metal-organic compounds
Poly[(μ4-3-carboxypyrazine-2-carboxylato)(μ4-nitrato)dilithium]
aInstitute of Nuclear Chemistry and Technology, ul. Dorodna 16, 03-195 Warszawa, Poland
*Correspondence e-mail: j.leciejewicz@ichtj.waw.pl
In the title compound, [Li2(C6H3N2O4)2(NO3)]n, the two symmetry-independent LiI ions are each in a trigonal–bipyramidal coordination and are bridged by N,O-bonding ligands, forming molecular ribbons propagating in [010]. Each LiI ion is also coordinated by two O atoms from nitrate ions, connecting the ribbons into a three-dimensional network. Very strong intramolecular O—H⋯O hydrogen bonds occur between the carboxyl and the carboxylate group.
Related literature
For three structures of lithium(I) complexes with pyrazine-2,3-dicarboxylate and water ligands, see: Tombul et al. (2008); Tombul & Güven (2009); Starosta & Leciejewicz (2011). For structures of calcium(II) complexes with the title ligand, see: Ptasiewicz-Bąk & Leciejewicz (1997); Starosta & Leciejewicz (2004, 2005a,b).
Experimental
Crystal data
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Refinement
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Data collection: CrysAlis PRO (Agilent, 2011); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.
Supporting information
https://doi.org/10.1107/S1600536812050738/kp2442sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536812050738/kp2442Isup2.hkl
An aqueous solution containing 1 mmol of lithium(I) nitrate and 1 mmol of pyrazine-2,3-dicarboxylic acid dihydrate was boiled with stirring under reflux for 6 h. After cooling to room temperature three drops of 1 N nitric acid were added to maintain pH of 5. Then the solution was left to evaporate to dryness. Deposited single crystal plates were washed with cold ethanol and dried in the air.
The hydrogen atom of carboxylate group was located in a difference map and was refined independently with an isotropic displacement parameter. H atoms bonded to pyrazine ring C atoms were placed in calculated positions with C—H = 0.93 and 0.96 Å and treated as riding on the parent atoms with Uiso(H)= 1.2Ueq(C).
# Used for convenience to store draft or replaced versions
of the abstract, comment etc. Its contents will not be outputData collection: CrysAlis PRO (Agilent, 2011); cell
CrysAlis PRO (Agilent, 2011); data reduction: CrysAlis PRO (Agilent, 2011); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Fig. 1. A fragment of the structure of the title compound with atom labelling scheme and 50% probability displacement ellipsoids. Symmetry code: (i) x + 1, y, z; (ii) -x + 1, y + 1/2, -z + 2; (iii) -x + 1, y - 1/2, -z + 2; (iv) -x + 1, y - 1/2, -z + 1; (v) -x, y - 1/2, -z + 1. | |
Fig. 2. The packing of molecular ribbons in the structure of the title compound showing nitrate bridging mode. |
