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Crystal structure of a tetra­kis-substituted pyrazine compound: 2,3,5,6-tetra­kis­(bromo­meth­yl)pyrazine

aCanAm Bioresearch Inc., 6-1200 Waverley Street, Winnipeg, Manitoba, R3T 6C6, Canada, and bInstitute of Physics, University of Neuchâtel, rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland
*Correspondence e-mail: helen.stoeckli-evans@unine.ch

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 22 April 2014; accepted 16 May 2014; online 19 July 2014)

The title compound, C8H8Br4N2, crystallizes in the enanti­omorphic-defining space group P41212 and has a refined Flack x parameter of 0.04 (4). In the asymmetric unit, there are two half-mol­ecules; the whole mol­ecules (A and B) are generated by twofold rotation symmetry. In mol­ecule A, the twofold axis is normal to the pyrazine ring passing through the centre of the ring, while in mol­ecule B, the twofold rotation axis lies in the plane of the pyrazine ring bis­ecting the C—C aromatic bonds. The two mol­ecules are pseudo-mirror images of one another, and the best fit of the two mol­ecules was obtained for inverted mol­ecule B on mol­ecule A, with an r.m.s. deviation of 0.1048 Å and a maximum deviation of any two equivalent atoms of 0.2246 Å. In the crystal, the A mol­ecules are linked by weak C—H⋯Br hydrogen bonds and Br⋯Br inter­actions [3.524 (3) Å], forming a three-dimensional framework. The B mol­ecules are also linked by weak C—H⋯Br hydrogen bonds and Br⋯Br inter­actions [3.548 (3) Å], forming a three-dimensional network that inter­penetrates the network of A mol­ecules.

1. Chemical context

The title compound is the starting material used for the synthesis of a number of 2,3,5,6-tetra­kis-substituted pyrazine compounds (Ferigo et al., 1994[Ferigo, M., Bonhote, P., Marty, W. & Stoeckli-Evans, H. (1994). J. Chem. Soc. Dalton Trans. pp. 1549-1554.]; Assoumatine, 1999[Assoumatine, T. (1999). PhD thesis, University of Neuchâtel, Switzerland.]). For example, 2,3,5,6-tetra­kis­(amino­meth­yl)pyrazine has been used as a ligand to prepare copper(II), zinc(II) and manganese(II) binuclear and polymeric complexes (Ferigo et al., 1994[Ferigo, M., Bonhote, P., Marty, W. & Stoeckli-Evans, H. (1994). J. Chem. Soc. Dalton Trans. pp. 1549-1554.]).

[Scheme 1]

2. Structural commentary

The title compound, Fig. 1[link], crystallizes with two half-mol­ecules per asymmetric unit. The whole mol­ecules (A and B) are generated by twofold rotation symmetry. In mol­ecule A, the twofold axis is normal to the pyrazine ring passing through the centre of the ring. In mol­ecule B, the twofold rotation axis lies in the plane of the pyrazine ring bis­ecting the C6—6ii and C7—C7ii bonds [symmetry code: (ii) y, x, −z]. Placed side by side, it can be seen that the two mol­ecules are almost perfect mirror images of each other (Fig. 1[link]). The best fit of the two mol­ecules, calculated using the Mol­ecular Overlay routine in Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]), was obtained for inverted mol­ecule B on mol­ecule A with an r.m.s. deviation of 0.1048 Å and a maximum deviation of any two equivalent atoms of 0.2246 Å.

[Figure 1]
Figure 1
A view of the mol­ecular structure of the two independent mol­ecules (A and B) of the title compound, with atom labelling [symmetry codes: (i) −y + 1, −x + 1, −z + [{1\over 2}]; (ii) y, x, −z]. The displacement ellipsoids are drawn at the 50% probability level.

The main difference appears for the torsion angles Br1—C1—C2—C3 = −92.6 (15) ° in mol­ecule A and Br4—C5—C6—C6ii = 84.8 (17) ° in mol­ecule B [Table 1[link]; symmetry code: (ii) y, x, −z]. The other torsion angles involving the Br—C—Car—Car (ar = aromatic) arms do not differ significantly (Table 2[link]).

