Dibromido(4,7-diazadecane-1,10-di­amine)­copper(II)

Assey, G.E.; Butcher, R.J.; Gultneh, Y.

doi:10.1107/S160053681103251X

metal-organic compounds

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ISSN: 2056-9890

Volume 67| Part 9| September 2011| Page m1266

doi:10.1107/S160053681103251X

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Dibromido(4,7-diazadecane-1,10-diamine)copper(II)

Gervas E. Assey,^a Ray J. Butcher ^a ^* and Yilma Gultneh ^a

^aDepartment of Chemistry, Howard University, 525 College Street NW, Washington DC 20059, USA
^*Correspondence e-mail: rbutcher99@yahoo.com

(Received 8 August 2011; accepted 10 August 2011; online 17 August 2011)

In the title compound, [CuBr₂(C₈H₂₂N₄)], the Cu^II atom is six-coordinate forming a distorted octahedral complex and is bonded to two axial bromide anions and four equatorial nitrogen donors. The equatorial Cu—N bond distances range from 2.005 (8) to 2.046 (8) Å while the axial Cu—Br distances are 2.8616 (17) and 2.9402 (17) Å, thus the six-coordinate Cu complex shows the usual Jahn–Teller distortion. All amine hydrogen atoms participate in either inter- or intramolecular hydrogen bonding to the Br anions.

Related literature

For related structues, see: Lee et al. (1986 ). For other related literature, see: Jahn & Teller (1937 ).

Experimental

Crystal data

[CuBr₂(C₈H₂₂N₄)]
M_r = 397.66
Orthorhombic, P 2₁ 2₁ 2₁
a = 6.9666 (4) Å
b = 8.4146 (6) Å
c = 24.0261 (15) Å
V = 1408.45 (15) Å³
Z = 4
Mo Kα radiation
μ = 7.20 mm⁻¹
T = 110 K
0.47 × 0.31 × 0.22 mm

Data collection

Oxford Diffraction Xcalibur diffractometer with a Ruby detector
Absorption correction: analytical (CrysAlis PRO; Oxford Diffraction, 2007 $[Oxford Diffraction (2007). CrysAlis PRO and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ) T_min = 0.157, T_max = 0.282
9561 measured reflections
2758 independent reflections
2262 reflections with I > 2σ(I)
R_int = 0.072

Refinement

R[F² > 2σ(F²)] = 0.071
wR(F²) = 0.183
S = 1.07
2758 reflections
136 parameters
24 restraints
H-atom parameters constrained
Δρ_max = 2.51 e Å⁻³
Δρ_min = −1.98 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1C⋯Br2ⁱ	0.92	2.66	3.466 (9)	147
N1—H1D⋯Br2	0.92	2.80	3.339 (8)	119
N2—H2C⋯Br1ⁱⁱ	0.93	2.66	3.407 (8)	138
N2—H2C⋯Br2	0.93	3.01	3.519 (7)	116
N3—H3C⋯Br1	0.93	2.90	3.409 (8)	116
N4—H4C⋯Br2ⁱ	0.92	2.60	3.515 (8)	171
N4—H4D⋯Br2ⁱⁱⁱ	0.92	2.69	3.425 (8)	138
N4—H4D⋯Br1	0.92	2.94	3.433 (8)	115
Symmetry codes: (i) $[x+{\script{1\over 2}}, -y+{\script{3\over 2}}, -z]$ ; (ii) x-1, y, z; (iii) x+1, y, z.