[Li2(C6H3N2O4)2(NO3)] | F(000) = 242 |
Mr = 241.99 | Dx = 1.783 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 2509 reflections |
a = 4.6273 (1) Å | θ = 3.3–30.7° |
b = 15.8565 (3) Å | µ = 0.16 mm−1 |
c = 6.1719 (2) Å | T = 293 K |
β = 95.598 (2)° | Block, colourless |
V = 450.69 (2) Å3 | 0.20 × 0.14 × 0.12 mm |
Z = 2 |
Agilent SuperNova (Dual, Cu at zero, Eos) diffractometer | 2572 independent reflections |
Radiation source: SuperNova (Mo) X-ray Source | 2401 reflections with I > 2σ(I) |
Mirror monochromator | Rint = 0.015 |
Detector resolution: 16.0131 pixels mm-1 | θmax = 30.7°, θmin = 3.3° |
ω scans | h = −5→6 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011) | k = −21→22 |
Tmin = 0.936, Tmax = 1.000 | l = −5→8 |
4032 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.036 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.084 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | w = 1/[σ2(Fo2) + (0.0337P)2 + 0.0702P] where P = (Fo2 + 2Fc2)/3 |
2572 reflections | (Δ/σ)max < 0.001 |
167 parameters | Δρmax = 0.21 e Å−3 |
1 restraint | Δρmin = −0.20 e Å−3 |
[Li2(C6H3N2O4)2(NO3)] | V = 450.69 (2) Å3 |
Mr = 241.99 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 4.6273 (1) Å | µ = 0.16 mm−1 |
b = 15.8565 (3) Å | T = 293 K |
c = 6.1719 (2) Å | 0.20 × 0.14 × 0.12 mm |
β = 95.598 (2)° |
Agilent SuperNova (Dual, Cu at zero, Eos) diffractometer | 2572 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2011) | 2401 reflections with I > 2σ(I) |
Tmin = 0.936, Tmax = 1.000 | Rint = 0.015 |
4032 measured reflections |
R[F2 > 2σ(F2)] = 0.036 | 1 restraint |
wR(F2) = 0.084 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | Δρmax = 0.21 e Å−3 |
2572 reflections | Δρmin = −0.20 e Å−3 |
167 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.5316 (3) | 0.40681 (8) | 0.6101 (2) | 0.0322 (3) | |
O5 | 0.4586 (3) | 0.48672 (8) | 0.0630 (2) | 0.0297 (3) | |
C2 | 0.4874 (4) | 0.27654 (10) | 0.4273 (3) | 0.0223 (3) | |
N4 | 0.5051 (4) | 0.14644 (9) | 0.2348 (2) | 0.0279 (3) | |
N1 | 0.6499 (3) | 0.31421 (9) | 0.2871 (2) | 0.0278 (3) | |
N2 | 0.1867 (3) | 0.47658 (9) | 0.0539 (2) | 0.0243 (3) | |
O2 | 0.2330 (4) | 0.31513 (9) | 0.7378 (3) | 0.0427 (4) | |
C8 | 0.2425 (4) | 0.13507 (11) | 0.5462 (3) | 0.0261 (3) | |
C3 | 0.4152 (4) | 0.19074 (10) | 0.4027 (3) | 0.0228 (3) | |
O7 | 0.0838 (3) | 0.43786 (9) | 0.2022 (3) | 0.0393 (3) | |
O6 | 0.0354 (3) | 0.50501 (10) | −0.1046 (2) | 0.0388 (3) | |
C5 | 0.6615 (4) | 0.18550 (12) | 0.0970 (3) | 0.0326 (4) | |
H5 | 0.7223 | 0.1559 | −0.0205 | 0.039* | |
C7 | 0.4118 (4) | 0.33782 (11) | 0.6048 (3) | 0.0267 (3) | |
C6 | 0.7368 (5) | 0.27000 (11) | 0.1245 (3) | 0.0338 (4) | |
H6 | 0.8500 | 0.2957 | 0.0269 | 0.041* | |
Li1 | 0.7058 (7) | 0.44849 (19) | 0.3298 (5) | 0.0289 (6) | |
