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

Starosta, W.; Leciejewicz, J.

doi:10.1107/S1600536810050762

metal-organic compounds

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ISSN: 2056-9890

Volume 67| Part 1| January 2011| Pages m50-m51

https://doi.org/10.1107/S1600536810050762

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

Wojciech Starosta ^a and Janusz Leciejewicz ^a ^*

^aInstitute of Nuclear Chemistry and Technology, ul.Dorodna 16, 03-195 Warszawa, Poland
^*Correspondence e-mail: j.leciejewicz@ichtj.waw.pl

(Received 29 November 2010; accepted 3 December 2010; online 8 December 2010)

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, P 2₁ /n
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 $[Oxford Diffraction (2008). CrysAlis RED. Oxford Diffraction Ltd, Yarnton, England.]$ ) 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[F² > 2σ(F²)] = 0.054
wR(F²) = 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

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)
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (ii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (iii) -x+2, -y, -z+2; (iv) $[-x+{\script{3\over 2}}, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

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)
Symmetry codes: (v) x, y+1, z; (vi) -x+1, -y, -z+2; (vii) -x+2, -y+1, -z+2; (viii) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{5\over 2}}]$ .

Data collection: KM-4 Software (Kuma, 1996 $[Kuma (1996). KM-4 Software. Kuma Diffraction Ltd, Wrocław, Poland.]$ ); cell refinement: KM-4 Software; data reduction: DATAPROC (Kuma, 2001 $[Kuma (2001). DATAPROC. Kuma Diffraction Ltd, Wrocław, Poland.]$ ); 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

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

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810050762/hb5759Isup2.hkl

checkCIF report

Comment top

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.

Related literature top

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 top

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.

Structure description top

# Used for convenience to store draft or replaced versions # of the abstract, comment etc. # Its contents will not be output

Computing details top

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

Figures top

	Fig. 1. A structural unit of (I) with 50% probability displacement ellipsoids. Symmetry code: (i) -x + 2,-y,-z + 2. (ii) x + 1/2, -y + 1/2, z - 1/2. (iii) x - 1/2, -y + 1/2, z + 1/2. (iv) -x + 3/2, y + 1/2, -z + 3/2. (v) -x + 3/2, y - 1/2, -z + 3/2.
	Fig. 2. A fragment of a molecular layer.

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

Crystal data top

[Li₂(C₆H₂N₂O₂)(H₂O)₂]	F(000) = 440
M_r = 216.01	D_x = 1.788 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 7.2107 (14) Å	θ = 6–15°
b = 7.3646 (15) Å	µ = 0.16 mm⁻¹
c = 15.327 (3) Å	T = 293 K
β = 99.71 (3)°	Plates, colourless
V = 802.2 (3) Å³	0.33 × 0.17 × 0.15 mm
Z = 4

Data collection top

Kuma KM-4 four-circle diffractometer	1694 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.069
Graphite monochromator	θ_max = 30.1°, θ_min = 2.7°
profile data from ω/2θ scans	h = 0→10
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008)	k = 0→10
T_min = 0.976, T_max = 0.985	l = −21→21
2520 measured reflections	3 standard reflections every 200 reflections
2348 independent reflections	intensity decay: 0.6%

Refinement top

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)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.161	H atoms treated by a mixture of independent and constrained refinement
S = 0.99	w = 1/[σ²(F_o²) + (0.1327P)² + 0.0049P] where P = (F_o² + 2F_c²)/3
2348 reflections	(Δ/σ)_max = 0.001
161 parameters	Δρ_max = 0.73 e Å⁻³
0 restraints	Δρ_min = −0.62 e Å⁻³

Crystal data top

[Li₂(C₆H₂N₂O₂)(H₂O)₂]	V = 802.2 (3) Å³
M_r = 216.01	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 7.2107 (14) Å	µ = 0.16 mm⁻¹
b = 7.3646 (15) Å	T = 293 K
c = 15.327 (3) Å	0.33 × 0.17 × 0.15 mm
β = 99.71 (3)°

Data collection top

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

Refinement top

R[F² > 2σ(F²)] = 0.054	0 restraints
wR(F²) = 0.161	H atoms treated by a mixture of independent and constrained refinement
S = 0.99	Δρ_max = 0.73 e Å⁻³
2348 reflections	Δρ_min = −0.62 e Å⁻³
161 parameters

