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Possible strong symmetric hydrogen bonding in disodium tri­hydrogen bis­(2,2′-oxydi­acetate) nitrate

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aSchool of Chemical Sciences, University of East Anglia, University Plain, Norwich NR4 7TJ, England
*Correspondence e-mail: d.price@chem.gla.ac.uk

(Received 21 April 2005; accepted 10 May 2005; online 21 May 2005)

In the title compound, 2Na+·C8H11O10·NO3, the NaI atom is heptacoordinate with an approximately pentagonal–bipyramidal geometry. A possible strong symmetric hydrogen bond, with the H atom located at an inversion centre and an O⋯O distance of 2.450 (2) Å, is observed in the crystal structure.

Comment

The nature of short hydrogen-bonding interactions is still a subject of much interest and debate (Meot-Ner, 2005[Meot-Ner, M. (2005). Chem. Rev. 105, 213-284.]). It appears that, for O—H—O interactions where O⋯O is less than about 2.50 Å, examples can be found of truly symmetric hydrogen bonds (Catti & Ferraris, 1976[Catti, M. & Ferraris, G. (1976). Acta Cryst. B32, 2754-2756.]), most of which have crystallographic equivalence between donor–acceptor atoms. The title sodium compound, (I[link]), displays just such a short and possibly symmetric hydrogen-bonding interaction.[link]

[Scheme 1]

The compound can be viewed as a mixed sodium salt containing two monoanionic components, viz. nitrate and tri­hydrogen bis(2,2′-oxydi­acetate) (a hydrogen-bonded adduct formed by the loss of a single H atom from two of the di­carboxyl­ic acid mol­ecules). These 2,2′-oxydi­acetate mol­ecules adopt the fairly common planar all-trans configuration (Albertsson & Grenthe, 1973[Albertsson, J. & Grenthe, I. (1973). Acta Cryst. B29, 2751-2760.]; Albertsson et al., 1973a[Albertsson, J., Grenthe, I. & Herbertsson, H. (1973a). Acta Cryst. B29, 1855-1860.],b; Hatfield et al., 1987[Hatfield, W. E., Helms, J. H., Rohrs, B. R., Singh, P., Wasson, J. R. & Weller, R. R. (1987). Proc. Indian Acad. Sci. (Chem. Sci.), 98, 23-31.]). The NaI cation in (I[link]) is heptacoordinate with an approximately pentagonal–bipyramidal geometry (Fig. 1[link]); Na—O distances range from 2.4075 (17) to 2.5861 (18) Å. A tridentate chelating 2,2′-oxydi­acetate mol­ecule occupies three of the equatorial sites bonding through the two carboxyl and one ether O atoms. Symmetry-equivalent carboxyl atoms O2iii, O5iv and O1v [symmetry codes: (iii) 1 − x, 1 − y, 1 − z; (iv) 1 − x, −y, 1 − z; (v) x − ½, y − ½, z] from neighbouring 2,2′-oxydi­acetate mol­ecules and atom O6 of a bridging nitrate make up the rest of the coordination sphere.

The nitrate anion lies on the crystallographic twofold axis and links pairs of NaI ions in an antianti-1,3-bridging coordination mode. The carboxyl O atoms act in a bis-μ-bridging capacity between NaI ions, forming the polymeric structure.

