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Acta Crystallogr Sect E Struct Rep Online. 2010 December 1; 66(Pt 12): m1581.
Published online 2010 November 17. doi:  10.1107/S1600536810046696
PMCID: PMC3011450

Hexaaqua­magnesium(II) bis­(pyridinium-2,6-dicarboxyl­ate)

Abstract

In the title compound, [Mg(H2O)6](C7H4NO4)2, a single six-coordinate Mg2+ cation (site symmetry 2/m) is bonded to six water mol­ecules in a distorted octa­hedral geometry. The crystal packing between the complex cation and the zwitterionic organic cation (m symmetry) is stabilized by inter­molecular O—H(...)O hydrogen bonds and weak inter­molecular C—H(...)O inter­actions.

Related literature

For background to proton-transfer compounds, see: Aghabozorg et al. (2008 [triangle]). For related structures, see: Aghabozorg et al. (2005 [triangle]); Grossel et al. (2006 [triangle]); Ptasiewicz-Bak & Leciejewicz (2003 [triangle]); Dale et al. (2003 [triangle]); Yang et al. (2005 [triangle]); Kariuki & Jones (1989 [triangle])

An external file that holds a picture, illustration, etc.
Object name is e-66-m1581-scheme1.jpg

Experimental

Crystal data

  • [Mg(H2O)6](C7H4NO4)2
  • M r = 464.63
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-m1581-efi1.jpg
  • a = 13.432 (3) Å
  • b = 11.108 (2) Å
  • c = 6.5845 (13) Å
  • β = 92.79 (3)°
  • V = 981.3 (3) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.17 mm−1
  • T = 298 K
  • 0.35 × 0.30 × 0.15 mm

Data collection

  • Stoe IPDS II diffractometer
  • Absorption correction: numerical (X-RED and X-SHAPE; Stoe & Cie, 2005 [triangle]) T min = 0.940, T max = 0.973
  • 5499 measured reflections
  • 1383 independent reflections
  • 1178 reflections with I > 2σ(I)
  • R int = 0.031

Refinement

  • R[F 2 > 2σ(F 2)] = 0.038
  • wR(F 2) = 0.095
  • S = 1.12
  • 1383 reflections
  • 94 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.33 e Å−3
  • Δρmin = −0.18 e Å−3

Data collection: X-AREA (Stoe & Cie, 2005 [triangle]); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 [triangle]); software used to prepare material for publication: WinGX (Farrugia, 1999 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, glolbal. DOI: 10.1107/S1600536810046696/jj2069sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810046696/jj2069Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

The authors are grateful to the Islamic Azad University, North Branch, for financial support of this work.

supplementary crystallographic information

Comment

Pyridine-2,6-dicarboxylic acid is commonly used as proton donor in proton transfer systems (Aghabozorg et al. 2008). It has been reported that the carboxylate groups are deprotonated and the pyridine ring is protonated in compounds containing pyridine-2,6-dicarboxylic acid( Aghabozorg et al. 2005; Grossel et al. 2006). In addition, the formation of a six-coordinated magnesium (II) ion by water molecules in aqueous solution in the presence of poly carboxylic acids has been observed (Dale et al. 2003; Ptasiewicz-Bak & Leciejewicz 2003; Yang et al. 2005). The structure of hexa-aquamagnesium(II) pyrazine-2,6-dicarboxylate, [Mg(H2O)6][pz-2,6-dc], has also been reported which exhibits hydrogen bonding between the cationic magnesium species and a pyrazine-2,6-dicarboxylate anion (Ptasiewicz-Bak & Leciejewicz 2003).

In the title compound, [Mg(H2O)6][pyH-2,6-dc]2, the cation is comprised of a six-coordinate MgII ion bound by water molecules in a distorted octahedral geometry. The dianion is comprised of a pyridine-2,6-dicarboxylic acid group (Fig. 1). Bond lengths and angles for Mg—O are in normal ranges. Crystal packing is stabilized by O—H···O intra and intermolecular hydrogen bonds and weak C—H···O intermolecular hydrogen bond interactions with the coordinated water molecules (Fig. 2). The pyridine ring in the dianion is protonated and the two carboxylic acid groups are deprotonated forming a proton transfer fragment.

