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

Assoumatine, T.; Stoeckli-Evans, H.

doi:10.1107/S1600536814011337

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Volume 70| Part 8| August 2014| Pages 51-53

doi:10.1107/S1600536814011337

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

Tokouré Assoumatine ^a and Helen Stoeckli-Evans ^b ^*

^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.

Keywords: crystal structure; tetrakis-substituted; pyrazine; chiral.

CCDC reference: 1004263

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 ; 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).

2. Structural commentary

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.

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; symmetry code: (ii) y, x, −z]. The other torsion angles involving the Br—C—C_ar—C_ar (ar = aromatic) arms do not differ significantly (Table 2).

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	D⋯A	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⋯Br3^iv	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) 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⋯Br4^iv interactions [3.548 (3) Å, symmetry code: (iv) x, y − 1, z] (Table 2 and Fig. 3).

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

for details).

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

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 ) 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 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). 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; R_F 0.54 (toluene/light petroleum, 10/1 v/v). Analysis for C₈H₈Br₄N₂ (M_r = 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. The C-bound H atoms were included in calculated positions and treated as riding atoms: C—H = 0.97 Å with U_iso(H) = 1.2U_eq(C).

Table 3
Experimental details

Crystal data
Chemical formula	C₈H₈Br₄N₂
M_r	451.80
Crystal system, space group	Tetragonal, P4₁2₁2
Temperature (K)	293
a, c (Å)	9.6858 (4), 26.5116 (17)
V (Å³)	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 )
T_min, T_max	0.430, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	19463, 2417, 1276
R_int	0.113
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	0.69, −0.54
Absolute structure	Flack x determined using 419 quotients [(I⁺)−I⁻)]/[(I⁺)+(I⁻)] (Parsons & Flack, 2004 )
Absolute structure parameter	0.04 (4)
Computer programs: EXPOSE, CELL and INTEGRATE in IPDS-I (Stoe & Cie, 2004 ), SHELXS97 and SHELXL2013 (Sheldrick, 2008 ), Mercury (Macrae et al., 2008), PLATON (Spek, 2009) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1004263

Crystal structure: contains datablock I. DOI: 10.1107/S1600536814011337/hb0005sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536814011337/hb0005Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536814011337/hb0005Isup3.cml

checkCIF report

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—C_ar—C_ar (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···Br4^iv 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 (M_r = 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 U_iso(H) = 1.2U_eq(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

	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.
	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).
	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

C₈H₈Br₄N₂	D_x = 2.413 Mg m⁻³
M_r = 451.80	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P4₁2₁2	Cell parameters from 5000 reflections
Hall symbol: P 4abw 2nw	θ = 2.2–26.0°
a = 9.6858 (4) Å	µ = 12.91 mm⁻¹
c = 26.5116 (17) Å	T = 293 K
V = 2487.2 (3) Å³	Rod, colourless
Z = 8	0.50 × 0.40 × 0.30 mm
F(000) = 1680

Data collection top

Stoe IPDS 1 diffractometer	2417 independent reflections
Radiation source: fine-focus sealed tube	1276 reflections with I > 2σ(I)
Plane graphite monochromator	R_int = 0.113
ϕ rotation scans	θ_max = 26.0°, θ_min = 2.2°
Absorption correction: multi-scan (MULscanABS in PLATON; Spek, 2009)	h = −11→11
T_min = 0.430, T_max = 1.000	k = −11→11
19463 measured reflections	l = −32→32

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.043	H-atom parameters constrained
wR(F²) = 0.096	w = 1/[σ²(F_o²) + (0.0401P)²] where P = (F_o² + 2F_c²)/3
S = 0.84	(Δ/σ)_max < 0.001
2417 reflections	Δρ_max = 0.69 e Å⁻³
127 parameters	Δρ_min = −0.54 e Å⁻³
0 restraints	Absolute structure: Flack x determined using 419 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons & Flack, 2004)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.04 (4)

