Bromidotetra­kis­(1H-2-ethyl-5-methyl­imidazole-κN³)copper(II) bromide

The Cu^II 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 Cu^II 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).

Key indicators

• Single-crystal X-ray study
• T = 294 K
• Mean [sigma](C-C) = 0.004 Å
• Disorder in main residue
• R factor = 0.027
• wR factor = 0.076
• Data-to-parameter ratio = 13.5

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT413_ALERT_2_B Short Inter XH3 .. XHn     H4C    ..  H6A2    ..       1.95 Ang.

Alert level C
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C5     --  C6      ..        5.3 su
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT152_ALERT_1_G The Supplied and Calc. Volume s.u. Differ by ...          2 Units
PLAT232_ALERT_2_G Hirshfeld Test Diff (M-X)  Br1    --  Cu1     ..       21.5 su
PLAT242_ALERT_2_G Check Low       Ueq as Compared to Neighbors for        C5A
PLAT301_ALERT_3_G Note: Main Residue  Disorder ...................         24 Perc.
PLAT432_ALERT_2_G Short Inter X...Y Contact  C6     ..  C6      ..       3.00 Ang.
PLAT720_ALERT_4_G Number of Unusual/Non-Standard Labels ..........          5
PLAT811_ALERT_5_G No ADDSYM Analysis: Too Many Excluded Atoms ....          !

   0 ALERT level A = Most likely a serious problem - resolve or explain
   1 ALERT level B = A potentially serious problem, consider carefully
   2 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   8 ALERT level G = General information/check it is not something unexpected

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   5 ALERT type 2 Indicator that the structure model may be wrong or deficient
   2 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

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S1. Comment

The composition of (I) is very similar to the bromidotetrakis(1H2-isopropylimidazole-κN³)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-κN³)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(C₆H₁₀N₂)₄Br]⁺ 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.

Related literature

For more copper(II) complexes with bromido and imidazole ligands, see: Godlewska et al. (2011); Hossaini Sadr et al. (2004); Li et al. (2007); Liu et al. (2007); Näther et al. (2002a,b). For the alignment of dipoles in crystalline materials, see: Anthony & Radhakrishnan (2001).

S2. 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.

S3. 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).

Computing details

Data collection: CrysAlis PRO (Oxford Diffraction, 2006); cell refinement: CrysAlis PRO (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); 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).

Figures

	Fig. 1. A view of (I), showing displacement ellipsoids drawn at the 30% probability level. Labels are given only for the independent part.
	Fig. 2. The packing of dipoles in crystals of (I).

Bromidotetrakis(1H-2-ethyl-5-methylimidazole-κN³)copper(II) bromide

Crystal data

[CuBr(C6H10N2)4]Br	Dx = 1.475 Mg m^−3
Mr = 664	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P4/n	Cell parameters from 2155 reflections
Hall symbol: -P 4a	θ = 2.7–28.8°
a = 14.0961 (4) Å	µ = 3.43 mm^−1
c = 7.5236 (4) Å	T = 294 K
V = 1494.94 (10) Å^3	Prism, blue
Z = 2	0.54 × 0.45 × 0.33 mm
F(000) = 678

Data collection

Oxford Diffraction Xcalibur Sapphire2 diffractometer	1395 independent reflections
Graphite monochromator	898 reflections with I > 2s(I)
Detector resolution: 8.1883 pixels mm^-1	Rint = 0.025
ω scans	θmax = 25.5°, θmin = 2.7°
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2006), based on expressions derived by Clark & Reid (1995)]	h = −17→10
Tmin = 0.248, Tmax = 0.44	k = −17→15
5099 measured reflections	l = −9→7

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.076	H-atom parameters constrained
S = 0.95	w = 1/[σ^2(Fo^2) + (0.0447P)^2] where P = (Fo^2 + 2Fc^2)/3
1395 reflections	(Δ/σ)max = 0.004
103 parameters	Δρmax = 0.63 e Å^−3
0 restraints	Δρmin = −0.39 e Å^−3

