Tetra­aqua­bis(isonicotinamide-κN (1))nickel(II) bis­(4-formyl­benzoate) dihydrate

The asymmetric unit of the title complex, [Ni(C(6)H(6)N(2)O)(2)(H(2)O)(4)](C(8)H(5)O(3))(2)·2H(2)O, contains one-half of the complex cation with the Ni(II) atom located on an inversion center, a 4-formyl­benzoate (FB) counter-anion and an uncoordinated water mol­ecule. The four O atoms in the equatorial plane around the Ni atom form a slightly distorted square-planar arrangement and the slightly distorted octa­hedral coordination is completed by the two N atoms of the isonicotinamide (INA) ligands at a sligthly longer distance in the axial positions. The dihedral angle between the carboxyl­ate group and the attached benzene ring is 8.14 (11)°, while the pyridine and benzene rings are oriented at a dihedral angle of 3.46 (6)°. In the crystal structure, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional network. π–π Contacts between the benzene and pyridine rings [centroid–centroid distance = 3.751 (1) Å] may further stabilize the crystal structure.