Poly[triaqua­(μ-butane-1,2,3,4-tetra­carboxyl­ato)dicadmium(II)]

The asymmetric unit of the title Cd(II) coordination polymer, [Cd(2)(C(8)H(6)O(8))(H(2)O)(3)](n), contains two crystallographically independent Cd(II) cations, one-half each of two independent anionic butane-1,2,3,4-tetra­carboxyl­ate units (L) and three water mol­ecules. Both anionic units lie on inversion centers. One of the Cd(II) ions is six-coordinated by four carboxyl­ate O atoms from four L anions and two water O atoms in a distorted octa­hedral coordination environment. The other Cd(II) ion is eight-coordinated by seven carboxyl­ate O atoms from four L anions and one water O atom. The anionic units bridge neighboring Cd(II) centers, forming a three-dimensional framework. O—H⋯O hydrogen-bonding inter­actions between the water mol­ecules and carboxyl­ate O atoms further stabilize the structure.