Experimental

A solution of pyridine-2,6-dicarboxylic acid (pydcH2) (0.1671 g, 1 mmol) in ethanol (20 ml) was added to a solution of pyridazine (pydz) (0.072 ml, 1 mmol) in ethanol (8 ml) and stirred for 2 hrs. Then an aqueous solution of Mg(NO3)2.6H2O (0.1282 g, 0.5 mmol) was added to mixture of pydcH2-pydz and stirred for 1 h. 1 mL DMSO was then added to the mixture to clear the solution and stirred for more 2 hrs. Slow evaporation of the resulting solution gave colorless crystals of the title compound after three weeks which were suitable for X-ray analysis (decomposition > 260 °C).

Refinement

The hydrogen atoms from the water molecules and pyridinium group were found in a difference Fourier map and refined isotropically without restraint. The C—H protons of the aromatic ring were positioned geometrically and refined as riding atoms, with C–H = 0.93Å and Uiso(H) = 1.2Ueq(C).

Figures

Fig. 1.
The molecular structure of [Mg(H2O)6][pyH-2,6-dc]2 with displacement ellipsoids drawn at 30% probability level. Symmetry codes: (i: x, 1 - y, z; ii: 1 - x, y, -z; iv: 1 - x, -y, -z).
Fig. 2.
The packing diagram of [Mg(H2O)6][pyH-2,6-dc]2 viewed down the c-axis. The intra and intermolecular O—H···O and intermolecular C—H···O hydrogen bonds are shown as blue and green dashed lines, ...

Crystal data

[Mg(H2O)6](C7H4NO4)2F(000) = 484.0
Mr = 464.63Dx = 1.572 Mg m3
Monoclinic, C2/mMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yCell parameters from 1383 reflections
a = 13.432 (3) Åθ = 2.4–29.1°
b = 11.108 (2) ŵ = 0.17 mm1
c = 6.5845 (13) ÅT = 298 K
β = 92.79 (3)°Plate, colorless
V = 981.3 (3) Å30.35 × 0.30 × 0.15 mm
Z = 2

Data collection

Stoe IPDS II diffractometer1383 independent reflections
Radiation source: fine-focus sealed tube1178 reflections with I > 2σ(I)
graphiteRint = 0.031
Detector resolution: 0.15 pixels mm-1θmax = 29.1°, θmin = 2.4°
rotation method scansh = −17→18
Absorption correction: numerical (X-RED and X-SHAPE; Stoe & Cie, 2005)k = −14→15
Tmin = 0.940, Tmax = 0.973l = −9→8
5499 measured reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.095H atoms treated by a mixture of independent and constrained refinement
S = 1.12w = 1/[σ2(Fo2) + (0.0414P)2 + 0.5177P] where P = (Fo2 + 2Fc2)/3
1383 reflections(Δ/σ)max = 0.001
94 parametersΔρmax = 0.33 e Å3
0 restraintsΔρmin = −0.18 e Å3

Special details

Experimental. shape of crystal determined optically
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
Mg10.50000.00000.00000.0249 (2)
O10.40364 (11)0.31353 (9)0.27234 (16)0.0499 (3)
O20.36594 (9)0.18375 (8)0.51657 (15)0.0396 (3)
O30.50000.18182 (12)0.00000.0360 (3)
O40.41819 (12)0.00000.2566 (2)0.0357 (3)
O50.36739 (11)0.0000−0.1931 (2)0.0341 (3)
N10.37142 (12)0.50000.4931 (2)0.0257 (3)
C10.31770 (16)0.50000.8796 (3)0.0347 (4)
H10.29890.50001.01370.042*
C20.33156 (11)0.39121 (12)0.78070 (19)0.0312 (3)
H20.32250.31860.84760.037*
C30.35898 (9)0.39277 (10)0.58164 (18)0.0253 (3)
C40.37779 (11)0.28571 (11)0.4447 (2)0.0310 (3)
H30.4708 (14)0.2281 (19)0.084 (3)0.053 (5)*
H40.4046 (15)0.0617 (19)0.327 (3)0.057 (6)*
H50.3664 (16)0.0661 (19)−0.270 (3)0.065 (6)*
H1A0.3899 (19)0.50000.366 (4)0.046 (7)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Mg10.0367 (5)0.0173 (4)0.0211 (4)0.0000.0062 (3)0.000
O10.0892 (9)0.0278 (5)0.0351 (5)0.0102 (5)0.0267 (6)−0.0011 (4)
O20.0626 (7)0.0192 (4)0.0374 (5)0.0041 (4)0.0054 (5)0.0011 (4)
O30.0602 (10)0.0177 (6)0.0315 (7)0.0000.0172 (6)0.000
O40.0566 (9)0.0226 (6)0.0296 (7)0.0000.0179 (6)0.000
O50.0467 (8)0.0295 (7)0.0262 (6)0.0000.0034 (6)0.000
N10.0353 (8)0.0203 (7)0.0220 (6)0.0000.0081 (6)0.000
C10.0486 (12)0.0344 (10)0.0217 (8)0.0000.0080 (7)0.000
C20.0422 (8)0.0253 (6)0.0265 (6)0.0000 (5)0.0059 (5)0.0048 (5)
C30.0303 (6)0.0192 (5)0.0267 (5)0.0018 (4)0.0036 (4)0.0007 (4)
C40.0410 (7)0.0210 (6)0.0312 (6)0.0050 (5)0.0048 (5)−0.0027 (5)