Li2 | 0.3903 (7) | 0.0133 (2) | 0.2244 (5) | 0.0300 (6) | |
O3 | 0.2524 (3) | 0.05895 (8) | 0.5143 (2) | 0.0329 (3) | |
O4 | 0.1008 (4) | 0.16985 (8) | 0.6880 (3) | 0.0444 (4) | |
H1 | 0.153 (8) | 0.252 (2) | 0.713 (6) | 0.093 (11)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0444 (8) | 0.0222 (6) | 0.0311 (7) | −0.0058 (6) | 0.0086 (6) | −0.0054 (5) |
O5 | 0.0184 (5) | 0.0402 (7) | 0.0307 (6) | −0.0033 (5) | 0.0045 (4) | 0.0052 (5) |
C2 | 0.0242 (7) | 0.0194 (7) | 0.0236 (7) | 0.0013 (6) | 0.0044 (6) | 0.0004 (6) |
N4 | 0.0352 (8) | 0.0224 (7) | 0.0275 (8) | −0.0012 (6) | 0.0092 (6) | −0.0022 (6) |
N1 | 0.0337 (8) | 0.0208 (6) | 0.0303 (8) | −0.0019 (6) | 0.0103 (6) | 0.0006 (6) |
N2 | 0.0223 (6) | 0.0230 (6) | 0.0285 (7) | −0.0014 (5) | 0.0073 (5) | −0.0009 (5) |
O2 | 0.0596 (9) | 0.0274 (6) | 0.0463 (9) | −0.0092 (7) | 0.0320 (7) | −0.0110 (6) |
C8 | 0.0308 (9) | 0.0230 (8) | 0.0249 (9) | −0.0012 (7) | 0.0039 (7) | 0.0008 (6) |
C3 | 0.0237 (8) | 0.0214 (7) | 0.0239 (8) | 0.0003 (6) | 0.0050 (6) | 0.0017 (6) |
O7 | 0.0332 (7) | 0.0416 (8) | 0.0461 (8) | 0.0019 (6) | 0.0197 (6) | 0.0144 (6) |
O6 | 0.0280 (7) | 0.0479 (8) | 0.0392 (7) | −0.0007 (6) | −0.0036 (6) | 0.0101 (6) |
C5 | 0.0433 (10) | 0.0271 (9) | 0.0301 (9) | 0.0005 (8) | 0.0173 (8) | −0.0051 (7) |
C7 | 0.0322 (9) | 0.0217 (7) | 0.0265 (8) | 0.0010 (6) | 0.0045 (7) | −0.0022 (6) |
C6 | 0.0426 (11) | 0.0258 (8) | 0.0356 (10) | −0.0016 (8) | 0.0171 (8) | 0.0032 (7) |
Li1 | 0.0342 (16) | 0.0249 (14) | 0.0288 (15) | 0.0009 (12) | 0.0097 (12) | 0.0000 (12) |
Li2 | 0.0382 (16) | 0.0234 (13) | 0.0287 (15) | 0.0015 (13) | 0.0052 (13) | 0.0008 (12) |
O3 | 0.0495 (8) | 0.0207 (6) | 0.0293 (6) | −0.0037 (5) | 0.0085 (6) | 0.0027 (5) |
O4 | 0.0629 (10) | 0.0275 (7) | 0.0488 (9) | −0.0113 (7) | 0.0359 (8) | −0.0059 (6) |
O1—C7 | 1.225 (2) | O2—C7 | 1.273 (2) |
O1—Li2i | 1.989 (3) | O2—H1 | 1.07 (4) |
Li1—O1 | 2.086 (3) | C8—O3 | 1.224 (2) |
O5—N2 | 1.2643 (18) | C8—O4 | 1.269 (2) |
Li1—O5 | 2.005 (3) | C8—C3 | 1.530 (2) |
Li1—N1 | 2.158 (3) | O7—Li1iv | 1.994 (3) |
Li1—O7ii | 1.994 (3) | O6—Li2v | 2.040 (4) |
Li1—O3i | 1.999 (3) | C5—C6 | 1.391 (3) |
O5—Li2iii | 2.014 (3) | C5—H5 | 0.9300 |
C2—N1 | 1.341 (2) | C6—H6 | 0.9300 |
C2—C3 | 1.406 (2) | Li1—Li2i | 3.011 (4) |
C2—C7 | 1.530 (2) | Li2—O1vi | 1.989 (3) |
N4—C5 | 1.324 (2) | Li2—O5vii | 2.014 (3) |
N4—C3 | 1.351 (2) | Li2—O6viii | 2.040 (4) |
Li2—N4 | 2.176 (3) | Li2—O3 | 2.086 (3) |
N1—C6 | 1.319 (2) | Li2—Li1vi | 3.011 (4) |
N2—O6 | 1.231 (2) | O3—Li1vi | 1.999 (3) |
N2—O7 | 1.2359 (19) | O4—H1 | 1.34 (4) |
C7—O1—Li2i | 146.19 (15) | C5—C6—H6 | 119.5 |
C7—O1—Li1 | 118.12 (15) | O7ii—Li1—O3i | 102.51 (15) |
Li2i—O1—Li1 | 95.24 (14) | O7ii—Li1—O5 | 98.83 (14) |
N2—O5—Li1 | 118.93 (13) | O3i—Li1—O5 | 98.69 (14) |
