trans-Diaqua-bis-[2,5-bis-(pyridin-2-yl)-1,3,4-thia-diazole]nickel(II) bis-(tetra-fluoridoborate).

The bidentate 1,3,4-thia-diazole ligand, namely, 2,5-bis-(2-pyrid-yl)-1,3,4-thia-diazole (denoted L), untested as a polydentate ligand, has been found to form the monomeric title complex, Ni(C(12)H(8)N(4)S)(2)(H(2)O)(2)(2). The complex shows an octa-hedral environment of the nickel cation in which the Ni(2+) ion is located on a center of symmetry, linked to two ligands and two water molecules. In this 1:2 complex (one metal for two organic ligands) each thia-diazole ligand uses one pyridyl and one thia-diazole N atom for chelate binding. In the second pyridyl substituent, the N atom is oriented towards the same direction as the S atom of the 1,3,4-thiadiazole ring. The mean plane of the thia-diazole and pyridyl rings linked to the nickel cation forms a dihedral angle with the other pyridine ring of 18.63 (8)°. The tetra-fluorido-borate ions can be regarded as free anions in the crystal lattice. Nevertheless, they are involved in an infinite two-dimensional network parallel to ([Formula: see text]01) through O-H⋯F hydrogen bonds.