Limits...
Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction.

Fortes AD - Acta Crystallogr E Crystallogr Commun (2015)

Bottom Line: Asian J.Acta Cryst.E63, i142] is in fact an ordinary two-centred 'linear' hydrogen bond.

View Article: PubMed Central - HTML - PubMed

Affiliation: ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, England ; Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, England ; Department of Earth and Planetary Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, England.

ABSTRACT
Time-of-flight neutron powder diffraction data have been measured from ∼90 mol% deuterated isotopologues of Na2MoO4·2H2O and Na2WO4·2H2O at 295 K to a resolution of sin (θ)/λ = 0.77 Å(-1). The use of neutrons has allowed refinement of structural parameters with a precision that varies by a factor of two from the heaviest to the lightest atoms; this contrasts with the X-ray based refinements where precision may be > 20× poorer for O atoms in the presence of atoms such as Mo and W. The accuracy and precision of inter-atomic distances and angles are in excellent agreement with recent X-ray single-crystal structure refinements whilst also completing our view of the hydrogen-bond geometry to the same degree of statistical certainty. The two structures are isotypic, space-group Pbca, with all atoms occupying general positions, being comprised of edge- and corner-sharing NaO5 and NaO6 polyhedra that form layers parallel with (010) inter-leaved with planes of XO4 (X = Mo, W) tetra-hedra that are linked by chains of water mol-ecules along [100] and [001]. The complete structure is identical with the previously described molybdate [Capitelli et al. (2006 ▸). Asian J. Chem. 18, 2856-2860] but shows that the purported three-centred inter-action involving one of the water mol-ecules in the tungstate [Farrugia (2007 ▸). Acta Cryst. E63, i142] is in fact an ordinary two-centred 'linear' hydrogen bond.

No MeSH data available.


(a) View down the b axis of the network of water-linked tetra­hedral oxyanions; chains linked by O5 extend along [001] whereas crosslinkages through O6 are staggered along [100]. (b) View of the same structure along the c axis. Ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) 1 − x,  + y,  − z; (iii)  + x,  − y, 1 − z; (iv)  + x, y,  − z; (v) x,  − y, − + z; (vi) x,  − y,  + z.]
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4518980&req=5

fig3: (a) View down the b axis of the network of water-linked tetra­hedral oxyanions; chains linked by O5 extend along [001] whereas crosslinkages through O6 are staggered along [100]. (b) View of the same structure along the c axis. Ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) 1 − x,  + y,  − z; (iii)  + x,  − y, 1 − z; (iv)  + x, y,  − z; (v) x,  − y, − + z; (vi) x,  − y,  + z.]

Mentions: Although it is more usual to find Na+ in octa­hedral coordination, there are abundant examples of Na+ in five-fold coordination, including instances where the NaO5 polyhedron adopts a square-pyramidal arrangement (Beurskens & Jeffrey, 1961 ▸; Císařová; et al., 2001 ▸; Sharma et al., 2005 ▸; Smith & Wermuth, 2014 ▸; Aksenov et al., 2014 ▸) or the alternative trigonal-bipyramidal arrangement (Mereiter, 2013 ▸; Smith, 2013 ▸). A similar combination of NaO6 and NaO5 polyhedra to that found in the title compounds occurs in the closely-related hydrates Na2CrO4·1.5H2O and Na2SeO4·1.5H2O (Kahlenberg, 2012 ▸; Weil & Bonneau, 2014 ▸). The two water mol­ecules form hydrogen-bonded chains between the O1 and O4 atoms of the tetra­hedral oxyanions; O5-related chains extend along [001] and O6-related chains crosslink them in a staggered fashion along [100]. Fig. 3 ▸(a) and 3(b) depict the spatial relationship between this ‘net’ of water linked tetra­hedra and the adjacent ‘slab’ of corner-linked Na—O polyhedral clusters. The layers shown in Fig. 3 ▸(b) alternate to create the three-dimensional structure and are no doubt responsible for the macro-scale platy habit of the crystals.


Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction.