N2—O5—Li2iii | 114.63 (14) | O7ii—Li1—O1 | 136.49 (18) |
Li1—O5—Li2iii | 124.59 (14) | O3i—Li1—O1 | 84.57 (13) |
N1—C2—C3 | 120.27 (14) | O5—Li1—O1 | 122.78 (17) |
N1—C2—C7 | 111.15 (14) | O7ii—Li1—N1 | 88.16 (13) |
C3—C2—C7 | 128.55 (15) | O3i—Li1—N1 | 158.15 (18) |
C5—N4—C3 | 118.59 (14) | O5—Li1—N1 | 98.41 (14) |
C5—N4—Li2 | 125.60 (15) | O1—Li1—N1 | 74.76 (11) |
C3—N4—Li2 | 115.76 (14) | O7ii—Li1—Li2i | 127.08 (16) |
C6—N1—C2 | 119.08 (15) | O3i—Li1—Li2i | 43.67 (9) |
C6—N1—Li1 | 125.14 (14) | O5—Li1—Li2i | 121.60 (15) |
C2—N1—Li1 | 115.41 (13) | O1—Li1—Li2i | 41.13 (9) |
O6—N2—O7 | 122.70 (15) | N1—Li1—Li2i | 114.95 (13) |
O6—N2—O5 | 118.37 (14) | O1vi—Li2—O5vii | 102.31 (15) |
O7—N2—O5 | 118.93 (15) | O1vi—Li2—O6viii | 104.59 (16) |
C7—O2—H1 | 114 (2) | O5vii—Li2—O6viii | 94.18 (14) |
O3—C8—O4 | 124.69 (17) | O1vi—Li2—O3 | 84.81 (13) |
O3—C8—C3 | 116.47 (15) | O5vii—Li2—O3 | 171.64 (18) |
O4—C8—C3 | 118.83 (14) | O6viii—Li2—O3 | 88.17 (14) |
N4—C3—C2 | 119.89 (14) | O1vi—Li2—N4 | 141.01 (18) |
N4—C3—C8 | 111.18 (14) | O5vii—Li2—N4 | 97.16 (14) |
C2—C3—C8 | 128.92 (14) | O6viii—Li2—N4 | 107.32 (15) |
N2—O7—Li1iv | 131.81 (15) | O3—Li2—N4 | 74.49 (12) |
N2—O6—Li2v | 139.98 (15) | O1vi—Li2—Li1vi | 43.63 (9) |
N4—C5—C6 | 121.23 (16) | O5vii—Li2—Li1vi | 145.93 (15) |
N4—C5—H5 | 119.4 | O6viii—Li2—Li1vi | 94.92 (13) |
C6—C5—H5 | 119.4 | O3—Li2—Li1vi | 41.41 (9) |
O1—C7—O2 | 123.79 (16) | N4—Li2—Li1vi | 111.21 (14) |
O1—C7—C2 | 116.83 (15) | C8—O3—Li1vi | 142.15 (15) |
O2—C7—C2 | 119.38 (15) | C8—O3—Li2 | 119.94 (14) |
N1—C6—C5 | 120.92 (17) | Li1vi—O3—Li2 | 94.92 (14) |
N1—C6—H6 | 119.5 | C8—O4—H1 | 113.8 (17) |
C3—C2—N1—C6 | 1.0 (3) | N2—O5—Li1—Li2i | −57.2 (2) |
C7—C2—N1—C6 | 179.39 (16) | Li2iii—O5—Li1—Li2i | 139.21 (19) |
C3—C2—N1—Li1 | 174.35 (15) | C7—O1—Li1—O7ii | −88.5 (3) |
C7—C2—N1—Li1 | −7.3 (2) | Li2i—O1—Li1—O7ii | 97.2 (3) |
Li1—O5—N2—O6 | 175.52 (16) | C7—O1—Li1—O3i | 168.99 (15) |
Li2iii—O5—N2—O6 | −19.3 (2) | Li2i—O1—Li1—O3i | −5.28 (15) |
Li1—O5—N2—O7 | −5.3 (2) | C7—O1—Li1—O5 | 72.1 (2) |
Li2iii—O5—N2—O7 | 159.91 (16) | Li2i—O1—Li1—O5 | −102.13 (19) |
C5—N4—C3—C2 | 0.3 (3) | C7—O1—Li1—N1 | −18.14 (18) |
Li2—N4—C3—C2 | 177.86 (16) | Li2i—O1—Li1—N1 | 167.59 (13) |
C5—N4—C3—C8 | −179.02 (17) | C7—O1—Li1—Li2i | 174.3 (2) |
Li2—N4—C3—C8 | −1.4 (2) | C6—N1—Li1—O7ii | −34.8 (2) |
N1—C2—C3—N4 | −1.3 (3) | C2—N1—Li1—O7ii | 152.34 (15) |
C7—C2—C3—N4 | −179.31 (17) | C6—N1—Li1—O3i | −155.0 (4) |
N1—C2—C3—C8 | 177.86 (17) | C2—N1—Li1—O3i | 32.2 (6) |
C7—C2—C3—C8 | −0.2 (3) | C6—N1—Li1—O5 | 63.8 (2) |
O3—C8—C3—N4 | 12.0 (2) | C2—N1—Li1—O5 | −109.00 (16) |
O4—C8—C3—N4 | −167.97 (17) | C6—N1—Li1—O1 | −174.35 (17) |
O3—C8—C3—C2 | −167.18 (17) | C2—N1—Li1—O1 | 12.80 (17) |
O4—C8—C3—C2 | 12.8 (3) | C6—N1—Li1—Li2i | −165.38 (18) |
O6—N2—O7—Li1iv | −32.3 (3) | C2—N1—Li1—Li2i | 21.8 (2) |
