Bromidotetrakis(1H-2-ethyl-5-methylimidazole-κN 3)copper(II) bromide

The CuII ion in the title compound, [CuBr(C6H10N2)4]Br, is coordinated in a square-based-pyramidal geometry by the N atoms of four imidazole ligands and a bromide anion in the apical site. Both the CuII and Br− atoms lie on a crystallographic fourfold axis. In the crystal, the [CuBr(C6H10N2)4]+ complex cations are linked to the uncoordinated Br− anions (site symmetry ) by N—H⋯Br hydrogen bonds, generating a three-dimensional network. The ethyl group of the imidazole ligand was modelled as disordered over two orientations with occupancies of 0.620 (8) and 0.380 (8).

The Cu II ion in the title compound, [CuBr(C 6 H 10 N 2 ) 4 ]Br, is coordinated in a square-based-pyramidal geometry by the N atoms of four imidazole ligands and a bromide anion in the apical site. Both the Cu II and Br À atoms lie on a crystallographic fourfold axis. In the crystal, the [CuBr(C 6 H 10 N 2 ) 4 ] + complex cations are linked to the uncoordinated Br À anions (site symmetry 4) by N-HÁ Á ÁBr hydrogen bonds, generating a three-dimensional network. The ethyl group of the imidazole ligand was modelled as disordered over two orientations with occupancies of 0.620 (8) and 0.380 (8).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB6533).

Comment
The composition of (I) is very similar to the bromidotetrakis(1H2-isopropylimidazole-κN 3 )copper(II) bromide described previously (Godlewska et al., 2011). However these compounds display substantially different crystal packing. Four NH···Br hydrogen bonds surrounding Br2 in bromidotetrakis(1H2-isopropylimidazole-κN 3 )copper(II) bromide are almost planar whereas the corresponding hydrogen bonds in (I) form distorted tetrahedron around Br2 and therefore build a network extending in all three directions in crystal. Complex cations [Cu(C 6 H 10 N 2 ) 4 Br] + are dipoles aligned perfectly parallel to c axis in a head-to-tail manner (see Fig. 2). The disorder of alkyl substituents is typical of room temperature determinations (e.g. Näther et al. (2002a), Acta Cryst. E58, m63-m64).
The structure of (I) is shown in Fig. 1 and packing diagram of complex dipoles is presented in Fig.2.

Experimental
The title compound was prepared by adding the solution of 0.223 g (1 mmol) copper(II) bromide in 4 ml of methanol to the solution of 0.496 g (4.5 mmol) 2-ethyl-4(5)-methylimidazole in 2 ml of methanol. After a few days blue prisms were obtained by slow evaporation of solvent from the reaction mixture.

Refinement
All C-H hydrogen atoms were refined as riding on carbon atoms with methyl C-H = 0.98 Å, methine C-H = 1 Å, aromatic C-H = 0.95 Å and U iso (H)=1.2 U eq (C)for aromatic and methine CH and 1.5U eq (C) for methyl groups. Ethyl group of imidazole was refined as disordered between two positions with occupancies 0.620 (8)/0.380 (8). Fig. 1. A view of (I), showing displacement ellipsoids drawn at the 30% probability level. Labels are given only for the independent part. supplementary materials sup-2 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.