Die Kristallstruktur des Ammoniumparawolframat-tetrahydrats (NH4)10[H2W12O42]·4H2O*

d’Amour, H.; Allmann, R.

doi:10.1524/zkri.1972.136.1-2.23

Cited by 33 publications

(22 citation statements)

References 6 publications

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“…The nonacid H atoms are bonded to the two central oxygen atoms O123 (Fig. 1 b) as predicted by D'Amour and Allmann [13]. According to the neutron diffraction study, the distance between the two H atoms in the polyanion is 2.14 A Ê which is consistent with the value of 2.22 A Ê found from NMR measurements [8,9] .…”

Section: Introductionsupporting

confidence: 85%

“…For reasons of clarity, no other atoms were included. The chosen perspective allows direct comparison with the representations for APT´4 H 2 O [13] and APT´10 H 2 O [7]. The polyhedral models in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…According to the X-ray structure analyses of APT´10 H 2 O [13] and APT´4 H 2 O [7], there are some favorable positions for the coordination of cations in the fragment of the hexagonal closest packing built up by 42 oxide ions. The`niche' formed by O4±O14±O36±O60 is especially appropriate (cf.…”

Section: Discussionmentioning

confidence: 99%

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Formation of Heterotypic Substitutional Solid Solutions (NH4)10-xKx[H2W12O42] · n H2O in the Ammonium Paratungstate ‘Z'/Potassium Paratungstate ‘Z' System

Lunk

Fait

Ziemer

et al. 1999

Z. anorg. allg. Chem.

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Section: Introductionsupporting

confidence: 85%

Section: Resultsmentioning

confidence: 99%

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Formation of Heterotypic Substitutional Solid Solutions (NH4)10-xKx[H2W12O42] · n H2O in the Ammonium Paratungstate ‘Z'/Potassium Paratungstate ‘Z' System

Lunk

Fait

Ziemer

et al. 1999

Z. anorg. allg. Chem.

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“…Since Souchay (1943) applied various spectroscopic and spectrometric methods to the system H+-WO] -, a number of isopolytungstate anions have been revealed. Only for a few species, however, have the structures been determined: paradodecatungstate [H2W~2042] ~°- (Allmann, 1971;d'Amour & Allmann, 1972,1973Tsay & Silverton, 1973;Evans & Rollins, 1976;Averbuch-Pouchot, Tordjman, Durif & Guitel, 1979), decatungstate [ W 10032 ]4- (Fuchs, Hartl, Schiller & Gerlach, 1976), and hexatungstate [W60~9] 2- (Fuchs, Freiwald & Hartl, 1978). The structure of [H2WI2040I 6-has been reported to be the Keggin (1934) type by X-ray powder patterns (Signer & Gross, 1934) and the presence of two non-labile protons in the central cavity of the molecule has been shown by NMR spectra in D20 (Pope & Varga, 1966).…”

mentioning

confidence: 99%

The structure of hexakis(tetramethylammonium) dihydrogendodecatungstate enneahydrate, [(CH3)4N]6[H2W12O40].9H2O

Asami¹,

Ichida²,

Sasaki³

1984

Acta Crystallogr C

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Abstract. M r = 3455.2, monoclinic, P21, a -----13. 122 (2), b= 21.457 (4), c= 13.223 (1)A, fl= 91.71(1) °, V=3721 (1)A 3, Z=2, Dm=3.11, D x =-3.09 Mg m -3, Mo Ka, /l = 0.71069 A, p = 19.7 mm -~, F(000) = 1559, T= 293 K, R = 0-085 for 6585 independent reflexions. The metadodecatungstate anion consists of four tetrahedrally corner-shared W3013 units made by edge-sharing WO 6, and is therefore confirmed to be the Keggin type. The molecule has T d symmetry and its framework is regarded as a regular cubo-octahedron. The average W-W distance is 3.33 (1)A within the same W30~3 unit and 3.63 (2)A, otherwise. The W-O bond lengths, formally classified into four types, are 1.71 (4), 1.91 (5), 1.96 (9) and 2.22 (9) A. The O atoms forming the tetrahedral cavity are 2.95 (6) A distant from one another, suggesting that the cavity is capable of containing two non-acidic H atoms.