O5—N2—O7—Li1iv | 148.58 (19) | C5—N4—Li2—O1vi | 112.0 (3) |
O7—N2—O6—Li2v | 1.3 (3) | C3—N4—Li2—O1vi | −65.4 (3) |
O5—N2—O6—Li2v | −179.55 (19) | C5—N4—Li2—O5vii | −7.8 (2) |
C3—N4—C5—C6 | 0.9 (3) | C3—N4—Li2—O5vii | 174.83 (14) |
Li2—N4—C5—C6 | −176.40 (18) | C5—N4—Li2—O6viii | −104.4 (2) |
Li2i—O1—C7—O2 | 9.4 (4) | C3—N4—Li2—O6viii | 78.16 (19) |
Li1—O1—C7—O2 | −160.34 (19) | C5—N4—Li2—O3 | 172.54 (18) |
Li2i—O1—C7—C2 | −170.2 (2) | C3—N4—Li2—O3 | −4.88 (16) |
Li1—O1—C7—C2 | 20.1 (2) | C5—N4—Li2—Li1vi | 153.02 (18) |
N1—C2—C7—O1 | −7.9 (2) | C3—N4—Li2—Li1vi | −24.4 (2) |
C3—C2—C7—O1 | 170.27 (18) | O4—C8—O3—Li1vi | −43.1 (4) |
N1—C2—C7—O2 | 172.51 (18) | C3—C8—O3—Li1vi | 136.9 (2) |
C3—C2—C7—O2 | −9.3 (3) | O4—C8—O3—Li2 | 162.41 (19) |
C2—N1—C6—C5 | 0.2 (3) | C3—C8—O3—Li2 | −17.6 (2) |
Li1—N1—C6—C5 | −172.44 (19) | O1vi—Li2—O3—C8 | 159.34 (16) |
N4—C5—C6—N1 | −1.2 (3) | O5vii—Li2—O3—C8 | 10.7 (14) |
N2—O5—Li1—O7ii | 158.55 (14) | O6viii—Li2—O3—C8 | −95.84 (18) |
Li2iii—O5—Li1—O7ii | −5.1 (2) | N4—Li2—O3—C8 | 12.71 (19) |
N2—O5—Li1—O3i | −97.24 (17) | Li1vi—Li2—O3—C8 | 164.6 (2) |
Li2iii—O5—Li1—O3i | 99.13 (17) | O1vi—Li2—O3—Li1vi | −5.27 (15) |
N2—O5—Li1—O1 | −8.1 (2) | O5vii—Li2—O3—Li1vi | −153.9 (13) |
Li2iii—O5—Li1—O1 | −171.75 (15) | O6viii—Li2—O3—Li1vi | 99.55 (14) |
N2—O5—Li1—N1 | 69.12 (17) | N4—Li2—O3—Li1vi | −151.90 (13) |
Li2iii—O5—Li1—N1 | −94.52 (18) |
Symmetry codes: (i) −x+1, y+1/2, −z+1; (ii) x+1, y, z; (iii) −x+1, y+1/2, −z; (iv) x−1, y, z; (v) −x, y+1/2, −z; (vi) −x+1, y−1/2, −z+1; (vii) −x+1, y−1/2, −z; (viii) −x, y−1/2, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H1···O4 | 1.07 (4) | 1.34 (4) | 2.3955 (19) | 170 (4) |
Experimental details
Crystal data | |
Chemical formula | [Li2(C6H3N2O4)2(NO3)] |
Mr | 241.99 |
Crystal system, space group | Monoclinic, P21 |
Temperature (K) | 293 |
a, b, c (Å) | 4.6273 (1), 15.8565 (3), 6.1719 (2) |
β (°) | 95.598 (2) |
V (Å3) | 450.69 (2) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.16 |
Crystal size (mm) | 0.20 × 0.14 × 0.12 |
Data collection | |
Diffractometer | Agilent SuperNova (Dual, Cu at zero, Eos) |
Absorption correction | Multi-scan (CrysAlis PRO; Agilent, 2011) |
Tmin, Tmax | 0.936, 1.000 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4032, 2572, 2401 |
Rint | 0.015 |
(sin θ/λ)max (Å−1) | 0.719 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.084, 1.10 |
No. of reflections | 2572 |
No. of parameters | 167 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.21, −0.20 |
Computer programs: CrysAlis PRO (Agilent, 2011), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
Li1—O1 | 2.086 (3) | Li2—N4 | 2.176 (3) |
Li1—O5 | 2.005 (3) | Li2—O1iii | 1.989 (3) |
Li1—N1 | 2.158 (3) | Li2—O5iv | 2.014 (3) |
Li1—O7i | 1.994 (3) | Li2—O6v | 2.040 (4) |
