Synthesis and crystal structure of a 6-chloro-nicotinate salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine.

A 6-chloro-nicotinate (6-Clnic) salt of a one-dimensional cationic nickel(II) coordination polymer with 4,4'-bi-pyridine (4,4'-bpy), namely, catena-poly[[[tetra-aqua-nickel(II)]-μ-4,4'-bi-pyridine-κ2 N:N'] bis-(6-chloro-nicotinate) tetra-hydrate], {[Ni(C10H8N2)(H2O)4](C6H3ClNO2)2·4H2O} n or {[Ni(4,4'-bpy)(H2O)4](6-Clnic)2·4H2O} n , (1), was prepared by the reaction of nickel(II) sulfate hepta-hydrate, 6-chloro-nicotinic acid and 4,4'-bi-pyridine in a mixture of water and ethanol. The mol-ecular structure of 1 comprises a one-dimensional polymeric {[Ni(4,4'-bpy)(H2O)4]2+} n cation, two 6-chloro-nicotinate anions and four water mol-ecules of crystallization per repeating polymeric unit. The nickel(II) ion in the polymeric cation is octa-hedrally coordinated by four water mol-ecule O atoms and by two 4,4'-bi-pyridine N atoms in the trans position. The 4,4'-bi-pyridine ligands act as bridges and, thus, connect the symmetry-related nickel(II) ions into an infinite one-dimensional polymeric chain extending along the b-axis direction. In the extended structure of 1, the polymeric chains of {[Ni(4,4'-bpy)(H2O)4]2+} n , the 6-chloro-nicotinate anions and the water mol-ecules of crystallization are assembled into an infinite three-dimensional hydrogen-bonded network via strong O-H⋯O and O-H⋯N hydrogen bonds, leading to the formation of the representative hydrogen-bonded ring motifs: tetra-meric R 2 4(8) and R 4 4(10) loops, a dimeric R 2 2(8) loop and a penta-meric R 4 5(16) loop.