Poly[hexa­aqua­bis­(μ4-pyrimidine-4,6-dicarboxyl­ato)tetra­lithium]

Wojciech Starosta; Janusz Leciejewicz

doi:10.1107/S1600536812038755

. 2012 Sep 15;68(Pt 10):m1270–m1271. doi: 10.1107/S1600536812038755

Poly[hexaaquabis(μ₄-pyrimidine-4,6-dicarboxylato)tetralithium]

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

PMCID: PMC3470151 PMID: 23125595

Abstract

The asymmetric unit of the title compound, [Li₄(C₆H₂N₂O₄)₂(H₂O)₆]_n, comprises two Li⁺ ions bridged by a completely deprotonated pyrimidine-3,6-dicarboxylate ligand and coordinated by two water molecules; the asymmetric units related by an inversion operation create a structural unit which forms part of a two-dimensional polymeric structure parallel to (10-1). One of the Li⁺ ions shows a distorted tetrahedral arrangement involving two symmetry-related coordinating water molecules and two carboxylate O atoms. The other Li⁺ ion is in distorted trigonal–bipyramidal geometry defined by N and O atoms of the ligands and a water molecule. Water O atoms are proton donors to carboxylate O atoms forming hydrogen bonds.

Related literature

For the crystal structures of pyrimidine-3,6-dicarboxylic acid dihydrate and two K⁺ complexes with pyrimidine-3,6-dicarboxylate and aqua ligands, see: Beobide et al. (2007 ▶). For the structures of Li⁺ complexes with a pyrimidine-2-carboxylato ligand, see: Starosta & Leciejewicz (2011 ▶) and with a pyrimidine-4-carboxylate ligand, see: Starosta & Leciejewicz (2012 ▶).

Experimental

Crystal data

[Li₄(C₆H₂N₂O₄)₂(H₂O)₆]
M _r = 234.02
Monoclinic,
a = 6.7014 (13) Å
b = 11.755 (2) Å
c = 12.251 (3) Å
β = 98.38 (3)°
V = 954.8 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.15 mm⁻¹
T = 293 K
0.48 × 0.20 × 0.13 mm

Data collection

Kuma KM-4 four-cricle diffractometer
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2008 ▶) T _min = 0.960, T _max = 0.988
3009 measured reflections
2792 independent reflections
2094 reflections with I > 2σ(I)
R _int = 0.023
3 standard reflections every 200 reflections intensity decay: 0.4%

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.126
S = 0.95
2792 reflections
178 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.47 e Å⁻³
Δρ_min = −0.41 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 datablock(s) I, global. DOI: 10.1107/S1600536812038755/kp2437sup1.cif

e-68-m1270-sup1.cif^{(16.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812038755/kp2437Isup2.hkl

e-68-m1270-Isup2.hkl^{(137.1KB, hkl)}

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

Table 1. Selected bond lengths (Å).

Li1—O5	2.081 (3)
Li1—O3ⁱ	2.100 (2)
Li1—N3ⁱ	2.153 (2)
Li1—O1	2.030 (2)
Li1—N1	2.156 (2)
Li2—O4ⁱⁱ	1.967 (2)
Li2—O7	1.898 (3)
Li2—O6	1.990 (3)
Li2—O3	1.949 (2)

Open in a new tab

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O7—H71⋯O6ⁱⁱⁱ	0.85 (3)	2.19 (3)	3.0409 (18)	175 (2)
O7—H72⋯O1^iv	0.96 (3)	1.75 (3)	2.6920 (15)	168 (2)
O6—H62⋯O2^v	0.91 (3)	1.85 (3)	2.7518 (15)	172 (2)
O6—H61⋯O5^vi	0.88 (3)	1.98 (3)	2.7889 (16)	151 (2)
O5—H51⋯O2^vii	0.87 (3)	1.89 (3)	2.7594 (14)	172 (3)
O5—H52⋯O4^viii	0.85 (3)	2.02 (3)	2.8670 (14)	178 (2)

Open in a new tab

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

supplementary crystallographic information

Comment

The asymmetric unit of the title compound contains two symmetry independent Li^I ions, one with distorted trigonal bipyramidal, the other with distorted tetrahedral coordination geometry, a deprotonated ligand molecule acting in µ₄ bridging mode and two independent water molecules coordinated to metal ions. The structural unit is built of asymmetric units related by an inversion centre. The ligand N1,O1 bonding group chelates the Li1 ion leaving the carboxylato O2 atom coordination inactive while its carboxylato O3 and O4 atoms bridge, related by an inversion centre, Li2 and Li2ⁱⁱ ions. The latter are also coordinated by O4ⁱⁱ and O3ⁱⁱ atoms donated by the adjacent one related by the same inversion center ligand forming a dimeric bonding loop which constitutes a core of a centrosymmetric structural unit composed of the Li1 ion, the ligand, the dimeric loop, the ligandⁱⁱ and the Li1ⁱⁱ ion (Fig. 1). Symmetry code; ⁱ -x + 1/2, y + 1/2, -z + 1/2; ⁱⁱ -x + 1, -y + 1,-z + 1; ⁱⁱⁱx + 1/2, -y + 1/2, z + 1/2; ^iv -x + 1/2, y - 1/2, -z + 1/2; ^vx - 1/2, -y + 1/2, z - 1/2. The plane of the loop [r.m.s. 0.2647 (5) Å] makes a dihedral angle of 24.0 (2)° with the ligand ring plane. This unit, terminated on both sides by Li1 and Li1ⁱⁱ ions linked to adjacent units via N3ⁱ,O3ⁱ and N3ⁱⁱⁱ,O3ⁱⁱⁱ bonding groups and via N3,O3 and N3ⁱⁱ,O3ⁱⁱ bonding groups to Li1^v and Li^ivions in adjacent units, generate a two-dimensional layer with Li1 ions as its nodes (Fig. 2). The arrangement of the layers in the unit cell is shown in Fig. 3. The coordination polyhedron of the Li1 ion, composed of the bridging N1,O1 and N3ⁱ⁾,O3⁽ⁱ⁾ bonding groups and the aqua O5 atom is a distorted trigonal bipyramid. Its equatorial plane is formed by N1, N3ⁱ and O5 atoms. The Li1 ion is 0.0908 (2) Å out of this plane, O1 and O3ⁱ atoms are at apical positions. The Li2 ion chelated by carboxylato O3,O4ⁱⁱ atoms and aqua O6 with inversion related atoms shows a distorted tetrahedral coordination geometry. The Li—O and Li—N bond lengths (Table 1) fit well to those observed in the structures of Li complexes with other pyrimidine carboxylate ligands (Starosta & Leciejewicz, 2011, 2012). The pyrimidine ring is planar with r.m.s. of 0.0121 (2) A°, C7/O1/O2 and C8/O3/O4 carboxylate groups make with it dihedral angles of 4.0 (1)° and 24.0 (2)°, respectively. Bond distances and bond angles are close to those observed in the structure of the parent acid and its two potassium complexes (Beobide et al., 2007). A network of hydrogen bonds (Table 2), in which coordinated water molecules act as donors and carboxylato O atoms are acceptors maintains the stability of the structure.

Experimental

1 mmol of pyrimidine-3,6-dicarboxylic acid dihydrate and 2 mmol s of lithium hydroxide were dissolved in 50 mL of hot, doubly distilled water and boiled under reflux with stirring for six hours. Left to crystallize at room temperature, colourless single-crystal blocks deposited after a week. They were washed with cold methanol and dried in the air.