catena-Poly(35-dicarb­oxy­pyrazine-26-dicarboxyl­ato-κ3 O 2N 1O 6)lithium(I)-μ-aqua-triaqua­lithium(I)-μ-aqua

摘要

The title coordination polymer, [Li2(C8H2N2O8)(H2O)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(C8H2N2O8)(H2O)2]⁻ anions and [Li(H2O)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.