Redetermination of (E)-N,N′-bis­(4-bromo­phen­yl)formamidine

Han, L.-J.

doi:10.1107/S1600536811013419

organic compounds

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Volume 67| Part 5| May 2011| Page o1159

doi:10.1107/S1600536811013419

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Redetermination of (E)-N,N′-bis(4-bromophenyl)formamidine

L.-J. Han ^a ^*

^aDepartment of Chemistry, Tongji University, Shanghai 200092, People's Republic of China
^*Correspondence e-mail: 08hanlij@tongji.edu.cn

(Received 1 April 2011; accepted 10 April 2011; online 16 April 2011)

In comprison with the previous structural study [Anulewicz et al. (1991 ). Pol. J. Chem. 65, 465–471], for which only the coordinates of all non-H atoms and of some H atoms were reported, the current redetermination of the title compound, C₁₃H₁₀Br₂N₂, additionally reports anisotropic displacement parameters for all non-H atoms and the coordinates of all H atoms, accompanied by higher accuracy of the geometric parameters. Two independent half-molecules are present in the asymmetric unit, which are completed by a twofold rotation axis as symmetry element. In the crystal, intermolecular N—H⋯N hydrogen bonds link the molecules into dimers. Linear chains parallel to [102] are formed by intermolecular Br⋯Br interactions of 3.4328 (7) Å between two Br atoms of adjacent molecules. The dihedral angles between the benzene rings are 50.05 (15) and 75.61 (11)° in the two independent molecules. Owing to the twofold symmetry of the molecules, H atoms attached to the N atoms are only half-occupied, leading to them being disordered over two positions of equal occupancy.

Related literature

For the previous structure determination, see: Anulewicz et al. (1991). For Br⋯Br interactions, see: Fujiwara et al. (2006 ); Reddy et al. (1996 ). For N—H⋯N hydrogen bonds, see: Del Bene & Elguero (2006 ); Grotjahn et al. (2000 ); Thar & Kirchner (2006 ).

Experimental

Crystal data

C₁₃H₁₀Br₂N₂
M_r = 354.05
Monoclinic, C 2/c
a = 11.563 (2) Å
b = 23.447 (5) Å
c = 9.881 (2) Å
β = 95.43 (3)°
V = 2666.9 (9) Å³
Z = 8
Mo Kα radiation
μ = 6.06 mm⁻¹
T = 293 K
0.15 × 0.07 × 0.06 mm

Data collection

Bruker SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ) T_min = 0.403, T_max = 0.695
5954 measured reflections
2611 independent reflections
1715 reflections with I > 2σ(I)
R_int = 0.061

Refinement

R[F² > 2σ(F²)] = 0.048
wR(F²) = 0.114
S = 1.00
2611 reflections
155 parameters
H-atom parameters constrained
Δρ_max = 0.48 e Å⁻³
Δρ_min = −0.91 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H2A⋯N2ⁱ	0.85	2.12	2.964 (4)	180
N2—H3A⋯N1ⁱⁱ	0.88	2.12	2.964 (4)	161
Symmetry codes: (i) $[x, -y+1, z-{\script{1\over 2}}]$ ; (ii) $[x, -y+1, z+{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker, 2004 ); cell refinement: SAINT-Plus (Bruker, 2001 ); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Sheldrick, 2008) and DIAMOND (Brandenburg, 1999 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811013419/wm2476sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811013419/wm2476Isup2.hkl

checkCIF report

Comment top

With the determination of reliable intermolecular distances, Br···Br interactions (Fujiwara et al., 2006; Reddy et al., 1996) and N–H···N hydrogen bonding (Del Bene & Elguero, 2006; Grotjahn et al. 2000; Thar & Kirchner, 2006) became important criteria in the description of supramolecular chemistry and in applied crystal engineering. The title compound C₁₃H₁₀Br₂N₂, (I), has been determined previously by Anulewicz et al. (1991). However, in that study only coordinates of all non-H atoms and of some H atoms were given. The present re-determination additionally reports anisotropic displacement parameters for all non-H atoms and the coordinates of all H atoms, accompanied by higher accuracy of all geometric parameters.

In (I) two independent half-molecules are present in the asymmetric unit which are completed by a twofold rotation axis as symmetry element that runs to the central C—H groups (C1—H1 and C2—H2, respectively). One molecule is displayed in Fig. 1. The dihedral angles between the two benzene rings in the individual molecules are 50.05 (15) ° for the first and and 75.61 (11) ° for the second molecule.

