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

L-J Han

doi:10.1107/S1600536811013419

. 2011 Apr 16;67(Pt 5):o1159. doi: 10.1107/S1600536811013419

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

L-J Han ^a,^*

PMCID: PMC3089148 PMID: 21754467

Abstract

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,
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[F ² > 2σ(F ²)] = 0.048
wR(F ²) = 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

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.

Supplementary Material

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

e-67-o1159-sup1.cif^{(14.9KB, cif)}

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

e-67-o1159-Isup2.hkl^{(128.3KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

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

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

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

supplementary crystallographic information

Comment

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.

Experimental

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.