catena-Poly[[[aqua­(5-nitro­benzene-1,2,3-tricarboxyl­ato-κO (1))nickel(II)]-di-μ-aqua-[diaqua­sodium]-di-μ-aqua] tetra­hydrate]

In the title complex, {[NaNi(C(9)H(2)NO(8))(H(2)O)(7)]·4H(2)O}(n), the Ni(II) atom has a distorted octa­hedral coordination, defined by five O atoms from five water mol­ecules and one O atom from one 5-nitro­benzene-1,2,3-tricarboxyl­ate ligand. The Na cation is coordinated by six water O atoms in an irregular trigonal-prismatic geometry. There are seven coordinated water mol­ecules in the asymmetic unit. The Ni and Na atoms are linked by water bridges, forming infinite chains, which are connected by strong O—H⋯O hydrogen bonds involving the coordinated and uncoordinated water mol­ecules into a three-dimensional network.