Poly[[(μ-aqua)[μ4-4-(carboxylatomethyl)benzoato]cobalt(II)] hemi[1,4-bis(pyridin-4-ylmethyl)piperazine] hemihydrate]

A divalent cobalt two-dimensional slab coordination polymer with cocrystallized species, {[Co(cmb)(H2O)].0.5(bpmp)·0.5H2O} n (where cmb is 4-(carboxylatomethyl)benzoate and bpmp is 1,4-bis(pyridin-4-ylmethyl)piperazine, was structurally characterized by single-crystal X-ray diffraction.


Figure 1
The cobalt coordination environment in the title compound with a full cmb ligand and cocrystallized species. Displacement ellipsoids are drawn at the 50% probability level. Water molecule O1W has been omitted. Color code: Co dark blue, O red, N light blue, C black, and H pink. The symmetry codes are as listed in Table 1.
[Co(-H 2 O)(cmb)] n layers are connected into the threedimensional crystal structure by hydrogen bonding mediated by the unligated bpmp molecules in the interlamellar regions. The pyridyl termini of the cocrystallized bpmp molecules accept hydrogen bonds from the bridging water molecules in two adjacent layer motifs (Fig. 4). Cocrystallized water molecules are held in the crystal by donating hydrogen bonds to the bpmp piperazine N atoms. Details regarding the hydrogenbonding patterns in the title compound are listed in Table 2.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. All H atoms attached to C atoms were placed in calculated positions and refined with a riding model. The H atoms bound to the water O5 atom were found via a difference map and were refined freely with a restraint of 0.85 Å for the O-H distances, but those bound to atom O1W were positioned geometrically and refined using a riding model.

Funding information
Funding for this research was provided by: Lyman Briggs College of Science at Michigan State University. Special details Experimental. Data was collected using a BRUKER CCD (charge coupled device) based diffractometer equipped with an Oxford low-temperature apparatus operating at 173 K. A suitable crystal was chosen and mounted on a nylon loop using Paratone oil. Data were measured using omega scans of 0.5° per frame for 30 s. The total number of images were based on results from the program COSMO where redundancy was expected to be 4 and completeness to 0.83Å to 100%. Cell parameters were retrieved using APEX II software and refined using SAINT on all observed reflections.Data reduction was performed using the SAINT software which corrects for Lp. Scaling and absorption corrections were applied using SADABS6 multi-scan technique, supplied by George Sheldrick. The structure was solved by the direct method using the SHELXT program and refined by least squares method on F2, SHELXL, incorporated in OLEX2. Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Refinement. The structure was refined by Least Squares using version 2018/3 of XL (Sheldrick, 2015) incorporated in Olex2 (Dolomanov et al., 2009). All non-hydrogen atoms were refined anisotropically. Hydrogen atom positions were calculated geometrically and refined using the riding model, except for the Hydrogen atom on the nitrogen atom which was found by difference Fourier methods and refined isotropically.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (