metal-organic compounds
Bis(μ3-pyrimidine-4-carboxylato)bis(μ2-pyrimidine-4-carboxylato)tetrakis(aqualithium)
aInstitute of Nuclear Chemistry and Technology, ul. Dorodna 16, 03-195 Warszawa, Poland
*Correspondence e-mail: j.leciejewicz@ichtj.waw.pl
The 4(C5H3N2O2)4(H2O)4], contains two symmetry-independent LiI ions, two symmetry-independent ligands and two symmetry-independent coordinated water molecules. They form a dinuclear unit in which the two LiI ions are bridged by two carboxylate O atoms from the two ligands. Two dinuclear units related by an inversion centre form the tetrameric molecule. One of the LiI ions shows a distorted tetrahedral coordination geometry, the other a distorted trigonal–bipyramidal environment. The tetramers are held together by hydrogen bonds in which coordinated water molecules act as donors, and the carboxylate O atoms act as acceptors. A hydrogen bond between coordinated water molecule as donor and a ring N atom as acceptor is also observed.
of the title compound, [LiRelated literature
For the crystal structures of four 3d metal complexes with pyrimidine-4-carboxylate and aqua ligands, see: Aakeröy et al. (2006). For the structure of an ionic LiI complex with pyridazine-3,6-dicarboxylate and water ligands, see: Starosta & Leciejewicz (2012).
Experimental
Crystal data
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Data collection
Refinement
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Data collection: KM-4 Software (Kuma, 1996); cell KM-4 Software; data reduction: DATAPROC (Kuma, 2001); 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/S160053681203142X/kp2430sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S160053681203142X/kp2430Isup2.hkl
1 Mmol of pyrimidine-4-carboxylic acid dissolved in 20 ml of water was titrated with an aqueous solution of LiOH until pH of 5.6 was reached. Then the mixture was boiled under reflux with stirring for 5 h. Left to crystallize at room temperature, well shaped single-crystal plates were found after evaporation to dryness. They were washed with cold metanol and dried in air.
Water H atoms were located in a difference map and refined isotropically, while the H atoms attached to pyrimidine C atoms were located at a calculated position and treated as riding on the parent atom with C—H=0.93 Å and Uiso(H)=1.2Ueq(C). Residual electron density values can be explained as due to the decomposition of the single-crystal sample (observed decay 2.8%).
# Used for convenience to store draft or replaced versions
of the abstract, comment etc. Its contents will not be outputData collection: KM-4 Software (Kuma, 1996); cell
KM-4 Software (Kuma, 1996); data reduction: DATAPROC (Kuma, 2001); 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. The tetrameric structural unit of the title compound with atom labelling scheme and 50% probability displacement ellipsoids. Symmetry code: (i) -x + 1, -y + 1, -z + 1. | |
Fig. 2. Packing of the tetramers with hydrogen bonds marked by dashed lines. |
[Li4(C5H3N2O2)4(H2O)4] | Z = 1 |
Mr = 592.20 | F(000) = 304 |
Triclinic, P1 | Dx = 1.462 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 7.2750 (15) Å | Cell parameters from 25 reflections |
