catena-Poly[[diaquacobalt(II)]-bis(μ-4-fluorobenzoato-κ2O:O′)]

The hydrothermal reaction of CoCO3 and 4-fluorobenzoic acid afforded the title Co-II complex, [Co(C7H4FO2)(2)(H2O)(2)](n). The Co-II atom is located on an inversion center and is coordinated by six O atoms from two water molecules and four mu(2)-carboxylate groups of 4-fluorobenzoate anions, forming a distorted CoO6 octahedron, with Co-O bond lengths in the range 2.071 (2)-2.130 (2) angstrom. All adjacent O-Co-O angles are in the range 84.78 (6)-95.22 (6)degrees and opposite angles are 180.0 degrees. Each mu-carboxylate group of the 4-fluorobenzoate anions bridges two symmetry-related Co-II atoms. Hydrogen-bonding interactions of the coordinated water molecules further connect the cobalt-carboxylate units, forming layers perpendicular to the a axis. The cobalt-oxygen layers are encased in a sandwich-like fashion by layers of pi-stacked 4-fluorobenzoate anions. Within these layers the benzene rings of the 4-fluorobenzoate anions are pi-stacked, with centroid-centroid distances of 3.432 (4) angstrom.