catena-Poly[[(6-carb­­oxy­pyrazine-2-carboxyl­ato)lithium]-μ-aqua]

The asymmetric unit of the title compound, [Li(C₆H₃N₂O₄)(H₂O)]_n, contains an Li^I ion with a distorted trigonal–bipyramidal coordination environment. It is chelated by a singly protonated ligand mol­ecule via its heterocyclic N atom, by two O aoms, each donated by an adjacent carboxyl­ate group, and is further coordinated by a water O atom which acts as a bridge, forming a mol­ecular ribbon. A proton attached to one of the carboxyl­ate O atoms is situated on an inversion centre and forms a short centrosymmetric hydrogen bond, generating mol­ecular layers parallel to the ac plane. These layers are held together by weak O—H⋯O hydrogen bonds in which the coordinated water mol­ecules act as donors, whereas carboxyl­ate O atoms are acceptors.

Related literature

For the structures of three lithium complexes with pyrazine-2,3-dicarboxyl­ate and water ligands, see: Tombul et al. (2008); Tombul & Guven (2009); Starosta & Leciejewicz (2011b). For the structure of a Li^I complex with a pyrazine-2,5-dicarboxyl­ate ligand, see: Starosta & Leciejewicz (2011a) and for the structure of a Li^I complex with pyrazine-2,3,5,6-tetra­carboxyl­ate, see: Starosta & Leciejewicz (2010). The structure of pyrazine-2,6-dicarboxyl­ate acid dihydrate has been also reported, see: Ptasiewicz-Bąk & Leciejewicz (2003).

Experimental

Crystal data

• [Li(C₆H₃N₂O₄)(H₂O)]

• M_r = 192.06

• Monoclinic, P 2₁ /m

• a = 3.5346 (7) Å

• b = 12.519 (3) Å

• c = 8.3583 (17) Å

• β = 97.86 (3)°

• V = 366.37 (13) ų

• Z = 2

• Mo Kα radiation

• μ = 0.15 mm⁻¹

• T = 293 K

• 0.31 × 0.22 × 0.08 mm

Data collection

• Kuma KM-4 four-circle diffractometer

• Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008) T_min = 0.954, T_max = 0.973

• 1262 measured reflections

• 1106 independent reflections

• 729 reflections with I > 2σ(I)

• R_int = 0.027

• 3 standard reflections every 200 reflections intensity decay: 1.3%

Refinement

• R[F² > 2σ(F²)] = 0.054

• wR(F²) = 0.171

• S = 1.09

• 1106 reflections

• 75 parameters

• 2 restraints

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

• Δρ_max = 0.38 e Å⁻³

• Δρ_min = −0.31 e Å⁻³

Table 1
Selected bond lengths (Å)

N1—Li1	2.115 (7)
O1—Li1	2.271 (2)
O3—Li1	1.950 (7)
O3—Li1^i	2.085 (7)
Li1—O1^ii	2.271 (2)
Symmetry codes: (i) x+1, y, z; (ii) .

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H31⋯O2^iii	0.83 (2)	2.24 (2)	2.9987 (19)	152 (3)
O1—H1⋯O1^iii	1.23 (1)	1.23 (1)	2.455 (3)	180 (1)
Symmetry code: (iii) -x+1, -y+1, -z.

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.

Supporting information

S1. Comment

The asymmetric unit of the title compound consists of a Li^I ion, a singly deprotonated pyrazine-2,6-dicarboxylate iigand molecule and a coordinated water molecule (Fig. 1). The coordination environment of the Li1 ion is composed of five atoms: ligand carboxylate O1, O1ⁱ, hetero-ring N1, aqua O3 and O3ⁱⁱⁱ atoms. The coplanar Li1, N1, O3 and O3ⁱⁱⁱ form the base of a distorted trigonal bipyramid with O1 and O1ⁱ atoms at its apices.[Symmetry code: ⁱ x, -y + 3/2, z; ⁱⁱ x + 1, y, z, ⁱⁱⁱ x - 1, y, z, ^iv 1 - x, 1 - y, -z]. The observed Li—O and Li—N bond distances (Table 1) are typical for Li^I complexes with diazine carboxylate ligands, see, for example: Tombul & Guven, (2009); Starosta & Leciejewicz, (2010); Starosta & Leciejewicz,(2011b). Coordinated aqua O3 atom bridges Li1 with Liⁱⁱ ion to form molecular ribbons which propagate in the crystal alon [001] direction (Fig. 2). The carboxylato O1 atom remains protonated and mantains the charge balance. This proton, located at an inversion centre, forms a short centrosymmetric O1—H1···O1^iv hydrogen bond of 2.455 (3) A° which links adjacent ribbons to form molecular layers. The pyrazine ring is planar with r.m.s of 0.0024 (1) Å.The C7/O1/O2 and C7ⁱ/O1ⁱ/O2ⁱ carboxylic groups make with it dihedral angles of 3.0 (1)°. Bond distances and bond angles within the ligand molecule do not differ from those reported in the structure of pyrazine-2,6-dicarboxylic acid dihydrate (Ptasiewicz-Bąk & Leciejewicz, 2003). The layers are held together by weak hydrogen bonds in which the coordinated water molecules act as donors and carboxylate O atoms and hetero-ring N atoms from adjacent layers are as acceptors (Table 2). Protonated ligand carboxylate groups have been observed in the structures of Li^I complexes with pyrazine-2,3-carboxylate (Tombul et al., 2008, Starosta & Leciejewicz, 2011b) and pyrazine-2,5-dicarboxylate (Starosta & Leciejewicz, 2011a) ligands and in the structure of a Li^I complex with pyrazine-2,3,5,6-tetracarboxylate ligand (Starosta & Leciejewicz, 2010). In the above structures, protons participate in short hydrogen bonds in which O atoms from adjacent intra-ligand carboxylate groups are donors and acceptors.