b = 7.9108 (16) Å | θ = 6–15° |
c = 12.966 (3) Å | µ = 0.12 mm−1 |
α = 77.91 (3)° | T = 293 K |
β = 84.59 (3)° | Plate, colourless |
γ = 67.23 (3)° | 0.24 × 0.20 × 0.08 mm |
V = 672.7 (2) Å3 |
Kuma KM-4 four-cricle diffractometer | 2417 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.048 |
Graphite monochromator | θmax = 30.1°, θmin = 1.6° |
profile data from ω/2θ scans | h = 0→9 |
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008) | k = −10→10 |
Tmin = 0.982, Tmax = 0.991 | l = −18→18 |
4167 measured reflections | 3 standard reflections every 200 reflections |
3874 independent reflections | intensity decay: 2.8% |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.044 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.164 | w = 1/[σ2(Fo2) + (0.1119P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.07 | (Δ/σ)max < 0.001 |
3874 reflections | Δρmax = 0.50 e Å−3 |
216 parameters | Δρmin = −0.43 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.045 (10) |
[Li4(C5H3N2O2)4(H2O)4] | γ = 67.23 (3)° |
Mr = 592.20 | V = 672.7 (2) Å3 |
Triclinic, P1 | Z = 1 |
a = 7.2750 (15) Å | Mo Kα radiation |
b = 7.9108 (16) Å | µ = 0.12 mm−1 |
c = 12.966 (3) Å | T = 293 K |
α = 77.91 (3)° | 0.24 × 0.20 × 0.08 mm |
β = 84.59 (3)° |
Kuma KM-4 four-cricle diffractometer | 2417 reflections with I > 2σ(I) |
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008) | Rint = 0.048 |
Tmin = 0.982, Tmax = 0.991 | 3 standard reflections every 200 reflections |
4167 measured reflections | intensity decay: 2.8% |
3874 independent reflections |
R[F2 > 2σ(F2)] = 0.044 | 0 restraints |
wR(F2) = 0.164 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.07 | Δρmax = 0.50 e Å−3 |
3874 reflections | Δρmin = −0.43 e Å−3 |
216 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 | ||
O11 | 0.88666 (17) | 0.45353 (18) | 0.30827 (9) | 0.0367 (3) | |
O22 | 0.58826 (18) | 0.34392 (18) | 0.40929 (9) | 0.0388 (3) | |
O1 | 0.95392 (19) | 0.29323 (18) | 0.55962 (10) | 0.0375 (3) | |
O12 | 1.12854 (18) | 0.55986 (19) | 0.25411 (10) | 0.0399 (3) | |
C14 | 1.0751 (2) | 0.3590 (2) | 0.15808 (11) | 0.0271 (3) | |
C17 | 1.0257 (2) | 0.4686 (2) | 0.24760 (11) | 0.0271 (3) | |
N13 | 0.9603 (2) | 0.2639 (2) | 0.15315 (11) | 0.0384 (3) | |
N11 | 1.1556 (3) | 0.1439 (3) | 0.00732 (13) | 0.0535 (5) | |
C15 | 1.2310 (3) | 0.3528 (3) | 0.08744 (12) | 0.0363 (4) | |
H15 | 1.3087 | 0.4217 | 0.0893 | 0.044* | |
C12 | 1.0059 (3) | 0.1634 (3) | 0.07720 (16) | 0.0536 (5) | |
H12 | 0.9239 | 0.0998 | 0.0724 | 0.064* | |
C16 | 1.2665 (3) | 0.2393 (3) | 0.01366 (14) | 0.0458 (5) | |
H16 | 1.3732 | 0.2302 | −0.0334 | 0.055* | |
Li1 | 0.7612 (4) | 0.4527 (4) | 0.4490 (2) | 0.0339 (6) | |
Li2 | 0.7150 (4) | 0.3328 (4) | 0.2642 (2) | 0.0371 (6) | |
N23 | 0.6007 (2) | 0.10648 (19) | 0.28871 (10) | 0.0326 (3) | |
C27 | 0.4559 (2) | 0.27807 (19) | 0.43070 (11) | 0.0253 (3) | |
C24 | 0.4582 (2) | 0.14055 (19) | 0.36333 (11) | 0.0249 (3) | |
C25 | 0.3226 (2) | 0.0542 (2) | 0.37941 (12) | 0.0313 (3) | |
H25 | 0.2217 | 0.0804 | 0.4303 | 0.038* | |
C22 | 0.6095 (3) | −0.0203 (3) | 0.23334 (14) | 0.0415 (4) | |
H22 | 0.7098 | −0.0463 | 0.1822 | 0.050* | |
