the solid-state luminescence properties of 2Tb and 3Dy. The catalysis properties of 1Gd, 2Tb, and 3Dy for thioether oxidization have been investigated using hydrogen peroxide (H2O2) as an oxidant. The catalysis study demonstrated the efficient and selective conversion of various thioethers to their corresponding sulfones in excellent yields.
ABSTRACT
The high-nuclearity polyoxovanadate-based carboxylate derivative K6H[VV17VIV12(OH)4O60(OOC(CH2)4COO)8]·nH2O (1) has been successfully synthesized by conventional aqueous methods and structurally characterized. The [VV17VIV12(OH)4O60(OOC(CH2)4COO)8]7- polyanion is built up from three cages: one {VV17(OH)4O44} cage and two identical [(VIV3O6)2(OOC(CH2)4COO)4]8- cages. Of the three cages, the {VV17(OH)4O44} is a purely inorganic polyoxovanadate cluster, whereas each of the [(VIV3O6)2(OOC(CH2)4COO)4]8- cages is a vanadium-based organic-inorganic hybrid cluster framed via four adipate ligands linking simultaneously to two triangular {V3} units. The two [(VIV3O6)2(OOC(CH2)4COO)4]8- cages are covalently attached to the central {VV17(OH)4O44} cage via V-O-V bonds in a linear arrangement, resulting in a {V29}-based hybrid cluster skeleton. The catalytic properties of compound 1 for the oxidation of sulfides by tert-butyl hydroperoxide were investigated, and the result indicates that 1 exhibits excellent catalytic activity for the oxidation of sulfides under mild conditions.
ABSTRACT
A monomeric tricobalt(II)-substituted phosphotungstate polyanion, [H9P2W15O62Co3]9-, is stabilized by the attachement of an organometallic group, {Mn(CO)3}, for the first time. The resulting polyoxometalate-supported [Mn(CO)3]+ complex (1) can be used as an efficient catalyst in the cycloaddition of CO2 with epoxides under mild reaction conditions with pyrrolidinium bromide as a cocatalyst. Besides, magnetic measurements show that the compound exhibits weaker ferromagnetic interactions at low temperature.
ABSTRACT
A new polytungstoarsenate, K6LiH6[Ce4(H2O)14(pzdc)(H2pzdc)As3W29O103]·22H2O (1) (H2pzdc = 2,3-pyrazinedicarboxylic acid), was synthesized via a conventional aqueous solution method. In this synthetic approach, the organic ligand pyrazine dicarboxylate acid was introduced into the arsenotungstate system. The synthesized compound 1 was well characterized using elemental analysis, IR spectroscopy, UV-vis spectroscopy, thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction. The catalytic activity of compound 1 was tested in acetonitrile to oxidize organosulfur compounds (benzothiophene (BT) and dibenzothiophene (DBT)) with hydrogen peroxide as an oxidant at room temperature. Two substrates were oxidized to their corresponding sulfones with high conversion and selectivity. Taking advantage of this remarkable catalytic move, the 1/H2O2/CH3CN system was further utilized in the oxidation of model fuels (MF) including a mixture of BT and DBT in octane. As a result, the organosulfur compounds in the model fuels were fully converted into their corresponding sulfones. Furthermore, the fluorescence properties of 1 were also investigated.
ABSTRACT
A Sb-containing Anderson-based polyoxomolybdate cluster, [(CH3)4N]4H8[Na5Sb3(Sb2Mo12O57)]·17H2O [1; (CH3)4N+ = TMA+], has been successfully synthesized by using an aqueous solution method and structurally characterized. In particular, UV-Vis spectroscopy has been employed to elucidate the stability of the polyoxoanions. Under mild conditions, the catalyst demonstrates high activity and selectivity for the sulfoxidation of various sulfides in the presence of hydrogen peroxide. For example, thioanisole undergoes up to 100% conversion and 100% sulfone selectivity at 25 °C in aqueous solution.
ABSTRACT
A series of new lanthanide-containing peroxoisopolyoxotungstates, K6Na4[H32{Ln4(WO4)(H2O)16[W7O22(O2)2]4}3]·105H2O [Ln = CeIII (1), NdIII (2), SmIII (3), TbIII (4), ErIII (5)], have been successfully synthesized and structurally characterized. All polyanions [Ln(WO4)(H2O)16{W7O22(O2)2}4]14- are isostructural and consist of a central [Ln(WO4)(H2O)16]10+ cluster surrounded by four peripheral [W7O22(O2)2]6- units. They could act as efficient recyclable catalysts for the epoxidation of various alkenes including different cycloalkenes, styrene derivatives, internal and long-chain alkenes. Under optimal conditions, catalyst 2 displays the best catalytic activity for the oxidation of cyclooctene with high cyclooctene conversion (98.3%) and excellent selectivity (up to 99%) and could be reused for three cycles with a negligible decrease in reactivity.