Bis(2,2′-bipyridyl-κ(2) N,N′)(sulfato-κ(2) O,O′)nickel(II) 2.5-hydrate

The title compound, [Ni(SO(4))(C(10)H(8)N(2))(2)]·2.5H(2)O, is a nickel(II) complex with a distorted octa­hedral coordination geometry. The Ni(II) atom is bonded by two O atoms of the bidentate chelating sulfate ligand and the four N atoms of two chelating 2,2′-bi­pyridine ligands. The Ni—N bond lengths range from 2.059 (3) to 2.075 (3) Å and the Ni—O bond lengths are 2.098 (3) and 2.123 (3) Å. The bipyridyl ligands are both close to planar (r.m.s. deviations of 0.254 and 0.0572 Å) and are almost orthogonal, making a dihedral angle of 82.77 (1)°. In the crystal, the complex and water mol­ecules are connected by O—H⋯O hydrogen bonds. Inter­estingly, six water mol­ecules form a chain linking two complex mol­ecules via sulfate O atoms. There are also stacking inter­actions between the aromatic rings of neighbouring 2,2′-bi­pyridine ligands with shortest non-covalent contacts of 3.268 (6), 3.393 (6) and 3.435 (5) Å. One of the three unique water molecules shows half-occupation.