O21 | 0.32633 (17) | 0.31149 (16) | 0.50106 (9) | 0.0336 (3) | |
N21 | 0.4884 (2) | −0.1138 (2) | 0.24405 (12) | 0.0405 (4) | |
C26 | 0.3446 (3) | −0.0731 (2) | 0.31605 (14) | 0.0383 (4) | |
H26 | 0.2546 | −0.1326 | 0.3244 | 0.046* | |
O2 | 0.5018 (2) | 0.55144 (19) | 0.18214 (11) | 0.0402 (3) | |
H1 | 0.922 (4) | 0.340 (3) | 0.614 (2) | 0.055 (7)* | |
H3 | 0.378 (4) | 0.549 (4) | 0.208 (2) | 0.068 (8)* | |
H2 | 1.071 (5) | 0.274 (4) | 0.531 (2) | 0.080 (9)* | |
H4 | 0.505 (5) | 0.649 (5) | 0.189 (3) | 0.085 (10)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O11 | 0.0329 (6) | 0.0583 (7) | 0.0359 (6) | −0.0296 (5) | 0.0146 (4) | −0.0274 (5) |
O22 | 0.0413 (6) | 0.0582 (8) | 0.0401 (6) | −0.0374 (6) | 0.0153 (5) | −0.0283 (5) |
O1 | 0.0344 (6) | 0.0499 (7) | 0.0410 (6) | −0.0248 (5) | 0.0082 (5) | −0.0217 (5) |
O12 | 0.0398 (6) | 0.0590 (7) | 0.0429 (6) | −0.0357 (6) | 0.0152 (5) | −0.0297 (6) |
C14 | 0.0279 (7) | 0.0358 (7) | 0.0252 (6) | −0.0174 (6) | 0.0055 (5) | −0.0138 (5) |
C17 | 0.0252 (6) | 0.0375 (7) | 0.0259 (6) | −0.0167 (6) | 0.0040 (5) | −0.0138 (5) |
N13 | 0.0384 (7) | 0.0538 (8) | 0.0413 (7) | −0.0309 (7) | 0.0145 (6) | −0.0278 (6) |
N11 | 0.0659 (11) | 0.0736 (11) | 0.0482 (9) | −0.0461 (10) | 0.0266 (8) | −0.0421 (8) |
C15 | 0.0386 (8) | 0.0528 (10) | 0.0323 (7) | −0.0300 (7) | 0.0132 (6) | −0.0202 (7) |
C12 | 0.0612 (12) | 0.0773 (13) | 0.0555 (11) | −0.0511 (11) | 0.0262 (9) | −0.0457 (10) |
C16 | 0.0511 (10) | 0.0667 (12) | 0.0372 (8) | −0.0364 (10) | 0.0230 (8) | −0.0293 (8) |
Li1 | 0.0348 (13) | 0.0468 (15) | 0.0335 (13) | −0.0252 (12) | 0.0086 (10) | −0.0205 (11) |
Li2 | 0.0364 (14) | 0.0545 (16) | 0.0374 (13) | −0.0302 (13) | 0.0131 (11) | −0.0254 (12) |
N23 | 0.0345 (7) | 0.0371 (7) | 0.0376 (7) | −0.0215 (5) | 0.0107 (5) | −0.0206 (5) |
C27 | 0.0252 (6) | 0.0305 (7) | 0.0256 (6) | −0.0141 (5) | 0.0016 (5) | −0.0107 (5) |
C24 | 0.0258 (7) | 0.0260 (6) | 0.0278 (6) | −0.0132 (5) | 0.0013 (5) | −0.0094 (5) |
C25 | 0.0307 (7) | 0.0335 (7) | 0.0376 (8) | −0.0196 (6) | 0.0069 (6) | −0.0119 (6) |
C22 | 0.0487 (10) | 0.0469 (9) | 0.0451 (9) | −0.0298 (8) | 0.0187 (8) | −0.0286 (8) |
O21 | 0.0311 (6) | 0.0429 (6) | 0.0360 (6) | −0.0193 (5) | 0.0110 (4) | −0.0213 (5) |
N21 | 0.0517 (9) | 0.0387 (8) | 0.0460 (8) | −0.0280 (7) | 0.0072 (7) | −0.0212 (6) |
C26 | 0.0469 (9) | 0.0379 (8) | 0.0448 (9) | −0.0297 (7) | 0.0034 (7) | −0.0142 (7) |
O2 | 0.0412 (7) | 0.0468 (7) | 0.0485 (7) | −0.0290 (6) | 0.0118 (5) | −0.0239 (5) |
O11—C17 | 1.2491 (18) | N11—C12 | 1.332 (2) |
Li1—O11 | 1.961 (3) | C15—C16 | 1.386 (2) |
Li1—O22 | 1.932 (3) | C15—H15 | 0.9300 |
Li1—O21i | 1.953 (3) | C12—H12 | 0.9300 |
Li1—O1 | 1.967 (3) | C16—H16 | 0.9300 |
Li2—O11 | 2.021 (3) | N23—C22 | 1.3299 (19) |
Li2—O22 | 2.020 (3) | N23—C24 | 1.3370 (18) |
Li2—N13 | 2.155 (3) | C27—O21 | 1.2395 (17) |
Li2—O2 | 1.998 (4) | C27—C24 | 1.5257 (18) |
Li2—N23 | 2.205 (3) | C24—C25 | 1.3803 (19) |
O22—C27 | 1.2463 (17) | C25—C26 | 1.383 (2) |
O1—H1 | 0.83 (3) | C25—H25 | 0.9300 |
O1—H2 | 0.87 (3) | C22—N21 | 1.335 (2) |
O12—C17 | 1.2425 (18) | C22—H22 | 0.9300 |
C14—N13 | 1.3354 (18) | O21—Li1i | 1.953 (3) |
C14—C15 | 1.381 (2) | N21—C26 | 1.323 (2) |
