Bis(ethylenediamine-κ2 N,N′)bis(methanol-κO)copper(II) benzene-1,4-dicarboxylate methanol disolvate

In the cation of the title compound, [Cu(C2H8N2)2(CH3OH)2](C8H4O4)·2CH3OH, the CuII atom lies on an inversion centre. The four N atoms of two ethylenediamine ligands around the CuII atom form the equatorial plane, while two methanol O atoms in the axial positions complete a Jahn–Teller distorted octahedral coordination. The benzene-1,4-dicarboxylate anion is centrosymmetric. In the crystal, C—H⋯O, N—H⋯O and O—H⋯O hydrogen bonds link the cations, the anions and the methanol solvent molecules.

In the cation of the title compound, [Cu(C 2 H 8 N 2 ) 2 (CH 3 OH) 2 ]-(C 8 H 4 O 4 )Á2CH 3 OH, the Cu II atom lies on an inversion centre. The four N atoms of two ethylenediamine ligands around the Cu II atom form the equatorial plane, while two methanol O atoms in the axial positions complete a Jahn-Teller distorted octahedral coordination. The benzene-1,4-dicarboxylate anion is centrosymmetric. In the crystal, C-HÁ Á ÁO, N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds link the cations, the anions and the methanol solvent molecules.
Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999 Copper plays a role in a number of biological processes with therapeutically administered drugs (Kovala-Demertzi et al., 1997). Coordination chemistry of Cu(II) complexes is important as building-blocks to construct novel coordination architectures (Wen et al., 2005). Carboxylate anions are widely used in the synthesis of coordination polymers (Eddaoudi et al., 2001). In the recent years, we reported the synthesis and crystal structures of Cu(II) carboxylate complexes (Al-Hashemi et al., 2010a,b). In order to expand this field, the title compound has been synthesized and its crystal structure is reported herein.
The asymmetric unit of the title compound ( Fig. 1) consists a half of Cu II ion, one ethylenediamine (en), one coordinated methanol, one uncoordinated methanol and a half of benzene-1,4-dicarboxylate anion. The Cu II atom in the [Cu(en) 2 (CH 3 OH) 2 ] 2+ cation lies on an inversion centre. The four N atoms of the en ligands in the equatorial plane around the Cu II atom form a slightly distorted square-planar arrangement, while the slightly distorted Jahn-Teller octahedral coordination is completed by two methanol O atoms in the axial positions. In the crystal, intermolecular C-H···O, N-H···O and O-H···O hydrogen bonds (Table 1) link the cations, the anions and the methanol solvent molecules (Fig. 2), which are effective in the stabilization of the structure.

Experimental
Benzene-1,4-dicarboxylic acid (0.10 g, 0.59 mmol) was dissolved in 6 ml methanol and 3.9 ml ethylenediamine (0.30 mol L -1 in methanol). Then CuCl 2 .2H 2 O (0.10 g, 0.59 mmol) was added to the solution and the reaction mixture was stirred. After 10 min 2-methylimidazol (0.10 g, 1.18 mmol) was added to the stirred solution. The resulting violet solution stirred at 313 K for 25 min. This solution was left to evaporate slowly at room temperature. After one week, violet block crystals of the title compound were isolated (yield: 0.20 g, 70.2%).

Refinement
H atoms bonded to O and N atoms were found in a difference Fourier map and refined isotropically. H atoms bonded to C atoms were positioned geometrically and refined as riding atoms, with C-H = 0.95 (aromatic), 0.99 (CH 2 ) and 0.98 (CH 3 ) Å and with U iso (H) = 1.2(1.5 for methyl)U eq (C). SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).  The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level.  The packing diagram of the title compound showing hydrogen bonds as blue dashed lines. 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.