2,5-Di­bromo­pyridine

In the title compound, C₅H₃Br₂N, C—H⋯N hydrogen-bonding inter­actions and Br⋯Br inter­actions [3.9418 (3) and 3.8986 (3) Å] connect the mol­ecules into planar sheets stacked perpendicular to the b axis. In addition, pyrid­yl–pyridyl inter­sheet π–π stacking inter­actions [centroid–centroid distance = 4.12 (1) Å] result in a three-dimensional network.

Related literature

For hydrogen bonding, see: Desiraju (1997). For related structures, see: Al-Far & Ali (2007, 2008); Ali & Al-Far (2008); Ali et al. (2008a,b). For bond-length data, see: Allen et al. (1987). For theoretical analysis, see: Awwadi et al. (2006, 2007).

Experimental

Crystal data

• C₅H₃Br₂N

• M_r = 236.90

• Orthorhombic, P n m a

• a = 6.1063 (4) Å

• b = 6.5442 (4) Å

• c = 15.8196 (9) Å

• V = 632.17 (7) ų

• Z = 4

• Mo Kα radiation

• μ = 12.71 mm⁻¹

• T = 90 K

• 0.46 × 0.21 × 0.14 mm

Data collection

• Bruker SMART APEX diffractometer

• Absorption correction: numerical (SADABS; Bruker, 2004) T_min = 0.053, T_max = 0.170

• 8997 measured reflections

• 996 independent reflections

• 887 reflections with I > 2σ(I)

• R_int = 0.030

Refinement

• R[F² > 2σ(F²)] = 0.021

• wR(F²) = 0.054

• S = 1.05

• 996 reflections

• 49 parameters

• H-atom parameters constrained

• Δρ_max = 0.68 e Å⁻³

• Δρ_min = −0.77 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4A⋯N1^i	0.95	2.38	3.323 (3)	175
Symmetry code: (i) x+1, y, z.

Data collection: SMART (Bruker, 2006); cell refinement: SAINT-Plus (Bruker, 2006); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: XP (Bruker, 2004) and SHELXTL; software used to prepare material for publication: XCIF (Bruker, 2004) and SHELXTL.

Supporting information

S1. Comment

Non-covalent interactions play an important role in organizing structural units in both natural and artificial systems (Desiraju, 1997). The interactions governing the crystal organization are expected to affect the packing and specific properties of solids. Intermolecular interactions are the essence of supramolecular chemistry, and the field of crystal supramolecularity seeks to understand intermolecular interactions by analyses of crystal packing. We are presently interested in the synthesis and the structural aspects of halo-metal anion salts containing different organic cations (Al-Far & Ali 2007, 2008; Ali et al. 2008a, b; Ali & Al-Far 2008). The title compound, (I), arose accidentally when attempting to crystallize CdBr₄^2- with 2,5-bibromopyridinium cation. The compound had not been reported previously, thus, the structure of (I) has been characterized crystallographically and is presented here.

The bond distances and angles within the molecule of (I) (Fig. 1) are normal (Allen et al., 1987). There is a non-classical hydrogen bonding interaction of the type C—H···N in the crystal structure which links molecules into one-dimensional chains (Fig. 2) parallel to the a-axis. The strength of the hydrogen bonds is represented by relatively short D···A distance and D—H···A angle (H···A = 2.38 Å, D—H···A 175°, Table 1). The resulting chains are further connected through Br···Br interactions in a zig zag arrangement to form sheets in the ac plane (Fig. 2); the Br···Br separation being 3.9418 (3) and 3.8986 (3) Å. The sheets are stacked along the b-axis with pyridyl···pyridyl π···π stacking intermolecular inreactions with distance between the centroids of the rings being 4.12 (1) Å. It is noteworthy that structural and theoritical results (Awwadi et al., 2006; Awwadi et al., 2007), show the significance of Br···Br bonding synthons in influencing structures of crystalline materials and in use as potential building blocks in crystal engineering via supramolecular synthesis.

Related literature

For hydrogen bonding, see: Desiraju (1997). For related structures, see: Al-Far & Ali (2007, 2008); Ali & Al-Far (2008); Ali et al. (2008a,b). For bond-length data, see: Allen et al. (1987). For theoretical analysis, see: Awwadi et al. (2006, 2007).

S2. Experimental

The title compound crystallized during a reaction aiming to crystallize the anion [CuBr₄]^2- with 2,5-dibromopyridinium cation. Colorless diamond like crystals of the title compound were obtained from an ethanolic solution of the reaction which involved a sequential addition to excess 2,5-dibrormopyridine (2.25 mmole) in ethanol of CdCl₂ (1 mmole) and 60% HBr (1 ml) in ethanol.

S3. Refinement

Hydrogen atoms were positioned geometrically, with C—H = 0.95 Å, and constrained to ride on their parent atoms with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: SMART (Bruker, 2006); cell refinement: SAINT-Plus (Bruker, 2006); data reduction: SAINT-Plus (Bruker, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: XP (Bruker, 2004) and SHELXTL (Sheldrick, 2008); software used to prepare material for publication: XCIF (Bruker, 2004) and SHELXTL (Sheldrick, 2008).

