Tetrakis(μ-acetato-κ2 O:O′)-bis[(3-pyridinecarboxaldehyde-κN′)]dicopper(II)(Cu—Cu)

The binuclear title compound, [Cu2(CH3CO2)4(C6H5NO)], is located about a center of inversion. The CuII atoms are connected [Cu—Cu = 2.6134 (5) Å] and bridged by four acetate ligands. Their distorted octahedral coordination geometry is completed by a terminal pyridine N atom of a 3-pyridincarboxaldehyde ligand. In the crystal, the complex molecules are linked by C—H⋯O hydrogen bonds, forming two-dimensional networks lying parallel to the ab plane. These networks are linked via C—H⋯O hydrogen bonds involving inversion-related 3-pyridinecarboxaldehyde ligands, forming a three dimensional supramolecular architecture.


Campos-Gaxiola Comment
Bridged binuclear copper(II) complexes have been the subject of continuing interest because of their magneto-structural properties. Pyridine ligands have the potential to be used in the synthesis of supramolecular materials, particularly transition metal coordination polymers. Herein, we report on the synthesis and crystal structure of the new binuclear Cu 2 (OAc) 4 L 2 paddle-wheel complex with L = 3-pyridincarboxaldehyde.
In the crystal, the complex molecules are linked by C-H···O hydrogen bonds to form two-dimensional networks lying parallel to the ab plane (Table 1 and Fig. 2). These networks are linked via C-H···O hydrogen bonds involving inversion related 3-pyridincarboxaldehyde ligands forming a three dimensional supramolecular architecture (Table 1).

Experimental
A mixture of 3-pyridincarboxaldehyde (0.05 g, 0.466 mmol) and Cu(CH 3 COO) 2 H 2 O (0.093 g, 0.466 mmol) dissolved in methanol (5 ml) was stirred for 2 h at room temperature to give a blue solution. After one week, blue crystals suitable for X-ray diffraction analysis had been formed, which were collected by filtration [Yield: 65%]. Spectroscopic and TGA data are given in the archived CIF.

Refinement
The C-bound H-atoms were included in calculated positions and treated as riding atoms: C-H = 0.93 and 096 Å for CH and CH 3 H-atoms, respectively, with U iso (H) = k × U eq (parent C-atom), where k = 1.5 for CH 3 H-atoms and = 1.2 for other H-atoms.

Figure 1
The molecular structure of the title complex, showing the atom-labelling scheme. The displacement ellipsoids are drawn at the 50% probability level. The unlabelled atoms are related by the symmetry code: -x+1, -y+1, -z+2.

Figure 2
Perspective view of a fragment of the two-dimensional supramolecular network with the C-H···O hydrogen bonds shown as dashed lines.

Special details
Experimental. Spectroscopic and TGA data for the title compound: IR (KBr, cm -1 ): 3273,3076,2935,2871,1705,1615,1440,1218,1035,690; TGA Calcd. for 2(C 6 H 5 NO): 37.07. Found: 37.53% (303 -473 K). Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles 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.