Data collection: CrysAlis PRO (Oxford Diffraction, 2007 $[Oxford Diffraction (2007). CrysAlis PRO and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ); cell refinement: CrysAlis PRO; data reduction: CrysAlis RED (Oxford Diffraction, 2007 $[Oxford Diffraction (2007). CrysAlis PRO and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England.]$ ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053681103251X/pv2444sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S160053681103251X/pv2444Isup2.hkl

checkCIF report

Comment top

In this study, the title compound was prepared and its structure determined by X-ray analysis. Owing to the Jahn-Teller distortion (Jahn & Teller, 1937), the Cu(II) center adopts an axially distorted octahedral CuN₄Br₂ conformation with the axial positions are occupied by the bromide anions. The equatorial positions are occupied by the N₄ set of donor nitrogen atoms and the Cu1 lies in the N₄ plane; maximum deviation of any atom from the mean-plane formed by CuN₄ fragment being 0.042 (4) for N3. The structure of a related compound containing the same linear tetramine, has been reported (Lee et al. 1986) and its structural features compared with those of other linear Cu(II) aliphatic tetraamines of the type H₂N(CH₂)_lNH-(CH₂)_mNH(CH₂)_nNH₂ where l, m and n are 2 or 3. From this it can be seen that in the title complex, the equatorial Cu—N bond distances range from 2.005 (8) to 2.046 (8) Å and are in the normal range for such bonds. However, the axial Cu—Br distances are elongated at 2.8616 (17) and 2.9402 (17) Å, thus the 6-coordinate Cu complex shows the usual Jahn-Teller distortion. All amine H's participate in either inter or intramolecular hydrogen bonding to the Br anions.

Related literature top

For related structues, see: Lee et al. (1986). For other related literature, see: Jahn & Teller (1937).

Experimental top

The title compound was obtained as a byproduct of an attempt to prepare copper complexes of ethylenediamine N,N-bis(propylsalicylaldimine). A solution of N, N-bis(3-aminopropylethylene)diamine (5 g, 30.52 mmol) in methanol (20 ml) was added dropwise to a solution of salicylaldehyde (7.45 g, 61.04 mmol) in methanol (20 ml). The mixture was refluxed overnight while stirring with magnetic stirrer. Then the reaction mixture was evaporated under reduced pressure. An oily orange product was obtained which later solidified into a yellow compound, [2-(3-amino-propylamino)-ethyl]-propane-1,3-diamine-bis(salicyladimine), used as a ligand (H₂L₄) in the subsequent reaction. The synthesis of the title complex was achieved by the reaction of CuBr (1.5 g, 10.5 mmol) in methanol (20 ml) with of the ligand H₂L₄ (2 g, 5.2 mmol) dissolved in CH₂Cl₂ (25 ml). The ligand solution was added drop-wise to the solution of the metal salt and stirred at room temperature for 24 h. The mixture was then concentrated by evaporation under reduced pressure to afford a thick greenish liquid. Part of the complex was dissolved in dimethyl formamide (DMF), filtered and layered with diethyl ether for slow diffusion and X-ray quality crystals were obtained.

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2007); cell refinement: CrysAlis PRO (Oxford Diffraction, 2007); data reduction: CrysAlis RED (Oxford Diffraction, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. An ORTEP drawing of the title complex showing atom labeling. Thermal ellipsoids are drawn at the 30% probability level.
	Fig. 2. The molecular packing for the title compound viewed down the a axis. Hydrogen bonds are showed by dashed lines.

Dibromido(4,7-diazadecane-1,10-diamine)copper(II) top

Crystal data top

[CuBr₂(C₈H₂₂N₄)]	F(000) = 788
M_r = 397.66	D_x = 1.875 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 4805 reflections
a = 6.9666 (4) Å	θ = 4.6–32.8°
b = 8.4146 (6) Å	µ = 7.20 mm⁻¹
c = 24.0261 (15) Å	T = 110 K
V = 1408.45 (15) Å³	Prism, dark blue
Z = 4	0.47 × 0.31 × 0.22 mm

Data collection top

Goniometer Xcalibur, detector Ruby (Gemini Mo) diffractometer	2758 independent reflections
Radiation source: Enhance (Mo) X-ray Source	2262 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.072
Detector resolution: 10.5081 pixels mm^-1	θ_max = 32.8°, θ_min = 4.6°
ω scans	h = −10→9
Absorption correction: analytical (CrysAlis PRO; Oxford Diffraction, 2007)	k = −12→11
T_min = 0.157, T_max = 0.282	l = −36→35
9561 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.071	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.183	H-atom parameters constrained
S = 1.07	w = 1/[σ²(F_o²) + (0.103P)² + 8.8289P] where P = (F_o² + 2F_c²)/3
2758 reflections	(Δ/σ)_max < 0.001
136 parameters	Δρ_max = 2.51 e Å⁻³
24 restraints	Δρ_min = −1.98 e Å⁻³

