ChemInform Abstract: CRYSTAL STRUCTURE OF SODIUM NIOBATE (NA7)(H3O)NB6O19.14H2O

Goiffon, A.; Philippot, E.; Maurin, M.

doi:10.1002/chin.198123004

Cited by 24 publications

(45 citation statements)

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“…[8] However, under similar conditions, these oxoanion precursors in Nb and Nboxo chemistry are not available and are mainly dominated by the Lindqvist-type anion [Nb 6 O 19 ] 8À . [9] Although hexaniobates, one of which was first structurally characterized in 1980 as a monoprotonated cluster [HNb 6 O 19 ] 7À , [10] act as a cornerstone for the advancement of polyoxoniobate chemistry, they are very stable and possess lower reaction activity with paramagnetic transition-metal cations or transition-Abstract: Rational self-assembly of hexaniobate Lindqvist-type precursor [HNb 6 O 19 ] 7À with soluble Cu 2 + salts utilizing different strategies produces a series of giant polyniobate clusters, namely, (H 2 en) 1.25 [Cu(en) 19 ] 6À in the holes, whereas 3 and 4 represent an unprecedented giant cube-shaped framework. All the compounds are built from [Nb 7 O 22 ] 9À fundamental building blocks.…”

Section: Introductionmentioning

confidence: 99%

Giant Polyniobate Clusters Based on [Nb₇O₂₂]⁹⁻ Units Derived from a Nb₆O₁₉ Precursor

Niu

et al. 2007

Chemistry A European J

197

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Rational self-assembly of hexaniobate Lindqvist-type precursor [HNb6O19]7- with soluble Cu2+ salts utilizing different strategies produces a series of giant polyniobate clusters, namely, (H2en)1.25[Cu(en)2(H2O)]2Cl4[Nb24O72H21.5]7 H2O (1; en: ethylenediamine), [Cu(en)2]3[Cu(en)2(H2O)]9[{H2Nb6O19} subset{[({KNb24O72H10.25}{Cu(en)2})2{Cu3(en)3(H2O)3}{Na1.5Cu1.5(H2O)8}{Cu(en)2}4]6}]144 H2O (2), K12Na4[H23NaO8Cu24(Nb7O22)8]106 H2O (3), and K16Na12[H9Cu25.5O8(Nb7O22)8] 73.5 H2O (4). Their structures were determined and further characterized by single-crystal X-ray diffraction analysis, IR and Raman spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Structural analyses reveal that compound 2 comprises a giant capsule anion based on a wheel-shaped cluster encapsulating a Lindqvist diprotonated cluster [H2Nb6O19]6- unit, and forms a honeycomb-like structure with the inclusion of Lindqvist-type anions [H2Nb6O19]6- in the holes, whereas 3 and 4 represent an unprecedented giant cube-shaped framework. All the compounds are built from [Nb7O22]9- fundamental building blocks. Solution Raman spectroscopy studies of 2 and 3 reveal that the solid-state structures of these polyniobate cluster anions disassemble and exist in the form of the [Nb6O19]8- unit in solution. Magnetic susceptibility measurement of 3 shows antiferromagnetic coupling interactions between CuII ions with the spin-canting phenomenon.

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Section: Introductionmentioning

confidence: 99%

Giant Polyniobate Clusters Based on [Nb₇O₂₂]⁹⁻ Units Derived from a Nb₆O₁₉ Precursor

Niu

et al. 2007

Chemistry A European J

197

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“…The general differences between synthesis of heteropolyniobates and synthesis of heteropolymolybdates and heteropolytungstates have been discussed in detail previously. [13] The hydrothermal formation of Na 16 [15] is precipitated. After 2 h, a clear solution is observed with all solids dissolved, and 3 h results in the Nb Keggin ion salt as the only crystalline phase.…”

