Crystal structure and Hirshfeld surface analysis of tetra-aqua-bis-(isonicotinamide-κN 1)nickel(II) fumarate.

The reaction of NiCl2 with fumaric acid and isonicotinamide in a basic solution produces the title complex, [Ni(C6H6N2O)2(H2O)4](C4H2O4). The nickel(II) ion of the complex cation and the fumarate anion are each located on an inversion centre. The NiII 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 Owater-H⋯Ofumarate 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.