In the crystal, intermolecular N—H···N hydrogen bonds link the individual molecules into dimers (Fig. 2). Linear chains parallel to [102] are formed by intermolecular Br···Br interactions of 3.4328 (7) Å between two bromine atoms of adjacent molecules (Fig. 3). This interaction is significantly less than the van der Waals contact of 3.90 Å (Reddy et al., 1996; Fujiwara et al., 2006), hence making this interaction important for consolidation of the crystal packing.

Related literature top

For the previous structure determination, see: Anulewicz et al. (1991). For Br···Br interactions, see: Fujiwara et al. (2006); Reddy et al. (1996). For N—H···N hydrogen bonds, see: Del Bene & Elguero (2006); Grotjahn et al. (2000); Thar & Kirchner (2006).

Experimental top

The title compound was synthesized by the following reaction. 17.202 g (0.1 mol) of 4-bromobenzenamine and 8.33 ml (0.05 mol) of triethyl orthoformate were combined in a round-bottom flask equipped with a distillation tube and heated at 160 until the distillation of ethanol creased. The retained solid was washed with ether, and dried under a dynamic vacuum to yield 16.10 g of white solid, (91%). 0.04 g of the white solid was dissolved in THF (3 ml) and the solution was layered with hexane. Colourless needle-shaped crystals formed after several days. ¹HNMR(CDCl₃, p.p.m.): 8.08(s, 1H, –NCHN–), 7.43(d, 2H, aromatic), 7.40(d, 2H, aromatic), 6.93(d, 2H, aromatic), 6.91(d, 2H, aromatic). Anal. Calcd. C₁₃H₁₀Br₂N₂: C, 44.10; H, 2.85; N, 7.91; Found: C, 43.83; H, 2.69; N, 8.02.

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: XP (Sheldrick, 2008) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. Molecular structure of one of the two molecules of (I) drawn with displacement ellipsoids at the 30% probability level. [Symmetry code A) -x+1, y. -z+1/2.]
	Fig. 2. A dimer formed by intermolecular N–H···N hydrogen bonds.
	Fig. 3. Part of an one-dimensional linear chain of the title compound, viewed along [010]. Br···Br interactions are drawn with blue dashed lines.

(E)-N,N'-bis(4-bromophenyl)formamidine top

Crystal data top

C₁₃H₁₀Br₂N₂	F(000) = 1376
M_r = 354.05	D_x = 1.764 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 4303 reflections
a = 11.563 (2) Å	θ = 2.5–26.7°
b = 23.447 (5) Å	µ = 6.06 mm⁻¹
c = 9.881 (2) Å	T = 293 K
β = 95.43 (3)°	Needle, colourless
V = 2666.9 (9) Å³	0.15 × 0.07 × 0.06 mm
Z = 8

Data collection top

Bruker SMART CCD diffractometer	2611 independent reflections
Radiation source: fine-focus sealed tube	1715 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.061
ω scans	θ_max = 26.0°, θ_min = 1.7°
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	h = −12→14
T_min = 0.403, T_max = 0.695	k = −26→28
5954 measured reflections	l = −12→11

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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.114	H-atom parameters constrained
S = 1.00	w = 1/[σ²(F_o²) + (0.0533P)²] where P = (F_o² + 2F_c²)/3
2611 reflections	(Δ/σ)_max = 0.001
155 parameters	Δρ_max = 0.48 e Å⁻³
0 restraints	Δρ_min = −0.91 e Å⁻³

Crystal data top

C₁₃H₁₀Br₂N₂	V = 2666.9 (9) Å³
M_r = 354.05	Z = 8
Monoclinic, C2/c	Mo Kα radiation
a = 11.563 (2) Å	µ = 6.06 mm⁻¹
b = 23.447 (5) Å	T = 293 K
c = 9.881 (2) Å	0.15 × 0.07 × 0.06 mm
β = 95.43 (3)°

Data collection top

Bruker SMART CCD diffractometer	2611 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2004)	1715 reflections with I > 2σ(I)
T_min = 0.403, T_max = 0.695	R_int = 0.061
5954 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.048	0 restraints
wR(F²) = 0.114	H-atom parameters constrained
S = 1.00	Δρ_max = 0.48 e Å⁻³
2611 reflections	Δρ_min = −0.91 e Å⁻³
155 parameters

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.