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confidence: 99%

“…In conjunction with the extensive binding between the Na cations and the anionic cluster in the solid state, this crystal lattice contains remarkably few water molecules: only four water molecules per cluster, or 0.25 per Na cation. Normally, lattices of the Nbbased polyoxometalate salts, [13,15,[22][23][24] as well as those of the polyoxotungstates and polyoxomolybdates, [1] carry 15-50+ water molecules per cluster that both solvate the chargebalancing cations and hydrogen bond to the oxygen atoms of the cluster. This unusual feature of strong binding between the sodium atoms and the anionic Keggin clusters observed here is likely to be related to stabilization of the high surface charge of the clusters.…”

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confidence: 99%

“…Solution 23 Na NMR spectroscopy provided further evidence for this solution behavior of the Nb Keggin ions. The 23 Na NMR spectra of three different solution concentrations of 1, and the same three solution concentrations of Na 7 [15] normalized to sodium concentration were analyzed (see Table 2). The hexaniobate Lindqvist ion was used for comparison because it has a similar Na:Nb ratio as 1, an equal negative charge per NbO 6 octahedron (À1.33), and similar solution pH to concentration correlation.…”

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confidence: 99%

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[SiNb₁₂O₄₀]¹⁶⁻ and [GeNb₁₂O₄₀]¹⁶⁻: Highly Charged Keggin Ions with Sticky Surfaces

et al. 2004

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Heteropolyanions are negatively charged clusters of cornersharing and edge-sharing early transition-metal MO 6 octahedra and heteroatom XO 4 tetrahedra, in which the tetrahedra are usually located in the interior of the cluster.[1] The geometry, composition, and charge of these clusters are varied through synthesis parameters, and cluster properties are highly tunable as a function of these characteristics. Heteropolyanions have been employed in a range of applications that include virus-binding inorganic drugs, [2] homogeneous and heterogeneous catalysts, [3,4] electro-optic and electrochromic materials, [5,6] metal and protein binding, [7] and as building blocks for nanostructuring of materials.[8] The aKeggin geometry, which was first structurally characterized in 1933 by J. F. Keggin [9] for the phosphotungstic acid (H 3 PW 12 O 40 ) is one of the most widely recognized and thoroughly studied heteropolyanion geometries.[10] Following Keggin's initial discovery, solid-state and solution chemistries of the heteropolytungstates and heteropolymolybdates (i.e., H 4 SiMo 12 O 40 ) with the Keggin geometry have been well developed. These Keggin ions have been synthesized with a variety of atoms in the XO 4 tetrahedral site, numerous addenda atom substitutions in the MO 6 octahedral sites, as acids, and as salt compounds with a range of counter cations. [11,12] Given the apparent ubiquity of the Keggin geometry, it is not surprising that the first-observed heteropolyniobate (reported Nyman et al. in 2002 [13] ) was a Keggin ion. However, we first identified [13] O 2 are chemically quite different from the related heteropolymolybdate and heteropolytungstate Keggin ions in their synthetic approach, their pH stability, and their charge. The Nb Keggin ions are synthesized and stable in basic solutions (pH 7-12.5) and decompose in acidic solutions, whereas the Mo and W Keggin ions are synthesized and stable in acidic solutions (pH % 1-3) and decompose in more basic solutions. The Nb Keggin ions are synthesized hydrothermally at 190 8C from amorphous, hydrous niobium oxide and alkoxides of germanium or silicon, whereas the Mo and W Keggin ions are generally precipitated at room temperature from tungstic or molybdic acid or alkali precursors. Use of sodium silicate or sodium germanate as precursors rather than the alkoxides results in mixtures that contain the heteropolyniobate only as a minor phase, with poorly crystalline sodium niobates [14] as the major phase. The general differences between synthesis of heteropolyniobates and synthesis of heteropolymolybdates and heteropolytungstates have been discussed in detail previously. [13] The hydrothermal formation of Na 16

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“…These two peaks were refined and found to correspond to a niobium occupancy of approximately 2 %, which equals less , that is, they are somewhat longer than those found in the other two ions, but similar to those found in hexaniobate. [9] The niobyl oxygen atoms in hexaniobate are difficult to protonate, which may also be true in 1.…”

