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Acta Crystallogr Sect E Struct Rep Online. 2009 July 1; 65(Pt 7): o1671–o1672.
Published online 2009 June 24. doi:  10.1107/S1600536809020571
PMCID: PMC2969422

N-[3-(2,6-Dimethylanilino)-1-methylbut-2-enylidene]-2,6-dimethylanilinium chloride1

Abstract

The title salt, C21H27N2 +·Cl resulted from the condensation between 2,6-dimethyl­aniline and acetyl­acetone in acidified ethanol. The bulky cation is stabilized in a β-imino­enamine tautomeric form, and presents a W-shaped conformation. The benzene rings are arranged almost parallel, with a dihedral angle of 6.58 (4)° between the mean planes. Both N—H groups in the cation form strong hydrogen bonds with two symmetry-related chloride anions. The resulting supra­molecular structure is a one dimensional polymer running along [001], alternating cations and anions. The π–π inter­action observed in the mol­ecule, characterized by a centroid–centroid separation of 4.298 (4) Å, is thus extended to the chains, with separations of 5.222 (4) Å between benzene rings of neighbouring cations in the crystal.

Related literature

For the synthesis, properties, and uses of β-diketimines and β-diketiminates, see: Dorman (1966 [triangle]); Park (2007 [triangle]); Bourget-Merle et al. (2002 [triangle]); Nagendran & Roesky (2008 [triangle]); Holland & Tolman (2000 [triangle]); Stender et al. (2001 [triangle]); Carey et al., 2003 [triangle]. For W-shaped cations related to the title compound, see: Brownstein et al. (1983 [triangle]); Kuhn et al. (2000 [triangle]); Lesikar & Richards (2006 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-o1671-scheme1.jpg

Experimental

Crystal data

  • C21H27N2 +·Cl
  • M r = 342.90
  • Tetragonal, An external file that holds a picture, illustration, etc.
Object name is e-65-o1671-efi1.jpg
  • a = 28.639 (5) Å
  • c = 10.150 (3) Å
  • V = 8325 (3) Å3
  • Z = 16
  • Mo Kα radiation
  • μ = 0.19 mm−1
  • T = 298 K
  • 0.50 × 0.36 × 0.22 mm

Data collection

  • Bruker P4 diffractometer
  • Absorption correction: ψ scan XSCANS (Siemens, 1996 [triangle]) T min = 0.854, T max = 0.959
  • 7193 measured reflections
  • 3671 independent reflections
  • 1541 reflections with I > 2σ(I)
  • R int = 0.049
  • 3 standard reflections every 97 reflections intensity decay: 1.5%

Refinement

  • R[F 2 > 2σ(F 2)] = 0.062
  • wR(F 2) = 0.171
  • S = 1.12
  • 3671 reflections
  • 229 parameters
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.43 e Å−3
  • Δρmin = −0.32 e Å−3

Data collection: XSCANS (Siemens, 1996 [triangle]); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: Mercury (Macrae et al., 2006 [triangle]); software used to prepare material for publication: SHELXL97.

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809020571/fl2243sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809020571/fl2243Isup2.hkl

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

Acknowledgments

This work was supported by PROMEP (Programa de Mejoramiento del Profesorado), grant No. 103.5/08/3125.

supplementary crystallographic information

Comment

Many synthetic routes are currently available to synthesize symmetric and unsymmetric β-diketimines, including the co-condensation reaction of a ketone and a primary amine (Dorman, 1966; Park, 2007). These ligands proved to be very versatile and diverse, considering the possible variation of both coordination modes and of groups bonded to the N atoms and to the α- and β- C atoms. Indeed, β-diketiminates are the most used ligands in coordination chemistry for the stabilization of low coordinate and low oxidation states of main group or transition elements (Bourget-Merle et al., 2002; Nagendran & Roesky, 2008). β-Diketiminates complexes have been used as catalysts and even as structural models of protein active sites (Holland & Tolman, 2000).

Neutral β-diketimines invariably show a U-shaped conformation, favoured over other possible conformers by the formation of an intramolecular hydrogen bond involving the amine and imine N atoms (Dorman, 1966; Stender et al., 2001; Carey et al., 2003). However, if the β-diketimine is protonated, the backbone molecule adopts a new W-conformation, since the protonated N atom is able to form a strong intra-ionic N—H···Cl bond. Such behaviour has been observed in three salts closely related to the title compound where phenyl (Brownstein et al., 1983), methyl (Kuhn et al., 2000), and mesityl (Lesikar & Richards, 2006) have replaced the 2,6-dimethylphenyl. The supramolecular one-dimensional structure generated by this hydrogen bond is expected to be a strong stabilizing factor, as anions and cations alternate in a chain structure, which has a theoretical Madelung constant of 1.38.