Crystal data top

[CuBr₂(C₈H₂₂N₄)]	V = 1408.45 (15) Å³
M_r = 397.66	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 6.9666 (4) Å	µ = 7.20 mm⁻¹
b = 8.4146 (6) Å	T = 110 K
c = 24.0261 (15) Å	0.47 × 0.31 × 0.22 mm

Data collection top

Goniometer Xcalibur, detector Ruby (Gemini Mo) diffractometer	2758 independent reflections
Absorption correction: analytical (CrysAlis PRO; Oxford Diffraction, 2007)	2262 reflections with I > 2σ(I)
T_min = 0.157, T_max = 0.282	R_int = 0.072
9561 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.071	24 restraints
wR(F²) = 0.183	H-atom parameters constrained
S = 1.07	Δρ_max = 2.51 e Å⁻³
2758 reflections	Δρ_min = −1.98 e Å⁻³
136 parameters

Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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 (Å²) top

	x	y	z	U_iso*/U_eq
Cu	0.84387 (19)	0.88632 (13)	0.11140 (4)	0.0099 (2)
Br1	1.15943 (15)	1.06828 (12)	0.15326 (4)	0.0187 (2)
Br2	0.52369 (16)	0.69368 (14)	0.06892 (5)	0.0225 (3)
N1	0.8009 (12)	1.0062 (10)	0.0394 (3)	0.0132 (16)
H1C	0.9013	0.9823	0.0160	0.016*
H1D	0.6914	0.9661	0.0233	0.016*
N2	0.6456 (12)	1.0252 (8)	0.1509 (3)	0.0106 (13)
H2C	0.5256	0.9901	0.1392	0.013*
N3	0.8538 (13)	0.7653 (9)	0.1852 (3)	0.0125 (14)
H3C	0.9601	0.8035	0.2044	0.015*
N4	1.0360 (12)	0.7415 (9)	0.0756 (3)	0.0110 (14)
H4C	1.0215	0.7508	0.0376	0.013*
H4D	1.1562	0.7796	0.0841	0.013*
C1	0.7815 (17)	1.1841 (12)	0.0409 (4)	0.0178 (19)
H1A	0.9031	1.2316	0.0542	0.021*
H1B	0.7571	1.2240	0.0028	0.021*
C2	0.6201 (14)	1.2343 (11)	0.0785 (4)	0.0143 (18)
H2A	0.5018	1.1786	0.0666	0.017*
H2B	0.5983	1.3496	0.0734	0.017*
C3	0.6518 (15)	1.2020 (11)	0.1399 (4)	0.0123 (15)
H3A	0.7780	1.2451	0.1514	0.015*
H3B	0.5511	1.2559	0.1620	0.015*
C4	0.6583 (17)	0.9909 (12)	0.2110 (4)	0.0160 (17)
H4A	0.5407	1.0279	0.2302	0.019*
H4B	0.7700	1.0467	0.2274	0.019*
C5	0.6801 (16)	0.8160 (13)	0.2179 (4)	0.0179 (19)
H5A	0.5644	0.7606	0.2039	0.021*
H5B	0.6970	0.7891	0.2577	0.021*
C6	0.8734 (14)	0.5888 (11)	0.1836 (4)	0.0138 (18)
H6A	0.7584	0.5421	0.1658	0.017*
H6B	0.8813	0.5473	0.2221	0.017*
C7	1.0503 (15)	0.5394 (11)	0.1517 (4)	0.0158 (18)
H7A	1.0739	0.4248	0.1581	0.019*
H7B	1.1623	0.5986	0.1663	0.019*
C8	1.0339 (15)	0.5691 (11)	0.0892 (4)	0.0142 (17)
H8A	1.1419	0.5161	0.0700	0.017*
H8B	0.9130	0.5216	0.0754	0.017*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu	0.0119 (5)	0.0064 (4)	0.0113 (4)	0.0022 (4)	0.0026 (4)	0.0007 (4)
Br1	0.0107 (4)	0.0185 (5)	0.0270 (5)	−0.0016 (4)	−0.0007 (4)	−0.0062 (4)
Br2	0.0169 (5)	0.0213 (5)	0.0293 (5)	−0.0013 (4)	−0.0023 (4)	−0.0026 (4)
N1	0.011 (4)	0.011 (4)	0.017 (4)	−0.004 (3)	−0.001 (3)	0.002 (3)
N2	0.010 (3)	0.005 (3)	0.017 (3)	0.001 (3)	−0.001 (3)	−0.001 (3)
N3	0.011 (3)	0.012 (3)	0.015 (3)	−0.001 (3)	0.003 (3)	0.002 (3)
N4	0.008 (3)	0.009 (3)	0.016 (3)	0.002 (2)	0.002 (2)	0.000 (2)
C1	0.023 (5)	0.012 (4)	0.018 (4)	−0.002 (4)	0.003 (4)	0.005 (4)
C2	0.012 (4)	0.005 (3)	0.026 (5)	0.004 (3)	0.001 (3)	0.002 (3)
C3	0.012 (3)	0.006 (3)	0.019 (3)	0.001 (3)	0.001 (3)	0.002 (3)
C4	0.017 (4)	0.021 (4)	0.010 (3)	0.002 (4)	0.004 (4)	−0.002 (3)
C5	0.019 (5)	0.020 (4)	0.015 (4)	0.006 (4)	0.006 (4)	0.003 (4)
C6	0.016 (4)	0.009 (3)	0.017 (3)	0.003 (3)	0.002 (3)	0.004 (3)
C7	0.020 (4)	0.009 (3)	0.018 (3)	0.005 (3)	0.001 (3)	0.003 (3)
C8	0.016 (4)	0.009 (4)	0.017 (4)	0.004 (4)	0.004 (3)	−0.003 (3)