In addition to these ionic interactions, the crystal structure is also held together by a network of two types of hydrogen bonds. The first is formed between the O4-carboxyl group and the nitrate anion (Table 1[link]). This hydrogen bond is asymmetric and non-linear. The nature of the second type of hydrogen bond is ambiguous. Certainly there exists a short hydrogen-bond interaction between the O1-carboxyl group and its crystallographically equivalent group; the O1⋯O1i distance of 2.450 (2) Å [symmetry code:(i) [3\over2] − x, [3\over2] − y, 1 − z] falls within the normal range for symmetric hydrogen bonds (Catti & Ferraris, 1976[Catti, M. & Ferraris, G. (1976). Acta Cryst. B32, 2754-2756.]). A Fourier map section in the O1/C1/O2 plane (MAPVIEW; Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]) clearly indicates a peak of electron density centred on the crystallographic inversion (Fig. 2[link]). Two alternative structural models have been studied. Placing atom H1 on the inversion centre gives a symmetric structure. Full-matrix least-squares refinement converged to a stable solution which is reported here. The residual difference Fourier map has a largest peak and hole of 0.16 and −0.23 e Å−3, respectively. The crystallographic symmetry constrains the hydrogen-bond angle to 180° and the O1—H1 distance to 1.23 Å. A second structural model is one with the H1-atom site half occupied and displaced from the inversion centre towards O1. Free refinement of the x, y, z and Uiso parameters for the H1 atom (118 parameters in total) converged to give a sensible asymmetric hydrogen-bonding interaction; the crystallographic residuals are insignificantly different and the difference map shows essentially the same features. The limited data quality and resolution mean that we cannot unambiguously determine the nature of this hydrogen-bonding interaction. The compound clearly merits further study, if only to resolve this issue. Despite this uncertainty in the H-atom position, such a linear hydrogen-bonding interaction linking two 2,2′-oxydi­acetate mol­ecules in a trans fashion is not an unusual motif when an H atom is shared between two carboxyl­ic acid groups (Nahringbauer, 1969[Nahringbauer, I. (1969). Acta Chem. Scand. 23, 1653-1666.]; Longo & Richardson, 1982[Longo, J. & Richardson, M. F. (1982). Acta Cryst. B38, 2482-2483.]; Misaki et al., 1989[Misaki, S., Kashino, S. & Haisa, M. (1989). Acta Cryst. C45, 62-63.]).

An examination of the Cambridge Structural Database (CSD; Version 5.25; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]) for short hydrogen bonds between two carboxyl­ate groups reveals three distinct conformational/geometric groups (Fig. 3[link]). Group 1 have a C—O⋯O—C torsion angles of about 0° and have O⋯O separations mostly in the range 2.38–2.43 Å. Group 2 have C—O⋯O—C torsion angles of 180° (invariably fixed by crystallographic symmetry) and O⋯O separations in the range 2.43–2.53 Å. Group 3 have intermediate torsion angles (unrestricted by symmetry) and have O⋯O distances all within the range 2.42–2.47 Å. The possibly symmetric hydrogen bond observed in (I[link]) falls well within the known range for group 2 conformations, and this geometry is seen for many other di­carboxyl­ate compounds (see, for example, Kalsbeek & Larsen, 1991[Kalsbeek, N. & Larsen, S. (1991). Acta Cryst. C47, 1005-1009.]; Leban & Rupnik, 1992[Leban, I. & Rupnik, A. (1992). Acta Cryst. C48, 821-824.]; Flensburg et al., 1995[Flensburg, C., Larsen, S. & Stewart, R. (1995). J. Phys. Chem. 99, 10130-10141.]) and also in other 2,2′-oxydi­acetate salts (Albertsson & Grenthe, 1973[Albertsson, J. & Grenthe, I. (1973). Acta Cryst. B29, 2751-2760.]; Albertsson et al., 1973a[Albertsson, J., Grenthe, I. & Herbertsson, H. (1973a). Acta Cryst. B29, 1855-1860.],b[Albertsson, J., Grenthe, I. & Herbertsson, H. (1973b). Acta Cryst. B29, 2839-2844.]; Herbertsson & Hedman, 1982[Herbertsson, H. & Hedman, B. (1982). Acta Cryst. B38, 320-322.]; Urbańczyk-Lipkowska, 2000[Urbańczyk-Lipkowska, Z. (2000). Cryst. Eng. 3, 227-236.]).

We also note that the first hydrogen-bonding pattern (between the carboxyl­ic acid and the nitrate anion), although asymmetric, seems to be a strong and important structural motif. In nine out of 14 reported structures that contain both a carboxyl­ic acid and a nitrate anion, the acid is hydrogen bonded to the nitrate, and none of the structures displays the common R22(8) dimeric carboxyl­ic acid motif (see, for example, Sridhar et al., 2002[Sridhar, B., Srinivasan, N. & Rajaram, R. K. (2002). Acta Cryst. E58, o1103-o1105.]).

Together, these two hydrogen-bonded motifs form a network. Using the nomenclature for graph theoretical analysis developed by Etter et al. (1990[Etter, M. C., MacDonald, J. C. & Bernstein, J. (1990). Acta Cryst. B46, 256-262.]), we can describe this system as N1 = D22(4)D; N2 = C33(20), where the second-order net consists of infinite chains that zigzag through the crystal structure (Fig. 4[link]).