Table 1
Selected torsion angles (°)

Br1—C1—C2—N1 91.3 (13) Br4—C5—C6—N2 −93.3 (12)
Br1—C1—C2—C3 −92.6 (15) Br4—C5—C6—C6ii 84.8 (17)
N1i—C3—C4—Br2 103.1 (11) N2—C7—C8—Br3 −101.0 (12)
C2—C3—C4—Br2 −78.6 (15) C7ii—C7—C8—Br3 77.4 (18)
Symmetry codes: (i) [-y+1, -x+1, -z+{\script{1\over 2}}]; (ii) y, x, -z.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C1—H1A⋯Br2iii 0.97 3.02 3.863 (14) 146
C1—H1B⋯Br2 0.97 2.86 3.617 (16) 135
C5—H5A⋯Br4ii 0.97 3.04 3.748 (16) 131
C5—H5B⋯Br3iv 0.97 3.03 3.864 (14) 145
C8—H8A⋯Br3ii 0.97 2.96 3.654 (15) 130
Symmetry codes: (ii) y, x, -z; (iii) [-y+{\script{3\over 2}}, x-{\script{1\over 2}}, z+{\script{1\over 4}}]; (iv) [-x+{\script{1\over 2}}, y+{\script{1\over 2}}, -z+{\script{1\over 4}}].

3. Supra­molecular features

In the crystal, there are two inter­penetrating three-dimensional networks composed of a network of A mol­ecules, linked by weak C—H⋯Br hydrogen bonds (Fig. 2[link]) and Br1⋯Br2iii inter­actions [3.524 (3) Å; symmetry code: (iii) −y + 2, −x + 1, −z + [{1\over 2}]], and a network of B mol­ecules, are also linked by weak C-H⋯Br hydrogen bonds and Br3⋯Br4iv inter­actions [3.548 (3) Å, symmetry code: (iv) x, y − 1, z] (Table 2[link] and Fig. 3[link]).

[Figure 2]
Figure 2
A view along the b axis of the crystal packing of the A mol­ecules of the title compound. The weak C—H⋯Br hydrogen bonds and Br⋯Br inter­actions are shown as dashed lines (see Table 2[link] for details).
[Figure 3]
Figure 3
A view along the b axis of the crystal packing of the title compound. The C—H⋯Br hydrogen bonds and Br⋯Br inter­actions are shown as dashed lines (see Table 2[link] for details; A mol­ecules blue, B mol­ecules red).

4. Database survey

A search of the Cambridge Structural Database (Version 5.33, last update November 2013; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]) indicated the presence of a large number of tetra­substituted pyrazine deriv­atives and their metal complexes, mainly involving tetra­methyl­pyrazine. A small number of them involve 2,3,5,6-tetra­kis­(amino­meth­yl)pyrazine (tampyz), which was used to prepare transition metal binuclear complexes, for example [Cl2Zn(tampyz)ZnCl2], and a quasi-linear one-dimensional coordination polymer, {Mn(tampyz)Cl2·2H2O}n (Ferigo et al., 1994[Ferigo, M., Bonhote, P., Marty, W. & Stoeckli-Evans, H. (1994). J. Chem. Soc. Dalton Trans. pp. 1549-1554.]). The title compound has also been used in the synthesis of two triclinic polymorphs of 2,3,5,6 tetra­kis­(naphthalen-2-ylsulfanylmeth­yl)pyrazine (Pacifico & Stoeckli-Evans, 2004[Pacifico, J. & Stoeckli-Evans, H. (2004). Acta Cryst. C60, o152-o155.]), 2,3,5,6-tetra­kis­((naphthalen-2-yl­oxy)meth­yl)pyrazine (Gasser & Stoeckli-Evans, 2007[Gasser, G. & Stoeckli-Evans, H. (2007). Private communication (refcode ADUXAZ). CCDC, Cambridge, England.]), 2,3,5,6-tetra­kis­(phen­oxy­meth­yl)pyrazine and 2,3,5,6-tetra­kis­(phenyl­sulfanylmeth­yl)pyrazine (Assoumatine et al., 2007[Assoumatine, T., Gasser, G. & Stoeckli-Evans, H. (2007). Acta Cryst. C63, o219-o222.]). All five structures possess inversion symmetry. The sulfanyl derivatives crystallize in the triclinic space group P[\overline{1}], while the oxy derivatives crystallize in the monoclinic space group P21/c.

