2,4,6-Trimethyl-N-[1-(1H-pyrrol-2-yl)ethyl­idene]aniline

Bi-yun Su; Lei Li; Jia-Xiang Wang; Xuan-Yan Li

doi:10.1107/S1600536812037774

. 2012 Sep 8;68(Pt 10):o2889. doi: 10.1107/S1600536812037774

2,4,6-Trimethyl-N-[1-(1H-pyrrol-2-yl)ethylidene]aniline

Bi-yun Su ^a,^*, Lei Li ^a, Jia-Xiang Wang ^a, Xuan-Yan Li ^a

PMCID: PMC3470241 PMID: 23125685

Abstract

There are two independent molecules in the asymmetric unit of the title compound, C₁₅H₁₈N₂, each of which features a syn disposition of the N atoms. In each molecule, the pyrrole and benzene rings are essentially perpendicular, with dihedral angles of 78.90 (9) and 79.96 (9)°. In the crystal, the independent molecules are connected by a pair of pyrrole–imino N—H⋯N hydrogen bonds, forming a two-molecule aggregate.

Related literature

For general background to the iminopyrrole unit, see: Small et al. (1998 ▶); Su et al. (2009a ▶,b ▶); Britovsek et al. (2003 ▶); Dawson et al. (2000 ▶). For the pyrrole diimine unit, see: Matsuo et al. (2001 ▶) and for the pyrrole monoimine unit, see: He et al. (2009 ▶).

Experimental

Crystal data

C₁₅H₁₈N₂
M _r = 226.31
Monoclinic,
a = 29.848 (4) Å
b = 7.9668 (11) Å
c = 26.325 (4) Å
β = 119.940 (2)°
V = 5424.6 (13) Å³
Z = 16
Mo Kα radiation
μ = 0.07 mm⁻¹
T = 296 K
0.37 × 0.24 × 0.18 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.976, T _max = 0.988
14702 measured reflections
5675 independent reflections
2837 reflections with I > 2σ(I)
R _int = 0.054

Refinement

R[F ² > 2σ(F ²)] = 0.057
wR(F ²) = 0.159
S = 0.99
5675 reflections
316 parameters
H-atom parameters constrained
Δρ_max = 0.18 e Å⁻³
Δρ_min = −0.14 e Å⁻³

Data collection: APEX2 (Bruker, 2008 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: publCIF (Westrip, 2010 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812037774/tk5142sup1.cif

e-68-o2889-sup1.cif^{(24.7KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812037774/tk5142Isup2.hkl

e-68-o2889-Isup2.hkl^{(277.9KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536812037774/tk5142Isup3.cml

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—H1⋯N4	0.86	2.23	3.029 (3)	154
N3—H3⋯N2	0.86	2.28	3.060 (3)	151

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Acknowledgments

This work was supported by the Natural Science Basic Research Plan in Shaanxi Province (No. 2009JQ2006), the Scientific Research Plan Project of Shaanxi Education Department (12 J K0620) and the Important Science & Technology Specific Projects of Innovative Program of Shaanxi Province (No. 2010ZDKG-46).

supplementary crystallographic information

Comment

Recently, bis(imino)pyridine incorporated late transition metal catalysts have attracted much attention for their antioxidant properties and outstanding activities for olefin polymerization (Small et al., 1998; Su et al., 2009a,b). As a five-membered analogue of the pyridine ring (Matsuo et al., 2001; He et al., 2009), pyrrole has been frequently introduced into the skeleton of bis(imino)pyridine ligands to design new ligands and corresponding metal complexes (Britovsek et al., 2003; Dawson et al., 2000). Bis(imino)pyrrole is usually prepared from Schiff base condensation of 2,5-diacetylpyrrole and an aromatic amine (Matsuo et al., 2001). As a contribution to this research field, we present herein the synthesis of mono(imino)pyrrole from 2-acetyl pyrrole and 2,4,6-trimethylaniline, as well as the crystal structure of the title compound 2,4,6-trimethyl-N-[1-(1H-pyrrol-2-yl)ethylidene]aniline.

The asymmetric unit of the title compound (Fig. 1) comprises of two crystallographically independent molecules A and B. These two molecules are connected by a pair of nearly equal N(pyrrole)—H···N(imino) hydrogen bonds, Table 1. In each molecule the pyrrole ring and benzene ring are essentially perpendicular, with dihedral angles of 78.90 (9)° and 79.96 (9)°, respectively. The pyrrole rings of the molecules A and B present a nearly parallel spatial arrangement with a dihedral angle of 34.70 (11)°, and the benzene rings of the two molecules show a dihedral angle of 29.35 (13)°. Although the two molecules in the asymmetric unit are similar some minor differences in corresponding bond angles are evident, most notably C—N(imino)—C of 118.86 (19) and 120.2 (2)°, for A and B, respectively.

The crystal packing is stabilized by N—H···N hydrogen bonds (Table 1, Fig. 2) occurring between the independent molecules comprising the asymmetric unit.

Experimental

The reagents 2-acetyl pyrrole (0.1968 g, 1.80 mmol) and 2,4,6-trimethylaniline (0.2638 g, 1.80 mmol) were placed in a 50 ml flask. After a few drops of acetic acid were added, the mixture was subjected to radiation in a 800 W microwave oven for 3 min and 2 min on a medium–heat setting. The reaction was monitored by TLC, and the crude product was purified by silica gel column chromatography (eluant: petroleum ether/ethyl acetate, 5:1 v/v). The colourless crystals of the title compound were obtained by recrystallization from ethanol (yield 0.085 g, 20.9%). M.pt: 401.4–407.6 K. IR (KBr): ν_C_═_N 1646 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ 7.16 (s, 2H, phenyl-H), 6.84 (t, 1H, pyrrole-H), 6.63 (t, 1H, pyrrole-H), 6.19 (d, 1H, pyrrole-H), 2.23 (s, 3H, –N=C(CH₃)), 1.94 (d, 9H, phenyl-CH₃). MS (EI): m/z 225 (M). Anal. Calcd for C₁₅H₁₈N₂: C, 79.61; H, 8.02; N, 12.38. Found: C, 79.71; H, 7.362; N, 12.39.