Geometric parameters (Å, °)

Mg1—O3i2.0197 (14)O5—H50.89 (2)
Mg1—O32.0197 (14)N1—C3ii1.3401 (13)
Mg1—O4i2.0601 (15)N1—C31.3401 (13)
Mg1—O42.0601 (15)N1—H1A0.89 (3)
Mg1—O5i2.1375 (16)C1—C21.3897 (16)
Mg1—O52.1375 (16)C1—C2ii1.3897 (16)
O1—C41.2422 (17)C1—H10.9300
O2—C41.2406 (16)C2—C31.3788 (17)
O3—H30.862 (19)C2—H20.9300
O4—H40.85 (2)C3—C41.5208 (17)
O3i—Mg1—O3180.0Mg1—O5—H5109.1 (13)
O3i—Mg1—O4i90.0C3ii—N1—C3125.46 (15)
O3—Mg1—O4i90.0C3ii—N1—H1A117.27 (8)
O3i—Mg1—O490.0C3—N1—H1A117.27 (8)
O3—Mg1—O490.0C2—C1—C2ii120.82 (17)
O4i—Mg1—O4180.00 (8)C2—C1—H1119.6
O3i—Mg1—O5i90.0C2ii—C1—H1119.6
O3—Mg1—O5i90.0C3—C2—C1118.87 (12)
O4i—Mg1—O5i91.46 (6)C3—C2—H2120.6
O4—Mg1—O5i88.54 (6)C1—C2—H2120.6
O3i—Mg1—O590.0N1—C3—C2117.99 (12)
O3—Mg1—O590.0N1—C3—C4114.17 (11)
O4i—Mg1—O588.54 (6)C2—C3—C4127.84 (11)
O4—Mg1—O591.46 (6)O2—C4—O1128.49 (12)
O5i—Mg1—O5180.00 (8)O2—C4—C3117.37 (12)
Mg1—O3—H3126.6 (13)O1—C4—C3114.14 (11)
Mg1—O4—H4125.5 (14)
C2ii—C1—C2—C3−0.3 (3)N1—C3—C4—O2−178.85 (14)
C3ii—N1—C3—C2−0.3 (3)C2—C3—C4—O21.3 (2)
C3ii—N1—C3—C4179.77 (12)N1—C3—C4—O11.23 (19)
C1—C2—C3—N10.3 (2)C2—C3—C4—O1−178.66 (14)
C1—C2—C3—C4−179.83 (15)

Symmetry codes: (i) −x+1, −y, −z; (ii) x, −y+1, z.

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O3—H3···O10.862 (19)1.834 (19)2.6940 (14)174.6 (19)
O4—H4···O20.85 (2)1.93 (2)2.7758 (14)171 (2)
O5—H5···O2iii0.89 (2)1.92 (2)2.7960 (14)167.5 (19)
C1—H1···O5iv0.932.583.308 (3)136

Symmetry codes: (iii) x, y, z−1; (iv) −x+1/2, y+1/2, −z+1.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: JJ2069).

References

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  • Dale, S. H., Elsegood, M. R. J. & Kainth, S. (2003). Acta Cryst. C59, m505–m508. [PubMed]
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  • Grossel, M. C., Dwyer, A. N., Hursthouse, M. B. & Orton, J. B. (2006). CrystEngComm, 8, 123–128.
  • Kariuki, B. M. & Jones, W. (1989). Acta Cryst. C45, 1297–1299.
  • Ptasiewicz-Bak, H. & Leciejewicz, J. (2003). J. Coord. Chem 56, 173–180.
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