2,6-Bis[1-(2-isopropyl­phenyl­imino)­ethyl]­pyridine

Giuseppe Agrifoglio; Julian Reyes; Reinaldo Atencio; Alexander Briceño

doi:10.1107/S1600536807060254

. 2007 Dec 6;64(Pt 1):o28–o29. doi: 10.1107/S1600536807060254

2,6-Bis[1-(2-isopropylphenylimino)ethyl]pyridine

Giuseppe Agrifoglio ^a,^*, Julian Reyes ^a, Reinaldo Atencio ^a, Alexander Briceño ^a,^*

PMCID: PMC2914989 PMID: 21200845

Abstract

The title compound, C₂₇H₃₁N₃, has E substitution at each imine double bond where the two N atoms adopt a trans–trans relationship. The benzene rings are twisted out of the mean plane of the pyridine ring; the mean planes of the aromatic groups are rotated by 63.0 (1) and 72.58 (8)°. The crystal structure is sustained mainly by C—H⋯π and hydrophobic methyl–methyl interactions.

Related literature

For related literature, see: Alyea & Merrel (1974 ▶); Bernstein et al. (1995 ▶); Bianchini & Hon Man (2000 ▶); Britovsek et al. (1999 ▶); Huang et al. (2006 ▶); Mentes et al. (2001 ▶); Orrell et al. (1997 ▶); Small & Brookhart (1998 ▶); Togni & Venanzi (1994 ▶); Çetinkaya et al. (1999 ▶).

Experimental

Crystal data

C₂₇H₃₁N₃
M _r = 397.55
Monoclinic,
a = 16.9462 (18) Å
b = 6.791 (4) Å
c = 21.801 (4) Å
β = 104.551 (13)°
V = 2428.3 (16) Å³
Z = 4
Mo Kα radiation
μ = 0.06 mm⁻¹
T = 295 (2) K
0.48 × 0.40 × 0.20 mm

Data collection

Rigaku AFC-7S diffractometer
Absorption correction: ψ scan (North et al., 1968 ▶) T _min = 0.963, T _max = 0.987
4402 measured reflections
4248 independent reflections
2520 reflections with I > 2σ(I)
R _int = 0.016
3 standard reflections every 150 reflections intensity decay: none

Refinement

R[F ² > 2σ(F ²)] = 0.061
wR(F ²) = 0.188
S = 1.02
4248 reflections
272 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1993 ▶); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 1999 ▶); program(s) used to solve structure: SHELXTL-NT (Bruker, 1998 ▶); program(s) used to refine structure: SHELXTL-NT; molecular graphics: SHELXTL-NT and DIAMOND (Brandenburg, 1999 ▶); software used to prepare material for publication: SHELXTL-NT and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536807060254/hb2609sup1.cif

e-64-00o28-sup1.cif^{(20.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536807060254/hb2609Isup2.hkl

e-64-00o28-Isup2.hkl^{(208.2KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

Cg1, Cg2 and Cg3 are the centroids of the rings N1/C1–C5, C8–C13 and C19–C24, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C7—H7A⋯N1	0.96	2.46	2.799 (3)	100
C14—H14⋯N2	0.98	2.46	2.830 (4)	101
C18—H18A⋯N1	0.96	2.47	2.819 (3)	101
C25—H25⋯N3	0.98	2.39	2.892 (4)	111
C3—H3⋯Cg1ⁱ	0.93	2.75	3.450 (3)	133
C23—H23⋯Cg2ⁱⁱ	0.93	2.97	3.801 (4)	149
C12—H12⋯Cg3ⁱⁱ	0.93	3.16	3.961 (10)	146
C15—H15B⋯Cg1ⁱⁱⁱ	0.96	3.17	3.757 (13)	121
C15—H15C⋯Cg1ⁱⁱⁱ	0.96	3.44	3.757 (13)	102