Geometric parameters (Å, º) top

Cu—N4	2.005 (8)	C1—H1B	0.9900
Cu—N1	2.025 (8)	C2—C3	1.517 (13)
Cu—N2	2.043 (8)	C2—H2A	0.9900
Cu—N3	2.046 (8)	C2—H2B	0.9900
Cu—Br1	2.8616 (17)	C3—H3A	0.9900
Cu—Br2	2.9402 (17)	C3—H3B	0.9900
N1—C1	1.503 (13)	C4—C5	1.489 (15)
N1—H1C	0.9200	C4—H4A	0.9900
N1—H1D	0.9200	C4—H4B	0.9900
N2—C4	1.476 (12)	C5—H5A	0.9900
N2—C3	1.512 (11)	C5—H5B	0.9900
N2—H2C	0.9300	C6—C7	1.510 (14)
N3—C6	1.492 (11)	C6—H6A	0.9900
N3—C5	1.504 (13)	C6—H6B	0.9900
N3—H3C	0.9300	C7—C8	1.526 (14)
N4—C8	1.487 (12)	C7—H7A	0.9900
N4—H4C	0.9200	C7—H7B	0.9900
N4—H4D	0.9200	C8—H8A	0.9900
C1—C2	1.503 (14)	C8—H8B	0.9900
C1—H1A	0.9900