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

	x	y	z	U_iso*/U_eq
O5	0.92850 (16)	0.21032 (15)	1.23861 (7)	0.0235 (3)
N2	0.85719 (16)	0.06063 (16)	0.86051 (8)	0.0178 (3)
O3	0.99726 (17)	0.31016 (14)	0.76139 (7)	0.0248 (3)
O6	0.54300 (17)	0.41912 (16)	1.12325 (8)	0.0248 (3)
N1	0.76024 (18)	0.16459 (17)	1.02138 (8)	0.0194 (3)
O1	0.65141 (17)	−0.08194 (16)	1.12869 (7)	0.0258 (3)
C7	0.69244 (18)	−0.14435 (18)	1.05880 (8)	0.0171 (3)
C3	0.85787 (18)	0.23438 (19)	0.88494 (9)	0.0167 (3)
C8	0.9150 (2)	0.37044 (19)	0.82054 (9)	0.0194 (3)
O2	0.68766 (17)	−0.30725 (14)	1.03608 (7)	0.0252 (3)
O4	0.8671 (2)	0.53125 (16)	0.83062 (9)	0.0342 (3)
C5	0.80318 (19)	−0.06117 (19)	0.91591 (9)	0.0177 (3)
H5	0.7990	−0.1835	0.9006	0.021*
C6	0.75335 (17)	−0.00880 (18)	0.99566 (8)	0.0155 (3)
C2	0.8103 (2)	0.28635 (19)	0.96561 (9)	0.0202 (3)
H2	0.8136	0.4087	0.9808	0.024*
Li2	0.9486 (5)	0.0403 (4)	0.7358 (2)	0.0360 (7)
Li1	0.6732 (4)	0.1742 (4)	1.1630 (2)	0.0298 (6)
H51	0.908 (4)	0.263 (4)	1.284 (2)	0.063 (9)*
H62	0.609 (4)	0.503 (4)	1.1012 (17)	0.049 (7)*
H52	0.994 (4)	0.294 (4)	1.2126 (18)	0.051 (7)*
H61	0.472 (5)	0.375 (5)	1.079 (3)	0.093 (12)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O5	0.0301 (6)	0.0199 (5)	0.0225 (5)	−0.0017 (4)	0.0104 (4)	−0.0037 (4)
N2	0.0191 (5)	0.0162 (5)	0.0190 (5)	0.0008 (4)	0.0059 (4)	0.0006 (4)
O3	0.0301 (6)	0.0227 (5)	0.0246 (5)	0.0010 (4)	0.0137 (4)	0.0013 (4)
O6	0.0298 (6)	0.0216 (5)	0.0246 (5)	−0.0021 (4)	0.0096 (4)	0.0010 (4)
N1	0.0229 (6)	0.0172 (6)	0.0191 (5)	0.0018 (4)	0.0064 (4)	−0.0001 (4)
O1	0.0365 (6)	0.0212 (5)	0.0230 (5)	0.0003 (4)	0.0148 (5)	0.0015 (4)
C7	0.0148 (6)	0.0174 (6)	0.0191 (6)	−0.0001 (5)	0.0033 (5)	0.0010 (5)
C3	0.0156 (6)	0.0166 (6)	0.0182 (6)	0.0019 (4)	0.0037 (5)	0.0015 (4)
C8	0.0213 (7)	0.0169 (6)	0.0211 (6)	0.0007 (5)	0.0063 (5)	0.0025 (5)
O2	0.0335 (6)	0.0178 (5)	0.0259 (5)	−0.0039 (4)	0.0094 (4)	−0.0006 (4)
O4	0.0516 (8)	0.0171 (5)	0.0400 (7)	0.0061 (5)	0.0249 (6)	0.0042 (5)
C5	0.0197 (6)	0.0152 (6)	0.0192 (6)	−0.0008 (5)	0.0057 (5)	−0.0004 (4)
C6	0.0145 (6)	0.0145 (6)	0.0178 (6)	0.0008 (4)	0.0035 (5)	0.0014 (4)
C2	0.0264 (7)	0.0145 (6)	0.0211 (6)	0.0025 (5)	0.0082 (5)	0.0003 (5)
Li2	0.053 (2)	0.0239 (14)	0.0359 (16)	−0.0019 (13)	0.0218 (15)	−0.0027 (11)
Li1	0.0305 (14)	0.0250 (13)	0.0332 (14)	0.0005 (11)	0.0033 (11)	−0.0046 (11)

