Chloridotetrakis(pyridine-4-carbaldehyde-κN)copper(II) chloride

In the molecular structure of the title compound, [CuCl(C6H5NO)4]Cl, the CuII atom is coordinated by four N atoms of four pyridine-4-carboxaldehyde ligands and one chloride anion in a slightly distorted square-pyramidal coordination geometry. There is also a non-coordinating Cl− anion in the crystal structure. The CuII atom and both Cl atoms are situated on fourfold rotation axes. A weak C—H⋯Cl interaction is also present.

In the molecular structure of the title compound, [CuCl(C 6 H 5 -NO) 4 ]Cl, the Cu II atom is coordinated by four N atoms of four pyridine-4-carboxaldehyde ligands and one chloride anion in a slightly distorted square-pyramidal coordination geometry. There is also a non-coordinating Cl À anion in the crystal structure. The Cu II atom and both Cl atoms are situated on fourfold rotation axes. A weak C-HÁ Á ÁCl interaction is also present.
This compound is highly related to the title compound. In addition, three crystal structures with pyridine-4-carboxaldehyde acting as independent components were reported (Choi et al. 1999;Briand et al. 2007;Sie et al. 2008).
In the cation of the title compound [CuCl(OCHC 5 H 4 N) 4 ]Cl, the Cu II centre is coordinated to four N atoms from four pyridine-4-carboxaldehyde ligands and one chloro ligand. Cu exhibits a slightly distorted square-pyramidal coordination geometry. Another non-coordinating chloride anion is observed in the crystal structure. The [CuCl(C 5 H 4 N-CHO) 4 ] + ion has a perfect C 4 symmetry with the direction of the C 4 axis being collinear with the Cu1-Cl1 direction. Cu1, Cl1 and Cl2 are all situated on the same crystallographic 4-fold rotoinversion axis. In the cation therefore all Cu-N bond lengths and angles are equivalent.
Several donor CH functions and the chloride acceptor groups participate in the observed hydrogen bonding pattern forming a two-dimensional network in the ab plane (Fig. 2)

Experimental
For the preparation of the title compound, a solution of CuCl 2 × 2 H 2 O (0.08524 g, 0.5 mmol) in H 2 O(5 ml) was slowly added over a period of 2 h to a solution of L-Cysteic acid (0.094 g, 0.5 mmol), KOH (0.056 g, 1 mmol), pyridine-4-carboxaldehyde (0.06 ml, 0.6 mmol) and NaBH 4 (0.03028 g, 0.8 mmol) in methanol (20 ml) resulting in a blue solution that was stirred for another 4 h at 298 K. Then, the solution was left to evaporate slowly at room temperature. After ten days, blue block crystals of the title compoound were obtained with a yield of 70%.

Refinement
H atom bonded to C atom were positioned geometrically with the C-H distance of 0.9303 Å, and treated as riding atoms, with U iso (H) = 1.2U eq (C).

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 Rfactors(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.