N4—Cu—N1	92.0 (3)	H1A—C1—H1B	108.0
N4—Cu—N2	177.1 (3)	C1—C2—C3	115.2 (8)
N1—Cu—N2	90.7 (3)	C1—C2—H2A	108.5
N4—Cu—N3	92.7 (3)	C3—C2—H2A	108.5
N1—Cu—N3	173.4 (4)	C1—C2—H2B	108.5
N2—Cu—N3	84.6 (3)	C3—C2—H2B	108.5
N4—Cu—Br1	87.9 (2)	H2A—C2—H2B	107.5
N1—Cu—Br1	98.5 (2)	N2—C3—C2	110.0 (7)
N2—Cu—Br1	92.9 (2)	N2—C3—H3A	109.7
N3—Cu—Br1	86.3 (3)	C2—C3—H3A	109.7
N4—Cu—Br2	91.3 (2)	N2—C3—H3B	109.7
N1—Cu—Br2	82.3 (2)	C2—C3—H3B	109.7
N2—Cu—Br2	87.9 (2)	H3A—C3—H3B	108.2
N3—Cu—Br2	93.0 (3)	N2—C4—C5	107.9 (8)
Br1—Cu—Br2	178.89 (6)	N2—C4—H4A	110.1
C1—N1—Cu	119.3 (7)	C5—C4—H4A	110.1
C1—N1—H1C	107.5	N2—C4—H4B	110.1
Cu—N1—H1C	107.5	C5—C4—H4B	110.1
C1—N1—H1D	107.5	H4A—C4—H4B	108.4
Cu—N1—H1D	107.5	C4—C5—N3	107.7 (9)
H1C—N1—H1D	107.0	C4—C5—H5A	110.2
C4—N2—C3	111.2 (7)	N3—C5—H5A	110.2
C4—N2—Cu	107.6 (6)	C4—C5—H5B	110.2
C3—N2—Cu	117.6 (6)	N3—C5—H5B	110.2
C4—N2—H2C	106.6	H5A—C5—H5B	108.5
C3—N2—H2C	106.6	N3—C6—C7	111.2 (8)
Cu—N2—H2C	106.6	N3—C6—H6A	109.4
C6—N3—C5	111.7 (8)	C7—C6—H6A	109.4
C6—N3—Cu	118.5 (6)	N3—C6—H6B	109.4
C5—N3—Cu	106.5 (6)	C7—C6—H6B	109.4
C6—N3—H3C	106.5	H6A—C6—H6B	108.0
C5—N3—H3C	106.5	C6—C7—C8	113.1 (8)
Cu—N3—H3C	106.5	C6—C7—H7A	109.0
C8—N4—Cu	119.4 (6)	C8—C7—H7A	109.0
C8—N4—H4C	107.5	C6—C7—H7B	109.0
Cu—N4—H4C	107.5	C8—C7—H7B	109.0
C8—N4—H4D	107.5	H7A—C7—H7B	107.8
Cu—N4—H4D	107.5	N4—C8—C7	112.1 (8)
H4C—N4—H4D	107.0	N4—C8—H8A	109.2
C2—C1—N1	111.2 (8)	C7—C8—H8A	109.2
C2—C1—H1A	109.4	N4—C8—H8B	109.2
N1—C1—H1A	109.4	C7—C8—H8B	109.2
C2—C1—H1B	109.4	H8A—C8—H8B	107.9
N1—C1—H1B	109.4