In the title salt, the cation adopts the W-shaped conformation, and thus presents a non-crystallographic twofold axis passing through the central atom C9 (Fig. 1). Both N atoms are protonated, indicating that the β-iminoenamine tautomeric form is stabilized in the solid state. A parallel arrangement is observed for benzene rings, which are separated by 4.298 (4) Å. A similar arrangement was found with the mesityl-including cation, although the benzene separations are larger, probably because of the hindering character of mesityl (centroid-to-centroid distances: 4.348, 4.823, or 4.881 Å, depending of the nature of the counterion; Lesikar & Richards, 2006). Unexpectedly, the phenyl-containing salt has little intramolecular π–π interaction, with non-parallel phenyl rings separated by 5.480 Å (Brownstein et al., 1983). In the title cation, benzene rings are close to be parallel, the dihedral angle between mean planes being 6.58 (4)°.

Regarding the crystal structure, both amine and imine NH functionalities, N7 and N11, are involved in strong N—H···Cl hydrogen bonds with symmetry-related Cl- ions. The network of hydrogen bonds forms a one-dimensional supramolecular structure along the short cell axis c (Fig. 2). Cations and anions alternate in a chain, with all benzene rings oriented in the same direction. This arrangement allows to extend the π–π interactions to the whole polymeric structure, with a separation of 5.222 (4) Å between benzene rings of neighbouring cations. No significant contacts are observed between chains in the crystal.

Experimental

The title salt was prepared by mixing acetylacetone (25.03 g, 0.25 mol) and 2,6-dimethylaniline (60.5 g, 0.5 mol) in 12 N hydrochloric acid (20.8 ml, 0.25 mol HCl). The mixture was heated to 393 K for 4 h., allowing the water to distil. The reaction was then further heated to 413 K overnight. The resulting solid was recrystallized from hot ethanol, yielding 87.6 g of the title salt (94%). NMR data are in agreement with the X-ray structure (see archived CIF).

Refinement

All C-bonded H atoms were placed in calculated positions and refined as riding to their carrier atoms, with bond lengths fixed to 0.93 (aromatic CH) or 0.96 Å (methyl CH3). N-bonded H atoms (H7 and H11) were found in a difference map and refined freely. Isotropic displacement parameters for H atoms were calculated as Uiso(H) = 1.5Ueq(carrier atom) for methyl groups and Uiso(H) = 1.2Ueq(carrier atom) otherwise.

Figures

Fig. 1.
The title compound (asymmetric unit) with displacement ellipsoids at the 25% probability level. The dashed bond corresponds to the N—H···Cl hydrogen bond.
Fig. 2.
A part of the crystal structure of the title compound, with hydrogen bonds displayed as dashed lines. Two neighbouring chains are shown, with Cl- ions represented as green spheres, and omitting all C-bonded H atoms.

Crystal data

C21H27N2+·ClDx = 1.094 Mg m3
Mr = 342.90Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I41/aCell parameters from 77 reflections
Hall symbol: -I 4adθ = 4.6–12.3°
a = 28.639 (5) ŵ = 0.19 mm1
c = 10.150 (3) ÅT = 298 K
V = 8325 (3) Å3Prism, colorless
Z = 160.50 × 0.36 × 0.22 mm
F(000) = 2944

Data collection

Bruker P4 diffractometer1541 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.049
graphiteθmax = 25.1°, θmin = 2.0°
ω scansh = −34→13
Absorption correction: ψ scan XSCANS (Siemens, 1996)k = −34→1
Tmin = 0.854, Tmax = 0.959l = −12→12
7193 measured reflections3 standard reflections every 97 reflections
3671 independent reflections intensity decay: 1.5%

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.062Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.171H atoms treated by a mixture of independent and constrained refinement
S = 1.12w = 1/[σ2(Fo2) + (0.06P)2] where P = (Fo2 + 2Fc2)/3
3671 reflections(Δ/σ)max < 0.001
229 parametersΔρmax = 0.43 e Å3
0 restraintsΔρmin = −0.31 e Å3
0 constraints