[Figure 1]
Figure 1
The molecular structure and sodium environment, with 50% probability displacement ellipsoids and the atom-labelling scheme. Dashed lines indicate hydrogen bonds. [Symmetry codes: (i) [3\over2] − x, [3\over2] − y, 1 − z; (ii) x, y − 1, z; (iii) 1 − x, 1 − y, 1 − z; (iv) 1 − x, −y, 1 − z; (v) x − [1\over2], y − [1\over2], z; (vi) 1 − x, y, [3\over2] − z].
[Figure 2]
Figure 2
Difference Fourier map from a refined model where atom H1 is absent. The O1/C1/O2 plane is shown with the crystallographic inversion in the centre of the plot.
[Figure 3]
Figure 3
Graph showing the distribution of C—O⋯O—C torsion angles as a function of O⋯O interatomic separations for short hydrogen-bonded interactions between two carboxyl­ic acid groups. Data taken from 78 structures in the CSD (Version 5.25; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]).
[Figure 4]
Figure 4
The hydrogen-bonded network formed by both types of hydrogen-bonding interaction (dashed lines).

Experimental

Crystals of (I) were grown by slow evaporation from a methanolic solution which contained the bis(2,2′-oxydiacetic acid), sodium hydroxide and aluminium nitrate nonahydrate.

Crystal data
  • 2Na+·C8H11O10·NO3

  • Mr = 375.16

  • Monoclinic, C2/c

  • a = 12.010 (2) Å

  • b = 7.0290 (14) Å

  • c = 16.382 (3) Å

  • β = 94.84 (3)°

  • V = 1378.0 (4) Å3

  • Z = 4

  • Dx = 1.808 Mg m−3

  • Mo Kα radiation

  • Cell parameters from 101 reflections

  • θ = 3.2–24.8°

  • μ = 0.22 mm−1

  • T = 293 (2) K

  • Block, colourless

  • 0.16 × 0.16 × 0.06 mm

Data collection
  • Rigaku R-AXIS-IIc diffractometer

  • φ scans

  • Absorption correction: none

  • 1999 measured reflections

  • 1124 independent reflections

  • 996 reflections with I > 2σ(I)

  • Rint = 0.016

  • θmax = 24.8°

  • h = 0 → 14

  • k = −8 → 8

  • l = −19 → 19

Refinement
  • Refinement on F2

  • R[F2 > 2σ(F2)] = 0.033

  • wR(F2) = 0.103

  • S = 1.17

  • 1124 reflections

  • 115 parameters

  • H atoms treated by a mixture of independent and constrained refinement

  • w = 1/[σ2(Fo2) + (0.0446P)2 + 1.8079P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.16 e Å−3

  • Δρmin = −0.23 e Å−3

Table 1
Hydrogen-bonding geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O1—H1⋯O1i 1.225 1.225 2.450 (2) 180
O4—H4⋯O6ii 0.92 (4) 1.82 (4) 2.703 (3) 160 (3)
Symmetry codes: (i) [{\script{3\over 2}}-x,{\script{3\over 2}}-y,1-z]; (ii) x,y-1,z.

All methyl­ene H atoms were located in idealized positions and refined in riding mode. C—H distances were set at 0.97Å and Uiso(H) values were constained to be 1.5Ueq of the parent C atom. Both H atoms involved in hydrogen bonding were found in a Fourier difference map and were refined, subject only to the inversion centre constraint.

Data collection: MSC R-AXIS-II Control Software; cell refinement: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); program(s) used to solve structure: SHELXS86 (Robinson & Sheldrick, 1988[Robinson, W. T. & Sheldrick, G. M. (1988). Crystallographic Computing 4. Techniques and New Technologies, edited by N. W. Isaacs & M. R. Taylor, pp. 366-377. International Union of Crystallography and Oxford University Press.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXL97. University of Göttingen, Germany.]) in WinGX (Farrugia, 1999[Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837-838.]); molecular graphics: DIAMOND (Brandenburg, 1999[Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.]).

Supporting information


Computing details top

Data collection: MSC R-AXIS-II control Software; cell refinement: DENZO (Otwinowski & Minor, 1997); data reduction: SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS86 (Robinson & Sheldrick, 1988); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997) in WinGX (Farrugia, 1999); molecular graphics: DIAMOND (Brandenburg, 1999).