Related literature

For the structures of three lithium complexes with pyrazine-2,3-dicarboxylate and water ligands, see: Tombul et al. (2008); Tombul & Guven, (2009); Starosta & Leciejewicz, (2011b). For the structure of a Li^I complex with a pyrazine-2,5-dicarboxylate ligand, see: Starosta & Leciejewicz (2011a) and for the structure of a Li^I complex with pyrazine-2,3,5,6-tetracarboxylate, see: Starosta & Leciejewicz (2010). The structure of pyrazine-2,6-dicarboxylate acid dihydrate has been also reported, see: Ptasiewicz-Bąk & Leciejewicz (2003).

S2. Experimental

Hot aqueous solutions of 1 mmol of pyrazine-2,6-dicarboxylic acid dihydrate and 1 mmol of lithium hydroxide (Aldrich) were mixed and boiled under reflux with constant stirring for 6 h. Left for evaporation at room temperature, after a couple of days small single-crystal plates of the title complex were obtained. Crystals were washed with cold ethanol and dried in air.

S3. Refinement

Pyrazine ring H atoms atoms were placed in calculated positions with C—H = 0.93 and 0.96Å and treated as riding on the parent atoms with U_iso(H)= 1.2U_eq(C)or U_iso(H)=1.5U _eq(C_methyl). Water H atoms were found in Fourier map and refined isotropically.

Computing details

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

	Fig. 1. The asymmetric unit of the title compound with atom labelling scheme and 50% probability displacement ellipsoids. Symmetry code: ^i x, -y + 3/2, z; ^ii x + 1, y, z; ^iii x - 1, y, z; ^iv 1 - x, 1 - y, -z; ^v 1 - x, -1/2 + y, -z; ^vi x, 1/2 - y, z; ^vii 1 - x, 1/2 + y, -z; ^viii 2 - x, 1 - y, -z.
	Fig. 2. The alignment of the ribbons viewed along the axis a.

catena-Poly[[(6-carboxypyrazine-2-carboxylato)lithium]-µ-aqua]

Crystal data

[Li(C6H3N2O4)(H2O)]	F(000) = 196
Mr = 192.06	Dx = 1.741 Mg m^−3
Monoclinic, P21/m	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yb	Cell parameters from 25 reflections
a = 3.5346 (7) Å	θ = 6–15°
b = 12.519 (3) Å	µ = 0.15 mm^−1
c = 8.3583 (17) Å	T = 293 K
β = 97.86 (3)°	Plates, colourless
V = 366.37 (13) Å^3	0.31 × 0.22 × 0.08 mm
Z = 2

Data collection

Kuma KM-4 four-circle diffractometer	729 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.027
Graphite monochromator	θmax = 30.1°, θmin = 3.0°
Profile data from ω/2θ scans	h = 0→4
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008)	k = −17→0
Tmin = 0.954, Tmax = 0.973	l = −11→11
1262 measured reflections	3 standard reflections every 200 reflections
1106 independent reflections	intensity decay: 1.3%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.054	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.171	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.1039P)^2 + 0.0995P] where P = (Fo^2 + 2Fc^2)/3
1106 reflections	(Δ/σ)max < 0.001
75 parameters	Δρmax = 0.38 e Å^−3
2 restraints	Δρmin = −0.31 e Å^−3