Li1—O3ii | 1.999 (3) | Li2—O3 | 2.086 (3) |
Symmetry codes: (i) x+1, y, z; (ii) −x+1, y+1/2, −z+1; (iii) −x+1, y−1/2, −z+1; (iv) −x+1, y−1/2, −z; (v) −x, y−1/2, −z. |
D—H···A | D—H | H···A | D···A | D—H···A |
O2—H1···O4 | 1.07 (4) | 1.34 (4) | 2.3955 (19) | 170 (4) |
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Pyrazine-2,3-dicarboxylate dianion shows large versality in forming coordination compounds with metal ions. Depending on the adopted chemical synthesis procedures, compounds with a number of different polymeric structures have been observed, as for example, in the case of the Ca(II) ion (Ptasiewicz-Bąk & Leciejewicz, 1997; Starosta & Leciejewicz, 2004, 2005a, 2005b). Polymeric structures of three LiI complexes with the title ligand have been reported (Tombul et al., 2008; Tombul & Güven, 2009; Starosta & Leciejewicz, 2011). Recently we have obtained a new compund with the title ligand. The asymmetric unit of the title compound contains two symmetry independent LiI ions. Each shows a distorted trigonal-bipyramidal coordination geometry. The Li1 ion is coordinated by ligand N1,O1 bonding group, a carboxylato O3ii atom from the adjacent ligand and O5 and O7i atoms from two different nitrate ions. The O1, O5, O7i atoms form a base, the Li1 ion is 0.1572 (3) Å out of this plane; N1 and O3ii atoms are at the axial positions. The same coordination geometry shows the Li2 ion which is situated 0.3616 (3) Å out of the equatorial plane composed of N4, O1iii and O6v atoms, while the O3 and O5iv atoms form the apices. The observed Li—O and Li—N bond distances are typical of LiI complexes with diazine carboxylate ligands. Ligand carboxylate O2 and O4 atoms remain coordination inactive. Fourier maps indicate clearly, that the O2 atom is protonated acting as a donor in a low-barrier intramolecular hydrogen bond of 2.3955 (19) Å to the O4 atom suggesting a partial proton transfer(Table 2). The ligand is monovalent and with the nitrate anion maintains the charge balance in the structure. Pyrazine ring is planar with r.m.s. of 0.0051 (2) Å; carboxylate groups C7/O1/O2 and C8/O3/O4 form with it dihedral angles of 8.4 (1)° and 12.5 (1)°, respectively. Ligand molecule bridges metal ions in µ4 mode. Li1 and Li2 ions are chelated by both N,O groups of a ligand and bidentate O1ii and O3iiatoms [Fig. 1]. A dimeric moiety Li1/O1/L2ii/O3iii constitutes a link in a bridging pathway formed by ligand molecules, giving rise to molecular ribbons propagating in the [010] direction. A nitrate anion with r.m.s. of 0.0016 (1) Å acts also in the µ4 mode and forms the other bridging pathway: while the O6 atom coordinates the Li2v and the O7 atom - the Li1iv ion, the O5 atom acts as bidentate bridging to the Li1 and Li2iii ions giving rise to a three-dimensional framework (Fig. 2).