Geometric parameters (Å, º) top

O5—Li2ⁱ	2.056 (4)	O6—H62	0.88 (3)
O3—Li1ⁱⁱ	2.131 (3)	O6—H61	0.84 (4)
O6—Li2ⁱⁱⁱ	1.981 (3)	N1—C2	1.3303 (18)
O4—Li2^iv	2.332 (4)	N1—C6	1.3348 (18)
Li1—O1	1.958 (3)	O1—C7	1.2463 (17)
Li1—O5	2.020 (3)	C7—O2	1.2481 (17)
Li1—O6	2.077 (3)	C7—C6	1.5064 (18)
Li1—O3ⁱⁱⁱ	2.131 (3)	C3—C2	1.3913 (18)
Li1—N1	2.360 (3)	C3—C8	1.5117 (19)
Li2—O6ⁱⁱ	1.981 (3)	C8—O4	1.2506 (19)
Li2—O3	2.045 (3)	C5—C6	1.3857 (18)
Li2—O5ⁱ	2.056 (3)	C5—H5	0.9300
Li2—O4^v	2.332 (4)	C2—H2	0.9300
Li2—N2	2.129 (3)	Li2—Li1ⁱⁱ	2.983 (4)
O5—H51	0.83 (3)	Li2—Li1ⁱ	3.303 (5)
O5—H52	0.91 (3)	Li1—Li2ⁱⁱⁱ	2.983 (4)
N2—C3	1.3330 (18)	Li1—Li2ⁱ	3.303 (5)
N2—C5	1.3376 (17)	Li1—H61	2.30 (4)
O3—C8	1.2458 (17)

Li1—O5—Li2ⁱ	108.24 (14)	O3—Li2—N2	80.13 (12)
Li1—O5—H51	105 (2)	O5ⁱ—Li2—N2	94.63 (14)
Li2ⁱ—O5—H51	113 (2)	O6ⁱⁱ—Li2—O4^v	94.45 (15)
Li1—O5—H52	109.1 (17)	O3—Li2—O4^v	103.58 (15)
Li2ⁱ—O5—H52	117.0 (18)	O5ⁱ—Li2—O4^v	114.53 (15)
H51—O5—H52	103 (3)	N2—Li2—O4^v	88.10 (13)
C3—N2—C5	116.94 (12)	O6ⁱⁱ—Li2—Li1ⁱⁱ	43.94 (9)
C3—N2—Li2	109.43 (13)	O3—Li2—Li1ⁱⁱ	45.59 (9)
C5—N2—Li2	133.63 (13)	O5ⁱ—Li2—Li1ⁱⁱ	117.39 (15)
C8—O3—Li2	113.48 (13)	N2—Li2—Li1ⁱⁱ	123.78 (15)
C8—O3—Li1ⁱⁱ	155.36 (13)	O4^v—Li2—Li1ⁱⁱ	114.10 (14)
Li2—O3—Li1ⁱⁱ	91.16 (13)	O6ⁱⁱ—Li2—Li1ⁱ	95.92 (14)
Li2ⁱⁱⁱ—O6—Li1	94.61 (13)	O3—Li2—Li1ⁱ	105.87 (15)
Li2ⁱⁱⁱ—O6—H62	121.1 (18)	O5ⁱ—Li2—Li1ⁱ	35.51 (9)
Li1—O6—H62	118.3 (19)	N2—Li2—Li1ⁱ	88.18 (13)
Li2ⁱⁱⁱ—O6—H61	120 (3)	O4^v—Li2—Li1ⁱ	149.19 (14)
Li1—O6—H61	95 (3)	Li1ⁱⁱ—Li2—Li1ⁱ	93.17 (11)
H62—O6—H61	105 (3)	O1—Li1—O5	107.76 (15)
C2—N1—C6	117.11 (12)	O1—Li1—O6	138.27 (17)
C2—N1—Li1	135.56 (12)	O5—Li1—O6	112.16 (15)
C6—N1—Li1	107.34 (11)	O1—Li1—O3ⁱⁱⁱ	102.21 (15)
C7—O1—Li1	124.49 (14)	O5—Li1—O3ⁱⁱⁱ	100.41 (14)
O1—C7—O2	126.51 (13)	O6—Li1—O3ⁱⁱⁱ	82.36 (12)
O1—C7—C6	116.42 (12)	O1—Li1—N1	75.27 (11)
O2—C7—C6	117.07 (12)	O5—Li1—N1	100.00 (14)
N2—C3—C2	121.60 (12)	O6—Li1—N1	86.19 (12)
N2—C3—C8	116.19 (11)	O3ⁱⁱⁱ—Li1—N1	159.18 (16)
C2—C3—C8	122.21 (12)	O1—Li1—Li2ⁱⁱⁱ	139.07 (16)
O3—C8—O4	127.07 (13)	O5—Li1—Li2ⁱⁱⁱ	101.09 (13)
O3—C8—C3	117.04 (13)	O6—Li1—Li2ⁱⁱⁱ	41.45 (9)
O4—C8—C3	115.82 (12)	O3ⁱⁱⁱ—Li1—Li2ⁱⁱⁱ	43.25 (9)
C8—O4—Li2^iv	104.05 (13)	N1—Li1—Li2ⁱⁱⁱ	127.64 (14)
N2—C5—C6	121.33 (13)	O1—Li1—Li2ⁱ	71.81 (11)
N2—C5—H5	119.3	O5—Li1—Li2ⁱ	36.25 (8)
C6—C5—H5	119.3	O6—Li1—Li2ⁱ	148.18 (15)
N1—C6—C5	121.63 (12)	O3ⁱⁱⁱ—Li1—Li2ⁱ	103.68 (13)
N1—C6—C7	116.40 (11)	N1—Li1—Li2ⁱ	95.21 (12)
C5—C6—C7	121.96 (12)	Li2ⁱⁱⁱ—Li1—Li2ⁱ	128.23 (11)
N1—C2—C3	121.33 (13)	O1—Li1—H61	117.0 (10)
N1—C2—H2	119.3	O5—Li1—H61	131.5 (10)
C3—C2—H2	119.3	O6—Li1—H61	21.3 (10)
O6ⁱⁱ—Li2—O3	86.97 (13)	O3ⁱⁱⁱ—Li1—H61	88.0 (9)
O6ⁱⁱ—Li2—O5ⁱ	95.80 (14)	N1—Li1—H61	75.4 (9)
O3—Li2—O5ⁱ	141.4 (2)	Li2ⁱⁱⁱ—Li1—H61	54.9 (10)
O6ⁱⁱ—Li2—N2	167.10 (18)	Li2ⁱ—Li1—H61	164.0 (10)