N4—Cu—N1—C1	−139.1 (8)	N1—Cu—N4—C8	−138.9 (7)
N2—Cu—N1—C1	42.1 (8)	N3—Cu—N4—C8	36.5 (7)
Br1—Cu—N1—C1	−50.9 (8)	Br1—Cu—N4—C8	122.7 (7)
Br2—Cu—N1—C1	129.9 (8)	Br2—Cu—N4—C8	−56.6 (7)
N1—Cu—N2—C4	−170.1 (6)	Cu—N1—C1—C2	−57.3 (11)
N3—Cu—N2—C4	14.4 (6)	N1—C1—C2—C3	67.5 (11)
Br1—Cu—N2—C4	−71.6 (6)	C4—N2—C3—C2	−174.8 (8)
Br2—Cu—N2—C4	107.6 (6)	Cu—N2—C3—C2	60.6 (10)
N1—Cu—N2—C3	−43.7 (7)	C1—C2—C3—N2	−69.7 (11)
N3—Cu—N2—C3	140.8 (7)	C3—N2—C4—C5	−171.9 (9)
Br1—Cu—N2—C3	54.8 (6)	Cu—N2—C4—C5	−41.8 (10)
Br2—Cu—N2—C3	−126.0 (6)	N2—C4—C5—N3	56.4 (11)
N4—Cu—N3—C6	−37.2 (8)	C6—N3—C5—C4	−172.8 (8)
N2—Cu—N3—C6	141.9 (8)	Cu—N3—C5—C4	−42.0 (9)
Br1—Cu—N3—C6	−124.9 (7)	C5—N3—C6—C7	−178.8 (8)
Br2—Cu—N3—C6	54.3 (7)	Cu—N3—C6—C7	56.9 (10)
N4—Cu—N3—C5	−164.0 (7)	N3—C6—C7—C8	−70.4 (11)
N2—Cu—N3—C5	15.1 (6)	Cu—N4—C8—C7	−55.5 (10)
Br1—Cu—N3—C5	108.3 (6)	C6—C7—C8—N4	69.7 (11)
Br2—Cu—N3—C5	−72.5 (6)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1C···Br2ⁱ	0.92	2.66	3.466 (9)	147
N1—H1D···Br2	0.92	2.80	3.339 (8)	119
N2—H2C···Br1ⁱⁱ	0.93	2.66	3.407 (8)	138
N2—H2C···Br2	0.93	3.01	3.519 (7)	116
N3—H3C···Br1	0.93	2.90	3.409 (8)	116
N4—H4C···Br2ⁱ	0.92	2.60	3.515 (8)	171
N4—H4D···Br2ⁱⁱⁱ	0.92	2.69	3.425 (8)	138
N4—H4D···Br1	0.92	2.94	3.433 (8)	115

Symmetry codes: (i) x+1/2, −y+3/2, −z; (ii) x−1, y, z; (iii) x+1, y, z.

Experimental details

Crystal data
Chemical formula	[CuBr₂(C₈H₂₂N₄)]
M_r	397.66
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	110
a, b, c (Å)	6.9666 (4), 8.4146 (6), 24.0261 (15)
V (Å³)	1408.45 (15)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	7.20
Crystal size (mm)	0.47 × 0.31 × 0.22

Data collection
Diffractometer	Goniometer Xcalibur, detector Ruby (Gemini Mo) diffractometer
Absorption correction	Analytical (CrysAlis PRO; Oxford Diffraction, 2007)
T_min, T_max	0.157, 0.282
No. of measured, independent and observed [I > 2σ(I)] reflections	9561, 2758, 2262
R_int	0.072
(sin θ/λ)_max (Å⁻¹)	0.763

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.071, 0.183, 1.07
No. of reflections	2758
No. of parameters	136
No. of restraints	24
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	2.51, −1.98

Computer programs: CrysAlis PRO (Oxford Diffraction, 2007), CrysAlis RED (Oxford Diffraction, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1C···Br2ⁱ	0.92	2.66	3.466 (9)	146.5
N1—H1D···Br2	0.92	2.80	3.339 (8)	118.8
N2—H2C···Br1ⁱⁱ	0.93	2.66	3.407 (8)	138.3
N2—H2C···Br2	0.93	3.01	3.519 (7)	115.9
N3—H3C···Br1	0.93	2.90	3.409 (8)	116.0
N4—H4C···Br2ⁱ	0.92	2.60	3.515 (8)	171.4
N4—H4D···Br2ⁱⁱⁱ	0.92	2.69	3.425 (8)	138.0
N4—H4D···Br1	0.92	2.94	3.433 (8)	114.9

Symmetry codes: (i) x+1/2, −y+3/2, −z; (ii) x−1, y, z; (iii) x+1, y, z.

Acknowledgements

RJB wishes to acknowledge the NSF–MRI program (grant No. CHE-0619278) for funds to purchase the diffractometer.

References

Jahn, H. & Teller, E. (1937). Proc. R. Soc. London Ser. A, pp. 220–235. CrossRef Google Scholar
Lee, T.-Y., Lee, T.-J., Hong, C.-Y., Hsieh, M.-Y., Wu, D.-T. & Chung, C.-S. (1986). Acta Cryst. C42, 1316–1319. Google Scholar
Oxford Diffraction (2007). CrysAlis PRO and CrysAlis RED. Oxford Diffraction Ltd, Abingdon, England. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar