1,3-Bis(2-ethoxy­phen­yl)triazene

Mohammad Kazem Rofouei; Mohammad Reza Melardi; Yasaman Salemi; Saba Razi Kazemi

doi:10.1107/S1600536809008034

. 2009 Mar 11;65(Pt 4):o719. doi: 10.1107/S1600536809008034

1,3-Bis(2-ethoxyphenyl)triazene

Mohammad Kazem Rofouei ^a,^*, Mohammad Reza Melardi ^b, Yasaman Salemi ^b, Saba Razi Kazemi ^b

PMCID: PMC2969009 PMID: 21582455

Abstract

The title compound, C₁₆H₁₉N₃O₂, exhibits a trans geometry about the N=N double bond in the triazene unit in the solid state, and individual molecules are close to planar with r.m.s. deviations from planarity of 0.065 Å and 0.242 Å for the two independent molecules in the asymmetric unit. Distinct intermolecular N—H⋯N hydrogen bonds lead to the formation of dimers with an R ₂ ²(8) graph-set motif. The steric demands of the ethoxy groups in the ortho position prevent a coplanar arrangement of the two molecules in the dimers and these instead consist of two interlocked molecules that are related by a non-crystallographic pseudo-twofold rotation axis. Weak C—H⋯π interactions between the CH groups and the aromatic phenyl rings also occur.

Related literature

For aryl triazenes, their structural properties and metal complexes, see: Meldola et al. (1888 ▶); Leman et al. (1993 ▶); Chen et al. (2002 ▶); Vrieze et al. (1987 ▶). For a similar structure with cyano instead of ethoxy groups, see: Melardi et al. (2008 ▶). For the synthesis and characterization of a similar structure with methoxy instead of ethoxy groups, see: Rofouei et al. (2006 ▶). For the synthesis and crystal structures of mercury(II) and silver(I) complexes with 1,3-bis(2-methoxyphenyl)triazene, see: Hematyar et al. (2008 ▶) and Payehghadr et al. (2007 ▶), respectively. For the investigation of hydrogen-bond patterns and related graph sets, see: Grell et al. (2002 ▶).

Experimental

Crystal data

C₁₆H₁₉N₃O₂
M _r = 285.34
Triclinic,
a = 11.3971 (7) Å
b = 11.8696 (7) Å
c = 14.0627 (9) Å
α = 106.467 (5)°
β = 98.598 (5)°
γ = 116.512 (5)°
V = 1545.7 (2) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 120 K
0.30 × 0.20 × 0.15 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 1998 ▶) T _min = 0.973, T _max = 0.982
17109 measured reflections
8181 independent reflections
4988 reflections with I > 2σ(I)
R _int = 0.031

Refinement

R[F ² > 2σ(F ²)] = 0.058
wR(F ²) = 0.138
S = 1.00
8181 reflections
383 parameters
H-atom parameters constrained
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.31 e Å⁻³

Data collection: SMART (Bruker, 1998 ▶); cell refinement: SAINT-Plus (Bruker, 1998 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809008034/zl2178sup1.cif

e-65-0o719-sup1.cif^{(26.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809008034/zl2178Isup2.hkl

e-65-0o719-Isup2.hkl^{(400.2KB, 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—H1N⋯N4	0.91	2.12	3.018 (2)	170
N6—H6N⋯N3	0.91	2.11	3.008 (2)	170
C4—H4A⋯Cg1ⁱ	0.95	2.85	3.686 (2)	147
C32—H32B⋯Cg2ⁱⁱ	0.98	2.78	3.549 (3)	136

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Symmetry codes: (i) Inline graphic ; (ii) . Cg1 and Cg2 are the centroids of the C17–C22 and C25–C30 rings, respectively.

