Poly[di-μ-aqua-μ4-(pyrazine-2,5-dicarboxyl­ato)-dilithium(I)]

Wojciech Starosta; Janusz Leciejewicz

doi:10.1107/S1600536810050762

. 2010 Dec 8;67(Pt 1):m50–m51. doi: 10.1107/S1600536810050762

Poly[di-μ-aqua-μ₄-(pyrazine-2,5-dicarboxylato)-dilithium(I)]

Wojciech Starosta ^a, Janusz Leciejewicz ^a,^*

PMCID: PMC3050281 PMID: 21522570

Abstract

In the title coordination polymer, [Li₂(C₆H₂N₂O₂)(H₂O)₂]_n the pyrazine-2,5-dicarboxylate dianionic ligand bridges two symmetry-independent Li⁺ ions using both its N,O-chelating sites. The carboxylate O atom of one of them also bridges to another Li⁺ ion, while the second O atom of this group is bonded to another Li⁺ ion. Two symmetry-independent water O atoms participate also in the bridging system, which gives rise to a polymeric three-dimensional framework. Both Li⁺ ions show distorted trigonal–bipyramidal LiNO₄ coordination geometries, with the N atom in an axial site in both cases. The packing is consolidated by O—H⋯O hydrogen bonds, which occur between water molecules as donors and carboxylate O atoms as acceptors.

Related literature

For the crystal structures of transition metal complexes with the title ligand, see: Beobide et al. (2003 ▶); Xu et al. (2003 ▶); Beobide et al. (2006 ▶). For the structures of Cd and Zn complexes, see: Liu et al. (2009 ▶); Yang & Wu (2009 ▶); Yang et al. (2009 ▶). For the structures of polymeric lanthanide complexes, see: Zheng & Jin (2005 ▶); Yang et al. (2009 ▶). For the structure of a Th(IV) complex, see: Frisch & Cahill (2008 ▶). For the structure of an Sr(II) complex, see: Ptasiewicz-Bąk & Leciejewicz (1998a ▶). The structures of Li(I) complexes with pyrazine-2,3-dicarboxylate and water ligands (Tombul et al., 2008 ▶), 3-aminopyrazine-2-carboxylate and water ligands (Starosta & Leciejewicz, 2010a ▶) and pyrazine-2,3,5,6-tetracarboxylate and water ligands (Starosta & Leciejewicz, 2010b ▶) have been published. For the structure of pyrazine-2,5-dicarboxylic acid dihydrate, see: Ptasiewicz-Bąk & Leciejewicz (1998b ▶); Vishweshwar et al. (2002 ▶).

Experimental

Crystal data

[Li₂(C₆H₂N₂O₂)(H₂O)₂]
M _r = 216.01
Monoclinic,
a = 7.2107 (14) Å
b = 7.3646 (15) Å
c = 15.327 (3) Å
β = 99.71 (3)°
V = 802.2 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.16 mm⁻¹
T = 293 K
0.33 × 0.17 × 0.15 mm

Data collection

Kuma KM-4 four-circle diffractometer
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008 ▶) T _min = 0.976, T _max = 0.985
2520 measured reflections
2348 independent reflections
1694 reflections with I > 2σ(I)
R _int = 0.069
3 standard reflections every 200 reflections intensity decay: 0.6%

Refinement

R[F ² > 2σ(F ²)] = 0.054
wR(F ²) = 0.161
S = 0.99
2348 reflections
161 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.73 e Å⁻³
Δρ_min = −0.62 e Å⁻³

Data collection: KM-4 Software (Kuma, 1996 ▶); cell refinement: 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.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810050762/hb5759sup1.cif

e-67-00m50-sup1.cif^{(16.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810050762/hb5759Isup2.hkl

e-67-00m50-Isup2.hkl^{(115.4KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Li1—O1	1.958 (3)
Li1—O5	2.020 (3)
Li1—O6	2.077 (3)
Li1—O3ⁱ	2.131 (3)
Li1—N1	2.360 (3)
Li2—O6ⁱⁱ	1.981 (3)
Li2—O3	2.045 (3)
Li2—O5ⁱⁱⁱ	2.056 (3)
Li2—O4^iv	2.332 (4)
Li2—N2	2.129 (3)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O6—H62⋯O2^v	0.88 (3)	1.86 (3)	2.7210 (16)	165 (3)
O6—H61⋯O2^vi	0.84 (4)	2.00 (4)	2.8351 (19)	170 (4)
O5—H52⋯O4^vii	0.91 (3)	1.82 (3)	2.7292 (17)	175 (3)
O5—H51⋯O1^viii	0.83 (3)	1.87 (3)	2.6842 (16)	169 (3)