5. Synthesis and crystallization

The title compound was prepared by a modification of the procedure described by Ferigo et al. (1994[Ferigo, M., Bonhote, P., Marty, W. & Stoeckli-Evans, H. (1994). J. Chem. Soc. Dalton Trans. pp. 1549-1554.]). To 2,3,5,6-tetra­methyl­pyrazine (28 g, 0.28 mol) in CCl4 (1 l) was added well-ground N-bromo­succinimide (150 g, 0.84 mol). The mixture was stirred vigorously and heated to reflux. As soon as the reflux set in, the mixture was irradiated for 5 h with two 200 W lamps fitted at least 10 cm at opposite sides of the flask. After the mixture was then cooled firstly to room temperature and the floating succinimide filtered off. The orange filtrate was cooled overnight to 278 K to crystallize the remaining traces of succinimide, which was filtered off. The filtrate was evaporated and the residual orange oil dissolved in 50 ml of diethyl ether. This solution was maintained at 278 K for at least one week, whereupon a white crystalline material deposited. The solid was filtered off, then recrystallized in ethanol to give colourless rod-like crystals of the title compound: Yield 7.87 g (8%); m.p. 401–405 K; RF 0.54 (toluene/light petroleum, 10/1 v/v). Analysis for C8H8Br4N2 (Mr = 451.78 g/mol); Calculated (%): C 21.27; H 1.79; N 6.20. Found (%): C 21.41; H 1.72; N 6.10. Spectroscopic data: 1H-RMN (CDCl3, 400 MHz): δ = 4.69 (s, 8H, Pz-CH2-S) p.p.m.; 13C-RMN (CDCl3, 100 MHz): δ = 150.41, 28.75 p.p.m. MS (EI, 70 eV), m/z (%): 452 ([M+], 11.9), 371 (100), 292 (13.2), 211 (20.7), 131 (32.7), 92 (20.4), 65 (18.8); IR (KBr disc, cm−1): 3030 w, 2977 w, 1438 s, 1405 s, 1220 s, 1096 m, 923 w, 787 s, 731 m, 629 m, 596 w, 543 m, 445 m.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3[link]. The C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.97 Å with Uiso(H) = 1.2Ueq(C).

Table 3
Experimental details

Crystal data
Chemical formula C8H8Br4N2
Mr 451.80
Crystal system, space group Tetragonal, P41212
Temperature (K) 293
a, c (Å) 9.6858 (4), 26.5116 (17)
V3) 2487.2 (3)
Z 8
Radiation type Mo Kα
μ (mm−1) 12.91
Crystal size (mm) 0.50 × 0.40 × 0.30
 
Data collection
Diffractometer Stoe IPDS 1
Absorption correction Multi-scan (MULscanABS in PLATON; Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.])
Tmin, Tmax 0.430, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections 19463, 2417, 1276
Rint 0.113
(sin θ/λ)max−1) 0.616
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.096, 0.84
No. of reflections 2417
No. of parameters 127
H-atom treatment H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 0.69, −0.54
Absolute structure Flack x determined using 419 quotients [(I+)−I)]/[(I+)+(I)] (Parsons & Flack, 2004[Parsons, S. & Flack, H. (2004). Acta Cryst. A60, s61.])
Absolute structure parameter 0.04 (4)
Computer programs: EXPOSE, CELL and INTEGRATE in IPDS-I (Stoe & Cie, 2004[Stoe & Cie (2004). IPDSI Bedienungshandbuch. Stoe & Cie GmbH, Darmstadt, Germany.]), SHELXS97 and SHELXL2013 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]), PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Chemical context top

The title compound is the starting material used for the synthesis of a number of 2,3,5,6-tetra­kis-substituted pyrazine compounds (Ferigo et al., 1994; Assoumatine, 1999). For example, 2,3,5,6-tetra­kis(amino­methyl)­pyrazine has been used as a ligand to prepare copper(II), zinc(II) and manganese(II) binuclear and polymeric complexes (Ferigo et al., 1994).

Structural commentary top

The title compound, Fig. 1, crystallizes with two half-molecules per asymmetric unit. The whole molecules (A and B) are generated by twofold rotation symmetry. In molecule A, the twofold axis is normal to the pyrazine ring passing through the centre of the ring. In molecule B, the twofold rotation axis lies in the plane of the pyrazine ring bis­ecting the C6—6ii and C7—C7ii bonds [symmetry code: (ii) y, x, -z]. Placed side by side it can be seen that the two molecules are almost perfect mirror images of each other (Fig. 1). The best fit of the two molecules, calculated using the Molecular Overlay routine in Mercury (Macrae et al., 2008), was obtained for inverted molecule B on molecule A with an r.m.s. deviation of 0.1048 Å and a maximum deviation of any two equivalent atoms of 0.2246 Å.

