catena-Poly[[[tetraaquacobalt(II)]-μ-4,4′-bipyridine-κ2 N:N′] bis(perchlorate) 4,4′-bipyridine disolvate dihydrate]

In the title compound, {[Co(C10H8N2)(H2O)4](ClO4)2·2C10H8N2·2H2O}n, slightly distorted octahedrally coordinated CoII ions situated on inversion centers are linked into polycationic chains through 4,4′-bipyridine tethering ligands. These are connected into supramolecular layers by hydrogen bonding involving aqua ligands, perchlorate anions and uncoordinated water molecules. A twofold interpenetrated primitive cubic supramolecular network is formed by the interaction of pseudo-layers by hydrogen bonding between aqua ligands and unligated 4,4′-bipyridine molecules.

We gratefully acknowledge the donors of the American Chemical Society Petroleum Research Fund and Michigan State University for funding this work.
The asymmetric unit of the title compound contains a cobalt atom on a crystallographic inversion center, two aqua ligands, one-half of a 4,4′-bipyridine ligand, one uncoordinated perchlorate anion, one unligated 4,4′-bipyridine molecule and one water molecule of crystallization ( Figure 1).
These chains are connected into pseudolayer patterns by hydrogen-bonding mechanisms involving the aqua ligands, perchlorate anions, and water molecules of crystallization ( Figure 2), which lie parallel to the (1 1 0) crystal planes.
Unligated 4,4′-bipyridine molecules project axially into and out of the apertures in each pseudolayer.
In turn, the pseudolayers stack in an AB arrangement, and interact with their next nearest neighbors by hydrogenbonding donation from aqua ligands to the uncoordinated 4,4′-bipyridine molecules to form the three-dimensional structure of the title compound ( Figure 3). As a result a twofold interpenetrated primitive cubic supramolecular network can be invoked ( Figure 4).

S2. Experimental
All chemicals were obtained commercially. Cobalt perchlorate hexahydrate (135 mg, 0.37 mmol), 2-methylglutaric acid (59 mg, 0.37 mmol) and 4,4′-bipyridine (116 mg, 0.74 mmol) were placed into 10 ml H 2 O in a 23 ml Teflon-lined Parr acid digestion bomb. The bomb was heated at 120° C for 48 h and was then allowed to cool to 25° C. Yellow-orange crystals of the title compound were obtained along with a reddish amorphous solid.

S3. Refinement
All H atoms bound to C atoms were placed in calculated positions, with C-H = 0.95 Å and refined in riding mode with U iso = 1.2U eq (C). All H atoms bound to O atoms were found via Fourier difference map, restrained with O-H = 0.89 Å o, and refined with U iso =1.2U eq (O).    Packing diagram illustrating the ABAB layer stacking pattern, which forms the 3-D crystal structure of the title compound through hydrogen bonding between ligated water molecules and uncoordinated 4,4′-bipyridine molecules.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.