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 (Å²) top

	x	y	z	U_iso*/U_eq	Occ. (<1)
Br1	0.24399 (5)	0.73912 (2)	0.82770 (5)	0.0708 (2)
N1	0.4449 (3)	0.63281 (13)	0.3396 (3)	0.0429 (8)
H2A	0.4352	0.5975	0.3271	0.052*	0.50
C1	0.5000	0.6600 (2)	0.2500	0.0428 (13)
H1	0.5000	0.6997	0.2500	0.051*
C11	0.3994 (4)	0.65996 (16)	0.4505 (4)	0.0404 (9)
C12	0.4347 (4)	0.71277 (17)	0.4995 (4)	0.0525 (11)
H12A	0.4903	0.7329	0.4570	0.063*
C13	0.3885 (4)	0.73617 (18)	0.6108 (5)	0.0569 (11)
H13A	0.4131	0.7719	0.6428	0.068*
C14	0.3065 (4)	0.70681 (17)	0.6738 (4)	0.0459 (10)
C15	0.2716 (4)	0.65412 (19)	0.6293 (4)	0.0560 (11)
H15A	0.2171	0.6340	0.6737	0.067*
C16	0.3177 (4)	0.63066 (17)	0.5178 (4)	0.0546 (11)
H16A	0.2935	0.5947	0.4873	0.066*
Br2	0.02928 (6)	0.61567 (3)	1.05388 (8)	0.1036 (3)
N2	0.4121 (3)	0.49146 (13)	0.7963 (3)	0.0507 (8)
H3A	0.4085	0.4541	0.7936	0.061*	0.50
C2	0.5000	0.5180 (2)	0.7500	0.0520 (15)
H2B	0.5000	0.5577	0.7500	0.062*
C21	0.3242 (4)	0.52137 (16)	0.8556 (4)	0.0455 (10)
C22	0.2110 (4)	0.50352 (19)	0.8320 (5)	0.0588 (12)
H32A	0.1933	0.4723	0.7758	0.071*
C23	0.1229 (4)	0.53143 (19)	0.8908 (5)	0.0635 (12)
H33A	0.0466	0.5189	0.8746	0.076*
C24	0.1488 (4)	0.57764 (18)	0.9729 (5)	0.0561 (11)
C25	0.2603 (4)	0.59524 (19)	0.9991 (4)	0.0584 (12)
H35A	0.2774	0.6264	1.0557	0.070*
C26	0.3483 (4)	0.56719 (17)	0.9422 (4)	0.0561 (11)
H36A	0.4247	0.5791	0.9621	0.067*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0872 (4)	0.0873 (4)	0.0409 (3)	0.0246 (3)	0.0215 (2)	−0.0074 (2)
N1	0.046 (2)	0.0446 (17)	0.0413 (18)	0.0019 (15)	0.0199 (15)	−0.0018 (14)
C1	0.040 (3)	0.042 (3)	0.047 (3)	0.000	0.006 (3)	0.000
C11	0.044 (2)	0.046 (2)	0.033 (2)	0.0046 (18)	0.0111 (17)	0.0051 (17)
C12	0.059 (3)	0.056 (2)	0.045 (2)	−0.014 (2)	0.017 (2)	−0.001 (2)
C13	0.070 (3)	0.056 (2)	0.046 (3)	−0.009 (2)	0.012 (2)	−0.007 (2)
C14	0.056 (3)	0.055 (2)	0.028 (2)	0.010 (2)	0.0129 (18)	−0.0038 (18)
C15	0.053 (3)	0.073 (3)	0.047 (2)	−0.005 (2)	0.029 (2)	0.000 (2)
C16	0.064 (3)	0.051 (2)	0.053 (3)	−0.009 (2)	0.025 (2)	−0.003 (2)
Br2	0.0764 (5)	0.0940 (5)	0.1485 (7)	0.0149 (3)	0.0538 (4)	−0.0264 (4)
N2	0.046 (2)	0.0459 (18)	0.063 (2)	0.0002 (16)	0.0217 (17)	−0.0012 (17)
C2	0.055 (4)	0.043 (3)	0.059 (4)	0.000	0.011 (3)	0.000
C21	0.047 (3)	0.044 (2)	0.047 (2)	0.0014 (18)	0.0127 (19)	0.0011 (18)
C22	0.049 (3)	0.061 (3)	0.067 (3)	−0.010 (2)	0.014 (2)	−0.019 (2)
C23	0.035 (3)	0.078 (3)	0.079 (3)	−0.006 (2)	0.014 (2)	−0.016 (3)
C24	0.052 (3)	0.057 (3)	0.062 (3)	0.011 (2)	0.019 (2)	0.000 (2)
C25	0.057 (3)	0.053 (3)	0.067 (3)	0.000 (2)	0.017 (2)	−0.014 (2)
C26	0.047 (3)	0.059 (3)	0.061 (3)	−0.007 (2)	0.005 (2)	−0.010 (2)