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
N1	0.2901 (6)	0.7500	0.2305 (2)	0.0216 (4)
O1	0.4179 (5)	0.57853 (10)	0.07619 (15)	0.0333 (4)
C2	0.2425 (5)	0.65866 (13)	0.30619 (19)	0.0216 (4)
N2	0.0883 (7)	0.7500	0.5385 (2)	0.0297 (5)
O2	0.2587 (5)	0.47052 (12)	0.27081 (17)	0.0371 (4)
C3	0.1409 (5)	0.65888 (14)	0.4618 (2)	0.0269 (4)
H3	0.1092	0.5942	0.5130	0.032*
C7	0.3068 (5)	0.55822 (14)	0.2144 (2)	0.0245 (4)
O3	0.8304 (9)	0.7500	−0.1306 (3)	0.0572 (8)
Li1	0.3902 (17)	0.7500	−0.0132 (8)	0.0456 (13)
H31	0.866 (12)	0.6976 (8)	−0.186 (4)	0.092 (14)*
H1	0.5000	0.5000	0.0000	0.10 (2)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0281 (10)	0.0194 (9)	0.0187 (8)	0.000	0.0084 (7)	0.000
O1	0.0561 (9)	0.0228 (7)	0.0254 (6)	0.0003 (6)	0.0216 (6)	−0.0014 (5)
C2	0.0253 (8)	0.0206 (7)	0.0198 (7)	−0.0006 (6)	0.0059 (5)	0.0012 (6)
N2	0.0404 (12)	0.0314 (12)	0.0196 (9)	0.000	0.0124 (8)	0.000
O2	0.0584 (10)	0.0223 (7)	0.0340 (7)	0.0004 (6)	0.0186 (6)	0.0037 (5)
C3	0.0348 (9)	0.0261 (9)	0.0217 (7)	0.0000 (7)	0.0109 (6)	0.0031 (6)
C7	0.0300 (8)	0.0223 (7)	0.0225 (7)	0.0009 (6)	0.0080 (6)	0.0002 (6)
O3	0.0642 (18)	0.084 (2)	0.0247 (10)	0.000	0.0122 (10)	0.000
Li1	0.039 (3)	0.053 (3)	0.046 (3)	0.000	0.007 (2)	0.000

Geometric parameters (Å, º)

N1—C2^i	1.3287 (18)	O2—C7	1.216 (2)
N1—C2	1.3287 (18)	C3—H3	0.9300
N1—Li1	2.115 (7)	O3—Li1	1.950 (7)
O1—C7	1.295 (2)	O3—Li1^ii	2.085 (7)
O1—Li1	2.271 (2)	O3—H31	0.825 (17)
O1—H1	1.2275 (13)	Li1—O3^iii	2.085 (7)
C2—C3	1.396 (2)	Li1—O1^i	2.271 (2)
C2—C7	1.506 (2)	Li1—Li1^iii	3.5346 (7)
N2—C3^i	1.334 (2)	Li1—Li1^ii	3.5346 (7)
N2—C3	1.334 (2)
C2^i—N1—C2	118.8 (2)	O3—Li1—N1	137.3 (3)
C2^i—N1—Li1	120.51 (10)	O3^iii—Li1—N1	100.4 (3)
C2—N1—Li1	120.51 (10)	O3—Li1—O1^i	99.45 (16)
C7—O1—Li1	118.33 (19)	O3^iii—Li1—O1^i	98.65 (16)
C7—O1—H1	115.31 (13)	N1—Li1—O1^i	71.83 (16)
Li1—O1—H1	126.08 (17)	O3—Li1—O1	99.45 (16)
N1—C2—C3	120.51 (16)	O3^iii—Li1—O1	98.65 (16)
N1—C2—C7	115.98 (14)	N1—Li1—O1	71.84 (16)
C3—C2—C7	123.52 (15)	O1^i—Li1—O1	141.9 (3)
C3^i—N2—C3	117.5 (2)	O3—Li1—Li1^iii	150.10 (19)
N2—C3—C2	121.34 (16)	O3^iii—Li1—Li1^iii	27.79 (19)
N2—C3—H3	119.3	N1—Li1—Li1^iii	72.60 (17)
C2—C3—H3	119.3	O1^i—Li1—Li1^iii	89.89 (15)
O2—C7—O1	126.77 (16)	O1—Li1—Li1^iii	89.89 (15)
O2—C7—C2	121.16 (15)	O3—Li1—Li1^ii	29.90 (19)
O1—C7—C2	112.07 (15)	O3^iii—Li1—Li1^ii	152.21 (18)
Li1—O3—Li1^ii	122.3 (3)	N1—Li1—Li1^ii	107.40 (17)
Li1—O3—H31	119 (3)	O1^i—Li1—Li1^ii	90.11 (15)
Li1^ii—O3—H31	93 (3)	O1—Li1—Li1^ii	90.11 (15)
O3—Li1—O3^iii	122.3 (3)	Li1^iii—Li1—Li1^ii	179.999 (1)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H31···O2^iv	0.83 (2)	2.24 (2)	2.9987 (19)	152 (3)
O1—H1···O1^iv	1.23 (1)	1.23 (1)	2.455 (3)	180 (1)

Symmetry code: (iv) −x+1, −y+1, −z.