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Symmetry codes: (v) Inline graphic ; (vi) ; (vii) ; (viii) .

supplementary crystallographic information

Comment

Metal complexes with pyrazine dicarboxylate ligands are of interest as precursors for new polymeric materials with a wide spectrum of potential applications. Owing to a pair of N,O-chelating sites localized at opposite terminals of the hetero-ring, pyrazine-2,5-dicarboxylate ligand shows a marked tendency to form coordination polymers. Structures with a variety of polymeric patterns have been reported in compounds with 3d transition metal ions (Xu et al., 2003; Beobide et al. 2003; Beobide et al., 2006); with a number of lanthanide ions (Zheng & Jin, 2005; with Cd(II) ion (Liu et al., 2009; Yang & Wu, 2009); with Th(IV) ion (Frisch & Cahill, 2008) and with Sr(II) ion (Ptasiewicz-Bąk & Leciejewicz, 1998b). The asymmetric unit cell of the title complex, (I), contains a ligand dianion, two symmetry independent Li1 and Li2 ions and two symmetry independent O5 and O6 water molecules (Fig.1). The ligand molecule bridges the Li1 and Li2 ions using both its N,O-chelating sites; the carboxylate O2 atom remains coordination inactive. The O3 atom, which acts as bidentate, bridges the Li2 ion to the adjacent Li1ⁱⁱ ion and with the coordinated water O6 atom gives rise to a molecular chain in which metal ions are bridged by the ligand on one side and two O atoms on the other. Water O5 atoms link the chains into molecular layers. (Fig. 2). The latter, bridged by carboxylate O4 atoms which link the ligands with Li2^iv ions in adjacent layers give rise to a three-dimensional framework. The coordination environment of the Li1 ion is composed of N1, O5, O3ⁱⁱⁱ atoms: they form together with the metal ion an equatorial plane (r.m.s. of 0.0021 (1) Å) of a distorted trigonal bipyramid; the O1 and O6 atoms are at its opposite apices. The Li2 ion together with coordinated O3, O4^v and O5ⁱ atoms forms an equatorial plane (r.m.s. of 0.0307 (1) Å) of a distorted trigonal bipyramid, N2 and O6ⁱⁱ atoms are at its apices. The observed Li—O bond distances fall in the range from 1.958 (3) to 2.131 (3)Å observed also in Li complexes with pyrazine carboxylate and water ligands (Tombul et al., 2008; Starosta & Leciejewicz, 2010a, 2010b). The O4—Li2^iv bond distance is 2.332 (4) Å; the Li1—N1 and Li2—N2 bond lengths are 2.360 (3)Å and 2.129 (3) Å, respectively. The pyrazine ring is planar with r.m.s. of 0.0094 (1) Å, the carboxylate C7/O1/O2 and C8/O3/O4 groups make with it dihedral angles of 0.55 (20)° and 18.68 (17)°, respectively. Bond lengths and bond angles within the pyrazine ligand match those observed in the structure of the parent acid (Ptasiewicz-Bąk & Leciejewicz, 1998a; Vishweshwar et al., 2002). Hydrogen bond network is composed of coordinated water molecules which are as donors and carboxylate O atoms which act as acceptors.

Experimental

1 mmol of pyrazine-2,5-dicarboxylic acid dihydrate (Aldrich) dissolved in 30 ml of hot water and 2 mmols of lithium hydroxide (Aldrich) dissolved in 30 ml of hot water were mixed and boiled for 3 h under reflux with stirring. After cooling to room temperature, the solution was filtered and left to crystallize. After evaporation to dryness colourless blocks of (I) were found on the bottom of the reaction pot. They were washed with ethanol and dried in the air.