Geometric parameters (Å, º) top

Br1—C14	1.901 (4)	Br2—C24	1.886 (4)
N1—C1	1.305 (4)	N2—C2	1.311 (4)
N1—C11	1.412 (5)	N2—C21	1.407 (5)
N1—H2A	0.8422	N2—H3A	0.8763
C1—N1ⁱ	1.305 (4)	C2—N2ⁱⁱ	1.311 (4)
C1—H1	0.9300	C2—H2B	0.9300
C11—C12	1.377 (5)	C21—C22	1.373 (6)
C11—C16	1.388 (6)	C21—C26	1.385 (5)
C12—C13	1.381 (6)	C22—C23	1.383 (6)
C12—H12A	0.9300	C22—H32A	0.9300
C13—C14	1.369 (6)	C23—C24	1.369 (6)
C13—H13A	0.9300	C23—H33A	0.9300
C14—C15	1.360 (6)	C24—C25	1.355 (6)
C15—C16	1.383 (6)	C25—C26	1.375 (6)
C15—H15A	0.9300	C25—H35A	0.9300
C16—H16A	0.9300	C26—H36A	0.9300

C1—N1—C11	123.2 (3)	C2—N2—C21	121.5 (3)
C1—N1—H2A	116.6	C2—N2—H3A	120.0
C11—N1—H2A	120.1	C21—N2—H3A	118.5
N1ⁱ—C1—N1	121.4 (5)	N2ⁱⁱ—C2—N2	123.3 (5)
N1ⁱ—C1—H1	119.3	N2ⁱⁱ—C2—H2B	118.4
N1—C1—H1	119.3	N2—C2—H2B	118.4
C12—C11—C16	118.0 (4)	C22—C21—C26	118.3 (4)
C12—C11—N1	123.9 (4)	C22—C21—N2	119.4 (3)
C16—C11—N1	118.0 (3)	C26—C21—N2	122.2 (4)
C11—C12—C13	120.9 (4)	C21—C22—C23	120.8 (4)
C11—C12—H12A	119.6	C21—C22—H32A	119.6
C13—C12—H12A	119.6	C23—C22—H32A	119.6
C14—C13—C12	120.0 (4)	C24—C23—C22	119.6 (4)
C14—C13—H13A	120.0	C24—C23—H33A	120.2
C12—C13—H13A	120.0	C22—C23—H33A	120.2
C15—C14—C13	120.5 (4)	C25—C24—C23	120.3 (4)
C15—C14—Br1	119.8 (3)	C25—C24—Br2	119.8 (3)
C13—C14—Br1	119.7 (3)	C23—C24—Br2	119.8 (3)
C14—C15—C16	119.6 (4)	C24—C25—C26	120.2 (4)
C14—C15—H15A	120.2	C24—C25—H35A	119.9
C16—C15—H15A	120.2	C26—C25—H35A	119.9
C15—C16—C11	121.1 (4)	C25—C26—C21	120.7 (4)
C15—C16—H16A	119.5	C25—C26—H36A	119.7
C11—C16—H16A	119.5	C21—C26—H36A	119.7

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H2A···N2ⁱⁱⁱ	0.85	2.12	2.964 (4)	180
N2—H3A···N1^iv	0.88	2.12	2.964 (4)	161

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

Experimental details

Crystal data
Chemical formula	C₁₃H₁₀Br₂N₂
M_r	354.05
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	293
a, b, c (Å)	11.563 (2), 23.447 (5), 9.881 (2)
β (°)	95.43 (3)
V (Å³)	2666.9 (9)
Z	8
Radiation type	Mo Kα
µ (mm⁻¹)	6.06
Crystal size (mm)	0.15 × 0.07 × 0.06

Data collection
Diffractometer	Bruker SMART CCD diffractometer
Absorption correction	Multi-scan (SADABS; Sheldrick, 2004)
T_min, T_max	0.403, 0.695
No. of measured, independent and observed [I > 2σ(I)] reflections	5954, 2611, 1715
R_int	0.061
(sin θ/λ)_max (Å⁻¹)	0.617

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.048, 0.114, 1.00
No. of reflections	2611
No. of parameters	155
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.48, −0.91

Computer programs: APEX2 (Bruker, 2004), SAINT-Plus (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), XP (Sheldrick, 2008) and DIAMOND (Brandenburg, 1999).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H2A···N2ⁱ	0.85	2.12	2.964 (4)	180
N2—H3A···N1ⁱⁱ	0.88	2.12	2.964 (4)	161

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

Acknowledgements

This work was supported by the National Natural Scientific Foundation of China (No.20741004/B010303).

References

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