disodium trihydrogen bis(2,2'-oxydiacetate) nitrate top
Crystal data top
2Na+·C8H11O10·NO3F(000) = 768
Mr = 375.16Dx = 1.808 Mg m3
Monoclinic, C2/cMelting point: not measured K
Hall symbol: -C 2ycMo Kα radiation, λ = 0.71073 Å
a = 12.010 (2) ÅCell parameters from 101 reflections
b = 7.0290 (14) Åθ = 3.2–24.8°
c = 16.382 (3) ŵ = 0.22 mm1
β = 94.84 (3)°T = 293 K
V = 1378.0 (4) Å3Block, colourless
Z = 40.16 × 0.16 × 0.06 mm
Data collection top
Rigaku R-AXIS-IIc
diffractometer
996 reflections with I > 2σ(I)
Radiation source: Mo rotating anodeRint = 0.016
Graphite monochromatorθmax = 24.8°, θmin = 3.4°
φ scansh = 014
1999 measured reflectionsk = 88
1124 independent reflectionsl = 1919
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.033Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.103H atoms treated by a mixture of independent and constrained refinement
S = 1.17 w = 1/[σ2(Fo2) + (0.0446P)2 + 1.8079P]
where P = (Fo2 + 2Fc2)/3
1124 reflections(Δ/σ)max < 0.001
115 parametersΔρmax = 0.16 e Å3
0 restraintsΔρmin = 0.23 e Å3
Special details top

