Experimental

R factor = 0.039; wR factor = 0.092; data-to-parameter ratio = 15.7. The asymmetric unit of the title complex, [Ni(C10H8N2)-(H2O)4]SO4, consists of a complex [Ni(bipy)(H2O)4] 2+ cation (bipy = 2,20-bipyridine) and a non-coordinating [SO4] 2 anion. The NiII atom is six-coordinated in a distorted octahedral geometry defined by the two N atoms of the bipy ligand and four water O atoms. The crystal structure contains extensive classical O—H O hydrogen bonds, which link the ions into a two-dimensional array in the ab plane. Layers are connected into a three-dimensional supramolecular structure by C— H O interactions. Related literature For the structures and properties of coordination complexes with bipy as a ligand, see: Graaf & Sousa (2010); Baruah et al