The main difference appears for the torsion angles Br1—C1—C2—C3 = -92.6 (15) ° in molecule A and Br4—C5—C6—C6ii = 84.8 (17) ° in molecule B [Table 2; symmetry code: (ii) y, x, -z]. The other torsion angles involving the Br—C—Car—Car (ar = aromatic) arms do not differ significantly (Table 2).

Supra­molecular features top

In the crystal, there are two inter­penetrating three-dimensional networks composed of a network of A molecules, linked by weak C—H···Br hydrogen bonds and Br1···Br2iii inter­actions [3.524 (3) Å; symmetry code: (iii) -y+2, -x+1, -z+1/2], and a network of B molecules, are also linked by weak C—H···Br hydrogen bonds and Br3···Br4iv inter­actions [3.548 (3) Å, symmetry code: (iv) x, y-1, z] (Table 3 and Fig. 3).

Database survey top

A search of the Cambridge Structural Database (CSD; V5.33, last update Nov. 2013; Allen, 2002) indicated the presence of a large number of tetra­substituted pyrazine derivatives and their metal complexes, mainly involving tetra­methyl­pyrazine. A small number of them involve 2,3,5,6-tetra­kis(amino­methyl)­pyrazine (tampyz), which was used to prepare transition metal binuclear complexes, for example [Cl2Zn(tampyz)ZnCl2], and a quasi-linear one-dimensional coordination polymer, {Mn(tampyz)Cl2.2H2O}n (Ferigo et al., 1994). The title compound has also been used in the synthesis of two triclinic polymorphs of 2,3,5,6 tetra­kis(naphthalen-2-ylsulfanyl­methyl)­pyrazine (Pacifico & Stoeckli-Evans, 2004), 2,3,5,6-tetra­kis((naphthalen-2-yl­oxy)methyl)­pyrazine (Gasser & Stoeckli-Evans, 2007), 2,3,5,6-tetra­kis(phen­oxy­methyl)­pyrazine and 2,3,5,6-tetra­kis(phenyl­sulfanyl­methyl)­pyrazine (Assoumatine et al., 2007). All five structures possess inversion symmetry. The sulfanyl derivatives crystallize in the triclinic space group P1 , while the oxy derivatives crystallize in the monoclinic space group P21/c.

Synthesis and crystallization top

The title compound was prepared by a modification of the procedure described by Ferigo et al. (1994). To 2,3,5,6-tetra­methyl­pyrazine (28 g, 0.28 mol) in CCl4 (1 l) was added well-ground N-bromo­succinimide (150 g, 0.84 mol). The mixture was stirred vigorously and heated to reflux. As soon as the reflux set in, the mixture was irradiated for 5 h with two 200 W lamps fitted at least 10 cm at opposite sides of the flask. After the mixture was then cooled firstly to room temperature and the floating succinimide filtered off. The orange filtrate was cooled overnight to 278 K to crystallize the remaining traces of succinimide, which was filtered off. The filtrate was evaporated and the residual orange oil dissolved in 50 ml of di­ethyl ether. This solution was maintained at 278 K for at least one week, whereupon a white crystalline material deposited. The solid was filtered off, then recrystallized in ethanol to give colourless rod-like crystals of the title compound: Yield 7.87 g (8%); M.p. 401–405 K; Rf 0.54 (toluene/light petroleum, 10/1 v/v). Analysis for C8H8Br4N2 (Mr = 451.78 g/mol); Calculated (%): C 21.27; H 1.79; N 6.20. Found (%): C 21.41; H 1.72; N 6.10. Spectroscopic data: 1H-RMN (CDCl3, 400 MHz): δ = 4.69 (s, 8H, Pz—CH2—S) p.p.m.; 13C-RMN (CDCl3, 100 MHz): δ = 150.41, 28.75 p.p.m. MS (EI, 70 eV), m/z (%): 452 ([M+], 11.9), 371 (100), 292 (13.2), 211 (20.7), 131 (32.7), 92 (20.4), 65 (18.8); IR (KBr disc, cm-1): 3030 w, 2977 w, 1438 s, 1405 s, 1220 s, 1096 m, 923 w, 787 s, 731 m, 629 m, 596 w, 543 m, 445 m.