C14—C17 | 1.5263 (19) | C26—H26 | 0.9300 |
N13—C12 | 1.332 (2) | O2—H3 | 0.93 (3) |
N11—C16 | 1.318 (2) | O2—H4 | 0.81 (4) |
C17—O11—Li1 | 149.71 (13) | O2—Li2—O22 | 98.68 (14) |
C17—O11—Li2 | 117.79 (12) | O2—Li2—O11 | 102.08 (15) |
Li1—O11—Li2 | 91.26 (11) | O22—Li2—O11 | 86.21 (11) |
C27—O22—Li1 | 151.27 (13) | O2—Li2—N13 | 103.79 (15) |
C27—O22—Li2 | 116.48 (12) | O22—Li2—N13 | 155.06 (18) |
Li1—O22—Li2 | 92.15 (11) | O11—Li2—N13 | 78.69 (10) |
Li1—O1—H1 | 108.4 (17) | O2—Li2—N23 | 104.14 (13) |
Li1—O1—H2 | 106 (2) | O22—Li2—N23 | 77.76 (10) |
H1—O1—H2 | 121 (3) | O11—Li2—N23 | 150.98 (18) |
N13—C14—C15 | 121.20 (13) | N13—Li2—N23 | 106.61 (13) |
N13—C14—C17 | 115.74 (12) | C22—N23—C24 | 116.37 (13) |
C15—C14—C17 | 123.04 (13) | C22—N23—Li2 | 134.44 (13) |
O12—C17—O11 | 126.77 (13) | C24—N23—Li2 | 107.11 (11) |
O12—C17—C14 | 117.50 (12) | O21—C27—O22 | 126.68 (13) |
O11—C17—C14 | 115.71 (13) | O21—C27—C24 | 117.70 (12) |
C12—N13—C14 | 116.22 (14) | O22—C27—C24 | 115.61 (12) |
C12—N13—Li2 | 133.18 (14) | N23—C24—C25 | 121.87 (13) |
C14—N13—Li2 | 110.24 (12) | N23—C24—C27 | 116.20 (12) |
C16—N11—C12 | 115.34 (15) | C25—C24—C27 | 121.93 (13) |
C14—C15—C16 | 117.12 (15) | C24—C25—C26 | 116.60 (14) |
C14—C15—H15 | 121.4 | C24—C25—H25 | 121.7 |
C16—C15—H15 | 121.4 | C26—C25—H25 | 121.7 |
N11—C12—N13 | 127.28 (16) | N23—C22—N21 | 126.36 (15) |
N11—C12—H12 | 116.4 | N23—C22—H22 | 116.8 |
N13—C12—H12 | 116.4 | N21—C22—H22 | 116.8 |
N11—C16—C15 | 122.80 (15) | C27—O21—Li1i | 120.24 (12) |
N11—C16—H16 | 118.6 | C26—N21—C22 | 116.08 (13) |
C15—C16—H16 | 118.6 | N21—C26—C25 | 122.67 (14) |
O22—Li1—O21i | 125.60 (16) | N21—C26—H26 | 118.7 |
O22—Li1—O11 | 90.34 (12) | C25—C26—H26 | 118.7 |
O21i—Li1—O11 | 115.37 (15) | Li2—O2—H3 | 108.4 (17) |
O22—Li1—O1 | 115.40 (15) | Li2—O2—H4 | 112 (2) |
O21i—Li1—O1 | 99.05 (12) | H3—O2—H4 | 108 (3) |
O11—Li1—O1 | 111.64 (15) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O12ii | 0.83 (3) | 1.98 (3) | 2.8120 (18) | 175 (2) |
O2—H3···O12iii | 0.93 (3) | 1.84 (3) | 2.7671 (18) | 177 (3) |
O1—H2···O21iv | 0.87 (3) | 1.98 (3) | 2.7941 (18) | 155 (3) |
O2—H4···N21v | 0.81 (4) | 2.10 (4) | 2.8881 (19) | 166 (3) |
Symmetry codes: (ii) −x+2, −y+1, −z+1; (iii) x−1, y, z; (iv) x+1, y, z; (v) x, y+1, z. |
Experimental details
Crystal data | |
Chemical formula | [Li4(C5H3N2O2)4(H2O)4] |
Mr | 592.20 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 7.2750 (15), 7.9108 (16), 12.966 (3) |
α, β, γ (°) | 77.91 (3), 84.59 (3), 67.23 (3) |
V (Å3) | 672.7 (2) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.24 × 0.20 × 0.08 |
Data collection | |
Diffractometer | Kuma KM-4 four-cricle |
Absorption correction | Analytical (CrysAlis RED; Oxford Diffraction, 2008) |
Tmin, Tmax | 0.982, 0.991 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4167, 3874, 2417 |
Rint | 0.048 |
(sin θ/λ)max (Å−1) | 0.706 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.044, 0.164, 1.07 |
No. of reflections | 3874 |
No. of parameters | 216 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.50, −0.43 |
Computer programs: KM-4 Software (Kuma, 1996), DATAPROC (Kuma, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).
