Poly[aqua(μ3-pyridazine-4-carboxylato-κ2 O:O:O′)lithium]

The structure of the title compound, [Li(C5H3N2O2)(H2O)]n, is composed of centrosymmetric dimers in which two LiI ions are bridged by a carboxylate O atom, each donated by a ligand, acting in a bidentate mode. The second carboxylato O atoms bridge the dimers to LiI ions in adjacent dimers, forming molecular layers parallel to (001). Each LiI ion is coordinated by two bridging carboxylate O atoms, a bridging carboxylate O atom donated by the adjacent dimer and an aqua O atom, resulting in a distorted tetrahedral coordination geometry. The layers are held together by O—H⋯N hydrogen bonds in which coordinated water O atoms act as donors and ligand hetero-ring N atoms as acceptors.

The structure of the title compound, [Li(C 5 H 3 N 2 O 2 )(H 2 O)] n , is composed of centrosymmetric dimers in which two Li I ions are bridged by a carboxylate O atom, each donated by a ligand, acting in a bidentate mode. The second carboxylato O atoms bridge the dimers to Li I ions in adjacent dimers, forming molecular layers parallel to (001). Each Li I ion is coordinated by two bridging carboxylate O atoms, a bridging carboxylate O atom donated by the adjacent dimer and an aqua O atom, resulting in a distorted tetrahedral coordination geometry. The layers are held together by O-HÁ Á ÁN hydrogen bonds in which coordinated water O atoms act as donors and ligand hetero-ring N atoms as acceptors.

Table 2
Hydrogen-bond geometry (Å , ).  ion is also coordinated by two carboxylate O atoms of another ligand (Starosta & Leciejewicz, 2009). On the other hand, the structure of a Mg(II) complex is built of discrete centrosymmetric molecules in which the metal ion is coordinated by only one carboxylato O atom of two ligands and two pairs of aqua O atoms in octahedral geometry. Heterocyclic N atoms do not act in coordination mode (Starosta & Leciejewicz, 2011b). Discrete monomers have been also reported to constitute the structure of a Li I complex with the pyridazine-3-carboxylate and water ligands. A Li I ion is coordinated by ligand N,O chelating group and two aqua O atoms in a terahedral mode (Starosta & Leciejewicz, 2011a).

Experimental
The title compound was obtained by boiling under reflux with stirring 50 ml of an aqueous solution containig 1 mmol of pyridazine-4-carboxylic acid (Aldrich) and 1 mmol of LiOH (Aldrich). The solution was boiled for two h. After cooling to room temperature a 1 N solution of HCl was added dropwise until the pH reached the value of 5.5 and then left to crystallize.
Ten days later, colourless crystalline plates were found after evaporating to dryness. They were recrystallized from water a couple of times until well formed single crystals were found. They were washed with cold ethanol and dried in air.

Refinement
Water hydrogen atoms were located in a difference map and refined isotropically. H atoms arrached to pyridazine-ring C atoms were positioned at calculated positions and were treated as riding on the parent atoms, with C-H=0.93 Å and U iso (H)=1.5U eq (C). Fig. 1. A dimeric structural unit of the title compound with atom labelling scheme and 50% probability displacement ellipsoids. Symmetry code: (I) x, -y + 1/2, z -1/2. (II) -x, -y + 1, -z.

Poly[aqua(µ 3 -pyridazine-4-carboxylatoκ 2 O:O:O')lithium]
Crystal data [Li(C 5   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.