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

Acknowledgments

The authors thank FONACIT–MCT, Venezuela, for financial support (project LAB-199700821)

supplementary crystallographic information

Comment

The development of new ligand politopics bearing nitrogen heterocyclic units has been receiving increasing interest in the coordination chemistry of transition-metal based homogeneous catalysis (Togni & Venanzi, 1994). In this context, the planar tridentate–or potentially bidentate–ligand 2,6-bis(imino)pyridine and its derivatives (Orrell et al., 1997) have attracted great attention and the bis(arylimino)pyridine ligand [2,6-(ArN?CR)₂C₅H₃N] by (Alyea & Merrel, 1974). There are several recent examples of reactions catalyzed by complexes bearing the ligand 2,6-bis(arylimino)pyridine ligands such as epoxidation of olefins (Çetinkaya et al., 1999), cyclopropanation of styrene (Bianchini et al., 2000). Specially, it has been nearly a decade since sterically demanding bis(arylimino)pyridine ligands were found to impart transitions metals, iron and cobalt, catalytic activities for olefin polymerization (Small & Brookhart, 1998; Britovsek et al., 1999). Many reports have appared in the literature concerning the effects (sterically and/or electronic) of ligand modifications, to find a structure–activity relationships. The crystal structure of different 2,6-bis(arylimino)pyridine ligands and their transition metal complexes offer the possibilty to compare directly structural parameters. Here we report the synthesis and crystal structure of the title compound, (I), (Fig. 1).

The molecule adopts a nonplanar conformation in which an E configuration around each C?N imine group is observed, likewise the two N atoms display a trans-trans relationship. The conformation of the system N–N–N system is of course different in each case. In general, X-ray structures of bis(arylimino)pyridines reveal that in the solid state the imino nitrogen atoms prefer to be disposed trans with respect to the central pyridine nitrogen (Mentes, et al. 2001; Huang et al., 2006) in order to minimize the interaction between the nitrogen lone pairs. The phenyl rings in (I) are twisted out of the mean plane of the pyridine ring, the mean planes of C8–C13 and C19–C24 being rotated by 63.0 (1)° and 72.58 (8)°, respectively. This molecular conformation is determined by the formation of pairs of intramolecular C—H···N hydrogen bonds, involving methyl groups with the N of the pyridine ring and isopropyl groups with imine groups with a range of distances C···N = 2.799 (3)–2.892 (4) Å (Fig. 2). These interactions lead to the formation of five-membered rings described by graph-set simbol S(5) (Bernstein et al., 1995).

The crystal structure of (I) consists of dimers linked by self-complementary C—H···π interactions related by an inversion centre C15···Cg1 = 3.757 Å; were Cg1 is the centroid of the N1,C1–C5 ring (Fig. 2). Neighbouring dimers are connected through additional C—H···π between phenyl rings (Fig. 3), generating supramolecular sheets parallel to the c axis. Details of geometrical parameters of these hydrogen bonding interactions are summarized in Table 2. Finally, the stacking of adjacent sheets is sustained by hydrophobic methyl-methyl interactions along the a axis (Fig. 4).

Experimental

The tile compound was synthetized by condensation of 2,6-diacetylpiridine (1.63 g, 10 mmol) with 2-iso-propylaniline (2.74 g, 20.3 mmol) in 25 ml dry methanol and five drops of formic acid. The solution was refluxed for 18 h. Upon slow cooling to room temperature and overnight to 273 K. Yellow prisms of (I) were obtained and filtered with a yield 75%. ¹H-NMR (300 MHz, CDCl₃); (δ, p.p.m.) 1.16 (d, 12 H), 2.23(s, 6H), 2.75(sept,2 H), 6. 54(tt, 2H), 7.08(tt, 2 H), 7.20(tt, 2 H), 7.44(dd, 2 H), 7.95(t, 1 H), 8.43(d, 2 H). Elemental analysis calcd. for C₂₇H₃₁N₃(%): C 81.57; H 7.85; N 10.57%. Found: C 81.33; H 7.69; N 10.41%.