Li1—O11 | 1.961 (3) | Li2—O22 | 2.020 (3) |
Li1—O22 | 1.932 (3) | Li2—N13 | 2.155 (3) |
Li1—O21i | 1.953 (3) | Li2—O2 | 1.998 (4) |
Li1—O1 | 1.967 (3) | Li2—N23 | 2.205 (3) |
Li2—O11 | 2.021 (3) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1···O12ii | 0.83 (3) | 1.98 (3) | 2.8120 (18) | 175 (2) |
O2—H3···O12iii | 0.93 (3) | 1.84 (3) | 2.7671 (18) | 177 (3) |
O1—H2···O21iv | 0.87 (3) | 1.98 (3) | 2.7941 (18) | 155 (3) |
O2—H4···N21v | 0.81 (4) | 2.10 (4) | 2.8881 (19) | 166 (3) |
Symmetry codes: (ii) −x+2, −y+1, −z+1; (iii) x−1, y, z; (iv) x+1, y, z; (v) x, y+1, z. |
References
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Starosta, W. & Leciejewicz, J. (2012). Acta Cryst. E68, m324–m325. CSD CrossRef IUCr Journals Google Scholar
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The structure of the title compound is built of tetrameric molecular clusters, each composed of two dinuclear units related by an inversion centre. A dinuclear unit consists of two symmetry independent LiI ions, two symmetry independent ligand molecules and two symmetry independent coordinating water molecules (Fig. 1). The ligand molecule PMC1 shows µ2 coordination mode: its carboxylato O11 atom acts as bidentate bridging to Li1 and the Li2 ions, leaving the O12 atom chelating inactive. Ligand PMC2 shows µ3 bridging mode since both its carboxylato O atoms act as bridging: the O22 atom bridges the Li2 ion and the Li1 ion while the O21 atom links the Li2 ion and the Li1(i). The Li1—O11—Li2—O22—Li1 bridging pathway forms a core of a dinuclear unit with r.m.s. of 0.0133 (2) Å which through bridging O21 and O21(i) atoms generates a centrosymmetric tetrameric molecular cluster with a core represented by a bonding loop Li1—O22—C27—O21—Li1(i)—O22(i)—C37(i)—O21(i)—Li1(i) with r.m.s. of 0.1664 (3) Å. Li1 ion, chelated by O1, O11, O22 and O21(i) atoms shows distorted tetrahedral coordination geometry. On the other hand, Li2 coordination polyhedron is a distorted trigonal bipyramid with an equatorial plane composed of O11, O2 and N23 atoms. The Li2 ion is 0.1809 (2) Å out of this plane; N13 and O22 atoms are at axial positions. The observed Li—O and Li—N bond distances are typical (Table 1). Both pyrimidine rings are planar with r.m.s. of 0.0080 (2) Å and 0.0079 (2) Å for ligand PMC1 and PMC2, respectively. The carboxylate groups C17/O11/O12 and C27/O21/O22 make dihedral angles of 4.3 (1)° and 3.3 (1)/% with the respective rings. Bond distances and bond angles within both ligand molecules do not differ from those observed in the structures of 3 d-metal complexes with the title ligand (Aakeröy et al., 2006). A hydrogen bond system in which water molecules are donors and carboxylate O atoms are acceptors is responsible for the cohesion of the structure (Table 2, Fig. 2). Isolated neutral tetrameric clusters with a different internal structure have been detected in the structure of an ionic LiI complex with pyridazine-3,6-dicarboxylate and water ligands aside dimeric anions and hydrazine cations (Starosta & Leciejewicz, 2012).