| Summary: | The title coordination polymer, {[Li2(C8H2N2O8)(H2O)2]·2.5H2O}n, is built up from molecular ribbons propagating in the c-axis direction of the orthorhombic unit cell; the ligand bridges two Li+ ions using both its N,O,O′-bonding sites and adjacent Li+ ions are bridged by pairs of water molecules. The coordination geometry of the metal ion is distorted trigonal bipyramidal, with the ligand O atoms in the axial sites. Two of the carboxylate groups of the ligand remain protonated and form short symmetric O—H...O hydrogen bonds. In the crystal, the ribbons interact via a network of O—H...O hydrogen bonds in which coordinating water molecules act as donors and carboxylate O atoms within adjacent ribbons act as acceptors, giving rise to a three-dimensional framework. O—H...N interactions are also observed. The asymmetric unit contains quarter of the ligand and the complete ligand has 2/m symmetry; the Li+ ion lies on a special position with m.. site symmetry. Both bridging water molecules have m2m site symmetry and both lattice water molecules have m.. site symmetry; one of the latter was modelled with a site occupancy of 0.25.
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