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“…Accordingly, it has been proposed that a major reason for the existence (stability) of polyoxometalate ions is the ability of the corresponding elements to form Mn+-o bonds of bond order two so that the oxygen atom has little or no basic character and that the Mn+-o n-bonds are relatively localized [la, 2, 4a]. From the sum of the bond valences ("bond strengths") 1 about the oxygen atoms in several isopolyoxometalate ions [8][9][10][11][12][13], the present author [14a, 15a] concluded, contrary to the above proposal, that the ionic charge is mainly distributed over the terminal oxygen atoms which, therefore, are the most basic oxygen atoms of a polyoxometalate structure. This is in line with -the observation that the cations in polyoxometalates are in contact mainly with the terminal oxygen atoms of the polyanions [8][9][10][11][12][13][16][17][18][19], -the assumption that in ion pairs (i.e., in solution) the cations are in contact with terminal oxygen atoms of the polyanions [10,11,20], and -the view that terminal oxygen atoms behave as if they are bigger than the other oxygen atoms [21] or make available more space to the unshared electron pairs in which the charge electrons are merged in [14a, 22a].…”

Section: Introductionmentioning

confidence: 99%

A bond model for polyoxometalate ions composed of MO6 octahedra (MOk polyhedra with k>4)

Tytko¹

Structure and Bonding

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The literature relating to the bonding in polyoxometalate ions is reviewed. The author's opinions are presented and expanded to give a bond model for polyoxometalate ions of the early transition elements (groups V and VI) composed of MO 6 octahedra (MOk polyhedra with k > 4). This bond model concerns in particular the bond valence (bond lengths) and charge distribution in the polyoxometalate ions and the factors modifying them. It is based on the following commonly used concepts and principles as applied to polyoxometalate ions: -Lewis's octet rule, extended to the decet and dodecet rule for M v and MVI; -prc-drc M----O double bond and the coordinate bond (dative bond); -the resonance concept; -the resonance bond number (or the bond valence concept and the valence sum rule); -polydentate ligands and the chelate effect; -the larger space requirements of unshared electron pairs (cf. the VSEPR model); -the model of multicenter prc-drc multiple bonds for certain #-oxo bridges between metal atoms; -Bronsted's acid/base concept and acid/base equilibria; -Pauling's rules for the acid/base strength of (monomeric) oxoacids/oxoanions; -the law of mass action (Le Chatelier's principle), and others. The result is a set of resonance structures for polyoxometalate species in which three types of resonance can be distinguished. These, in turn, explain: -the cohesion of the strongly distorted tetrahedral M04 building units in the structures by formation of MO 6 octahedra and hence the enhanced stability of the polyoxometalate ions; -the distribution of the formal ionic charge over (nearly) all types of oxygen atoms, but preferably the terminal ones; -the occurrence of positively charged oxygen atoms, caused by charge separation processes; -the enhanced basicity of polyoxometalate ions; and further features. A "meshing effect" defines the increase of the bond valence in inner (bridging) M-O bonds and hence the stabilization of the structures due to extension of the coordination spheres of MO4 tetrahedra. Thus, the bond lengths of the different structure types are governed by a maximization of the bond valence of the inner, bridging (or minimization of the bond valence of the outer, terminal, in contrast to frequent statements in the literature) M-O bonds. The limits of the maximization of the inner bond valences of the polyoxometalate ions are determined -by minimum stoichiometric requirements for corresponding resonance formulae (inevitability of charge on bridging oxygen atoms); -by the necessity to fulfill simultaneously the geometrical relationships of the M-O bond lengths (as defined by their interdependence in the M-O frameworks) and the valence

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Die Kristallstruktur des Ammoniumparawolframat-tetrahydrats (NH₄)₁₀[H₂W₁₂O₄₂]·4H₂O*

Cited by 33 publications

References 6 publications

Formation of Heterotypic Substitutional Solid Solutions (NH4)10-xKx[H2W12O42] · n H2O in the Ammonium Paratungstate ‘Z'/Potassium Paratungstate ‘Z' System

Formation of Heterotypic Substitutional Solid Solutions (NH4)10-xKx[H2W12O42] · n H2O in the Ammonium Paratungstate ‘Z'/Potassium Paratungstate ‘Z' System

The structure of hexakis(tetramethylammonium) dihydrogendodecatungstate enneahydrate, [(CH3)4N]6[H2W12O40].9H2O

A bond model for polyoxometalate ions composed of MO6 octahedra (MOk polyhedra with k>4)

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