Special details

Experimental. CrysAlisPro (Oxford Diffraction Ltd., 2006) Analytical numeric absorption correction using a multifaceted crystal model based on expressions derived by R.C. Clark & J.S. (Clark, R. C. & Reid, J. S. (1995). Acta Cryst. A51, 887-897)

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 F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² 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 (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
Br1	0.25	0.25	0.31140 (7)	0.0495 (2)
Br2	0.75	0.25	0	0.05286 (19)
Cu1	0.25	0.25	0.67466 (8)	0.0366 (2)
N1	0.22250 (14)	0.39093 (14)	0.6939 (3)	0.0397 (5)
N2	0.21196 (15)	0.54003 (15)	0.7653 (3)	0.0486 (6)
H2	0.2195	0.5922	0.823	0.058*
C1	0.16846 (19)	0.4385 (2)	0.5685 (4)	0.0481 (7)
H1	0.141	0.4104	0.4693	0.058*
C2	0.16140 (19)	0.5299 (2)	0.6100 (4)	0.0520 (8)
C3	0.24764 (19)	0.4552 (2)	0.8122 (4)	0.0446 (7)
C4	0.1150 (3)	0.6113 (2)	0.5178 (5)	0.0900 (14)
H4A	0.0826	0.5888	0.4138	0.135*
H4B	0.1623	0.6568	0.4836	0.135*
H4C	0.0702	0.6408	0.5966	0.135*
C5	0.2915 (9)	0.4385 (17)	0.980 (3)	0.059 (3)	0.620 (8)
H5A	0.2972	0.3709	1.001	0.071*	0.620 (8)
H5B	0.2533	0.4658	1.0744	0.071*	0.620 (8)
C6	0.3952 (5)	0.4870 (5)	0.9776 (9)	0.087 (3)	0.620 (8)
H6A	0.3886	0.5546	0.9672	0.131*	0.620 (8)
H6B	0.4307	0.4632	0.8783	0.131*	0.620 (8)
H6C	0.4279	0.4721	1.0859	0.131*	0.620 (8)
C5A	0.3233 (13)	0.438 (2)	0.966 (4)	0.043 (5)	0.380 (8)
H5A1	0.3232	0.3711	0.9977	0.052*	0.380 (8)
H5A2	0.386	0.4535	0.9218	0.052*	0.380 (8)
C6A	0.3036 (11)	0.4935 (7)	1.1209 (14)	0.123 (6)	0.380 (8)
H6A1	0.3115	0.5595	1.0934	0.184*	0.380 (8)
H6A2	0.3466	0.476	1.2143	0.184*	0.380 (8)
H6A3	0.2395	0.4822	1.1588	0.184*	0.380 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0587 (3)	0.0587 (3)	0.0311 (3)	0	0	0
Br2	0.0394 (2)	0.0394 (2)	0.0798 (5)	0	0	0
Cu1	0.0350 (2)	0.0350 (2)	0.0397 (4)	0	0	0
N1	0.0396 (13)	0.0367 (12)	0.0428 (14)	0.0018 (10)	−0.0011 (10)	−0.0029 (10)
N2	0.0519 (15)	0.0364 (13)	0.0576 (17)	−0.0021 (11)	0.0071 (13)	−0.0080 (12)
C1	0.0411 (17)	0.0519 (19)	0.0514 (18)	0.0037 (14)	−0.0084 (14)	−0.0031 (15)
C2	0.0455 (18)	0.0466 (19)	0.064 (2)	0.0092 (14)	−0.0011 (16)	0.0027 (16)
C3	0.0485 (18)	0.0436 (17)	0.0418 (17)	−0.0049 (13)	0.0058 (14)	−0.0022 (14)
C4	0.086 (3)	0.058 (2)	0.127 (4)	0.0231 (19)	−0.030 (2)	0.007 (2)
C5	0.060 (9)	0.070 (5)	0.048 (6)	−0.003 (8)	−0.003 (7)	−0.007 (4)
C6	0.104 (6)	0.079 (4)	0.079 (6)	0.010 (4)	−0.047 (4)	−0.021 (3)
C5A	0.038 (11)	0.060 (8)	0.033 (8)	−0.024 (10)	−0.007 (8)	0.007 (6)
C6A	0.252 (18)	0.065 (7)	0.051 (7)	0.045 (8)	−0.051 (9)	−0.023 (6)

