trans-Tetraaquabis[1,3-bis(4-pyridyl)propane-κN]cobalt(II) biphenyl-4,4′-disulfonate monohydrate

In the title compound, [Co(C13H14N2)2(H2O)4](C12H8O6S2)·H2O, the cation, anion and uncoordinated water molecule have crystallographically imposed twofold symmetry. The cobalt(II) atom exhibits a slightly distorted octahedral coordination geometry provided by two N atoms from two 1,3-bis(4-pyridyl)propane ligands and the O atoms from four water molecules. The dihedral angle between the pyridine rings in the ligand is 86.14 (11)°, whereas the dihedral angle formed by the symmetry-related benzene rings in the anion is 35.81 (12)°. In the crystal, cations, anions and water molecules are linked into layers parallel to the ac plane by O—H⋯O and O—H⋯N hydrogen-bond interactions. The layers are further connected into a three-dimensional network by C—H⋯O hydrogen bonds.

In the title compound, [Co(C 13 H 14 N 2 ) 2 (H 2 O) 4 ](C 12 H 8 O 6 S 2 )Á-H 2 O, the cation, anion and uncoordinated water molecule have crystallographically imposed twofold symmetry. The cobalt(II) atom exhibits a slightly distorted octahedral coordination geometry provided by two N atoms from two 1,3-bis(4-pyridyl)propane ligands and the O atoms from four water molecules. The dihedral angle between the pyridine rings in the ligand is 86.14 (11) , whereas the dihedral angle formed by the symmetry-related benzene rings in the anion is 35.81 (12) . In the crystal, cations, anions and water molecules are linked into layers parallel to the ac plane by O-HÁ Á ÁO and O-HÁ Á ÁN hydrogen-bond interactions. The layers are further connected into a three-dimensional network by C-HÁ Á ÁO hydrogen bonds.
In the present work, we report a cobalt(II) complex, [Co(C 13 H 14 N 2 ) 2 (H 2 O) 4 ](C 12 H 8 O 6 S 2 ).H 2 O (I), with a two-dimensional H-bonding network structure created by the sulfonate dianions acting as hydrogen-bond acceptors.
In the title compound, cation, anion and uncoordinated water molecule have all crystallographically imposed twofold axis. As shown in Fig. 1, four water molecules coordinate to the cobalt(II) ion in the equatorial positions with Co-O bonds ranging from 2.059 (3) to 2.110 (2) Å, while two bpp ligands coordinate to the metal through N atoms [Co-N = 2.1772 (2) Å] in the axial positions to complete a slightly distorted octahedral coordination geometry. The dihedral angle between the two pyridyl planes in the cation is 86.14 (11)°, and the N···N separation is 10.169 (3) Å. The BPDS dianion does not coordinate to the cobalt(II) ion, but balances the charge. The dihedral angle formed by the symmetry-related benzene rings in the anion is 35.81 (12)°. Hydrogen bonds play an important role for enhancing the stability of the solid-state structure (Table 1). Two intermolecular hydrogen bonds are formed between oxygen atoms of the two coordinated water molecules with two oxygen atoms of sulfonate groups. Additional intermolecular hydrogen bond are formed between atom O3W of the uncoordinated water molecule and the sulfonate atom O1, and between the uncoordinated N atom of bpp and the coordinated O2W atom. All these intermolecular hydrogen bonds result in a two-dimensional layer structure (Fig. 2) parallel to the ac plane. The layers are further linked via C-H···O hydrogen bonds to give rise to a three-dimensional network (Fig. 3).

Experimental
A mixture containing Co(NO 3 ) 2 .6H 2 O (0.1 mmol), bpp (0.1 mmol), H 2 BPDS (0.1 mmol), NaOH (0.2 mmol) dissolved in water (15 ml) was sealed in a 25 ml Teflon lined stainless steel container and heated at 160 °C for 120 h. Orange crystals of (I) suitable for X-ray analysis were collected by filtration and washed with water and ethanol several times (yield 56%).

Refinement
The water H atoms were located in a difference Fourier map and refined freely. All other H atoms were positioned geometrically, with C-H = 0.93 and 0.97 Å for aromatic and methylene H atoms, respectively, and constrained to ride on their parent atoms, with Uiso(H) = xUeq(C), where x = 1.5 for methyl H and x = 1.2 for all other H atoms.