Bis(methacrylato-κO)bis(2,4,6-trimethylpyridine-κN)copper(II)

In the monomeric title complex, [Cu(C4H5O2)2(C8H11N)2], the CuII atom lies on a centre of inversion. Its coordination by two substituted pyridine ligands and two carboxylate anions leads to a slightly distorted trans-CuN2O2 square-planar geometry. The dihedral angle between the mean planes of the pyridine (py) ring and the carboxylate group is 74.71 (7)°. The dihedral angles between the planar CuN2O2 core and the py ring and carboxylate plane are 67.72 (5) and 89.95 (5)°, respectively. Based on the refined C=C and C—C bond lengths, the terminal =CH2 and –CH3 groups of the carboxylate anion may be disordered, but the disorder could not be resolved in the present experiment. Several intramolecular C—H⋯O interactions occur. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds, generating chains propagating in [100].

In the monomeric title complex, [Cu(C 4 H 5 O 2 ) 2 (C 8 H 11 N) 2 ], the Cu II atom lies on a centre of inversion. Its coordination by two substituted pyridine ligands and two carboxylate anions leads to a slightly distorted trans-CuN 2 O 2 square-planar geometry. The dihedral angle between the mean planes of the pyridine (py) ring and the carboxylate group is 74.71 (7) . The dihedral angles between the planar CuN 2 O 2 core and the py ring and carboxylate plane are 67.72 (5) and 89.95 (5) , respectively. Based on the refined C C and C-C bond lengths, the terminal CH 2 and -CH 3 groups of the carboxylate anion may be disordered, but the disorder could not be resolved in the present experiment. Several intramolecular C-HÁ Á ÁO interactions occur. In the crystal, molecules are linked by weak C-HÁ Á ÁO hydrogen bonds, generating chains propagating in [100].
IUK thanks the Higher Education Commission of Pakistan for its financial support under the project to strengthen the Materials Chemistry Laboratory at GCUL. The title compound, (I), is a centrosymmetric neutral monomeric copper(II) complex (Fig. 1). Related structures containing a copper(II) ion bonded to a pair of susbtituted pyridine ligands and a pair of monodentate carboxylate anions have been described previously (Borel et al., 1981;Heimer & Ahmed, 1982;Jedrzejas et al., 1994).
The Cu ion in (I) lies on an inversion centre, resulting in a slightly distorted trans-CuN 2 O 2 square planar geometry for the metal ion (Table 1). If a very long contact between Cu1 and O1 [2.8229 (17) (Table 1). In the crystal, the molecules are linked by C-H···O hydrogen bonds to generate chains in the [100] direction.

Experimental
Copper sulfate (0.16 g, 1.0 mmol) was dissolved in methanol (20 ml). Then, 2,4,6-trimethyl pyridine (0.264 ml, 2.0 mmol) was added to this solution, which turned green. This reaction mixture was refluxed for 30 minutes followed by addition of methacrylic acid (0.169 ml, 2.0 mmol), at which point the solution remained green. After refluxing for one hour, the solution was filtered and kept for a few days. Blue-green blocks of (I) were obtained from filtrate by slow evaporation.

Refinement
Attempts were made to represent the disordered C11 (nominal CH 2 group) and C12 (nominal CH 3 group) atoms with a double-site model, but the refinement was unstable. The hydrogen atoms were placed in calculated positions (C-H = supplementary materials sup-2 Acta Cryst. (2012). E68, m469-m470 0.93-0.96Å) and refined as riding atoms with U iso (H) = 1.2U eq (C) or 1.5U eq (methyl C). The methyl groups were allowed to rotate, but not to tip, to best fit the electron density.

Figure 1
The molecular structure of (I) showing 50% displacement ellipsoids. Symmetry code: (i) 1-x, 1-y, 1-z.   where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.24 e Å −3 Δρ min = −0.21 e Å −3 Special details 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. 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 > 2sigma(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.