Geometric parameters (Å, º)

Cu1—Br1	2.7330 (8)	C4—H4A	0.96
Cu1—N1^i	2.029 (2)	C4—H4B	0.96
Cu1—N1	2.029 (2)	C4—H4C	0.96
Cu1—N1^ii	2.029 (2)	C5—C6	1.613 (14)
Cu1—N1^iii	2.029 (2)	C5—H5A	0.97
N1—C3	1.319 (3)	C5—H5B	0.97
N1—C1	1.385 (3)	C6—H6A	0.96
N2—C3	1.344 (3)	C6—H6B	0.96
N2—C2	1.376 (4)	C6—H6C	0.96
N2—H2	0.86	C5A—C6A	1.43 (3)
C1—C2	1.330 (4)	C5A—H5A1	0.97
C1—H1	0.93	C5A—H5A2	0.97
C2—C4	1.492 (4)	C6A—H6A1	0.96
C3—C5	1.42 (2)	C6A—H6A2	0.96
C3—C5A	1.59 (3)	C6A—H6A3	0.96
N1^i—Cu1—N1	89.708 (9)	N2—C3—C5A	125.4 (12)
N1^i—Cu1—N1^ii	89.707 (9)	C2—C4—H4A	109.5
N1—Cu1—N1^ii	171.81 (12)	C2—C4—H4B	109.5
N1^i—Cu1—N1^iii	171.81 (12)	H4A—C4—H4B	109.5
N1—Cu1—N1^iii	89.707 (9)	C2—C4—H4C	109.5
N1^ii—Cu1—N1^iii	89.708 (9)	H4A—C4—H4C	109.5
N1^i—Cu1—Br1	94.10 (6)	H4B—C4—H4C	109.5
N1—Cu1—Br1	94.10 (6)	C3—C5—C6	108.3 (12)
N1^ii—Cu1—Br1	94.10 (6)	C3—C5—H5A	110
N1^iii—Cu1—Br1	94.10 (6)	C6—C5—H5A	110
C3—N1—C1	106.0 (2)	C3—C5—H5B	110
C3—N1—Cu1	132.03 (19)	C6—C5—H5B	110
C1—N1—Cu1	122.00 (18)	H5A—C5—H5B	108.4
C3—N2—C2	108.9 (2)	C6A—C5A—C3	112.1 (18)
C3—N2—H2	125.5	C6A—C5A—H5A1	109.2
C2—N2—H2	125.5	C3—C5A—H5A1	109.2
C2—C1—N1	110.5 (3)	C6A—C5A—H5A2	109.2
C2—C1—H1	124.7	C3—C5A—H5A2	109.2
N1—C1—H1	124.7	H5A1—C5A—H5A2	107.9
C1—C2—N2	105.1 (2)	C5A—C6A—H6A1	109.5
C1—C2—C4	132.0 (3)	C5A—C6A—H6A2	109.5
N2—C2—C4	122.8 (3)	H6A1—C6A—H6A2	109.5
N1—C3—N2	109.5 (2)	C5A—C6A—H6A3	109.5
N1—C3—C5	127.0 (10)	H6A1—C6A—H6A3	109.5
N2—C3—C5	122.8 (10)	H6A2—C6A—H6A3	109.5
N1—C3—C5A	124.3 (12)

Symmetry codes: (i) −y+1/2, x, z; (ii) −x+1/2, −y+1/2, z; (iii) y, −x+1/2, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···Br2^iv	0.86	2.63	3.488 (2)	178

Symmetry code: (iv) −x+1, −y+1, −z+1.