Symmetry codes: (i) −x+2, −y, −z+2; (ii) x+1/2, −y+1/2, z−1/2; (iii) x−1/2, −y+1/2, z+1/2; (iv) −x+3/2, y+1/2, −z+3/2; (v) −x+3/2, y−1/2, −z+3/2.

Hydrogen-bond geometry (Å, º) top

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

Symmetry codes: (vi) x, y+1, z; (vii) −x+1, −y, −z+2; (viii) −x+2, −y+1, −z+2; (ix) −x+3/2, y+1/2, −z+5/2.

Experimental details

Crystal data
Chemical formula	[Li₂(C₆H₂N₂O₂)(H₂O)₂]
M_r	216.01
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	293
a, b, c (Å)	7.2107 (14), 7.3646 (15), 15.327 (3)
β (°)	99.71 (3)
V (Å³)	802.2 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.16
Crystal size (mm)	0.33 × 0.17 × 0.15

Data collection
Diffractometer	Kuma KM-4 four-circle
Absorption correction	Analytical (CrysAlis RED; Oxford Diffraction, 2008)
T_min, T_max	0.976, 0.985
No. of measured, independent and observed [I > 2σ(I)] reflections	2520, 2348, 1694
R_int	0.069
(sin θ/λ)_max (Å⁻¹)	0.705

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.054, 0.161, 0.99
No. of reflections	2348
No. of parameters	161
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.73, −0.62

Computer programs: KM-4 Software (Kuma, 1996), DATAPROC (Kuma, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected bond lengths (Å) top

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

Symmetry codes: (i) x−1/2, −y+1/2, z+1/2; (ii) x+1/2, −y+1/2, z−1/2; (iii) −x+2, −y, −z+2; (iv) −x+3/2, y−1/2, −z+3/2.

Hydrogen-bond geometry (Å, º) top

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)

Symmetry codes: (v) x, y+1, z; (vi) −x+1, −y, −z+2; (vii) −x+2, −y+1, −z+2; (viii) −x+3/2, y+1/2, −z+5/2.

References

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Volume 67| Part 1| January 2011| Pages m50-m51

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