Refinement top

Crystal data, data collection and structure refinement details are summarized in Table 1. The C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.97 Å with Uiso(H) = 1.2Ueq(C).

Related literature top

(type here to add)

For related literature, see: Allen (2002); Assoumatine (1999); Assoumatine et al. (2007); Ferigo et al. (1994); Gasser & Stoeckli-Evans (2007); Macrae et al. (2008); Pacifico & Stoeckli-Evans (2004).

Computing details top

Data collection: EXPOSE in IPDS-I (Stoe & Cie, 2004); cell refinement: CELL in IPDS-I (Stoe & Cie, 2004); data reduction: INTEGRATE in IPDS-I (Stoe & Cie, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2013 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2013 (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. A view of the molecular structure of the two independent molecules (A and B) of the title compound, with atom labelling [symmetry codes: (i) -y + 1, -x + 1, -z + 1/2; (ii) y, x, -z]. The displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. A view along the b axis of the crystal packing of the A molecules of the title compound. The weak C—H···Br hydrogen bonds and Br···Br interactions are shown as dashed lines (see Table 3 for details).
[Figure 3] Fig. 3. A view along the b axis of the crystal packing of the title compound. The C—H···Br hydrogen bonds and Br···Br interactions are shown as dashed lines (see Table 3 for details; A molecules blue, B molecules red).
2,3,5,6-Tetrakis(bromomethyl)pyrazine top
Crystal data top
C8H8Br4N2Dx = 2.413 Mg m3
Mr = 451.80Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P41212Cell parameters from 5000 reflections
Hall symbol: P 4abw 2nwθ = 2.2–26.0°
a = 9.6858 (4) ŵ = 12.91 mm1
c = 26.5116 (17) ÅT = 293 K
V = 2487.2 (3) Å3Rod, colourless
Z = 80.50 × 0.40 × 0.30 mm
F(000) = 1680
Data collection top
Stoe IPDS 1
diffractometer
2417 independent reflections
Radiation source: fine-focus sealed tube1276 reflections with I > 2σ(I)
Plane graphite monochromatorRint = 0.113
ϕ rotation scansθmax = 26.0°, θmin = 2.2°
Absorption correction: multi-scan
(MULscanABS in PLATON; Spek, 2009)
h = 1111
Tmin = 0.430, Tmax = 1.000k = 1111
19463 measured reflectionsl = 3232
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.043H-atom parameters constrained
wR(F2) = 0.096 w = 1/[σ2(Fo2) + (0.0401P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.84(Δ/σ)max < 0.001
2417 reflectionsΔρmax = 0.69 e Å3
127 parametersΔρmin = 0.54 e Å3
0 restraintsAbsolute structure: Flack x determined using 419 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004)
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.04 (4)
Crystal data top
C8H8Br4N2Z = 8
Mr = 451.80Mo Kα radiation
Tetragonal, P41212µ = 12.91 mm1
a = 9.6858 (4) ÅT = 293 K
c = 26.5116 (17) Å0.50 × 0.40 × 0.30 mm
V = 2487.2 (3) Å3
Data collection top
Stoe IPDS 1
diffractometer
2417 independent reflections
Absorption correction: multi-scan
(MULscanABS in PLATON; Spek, 2009)
1276 reflections with I > 2σ(I)
Tmin = 0.430, Tmax = 1.000Rint = 0.113
19463 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.043H-atom parameters constrained
wR(F2) = 0.096Δρmax = 0.69 e Å3
S = 0.84Δρmin = 0.54 e Å3
2417 reflectionsAbsolute structure: Flack x determined using 419 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004)
127 parametersAbsolute structure parameter: 0.04 (4)
0 restraints
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br11.2259 (2)0.2336 (2)0.31902 (9)0.0928 (7)