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) top
xyzUiso*/Ueq
Na10.48509 (7)0.24986 (12)0.55036 (5)0.0308 (3)
O30.67561 (12)0.1858 (2)0.60051 (9)0.0301 (4)
O20.62402 (12)0.4925 (2)0.51549 (9)0.0296 (4)
O60.48709 (15)0.4402 (3)0.68343 (9)0.0407 (5)
N10.50000.3494 (4)0.75000.0348 (7)
C10.71748 (17)0.4937 (3)0.55231 (11)0.0228 (5)
C20.75705 (17)0.3318 (3)0.60802 (13)0.0269 (5)
H2A0.82810.28390.59260.040*
H2B0.76710.37560.66430.040*
C30.70115 (18)0.0316 (3)0.65405 (12)0.0276 (5)
H3A0.70830.07540.71040.041*
H3B0.77130.02630.64210.041*
O70.50000.1751 (4)0.75000.0792 (11)
O50.53165 (13)0.0997 (2)0.58891 (9)0.0317 (4)
O40.62185 (14)0.2512 (2)0.69492 (10)0.0364 (4)
C40.60827 (17)0.1102 (3)0.64181 (12)0.0241 (5)
O10.78860 (12)0.6300 (2)0.54870 (9)0.0310 (4)
H40.568 (3)0.341 (5)0.6805 (17)0.058 (9)*
H10.75000.75000.50000.071 (14)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Na10.0263 (5)0.0288 (5)0.0361 (5)0.0002 (4)0.0038 (4)0.0014 (3)
O30.0254 (8)0.0217 (8)0.0416 (9)0.0057 (7)0.0069 (6)0.0124 (7)
O20.0235 (8)0.0269 (8)0.0374 (8)0.0024 (7)0.0043 (6)0.0074 (6)
O60.0509 (11)0.0411 (10)0.0298 (8)0.0082 (9)0.0018 (7)0.0005 (7)
N10.0335 (15)0.0254 (15)0.0480 (17)0.0000.0173 (12)0.000
C10.0228 (10)0.0199 (11)0.0260 (10)0.0012 (9)0.0040 (8)0.0001 (8)
C20.0240 (11)0.0228 (11)0.0331 (11)0.0050 (9)0.0031 (8)0.0043 (9)
C30.0273 (11)0.0250 (11)0.0291 (10)0.0020 (9)0.0051 (8)0.0084 (9)
O70.120 (3)0.0227 (15)0.104 (3)0.0000.064 (2)0.000
O50.0286 (8)0.0313 (9)0.0340 (8)0.0041 (7)0.0051 (6)0.0038 (6)
O40.0427 (10)0.0282 (9)0.0365 (9)0.0095 (8)0.0073 (7)0.0121 (7)
C40.0270 (11)0.0217 (11)0.0237 (10)0.0004 (9)0.0032 (8)0.0019 (8)
O10.0258 (8)0.0243 (8)0.0420 (9)0.0068 (7)0.0027 (6)0.0080 (7)
Geometric parameters (Å, º) top
Na1—O32.4075 (17)N1—O6iv1.262 (2)
Na1—O2i2.4333 (17)C1—O11.288 (2)
Na1—O22.4860 (17)C1—C21.511 (3)
Na1—O1ii2.5038 (17)C2—H2A0.9700
Na1—O5iii2.5065 (18)C2—H2B0.9700
Na1—O62.5562 (19)C3—C41.496 (3)
Na1—O52.5861 (18)C3—H3A0.9700
Na1—Na1iii3.9100 (18)C3—H3B0.9700
Na1—Na1i3.9135 (18)O5—C41.212 (2)
O3—C31.412 (2)O5—Na1iii2.5065 (18)
O3—C21.416 (3)O4—C41.320 (3)
O2—C11.229 (2)O4—H40.92 (3)
O2—Na1i2.4333 (17)O1—Na1v2.5038 (17)
O6—N11.262 (2)O1—H11.2250 (14)
N1—O71.225 (4)
O3—Na1—O2i138.69 (6)C3—O3—C2112.97 (15)
O3—Na1—O264.51 (5)C3—O3—Na1120.39 (12)
O2i—Na1—O274.59 (6)C2—O3—Na1121.61 (12)
O3—Na1—O1ii143.96 (6)C1—O2—Na1i130.39 (14)
O2i—Na1—O1ii76.93 (6)C1—O2—Na1119.67 (13)
O2—Na1—O1ii151.48 (6)Na1i—O2—Na1105.41 (6)
O3—Na1—O5iii103.47 (7)N1—O6—Na1117.66 (15)
O2i—Na1—O5iii84.90 (6)O7—N1—O6iv120.38 (13)
O2—Na1—O5iii94.80 (6)O7—N1—O6120.38 (13)
O1ii—Na1—O5iii81.09 (6)O6iv—N1—O6119.2 (3)
O3—Na1—O682.33 (7)O2—C1—O1124.38 (18)
O2i—Na1—O687.40 (6)O2—C1—C2121.28 (18)
O2—Na1—O683.03 (6)O1—C1—C2114.34 (17)
O1ii—Na1—O697.27 (7)O3—C2—C1108.29 (16)
O5iii—Na1—O6172.29 (7)O3—C2—H2A110.0
O3—Na1—O563.86 (5)C1—C2—H2A110.0
O2i—Na1—O5155.85 (6)O3—C2—H2B110.0
O2—Na1—O5124.92 (6)C1—C2—H2B110.0
O1ii—Na1—O582.36 (5)H2A—C2—H2B108.4
O5iii—Na1—O579.71 (6)O3—C3—C4107.92 (16)
O6—Na1—O5107.62 (6)O3—C3—H3A110.1
O3—Na1—Na1iii81.83 (5)C4—C3—H3A110.1
O2i—Na1—Na1iii123.13 (5)O3—C3—H3B110.1
O2—Na1—Na1iii115.62 (6)C4—C3—H3B110.1
O1ii—Na1—Na1iii79.21 (5)H3A—C3—H3B108.4
O5iii—Na1—Na1iii40.60 (4)C4—O5—Na1iii128.54 (14)
O6—Na1—Na1iii146.66 (6)C4—O5—Na1111.59 (14)
O5—Na1—Na1iii39.10 (4)Na1iii—O5—Na1100.29 (6)
O3—Na1—Na1i101.17 (5)C4—O4—H4107.3 (18)
O2i—Na1—Na1i37.76 (4)O5—C4—O4124.1 (2)
O2—Na1—Na1i36.83 (4)O5—C4—C3124.60 (18)
O1ii—Na1—Na1i114.68 (5)O4—C4—C3111.24 (17)
O5iii—Na1—Na1i89.88 (5)C1—O1—Na1v151.39 (13)
O6—Na1—Na1i83.95 (5)C1—O1—H1109.02 (14)
O5—Na1—Na1i158.59 (6)Na1v—O1—H194.58 (8)
Na1iii—Na1—Na1i127.91 (5)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x1/2, y1/2, z; (iii) x+1, y, z+1; (iv) x+1, y, z+3/2; (v) x+1/2, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O1—H1···O1vi1.231.232.450 (2)180
O4—H4···O6vii0.92 (4)1.82 (4)2.703 (3)160 (3)
Symmetry codes: (vi) x+3/2, y+3/2, z+1; (vii) x, y1, z.
 

Footnotes

Present address: WestCHEM, Department of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland

§Present address: University Chemistry Laboratory, Lensfield Road, Cambridge CB2 1EW, England

Present address: Institut für Anorganische Chemie der Universität, D-76128 Karlsruhe, Germany

Acknowledgements

The authors are grateful to the EPSRC, UK, for financial support and the Wellcome Trust for the provision of X-ray facilities.

References

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