Fortes AD - Acta Crystallogr E Crystallogr Commun (2015)

(a) View down the b axis of the network of water-linked tetra­hedral oxyanions; chains linked by O5 extend along [001] whereas crosslinkages through O6 are staggered along [100]. (b) View of the same structure along the c axis. Ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) 1 − x,  + y,  − z; (iii)  + x,  − y, 1 − z; (iv)  + x, y,  − z; (v) x,  − y, − + z; (vi) x,  − y,  + z.]
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4518980&req=5

fig3: (a) View down the b axis of the network of water-linked tetra­hedral oxyanions; chains linked by O5 extend along [001] whereas crosslinkages through O6 are staggered along [100]. (b) View of the same structure along the c axis. Ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) 1 − x, 1 − y, 1 − z; (ii) 1 − x,  + y,  − z; (iii)  + x,  − y, 1 − z; (iv)  + x, y,  − z; (v) x,  − y, − + z; (vi) x,  − y,  + z.]
Mentions: Although it is more usual to find Na+ in octa­hedral coordination, there are abundant examples of Na+ in five-fold coordination, including instances where the NaO5 polyhedron adopts a square-pyramidal arrangement (Beurskens & Jeffrey, 1961 ▸; Císařová; et al., 2001 ▸; Sharma et al., 2005 ▸; Smith & Wermuth, 2014 ▸; Aksenov et al., 2014 ▸) or the alternative trigonal-bipyramidal arrangement (Mereiter, 2013 ▸; Smith, 2013 ▸). A similar combination of NaO6 and NaO5 polyhedra to that found in the title compounds occurs in the closely-related hydrates Na2CrO4·1.5H2O and Na2SeO4·1.5H2O (Kahlenberg, 2012 ▸; Weil & Bonneau, 2014 ▸). The two water mol­ecules form hydrogen-bonded chains between the O1 and O4 atoms of the tetra­hedral oxyanions; O5-related chains extend along [001] and O6-related chains crosslink them in a staggered fashion along [100]. Fig. 3 ▸(a) and 3(b) depict the spatial relationship between this ‘net’ of water linked tetra­hedra and the adjacent ‘slab’ of corner-linked Na—O polyhedral clusters. The layers shown in Fig. 3 ▸(b) alternate to create the three-dimensional structure and are no doubt responsible for the macro-scale platy habit of the crystals.

Bottom Line: Asian J.Acta Cryst.E63, i142] is in fact an ordinary two-centred 'linear' hydrogen bond.

View Article: PubMed Central - HTML - PubMed

Affiliation: ISIS Facility, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, England ; Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, England ; Department of Earth and Planetary Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, England.

ABSTRACT
Time-of-flight neutron powder diffraction data have been measured from ∼90 mol% deuterated isotopologues of Na2MoO4·2H2O and Na2WO4·2H2O at 295 K to a resolution of sin (θ)/λ = 0.77 Å(-1). The use of neutrons has allowed refinement of structural parameters with a precision that varies by a factor of two from the heaviest to the lightest atoms; this contrasts with the X-ray based refinements where precision may be > 20× poorer for O atoms in the presence of atoms such as Mo and W. The accuracy and precision of inter-atomic distances and angles are in excellent agreement with recent X-ray single-crystal structure refinements whilst also completing our view of the hydrogen-bond geometry to the same degree of statistical certainty. The two structures are isotypic, space-group Pbca, with all atoms occupying general positions, being comprised of edge- and corner-sharing NaO5 and NaO6 polyhedra that form layers parallel with (010) inter-leaved with planes of XO4 (X = Mo, W) tetra-hedra that are linked by chains of water mol-ecules along [100] and [001]. The complete structure is identical with the previously described molybdate [Capitelli et al. (2006 ▸). Asian J. Chem. 18, 2856-2860] but shows that the purported three-centred inter-action involving one of the water mol-ecules in the tungstate [Farrugia (2007 ▸). Acta Cryst. E63, i142] is in fact an ordinary two-centred 'linear' hydrogen bond.

No MeSH data available.