Br20.97546 (18)0.47643 (17)0.18421 (6)0.0654 (5)
N10.8843 (11)0.1271 (10)0.3022 (5)0.043 (3)
C11.0492 (15)0.3062 (16)0.3026 (6)0.058 (4)
H1A1.00160.33130.33350.069*
H1B1.06080.38930.28270.069*
C20.9639 (14)0.2070 (12)0.2742 (5)0.045 (3)
C30.9590 (13)0.2017 (12)0.2214 (4)0.038 (3)
C41.0501 (16)0.2865 (14)0.1876 (5)0.053 (4)
H4A1.05250.24630.15410.063*
H4B1.14350.28830.20080.063*
Br30.02090 (19)0.23131 (16)0.06101 (6)0.0663 (5)
Br40.2379 (2)0.4746 (2)0.07000 (7)0.0854 (6)
N20.1293 (10)0.1274 (11)0.0529 (5)0.042 (4)
C50.3130 (15)0.2938 (15)0.0568 (6)0.060 (4)
H5A0.39950.30300.03870.072*
H5B0.33170.24760.08850.072*
C60.2145 (13)0.2082 (13)0.0262 (4)0.041 (3)
C70.0442 (13)0.0470 (13)0.0261 (4)0.039 (3)
C80.0509 (16)0.0420 (17)0.0578 (5)0.056 (4)
H8A0.14260.04250.04320.068*
H8B0.05750.00410.09160.068*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.0587 (12)0.0884 (15)0.1313 (15)0.0040 (9)0.0371 (11)0.0122 (14)
Br20.0729 (11)0.0512 (9)0.0719 (10)0.0017 (7)0.0043 (10)0.0119 (9)
N10.046 (9)0.046 (9)0.037 (7)0.002 (5)0.002 (5)0.002 (5)
C10.056 (9)0.059 (9)0.058 (9)0.009 (8)0.009 (8)0.011 (8)
C20.051 (8)0.035 (7)0.050 (7)0.004 (6)0.003 (7)0.008 (6)
C30.034 (7)0.037 (7)0.043 (7)0.003 (6)0.001 (6)0.003 (6)
C40.053 (9)0.047 (8)0.059 (8)0.004 (6)0.007 (8)0.002 (7)
Br30.0813 (12)0.0468 (9)0.0710 (9)0.0060 (8)0.0011 (10)0.0101 (8)
Br40.0862 (13)0.0616 (11)0.1086 (15)0.0065 (9)0.0033 (12)0.0330 (11)
N20.046 (9)0.050 (9)0.030 (6)0.006 (5)0.007 (5)0.003 (5)
C50.053 (9)0.073 (10)0.054 (9)0.009 (8)0.015 (8)0.006 (8)
C60.047 (8)0.043 (7)0.033 (6)0.007 (6)0.002 (6)0.002 (6)
C70.036 (7)0.040 (7)0.042 (6)0.003 (6)0.000 (6)0.005 (6)
C80.060 (9)0.062 (9)0.047 (7)0.001 (8)0.000 (8)0.007 (8)
Geometric parameters (Å, º) top
Br1—C11.901 (15)Br3—C81.963 (17)
Br2—C41.978 (14)Br4—C51.928 (15)
N1—C21.319 (17)N2—C71.337 (15)
N1—C3i1.334 (15)N2—C61.339 (16)
C1—C21.474 (18)C5—C61.502 (17)
C1—H1A0.9700C5—H5A0.9700
C1—H1B0.9700C5—H5B0.9700
C2—C31.402 (15)C6—C6ii1.39 (2)
C3—N1i1.334 (15)C7—C7ii1.39 (2)
C3—C41.504 (17)C7—C81.516 (17)
C4—H4A0.9700C8—H8A0.9700
C4—H4B0.9700C8—H8B0.9700
C2—N1—C3i117.9 (13)C7—N2—C6116.1 (12)
C2—C1—Br1112.4 (10)C6—C5—Br4111.1 (9)
C2—C1—H1A109.1C6—C5—H5A109.4
Br1—C1—H1A109.1Br4—C5—H5A109.4
C2—C1—H1B109.1C6—C5—H5B109.4
Br1—C1—H1B109.1Br4—C5—H5B109.4
H1A—C1—H1B107.9H5A—C5—H5B108.0
N1—C2—C3121.3 (11)N2—C6—C6ii121.7 (7)
N1—C2—C1115.0 (12)N2—C6—C5115.4 (11)
C3—C2—C1123.6 (12)C6ii—C6—C5122.9 (8)
N1i—C3—C2120.8 (11)N2—C7—C7ii121.9 (7)
N1i—C3—C4115.3 (12)N2—C7—C8114.3 (11)
C2—C3—C4123.8 (11)C7ii—C7—C8123.7 (7)
C3—C4—Br2108.7 (9)C7—C8—Br3109.9 (10)
C3—C4—H4A109.9C7—C8—H8A109.7
Br2—C4—H4A109.9Br3—C8—H8A109.7
C3—C4—H4B109.9C7—C8—H8B109.7
Br2—C4—H4B109.9Br3—C8—H8B109.7
H4A—C4—H4B108.3H8A—C8—H8B108.2
C3i—N1—C2—C30.2 (16)C2—C3—C4—Br278.6 (15)
C3i—N1—C2—C1175.9 (12)C7—N2—C6—C6ii4 (2)
Br1—C1—C2—N191.3 (13)C7—N2—C6—C5177.8 (12)
Br1—C1—C2—C392.6 (15)Br4—C5—C6—N293.3 (12)
N1—C2—C3—N1i0.3 (19)Br4—C5—C6—C6ii84.8 (17)
C1—C2—C3—N1i175.5 (12)C6—N2—C7—C7ii2 (2)
N1—C2—C3—C4177.9 (12)C6—N2—C7—C8179.7 (12)
C1—C2—C3—C46 (2)N2—C7—C8—Br3101.0 (12)
N1i—C3—C4—Br2103.1 (11)C7ii—C7—C8—Br377.4 (18)
Symmetry codes: (i) y+1, x+1, z+1/2; (ii) y, x, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1A···Br2iii0.973.023.863 (14)146
C1—H1B···Br20.972.863.617 (16)135
C5—H5A···Br4ii0.973.043.748 (16)131
C5—H5B···Br3iv0.973.033.864 (14)145
C8—H8A···Br3ii0.972.963.654 (15)130
Symmetry codes: (ii) y, x, z; (iii) y+3/2, x1/2, z+1/4; (iv) x+1/2, y+1/2, z+1/4.

