Poly[hydrazin-1-ium [diaqua-bis-(μ(4)-pyridazine-3,6-dicarboxyl-ato)trilithate] monohydrate].

The structure of the title compound, {(N(2)H(5))[Li(3)(C(6)H(2)N(2)O(4))(2)(H(2)O)(2)]·H(2)O}(n), is composed of mol-ecular dimers, each built up of two symmetry-related Li(I) ions with distorted trigonal-bipyramidal coordinations bridged by two deprotonated ligand mol-ecules via their N,O-bonding sites. Doubly solvated Li(I) ions with a distorted tetra-hedral geometry link adjacent dimers, forming a polymer generated by bridging bidentate carboxyl-ato O atoms to Li(I) ions in adjacent dimers, forming anionic layers parallel to the ac plane with monoprotonated hydrazinium cations and crystal water mol-ecules positioned between them. The layers are held together by an extended system of hydrogen bonds in which the hydrazinium cations and coordinated and crystal water mol-ecules act as donors and carboxyl-ate O atoms act as acceptors.

Deprotonization by an addition of a small amount of hydrazine resulted in a compound with a polymeric structure composed of centrosymmetric tetramers in which two Li I ions, bridged by two fully deprotonated pyridazine-3,6-dicarboxylate ligands are linked to two triply solvated Li I ions. The latter bridge the tetramer via two aqua O atoms to adjacent tetramers (Starosta & Leciejewicz, 2011). An addition of few more drops of hydrazine gave rise to a compound with a structure built of centrosymmetric anions in which two Li I ions, are bridged by two fully deprotonated pyridazine-3,6-dicarboxylato ligands with the charge compensated by two mono protonated hydrazine cations and neutral centrosymmetric tetrameric molecules as in previous compound. While studying the reaction products of LiNO 3 with the title ligand we have obtained a new compound. Its structure is reported below. The structure of the title compound is polymeric. Its unit cell contains two symmetry independent dinuclear moieties (dimers) related by a centre of symmetry each built of two Li ions and two fully deprotonated pyridazine-3,6-dicarboxylate ligands (Fig. 1). The dimers are bridged by a doubly solvated symmetry independent Li3 ion. In each dimer, ligand carboxylato groups act as bidentate.
Apart from participation in the N,O-bonding groups chelating the intra-dimer Li ions, they use the second O atoms to bridge the dimers to doubly solvated Li3 ions forming an anionic ribbon propagating in the unit cell c direction (Symmetry code: i -x + 1, -y + 2, -z + 1; ii -x + 2, -y + 2, -z + 1; iv -x + 2, -y + 2,-z; v x + 1, y, z)( Fig. 1). A second bridging pathway with a direction normal to the ribbons links them into a polymeric two-dimensional framework (Fig. 2). The two dimers and two doubly solvated Li3 ions carry a charge of (2-) which is compensated by two inversion symmetry related mono-protonated hydrazinium cations positioned between adjacent dimers. In the asymmetric unit there is a crystal water molecule. The coordination polyhedron around the Li1 ion, a distorted trigonal-bipyramid, is composed of O13, O12 i , N12 ii atoms which make an equatorial plane, the Li1 ion is 0.0863 (2) Å out of it, N11 and O11 ii atoms are at apical positions. The strongly distorted trigonal-bipyramidal coordination of the Li2 ion consists of N21, O22 v and O24 iv atoms which constitute its equatorial plane with the Li2 ion 0.0893 (2) Å out of it; O21 and N22 iv atoms are at the apices. The penta-coordination mode of Li1 and Li2 ions can be also visualized as a transition from distorted trigonal-bipyramid to a deformed square-pyramid, the latter with O12 i and O24 iv atoms at apical positions in case of Li1 and Li2 ions, respectively. Li-O and Li-N bond distances (Table 1) fall in the same range as those observed in the Li I complexes with title and water ligands (Starosta & Leciejewicz, 2010, 2011, 2012 tetrahedral coordination geometry with a pair of bridging carboxylato O13 and O23 atoms and a pair of coordinated water O1, O2 atoms in trans arrangement. Li3 ion is neither coplanar with the dimer 1 nor the dimer 2 as indicated by the O14-Li3-O23 angle of 110.6 (3)°; its position in respect to adjacent dimers makes a half-open cavity which is occupied by the hydrazinium cation. The layers are held together by an extended system of hydrogen bonds in which hydrazinium cation, coordinated, and crystal water molecules act as donors to carboxylato O atoms (Table 2).

Experimental
A reaction of 1 mmol of pyridazine-3,6-dicarboxylic acid with 2 mmol s of lithium nitrate both dissolved in 50 ml of hot water and then boiled under reflux with stirring for 6 h yielded a compound which was identified by its lattice parameters as that one reported earlier (Starosta & Leciejewicz, 2010). After an addition of few drops of hydrazine, its warm aqueous solution was stirred for two h without heating. Left to crystallize at room temperature, single-crystal plates of the title compound were found after a couple of days. They were washed with cold ethanol and dried in air.

Refinement
Coordinated water, hydrazine hydrogen atoms and crystal water molecule were located in a difference map and refined isotropically, while H atoms attached to pyridazine-ring C atoms were located at calculated positions and treated as riding on the parent atoms with C-H=0.93 Å and U iso (H)=1.2U eq (C).

Poly[hydrazin-1-ium [diaquabis(µ 4 -pyridazine-3,6-dicarboxylato)trilithate] monohydrate]
Crystal data 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 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 R-factors(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.