Figures

	Fig. 1. A molecular drawing of (I) shown with 50% probability ellipsoids.
	Fig. 2. Packing diagram of (I) down the b-axis. Hydrogen bonding and Br···Br interactions are shown as dashed lines.

2,5-dibromopyridine

Crystal data

C5H3Br2N	F(000) = 440
Mr = 236.90	Dx = 2.489 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 5485 reflections
a = 6.1063 (4) Å	θ = 2.6–30.0°
b = 6.5442 (4) Å	µ = 12.71 mm^−1
c = 15.8196 (9) Å	T = 90 K
V = 632.17 (7) Å^3	Diamond, colourless
Z = 4	0.46 × 0.21 × 0.14 mm

Data collection

Bruker SMART APEX diffractometer	996 independent reflections
Radiation source: fine-focus sealed tube	887 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.030
Detector resolution: 8.3 pixels mm^-1	θmax = 30.0°, θmin = 3.6°
ω scans	h = −8→8
Absorption correction: numerical (SADABS; Bruker, 2004)	k = −9→9
Tmin = 0.053, Tmax = 0.170	l = −22→22
8997 measured reflections

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)] = 0.021	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.054	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0364P)^2 + 0.1337P] where P = (Fo^2 + 2Fc^2)/3
996 reflections	(Δ/σ)max < 0.001
49 parameters	Δρmax = 0.68 e Å^−3
0 restraints	Δρmin = −0.77 e Å^−3

Special details

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
Br2	0.41023 (4)	0.7500	0.171199 (12)	0.01101 (9)
N1	0.4781 (3)	0.7500	−0.00105 (12)	0.0077 (4)
Br5	0.98268 (4)	0.7500	−0.173378 (13)	0.01214 (9)
C2	0.5860 (4)	0.7500	0.07141 (12)	0.0063 (4)
C3	0.8124 (3)	0.7500	0.07962 (13)	0.0089 (4)
H3A	0.8808	0.7500	0.1336	0.011*
C4	0.9342 (4)	0.7500	0.00590 (14)	0.0088 (4)
H4A	1.0897	0.7500	0.0077	0.011*
C5	0.8236 (4)	0.7500	−0.07079 (12)	0.0074 (4)
C6	0.5958 (4)	0.7500	−0.07196 (12)	0.0083 (4)
H6A	0.5221	0.7500	−0.1248	0.010*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br2	0.01285 (15)	0.01709 (15)	0.00310 (12)	0.000	0.00345 (7)	0.000
N1	0.0081 (9)	0.0110 (9)	0.0041 (8)	0.000	0.0000 (6)	0.000
Br5	0.01335 (15)	0.01839 (15)	0.00466 (13)	0.000	0.00480 (7)	0.000
C2	0.0095 (11)	0.0078 (10)	0.0015 (8)	0.000	0.0012 (7)	0.000
C3	0.0087 (10)	0.0114 (10)	0.0066 (9)	0.000	−0.0024 (8)	0.000
C4	0.0067 (9)	0.0114 (10)	0.0084 (10)	0.000	−0.0018 (8)	0.000
C5	0.0088 (10)	0.0096 (10)	0.0040 (9)	0.000	0.0026 (7)	0.000
C6	0.0100 (11)	0.0100 (11)	0.0048 (9)	0.000	−0.0019 (7)	0.000

Geometric parameters (Å, º)

Br2—C2	1.909 (2)	C3—H3A	0.9500
N1—C2	1.322 (3)	C4—C5	1.389 (3)
N1—C6	1.332 (3)	C4—H4A	0.9500
Br5—C5	1.891 (2)	C5—C6	1.391 (3)
C2—C3	1.389 (3)	C6—H6A	0.9500
C3—C4	1.383 (3)
C2—N1—C6	117.43 (19)	C3—C4—H4A	120.8
N1—C2—C3	125.27 (19)	C5—C4—H4A	120.8
N1—C2—Br2	115.88 (16)	C4—C5—C6	119.87 (19)
C3—C2—Br2	118.85 (15)	C4—C5—Br5	119.98 (17)
C4—C3—C2	117.15 (19)	C6—C5—Br5	120.15 (16)
C4—C3—H3A	121.4	N1—C6—C5	121.91 (19)
C2—C3—H3A	121.4	N1—C6—H6A	119.0
C3—C4—C5	118.38 (19)	C5—C6—H6A	119.0
C6—N1—C2—C3	0.0	C3—C4—C5—C6	0.0
C6—N1—C2—Br2	180.0	C3—C4—C5—Br5	180.0
N1—C2—C3—C4	0.0	C2—N1—C6—C5	0.0
Br2—C2—C3—C4	180.0	C4—C5—C6—N1	0.0
C2—C3—C4—C5	0.0	Br5—C5—C6—N1	180.0

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4A···N1^i	0.95	2.38	3.323 (3)	175

Symmetry code: (i) x+1, y, z.