catena-Poly[[triaqua­nickel(II)]-μ-5-carb­oxy­benzene-1,3-dicarboxyl­ato-κ(2) O (1):O (3)]

In the title compound, [Ni(C(9)H(4)O(6))(H(2)O)(3)](n), the Ni(II) ion has a distorted NiO(5) square-pyramidal geometry, the maximum deviation from the least-squares plane formed by the basal atoms being 0.9351 (13) Å. The basal plane is formed by two O atoms from carboxyl­ate residues of the 5-carb­oxy­benzene-1,3-dicarboxyl­ate ligand and by two O atoms from water mol­ecules. The O atom of the third water mol­ecule is axially positioned, 1.7890 (19) Å perpendicular to the basal plane. The 5-carb­oxy­benzene-1,3-dicarboxyl­ate ligand bridges the metal atoms, forming a polymeric chain along the b axis. O—H⋯O hydrogen bonds between the water mol­ecules and carboxyl­ate groups stabilize the crystal structure.