Dibromidobis[1-(2-bromobenzyl)-3-(pyrimidin-2-yl)-1H-imidazol-2(3H)-one]copper(II)

In the title complex, [CuBr2(C14H11BrN4O)2], the CuII ion is located on an inversion centre and is coordinated by two ketonic O atoms, two N atoms and two Br atoms, forming a distorted octahedral coordination environment. The two carbonyl groups are trans positioned with C=O bond lengths of 1.256 (5) Å, in agreement with a classical carbonyl bond. The Cu—O bond length is 2.011 (3) Å. The two bromobenzyl rings are approximately parallel to one another, forming a dihedral angle of 70.1 (4)° with the coordination plane.

The author thanks the Natural Science Foundation of China (21072170).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RU2034).

Chun-Xin Lu Comment
Cu 2+ cation has been widely studied since a host of low-molecular-weight copper complexes have been proven beneficial against several diseases such as turberculosis, rheumatoid, gastric ulcers, and cancers. And it is well known that copper(II) complexes with different ligands usually show flexible coordination environment. The 1-(2-bromobenzyl)-3-(pyrimidin-2-yl)imidazolium bromide was used as the ligand, reacting with excessive copper powder in air, giving a Cu II compound. We here report the crystal structure of the title compound (I).
Bond lengths and angles in the title molecule ( Fig. 1) are within normal ranges. The C=O bond distance is 1.256 (5) Å and Cu-O bond distance is 2.013 (3) Å. The two bromobenzyl rings are approximately parallel to each other. The dihedral angle between the bromobenzyl ring and the coordination plane is 70.1 (4)°.

Experimental
A solution of 1-(2-bromobenzyl)-3-(pyrimidin-2-yl)imidazolium bromide (396 mg, 1.0 mmol) in 10 ml of CH 3 CN was treated with copper powder (38 mg, 0.6 mmol). The mixture was allowed to react at 80 °C for 2 days in air. The solution was filtered through silica to remove unreacted copper. The filtrate was concentrated to ca 2 ml. Addition of Et 2 O (20 ml) to the filtrate afforded a yellow precipitate. The crystals of this complex suitable for X-ray diffraction were obtained by slow diffusion of diethyl ether into its acetonitrile solution.

Refinement
H atoms were placed in calculated positions with C-H = 0.93-0.97 Å, and refined in riding mode 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 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.

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