Crystal data top

C₈H₈Br₄N₂	Z = 8
M_r = 451.80	Mo Kα radiation
Tetragonal, P4₁2₁2	µ = 12.91 mm⁻¹
a = 9.6858 (4) Å	T = 293 K
c = 26.5116 (17) Å	0.50 × 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)
T_min = 0.430, T_max = 1.000	R_int = 0.113
19463 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.043	H-atom parameters constrained
wR(F²) = 0.096	Δρ_max = 0.69 e Å⁻³
S = 0.84	Δρ_min = −0.54 e Å⁻³
2417 reflections	Absolute structure: Flack x determined using 419 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons & Flack, 2004)
127 parameters	Absolute 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

	x	y	z	U_iso*/U_eq
Br1	1.2259 (2)	0.2336 (2)	0.31902 (9)	0.0928 (7)
Br2	0.97546 (18)	0.47643 (17)	0.18421 (6)	0.0654 (5)
N1	0.8843 (11)	0.1271 (10)	0.3022 (5)	0.043 (3)
C1	1.0492 (15)	0.3062 (16)	0.3026 (6)	0.058 (4)
H1A	1.0016	0.3313	0.3335	0.069*
H1B	1.0608	0.3893	0.2827	0.069*
C2	0.9639 (14)	0.2070 (12)	0.2742 (5)	0.045 (3)
C3	0.9590 (13)	0.2017 (12)	0.2214 (4)	0.038 (3)
C4	1.0501 (16)	0.2865 (14)	0.1876 (5)	0.053 (4)
H4A	1.0525	0.2463	0.1541	0.063*
H4B	1.1435	0.2883	0.2008	0.063*
Br3	0.02090 (19)	−0.23131 (16)	0.06101 (6)	0.0663 (5)
Br4	0.2379 (2)	0.4746 (2)	0.07000 (7)	0.0854 (6)
N2	0.1293 (10)	0.1274 (11)	0.0529 (5)	0.042 (4)
C5	0.3130 (15)	0.2938 (15)	0.0568 (6)	0.060 (4)
H5A	0.3995	0.3030	0.0387	0.072*
H5B	0.3317	0.2476	0.0885	0.072*
C6	0.2145 (13)	0.2082 (13)	0.0262 (4)	0.041 (3)
C7	0.0442 (13)	0.0470 (13)	0.0261 (4)	0.039 (3)
C8	−0.0509 (16)	−0.0420 (17)	0.0578 (5)	0.056 (4)
H8A	−0.1426	−0.0425	0.0432	0.068*
H8B	−0.0575	−0.0041	0.0916	0.068*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0587 (12)	0.0884 (15)	0.1313 (15)	0.0040 (9)	−0.0371 (11)	−0.0122 (14)
Br2	0.0729 (11)	0.0512 (9)	0.0719 (10)	0.0017 (7)	0.0043 (10)	0.0119 (9)
N1	0.046 (9)	0.046 (9)	0.037 (7)	0.002 (5)	−0.002 (5)	0.002 (5)
C1	0.056 (9)	0.059 (9)	0.058 (9)	−0.009 (8)	−0.009 (8)	−0.011 (8)
C2	0.051 (8)	0.035 (7)	0.050 (7)	0.004 (6)	−0.003 (7)	−0.008 (6)
C3	0.034 (7)	0.037 (7)	0.043 (7)	0.003 (6)	0.001 (6)	−0.003 (6)
C4	0.053 (9)	0.047 (8)	0.059 (8)	0.004 (6)	0.007 (8)	0.002 (7)
Br3	0.0813 (12)	0.0468 (9)	0.0710 (9)	−0.0060 (8)	−0.0011 (10)	0.0101 (8)
Br4	0.0862 (13)	0.0616 (11)	0.1086 (15)	−0.0065 (9)	0.0033 (12)	−0.0330 (11)
N2	0.046 (9)	0.050 (9)	0.030 (6)	−0.006 (5)	−0.007 (5)	0.003 (5)
C5	0.053 (9)	0.073 (10)	0.054 (9)	−0.009 (8)	−0.015 (8)	−0.006 (8)
C6	0.047 (8)	0.043 (7)	0.033 (6)	0.007 (6)	−0.002 (6)	−0.002 (6)
C7	0.036 (7)	0.040 (7)	0.042 (6)	−0.003 (6)	0.000 (6)	0.005 (6)
C8	0.060 (9)	0.062 (9)	0.047 (7)	0.001 (8)	0.000 (8)	0.007 (8)

Geometric parameters (Å, º) top

Br1—C1	1.901 (15)	Br3—C8	1.963 (17)
Br2—C4	1.978 (14)	Br4—C5	1.928 (15)
N1—C2	1.319 (17)	N2—C7	1.337 (15)
N1—C3ⁱ	1.334 (15)	N2—C6	1.339 (16)
C1—C2	1.474 (18)	C5—C6	1.502 (17)
C1—H1A	0.9700	C5—H5A	0.9700
C1—H1B	0.9700	C5—H5B	0.9700
C2—C3	1.402 (15)	C6—C6ⁱⁱ	1.39 (2)
C3—N1ⁱ	1.334 (15)	C7—C7ⁱⁱ	1.39 (2)
C3—C4	1.504 (17)	C7—C8	1.516 (17)
C4—H4A	0.9700	C8—H8A	0.9700
C4—H4B	0.9700	C8—H8B	0.9700

