catena-Poly[[(3,5-dicarb­oxy­pyrazine-2,6-dicarboxyl­ato-κ(3) O (2),N (1),O (6))lithium(I)]-μ-aqua-[triaqua­lithium(I)]-μ-aqua]

The title coordination polymer, [Li(2)(C(8)H(2)N(2)O(8))(H(2)O)(5)](n) contains two symmetry-independent Li(+) ions; one is coordin­ated by five water O atoms, the other by an O,N,O′-tridentate doubly deprotonated pyrazine-2,3,5,6-tetra­carboxyl­ate ligand and two water O atoms. Water mol­ecules bridge adjacent Li(+) ions into ribbons propagating in [100]; an alternative analysis of the structure considers it to contain alternating [Li(C(8)H(2)N(2)O(8))(H(2)O)(2)](−) anions and [Li(H(2)O)(3)](+) cations. In the polymeric model, both lithium ions show distorted trigonal–bipyramidal coordination geometries. Within the ligand, the carboxyl H atoms participate in short, almost symmetric O⋯H⋯O hydrogen bonds in which the non-coordinated carboxyl­ate O atoms are donors and acceptors. In the crystal, the ribbons inter­act via a network of O—H⋯O hydrogen bonds in which the coordinated water mol­ecules act as donors and ligand carboxyl­ate O atoms as acceptors.