(E)-1,2-Bis(5-chloro-6-methyl­pyridin-2-yl)diazene

The structure of the centrosymmetric title compound, C₁₂H₁₀Cl₂N₄, is stabilized by C—Cl...π and π–π inter­actions. The C—Cl...π inter­actions result in a zigzag chain. The Cl...π chains are connected by π–π inter­actions and generate Cl...π and π–π inter­acting rings. The π–π inter­action occurs between the pyridyl rings of the mol­ecules lying about inversion centres; the centroid–centroid distance is 3.7130 (14) Å and the plane–plane separation is 3.563 Å.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.053
• wR factor = 0.171
• Data-to-parameter ratio = 18.1

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT481_ALERT_4_B Long D...A H-Bond Reported C4     ..  CG1     ..       4.72 Ang.

Alert level C
PLAT063_ALERT_3_C Crystal Probably too Large for Beam Size .......       0.65 mm

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

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

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S1. Comment

Organic compounds bearing aromatic group Lewis base functionalities are well known to form adducts with halogens (Cl, Br, I). The key interaction involves charge injection from π of electrons of the Lewis base to the σ* orbital of the halogen species, producing a three-centred bond. The Cl atom is a well known steering group in crystal engineering (Sarma & Desiraju, 1986). The motivation for understanding these interactions arises from their potential importance in generating supramolecular architectures for the design of molecular solids with novel properties. Organic molecules with such characteristics provide an excellent means of exploring the roles of nonconventional intermolecular forces in crystal engineering and supramolecular chemistry. Against this background, we report here the crystal structure of (E)-1,2-bis(5-chloro-6-methylpyridin-2-yl)diazene, (I).

Fig. 1 shows the structure of the title compound, with the atom-numbering scheme. The molecules of (I) are linked to each other by C—Cl···π and π–π interactions (Fig. 2); C—Cl···π interactions [Cl···(pyridyl centroid) = 3.460 (3) Å and 127.91 (3)°] resulting in a zigzag chain. The Cl···π chains are connected by π–π interactions and generate C—Cl···π and π–π interactions rings. The π–π interaction occurs between the pyridyl rings of the molecules related by inversion centers; details have been provided in Table 1.

Related literature

For literature on the chemistry of azoaromatic compounds, see: Camalli et al. (1990); Hartmann et al. (2000); Wong et al. (2000); Frantz et al. (2003); Baldwin et al. (1969). For a recent report on the structures of some pyridyldiazene derivatives, see: Arslan et al. (2006).

For related literature, see: Rivarola et al. (1985); Sarma & Desiraju (1986).

S2. Experimental

(E)-1,2-bis(5-chloro-6-methylpyridin-2-yl)diazene was prepared according to the method of Rivarola et al. (1985). The product was crystallized from n-hexane: n-heptane mixture (1:1/v:v) to obtain well shaped crystals (yield 17%; m.p. 387–391 K).

S3. Refinement

All C-bound H atoms were refined using the riding model approximation with d(C—H) = 0.93 for aromatic and d(C—H) = 0.96 for methyl C—H [U_iso(H) = 1.2U_eq(parent atom)].

Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. A view of (I) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry code: (i) -x, -y, -z].
	Fig. 2. Part of the crystal structure of (I), showing the formation of C—Cl···π and π–π interactions rings. H atoms not involved in intermolecular interactions have been ommited for clarity. [Symmetry codes: (i) x + 1/2, y, 3/2 - z; (ii) 2 - x, 1 - y, 1 - z].

(E)-1,2-Bis(5-chloro-6-methylpyridin-2-yl)diazene

Crystal data

C12H10Cl2N4	F(000) = 576
Mr = 281.14	Dx = 1.473 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 7309 reflections
a = 7.9501 (7) Å	θ = 2.3–28.0°
b = 11.4298 (9) Å	µ = 0.50 mm^−1
c = 13.9491 (12) Å	T = 296 K
V = 1267.53 (19) Å^3	Prism, orange
Z = 4	0.65 × 0.37 × 0.18 mm