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confidence: 98%

The [Ti₁₂Nb₆O₄₄]¹⁰⁻ Ion—A New Type of Polyoxometalate Structure

et al. 2008

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Titanates and niobates are among the most promising materials to catalyze the photolysis of water to yield molecular hydrogen and oxygen.[1] Solid-phase titanoniobate species, such as MTiNbO 5 (M = H, Li, K), have been attracting significant interest, but to our knowledge only one discrete homoleptic polyoxotitanoniobate cluster has so far been described, the cluster Na 8 [Ti 2 Nb 8 O 28 ].[2] Herein we describe a second discrete homoleptic polyoxotitanoniobate cluster and a whole new class of polyoxometalates [11] Figure 1)The orthogonal crystals of 1 were twinned, and exhibited dichroism under a polarizing microscope, making them easy to isolate. The crystals are readily soluble in water, and ESI-MS investigations of the stability of 1 show that it does not dissociate in neutral aqueous solutions, but remains stable for at least five days at room temperature. ESI-MS also confirms the assigned stoichiometry of the anion (see the Supporting Information [4] and decaniobate [5,6] unit. This makes the overall structure hexagonal, so that 1 is a kind of "super-Lindqvist" ion. The decatungstate ion [W 10 O 32 ] 4À has a similar but simpler arrangement, in which two [W 5 2+ fragments are connected through four m 2 -O bridges, also yielding a central cavity. [7] In 1, the cavity measures about 4.3 across, and appears to be essentially vacant. X-ray diffraction data allowed for calculating the maximum occupancy for different potential guest atoms-two of the top four peaks, both representing approximately 1.4 e À , in the final difference Fourier map were found to lie on special positions at the center of the complex. These two peaks were refined and found to correspond to a niobium occupancy of approximately 2 %, which equals less

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ChemInform Abstract: CRYSTAL STRUCTURE OF SODIUM NIOBATE (NA7)(H3O)NB6O19.14H2O

Abstract: Die Titelverbindung kristallisiert in der Raumgruppe Pmnn mit Z=2.

Cited by 24 publications

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Giant Polyniobate Clusters Based on [Nb₇O₂₂]⁹⁻ Units Derived from a Nb₆O₁₉ Precursor

Giant Polyniobate Clusters Based on [Nb₇O₂₂]⁹⁻ Units Derived from a Nb₆O₁₉ Precursor

[SiNb₁₂O₄₀]¹⁶⁻ and [GeNb₁₂O₄₀]¹⁶⁻: Highly Charged Keggin Ions with Sticky Surfaces

The [Ti₁₂Nb₆O₄₄]¹⁰⁻ Ion—A New Type of Polyoxometalate Structure

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ChemInform Abstract: CRYSTAL STRUCTURE OF SODIUM NIOBATE (NA7)(H3O)NB6O19.14H2O

Abstract: Die Titelverbindung kristallisiert in der Raumgruppe Pmnn mit Z=2.

Cited by 24 publications

References 0 publications

Giant Polyniobate Clusters Based on [Nb7O22]9− Units Derived from a Nb6O19 Precursor

Giant Polyniobate Clusters Based on [Nb7O22]9− Units Derived from a Nb6O19 Precursor

[SiNb12O40]16− and [GeNb12O40]16−: Highly Charged Keggin Ions with Sticky Surfaces

The [Ti12Nb6O44]10− Ion—A New Type of Polyoxometalate Structure

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Giant Polyniobate Clusters Based on [Nb₇O₂₂]⁹⁻ Units Derived from a Nb₆O₁₉ Precursor

Giant Polyniobate Clusters Based on [Nb₇O₂₂]⁹⁻ Units Derived from a Nb₆O₁₉ Precursor

[SiNb₁₂O₄₀]¹⁶⁻ and [GeNb₁₂O₄₀]¹⁶⁻: Highly Charged Keggin Ions with Sticky Surfaces

The [Ti₁₂Nb₆O₄₄]¹⁰⁻ Ion—A New Type of Polyoxometalate Structure