C2—N1—C3ⁱ	117.9 (13)	C7—N2—C6	116.1 (12)
C2—C1—Br1	112.4 (10)	C6—C5—Br4	111.1 (9)
C2—C1—H1A	109.1	C6—C5—H5A	109.4
Br1—C1—H1A	109.1	Br4—C5—H5A	109.4
C2—C1—H1B	109.1	C6—C5—H5B	109.4
Br1—C1—H1B	109.1	Br4—C5—H5B	109.4
H1A—C1—H1B	107.9	H5A—C5—H5B	108.0
N1—C2—C3	121.3 (11)	N2—C6—C6ⁱⁱ	121.7 (7)
N1—C2—C1	115.0 (12)	N2—C6—C5	115.4 (11)
C3—C2—C1	123.6 (12)	C6ⁱⁱ—C6—C5	122.9 (8)
N1ⁱ—C3—C2	120.8 (11)	N2—C7—C7ⁱⁱ	121.9 (7)
N1ⁱ—C3—C4	115.3 (12)	N2—C7—C8	114.3 (11)
C2—C3—C4	123.8 (11)	C7ⁱⁱ—C7—C8	123.7 (7)
C3—C4—Br2	108.7 (9)	C7—C8—Br3	109.9 (10)
C3—C4—H4A	109.9	C7—C8—H8A	109.7
Br2—C4—H4A	109.9	Br3—C8—H8A	109.7
C3—C4—H4B	109.9	C7—C8—H8B	109.7
Br2—C4—H4B	109.9	Br3—C8—H8B	109.7
H4A—C4—H4B	108.3	H8A—C8—H8B	108.2

C3ⁱ—N1—C2—C3	−0.2 (16)	C2—C3—C4—Br2	−78.6 (15)
C3ⁱ—N1—C2—C1	175.9 (12)	C7—N2—C6—C6ⁱⁱ	4 (2)
Br1—C1—C2—N1	91.3 (13)	C7—N2—C6—C5	−177.8 (12)
Br1—C1—C2—C3	−92.6 (15)	Br4—C5—C6—N2	−93.3 (12)
N1—C2—C3—N1ⁱ	0.3 (19)	Br4—C5—C6—C6ⁱⁱ	84.8 (17)
C1—C2—C3—N1ⁱ	−175.5 (12)	C6—N2—C7—C7ⁱⁱ	2 (2)
N1—C2—C3—C4	−177.9 (12)	C6—N2—C7—C8	−179.7 (12)
C1—C2—C3—C4	6 (2)	N2—C7—C8—Br3	−101.0 (12)
N1ⁱ—C3—C4—Br2	103.1 (11)	C7ⁱⁱ—C7—C8—Br3	77.4 (18)

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	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···Br3^iv	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+3/2, x−1/2, z+1/4; (iv) −x+1/2, y+1/2, −z+1/4.

Experimental details

Crystal data
Chemical formula	C₈H₈Br₄N₂
M_r	451.80
Crystal system, space group	Tetragonal, P4₁2₁2
Temperature (K)	293
a, c (Å)	9.6858 (4), 26.5116 (17)
V (Å³)	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 diffractometer
Absorption correction	Multi-scan (MULscanABS in PLATON; Spek, 2009)
T_min, T_max	0.430, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	19463, 2417, 1276
R_int	0.113
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	0.69, −0.54
Absolute structure	Flack x determined using 419 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons & Flack, 2004)
Absolute structure parameter	0.04 (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—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+1/2; (ii) y, x, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	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···Br3^iv	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+3/2, x−1/2, 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

Allen, F. H. (2002). Acta Cryst. B58, 380–388. Web of Science CrossRef CAS IUCr Journals Google Scholar
Assoumatine, T. (1999). PhD thesis, University of Neuchâtel, Switzerland. Google Scholar
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Gasser, G. & Stoeckli-Evans, H. (2007). Private communication (refcode ADUXAZ). CCDC, Cambridge, England. Google Scholar
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. Web of Science CrossRef CAS IUCr Journals Google Scholar
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Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
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Volume 70| Part 8| August 2014| Pages 51-53

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Database survey

5. Synthesis and crystallization

6. Refinement

Supporting information

Footnotes

Acknowledgements

References

research communications

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

3. Supramolecular features