Data collection

Stoe IPDS2 diffractometer	1500 independent reflections
Radiation source: sealed X-ray tube, 12 x 0.4 mm long-fine focus	1253 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.039
Detector resolution: 6.67 pixels mm^-1	θmax = 27.9°, θmin = 2.9°
ω scans	h = −10→10
Absorption correction: integration (X-RED; Stoe & Cie, 2002)	k = −13→14
Tmin = 0.807, Tmax = 0.930	l = −15→18
7309 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)] = 0.053	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.171	H-atom parameters constrained
S = 1.09	w = 1/[σ^2(Fo^2) + (0.1012P)^2 + 0.5449P] where P = (Fo^2 + 2Fc^2)/3
1500 reflections	(Δ/σ)max < 0.001
83 parameters	Δρmax = 0.31 e Å^−3
0 restraints	Δρmin = −0.54 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
N2	0.7882 (2)	0.42313 (17)	0.60026 (15)	0.0398 (5)
C4	0.9971 (3)	0.5649 (2)	0.63185 (17)	0.0389 (5)
N1	0.5405 (2)	0.46417 (17)	0.52351 (16)	0.0417 (5)
C1	0.6977 (3)	0.5070 (2)	0.55861 (17)	0.0366 (5)
C5	0.9378 (3)	0.4508 (2)	0.63723 (18)	0.0396 (5)
C2	0.7482 (3)	0.6226 (2)	0.55239 (19)	0.0426 (5)
H2	0.6800	0.6787	0.5238	0.051*
C3	0.9029 (3)	0.6515 (2)	0.59006 (19)	0.0433 (6)
H3	0.9424	0.7280	0.5872	0.052*
C6	1.0332 (4)	0.3545 (3)	0.6847 (2)	0.0609 (8)
H6A	0.9765	0.2815	0.6741	0.091*
H6B	1.0400	0.3695	0.7523	0.091*
H6C	1.1446	0.3505	0.6583	0.091*
Cl1	1.19168 (9)	0.59937 (7)	0.67861 (6)	0.0629 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N2	0.0387 (9)	0.0335 (9)	0.0471 (11)	−0.0002 (7)	−0.0045 (8)	0.0049 (8)
C4	0.0348 (10)	0.0412 (12)	0.0407 (12)	−0.0024 (8)	0.0011 (8)	−0.0029 (9)
N1	0.0361 (9)	0.0356 (9)	0.0533 (12)	−0.0005 (7)	−0.0045 (8)	0.0044 (8)
C1	0.0340 (10)	0.0337 (11)	0.0421 (11)	0.0009 (8)	0.0002 (8)	0.0023 (9)
C5	0.0394 (11)	0.0372 (11)	0.0424 (12)	0.0036 (9)	−0.0028 (9)	0.0007 (9)
C2	0.0415 (11)	0.0325 (10)	0.0538 (13)	0.0026 (9)	−0.0040 (10)	0.0055 (10)
C3	0.0426 (11)	0.0342 (11)	0.0530 (14)	−0.0054 (9)	0.0008 (10)	0.0005 (10)
C6	0.0608 (16)	0.0467 (15)	0.075 (2)	0.0043 (12)	−0.0245 (14)	0.0109 (14)
Cl1	0.0486 (4)	0.0658 (5)	0.0744 (6)	−0.0092 (3)	−0.0149 (3)	−0.0042 (4)

Geometric parameters (Å, º)

N2—C1	1.331 (3)	C5—C6	1.492 (3)
N2—C5	1.334 (3)	C2—C3	1.378 (3)
C4—C3	1.372 (3)	C2—H2	0.9300
C4—C5	1.389 (3)	C3—H3	0.9300
C4—Cl1	1.724 (2)	C6—H6A	0.9600
N1—N1^i	1.231 (4)	C6—H6B	0.9600
N1—C1	1.429 (3)	C6—H6C	0.9600
C1—C2	1.383 (3)
C1—N2—C5	118.6 (2)	C3—C2—H2	121.2
C3—C4—C5	121.0 (2)	C1—C2—H2	121.2
C3—C4—Cl1	119.07 (19)	C4—C3—C2	118.4 (2)
C5—C4—Cl1	119.92 (19)	C4—C3—H3	120.8
N1^i—N1—C1	114.4 (2)	C2—C3—H3	120.8
N2—C1—C2	123.9 (2)	C5—C6—H6A	109.5
N2—C1—N1	112.04 (19)	C5—C6—H6B	109.5
C2—C1—N1	124.0 (2)	H6A—C6—H6B	109.5
N2—C5—C4	120.3 (2)	C5—C6—H6C	109.5
N2—C5—C6	116.8 (2)	H6A—C6—H6C	109.5
C4—C5—C6	122.9 (2)	H6B—C6—H6C	109.5
C3—C2—C1	117.7 (2)
C5—N2—C1—C2	−1.0 (4)	C3—C4—C5—C6	−178.0 (3)
C5—N2—C1—N1	−179.4 (2)	Cl1—C4—C5—C6	1.8 (4)
N1^i—N1—C1—N2	−173.5 (3)	N2—C1—C2—C3	1.3 (4)
N1^i—N1—C1—C2	8.1 (4)	N1—C1—C2—C3	179.5 (2)
C1—N2—C5—C4	−0.1 (4)	C5—C4—C3—C2	−0.7 (4)
C1—N2—C5—C6	178.9 (2)	Cl1—C4—C3—C2	179.5 (2)
C3—C4—C5—N2	1.0 (4)	C1—C2—C3—C4	−0.4 (4)
Cl1—C4—C5—N2	−179.26 (19)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—Cl1···Cg1^ii	1.72 (1)	3.46 (1)	4.720 (3)	128 (1)

Symmetry code: (ii) −x+1/2, y−3/2, z.