Experimental details

Crystal data
Chemical formulaC8H8Br4N2
Mr451.80
Crystal system, space groupTetragonal, P41212
Temperature (K)293
a, c (Å)9.6858 (4), 26.5116 (17)
V3)2487.2 (3)
Z8
Radiation typeMo Kα
µ (mm1)12.91
Crystal size (mm)0.50 × 0.40 × 0.30
Data collection
DiffractometerStoe IPDS 1
diffractometer
Absorption correctionMulti-scan
(MULscanABS in PLATON; Spek, 2009)
Tmin, Tmax0.430, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
19463, 2417, 1276
Rint0.113
(sin θ/λ)max1)0.616
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.096, 0.84
No. of reflections2417
No. of parameters127
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.69, 0.54
Absolute structureFlack x determined using 419 quotients [(I+)-(I-)]/[(I+)+(I-)] (Parsons & Flack, 2004)
Absolute structure parameter0.04 (4)

Computer programs: EXPOSE in IPDS-I (Stoe & Cie, 2004), CELL in IPDS-I (Stoe & Cie, 2004), INTEGRATE in IPDS-I (Stoe & Cie, 2004), SHELXS97 (Sheldrick, 2008), Mercury (Macrae et al., 2008), SHELXL2013 (Sheldrick, 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Selected torsion angles (º) top
Br1—C1—C2—N191.3 (13)Br4—C5—C6—N293.3 (12)
Br1—C1—C2—C392.6 (15)Br4—C5—C6—C6ii84.8 (17)
N1i—C3—C4—Br2103.1 (11)N2—C7—C8—Br3101.0 (12)
C2—C3—C4—Br278.6 (15)C7ii—C7—C8—Br377.4 (18)
Symmetry codes: (i) y+1, x+1, z+1/2; (ii) y, x, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1A···Br2iii0.973.023.863 (14)146
C1—H1B···Br20.972.863.617 (16)135
C5—H5A···Br4ii0.973.043.748 (16)131
C5—H5B···Br3iv0.973.033.864 (14)145
C8—H8A···Br3ii0.972.963.654 (15)130
Symmetry codes: (ii) y, x, z; (iii) y+3/2, x1/2, z+1/4; (iv) x+1/2, y+1/2, z+1/4.
 

Footnotes

This work forms part of the PhD thesis (Neuchâtel, 1999) of TA.

Acknowledgements

This work was supported by the Swiss National Science Foundation and the University of Neuchâtel.

References

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