supplementary crystallographic information

Comment

Aryl triazenes have been studied for over 130 years for their interesting structural, anticancer, and reactivity properties. The first extensive investigation of the coordination chemistry of a triazene derivative (1,3-diphenyltriazene) was carried out in 1887 by Meldola (Meldola et al., 1888). In the intervening years, numerous transition metal triazenide compounds have been studied (Leman et al., 1993). Triazene compounds characterized by having a diazoamino group commonly adopt a trans configuration in the ground state (Chen et al., 2002). The study of transition metal complexes containing 1,3-diaryltriazenide [RN═N—NR]^- ligands has increased greatly in the past few years, because of their potential reactivity in relation to their several coordination modes (Vrieze et al., 1987). We have recently reported the synthesis and characterization of the two molecules 1,3-bis(2-methoxyphenyl)triazene (Rofouei, et al., 2006) and 1,3-bis(2-cyanophenyl)triazene (Melardi, et al., 2008).

The title compound, C₁₆H₁₉N₃O₂, is a related triazene compound and crystallizes in the space group P1 with two crystallographically independent molecules per unit cell. It exhibits a trans stereo chemistry of the N═N double bond, and the C9—N3—N2—N1 and C17—N4—N5—N6 torsion angles are -179.45 (13) and 176.67 (13)°, respectively. The N1—N2, N2—N3, N4—N5 and N5—N6 bond distances are 1.3196 (18), 1.2909 (18), 1.2896 (18) and 1.3214 (18) Å, respectively, which indicates the presence of distinct single and double bonds between the nitrogen atoms. These values are in good agreement with the reported data for N—N and N═N bond distances (Hematyar, et al., 2008; Payehghadr, et al. 2007). For example, in 1,3-bis(2-cyanophenyl)triazene, the N—N and N═N bond distances are 1.335 (5) and 1.289 (5) Å (Melardi, et al., 2008). Individual molecules are mostly planar with an rms deviation from planarity of 0.0646 Å for all non-hydrogen atoms.

The two crystallographically independent molecules in the molecular structure (Fig. 1) are connected by two distinct classic N—H···N hydrogen bonds with D···A distances of 3.018 (2) and 3.008 (2) Å (Table 1). The N—H···N hydrogen bonds lead to the formation of dimers with an R₂²(8) graph set geometry (Grell et al., 2002). The steric demand of the ethoxy groups in the ortho position prevents a co-planar arrangement of the two molecules in the dimers and these do instead consist of two interlocked molecules that are related by a non-crystallographic pseudo-twofold rotation axis. The dihedral angle between the best least square planes of the two molecules is 63.15 (3) °.

Also, there are interesting weak C—H···π interactions between the CH groups and the aromatic phenyl rings with H···π and C···π distances of 2.85 and 3.686 (2) Å for C4–H4A···Cg1 (2 - x, 2 - y, 1 - z) and 2.78 and 3.549 (3) Å for C32–H32B···Cg2 (1 - x, 1 - y, -z) [Cg1 and Cg2 are centroids for C17—C22 and C25—C30 rings, respectively] (Fig. 2). The unit cell packing of the title compound is presented in Fig. 3.

Experimental

The compound was prepared by the following method: A 100 ml flask was charged with 10 g of ice and 15 ml of water and then cooled to 273 K in an ice-bath. To this was added 10 mmol (1.37 g) of o–phenetidin and 13 mmol of hydrochloric acid (37%). To this solution was added a solution containing NaNO₂ (6 mmol, 0.41 g) in 25 ml of water during a 15 min period. After mixing for 15 min, a solution containing 180 mmol (14.76 g) of sodium acetate in 45 ml of water was added. After mixing for 45 min the brown product was filtered off and dissolved in Et₂O, and was crystallized at 263 K. Yield, (50%) 24 mmol (6.85 g). Recrystallization from Et₂O afforded the product as an orange crystalline material. m. p. 374–375 K. ¹H NMR(300 MHz, DMSO): 1.36 (6H, CH₃), 4.10 (4H, CH₂), 6.91–7.53 (8H, aromatic), 11.26 (1H, NH). IR (KBr): 3149, 2977, 1599, 1489, 1253, 1045, 742 cm^-1.