Abstract
The reaction of NiCl(2) with fumaric acid and isonicotinamide in a basic solution produces the title complex, [Ni(C(6)H(6)N(2)O)(2)(H(2)O)(4)](C(4)H(2)O(4)). The nickel(II) ion of the complex cation and the fumarate anion are each located on an inversion centre. The Ni(II) ion is coordinated octa-hedrally by four water O atoms and two N atoms of isonicotinamide mol-ecules. The fumarate anion is linked to neighbouring complex cations via O(water)-H⋯O(fumarate) hydrogen bonds. In the crystal, the complex cations are further linked by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional supra-molecular architecture. Hirshfeld surface analysis and two-dimensional fingerprint plots were used to analyse the inter-molecular inter-actions present in the crystal and indicate that the most important contributions for the crystal packing are from H⋯O/O⋯H (41.8%), H⋯H (35.3%) and H⋯C/C⋯H (10.2%) inter-actions.