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
Cl10.89962 (3)0.22980 (3)0.87464 (9)0.0839 (4)
C10.84317 (12)0.14527 (11)0.1392 (5)0.0623 (9)
C20.79611 (13)0.15570 (13)0.1335 (6)0.0824 (11)
C30.76486 (14)0.11910 (17)0.1272 (7)0.1044 (14)
H3A0.73300.12510.12230.125*
C40.78047 (16)0.07434 (16)0.1282 (8)0.1031 (13)
H4A0.75910.04990.12510.124*
C50.82605 (17)0.06477 (14)0.1334 (7)0.1001 (13)
H5A0.83600.03390.13220.120*
C60.85857 (13)0.10015 (13)0.1404 (6)0.0800 (12)
N70.87572 (10)0.18264 (10)0.1423 (4)0.0623 (8)
H70.8870 (13)0.1961 (13)0.057 (3)0.075*
C80.89275 (12)0.20174 (12)0.2519 (3)0.0528 (9)
C90.87894 (9)0.18619 (10)0.3745 (3)0.0565 (8)
H9A0.85710.16220.37530.068*
C100.89372 (12)0.20212 (12)0.4965 (3)0.0527 (9)
N110.87729 (10)0.18288 (10)0.6051 (3)0.0592 (8)
H110.8875 (13)0.1952 (12)0.693 (3)0.071*
C120.84451 (12)0.14556 (11)0.6106 (5)0.0589 (9)
C130.79765 (13)0.15614 (12)0.6194 (7)0.0801 (10)
C140.76658 (13)0.11931 (15)0.6254 (7)0.1053 (13)
H14A0.73470.12530.62840.126*
C150.78209 (15)0.07445 (14)0.6271 (7)0.0982 (12)
H15A0.76070.05010.63350.118*
C160.82809 (16)0.06482 (12)0.6197 (6)0.0886 (11)
H16A0.83800.03390.61920.106*
C170.86083 (12)0.10022 (12)0.6127 (6)0.0725 (10)
C180.78029 (14)0.20557 (14)0.1303 (8)0.144 (2)
H18A0.79290.22190.20490.217*
H18B0.74680.20670.13360.217*
H18C0.79100.22010.05060.217*
C190.90988 (14)0.08956 (14)0.1468 (7)0.130 (2)
H19A0.91440.05640.14960.195*
H19B0.92300.10350.22450.195*
H19C0.92510.10210.07020.195*
C200.92742 (11)0.23930 (11)0.2268 (3)0.0681 (10)
H20A0.93030.24430.13360.102*
H20B0.95720.23030.26220.102*
H20C0.91720.26760.26830.102*
C210.92784 (11)0.23993 (11)0.5203 (3)0.0685 (10)
H21A0.93060.24540.61340.103*
H21B0.91740.26800.47770.103*
H21C0.95770.23100.48540.103*
C220.78164 (14)0.20619 (14)0.6190 (8)0.1295 (17)
H22A0.79740.22300.68760.194*
H22B0.74860.20730.63380.194*
H22C0.78870.22010.53540.194*
C230.91199 (13)0.08983 (13)0.6062 (7)0.1174 (17)
H23A0.91680.05670.61270.176*
H23B0.92770.10520.67780.176*
H23C0.92440.10090.52410.176*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cl10.1080 (7)0.1037 (7)0.0400 (4)−0.0103 (5)−0.0002 (6)0.0004 (6)
C10.077 (2)0.063 (2)0.047 (2)−0.0056 (19)−0.003 (2)−0.007 (2)
C20.084 (3)0.076 (2)0.087 (3)−0.002 (2)−0.023 (4)−0.011 (4)
C30.081 (3)0.119 (3)0.113 (3)−0.013 (3)−0.034 (5)0.002 (7)
C40.106 (3)0.098 (3)0.105 (3)−0.028 (3)0.000 (6)0.001 (6)
C50.121 (3)0.075 (3)0.105 (3)−0.007 (3)0.000 (5)−0.023 (4)
C60.089 (3)0.068 (2)0.083 (3)−0.009 (2)−0.006 (3)−0.003 (3)
N70.0791 (19)0.0624 (17)0.045 (2)−0.0064 (15)−0.0018 (18)−0.0033 (18)
C80.062 (2)0.054 (2)0.0422 (19)0.0017 (18)−0.0027 (17)−0.0015 (17)
C90.0653 (18)0.0616 (18)0.0426 (15)−0.0103 (14)−0.0007 (19)−0.0040 (19)
C100.060 (2)0.052 (2)0.045 (2)−0.0028 (17)−0.0009 (17)−0.0006 (17)
N110.0787 (18)0.0613 (17)0.038 (2)−0.0112 (14)−0.0008 (17)0.0027 (16)
C120.073 (2)0.064 (2)0.040 (2)−0.0079 (19)0.006 (2)0.004 (2)
C130.085 (3)0.072 (2)0.082 (3)−0.009 (2)0.011 (4)−0.001 (4)
C140.078 (3)0.106 (3)0.132 (4)−0.013 (3)0.007 (5)0.015 (7)
C150.105 (3)0.082 (3)0.107 (3)−0.021 (2)0.025 (5)0.011 (5)
C160.118 (3)0.068 (2)0.079 (3)−0.007 (2)0.009 (5)−0.005 (4)
C170.084 (2)0.066 (2)0.067 (3)−0.007 (2)−0.006 (3)0.011 (3)
C180.108 (3)0.104 (3)0.221 (6)0.025 (3)−0.046 (7)−0.006 (7)
C190.103 (3)0.092 (3)0.194 (6)0.016 (2)−0.004 (5)−0.012 (5)
C200.087 (2)0.070 (2)0.0476 (18)−0.017 (2)0.010 (2)0.0013 (17)
C210.083 (2)0.072 (2)0.0499 (19)−0.013 (2)−0.006 (2)0.0015 (18)
C220.103 (3)0.095 (3)0.190 (5)0.017 (2)0.028 (7)−0.001 (6)
C230.096 (3)0.092 (3)0.164 (5)0.013 (2)−0.022 (4)0.006 (4)

Geometric parameters (Å, °)

C1—C61.366 (4)C14—C151.360 (5)
C1—C21.382 (5)C14—H14A0.9300
C1—N71.419 (4)C15—C161.348 (5)
C2—C31.380 (5)C15—H15A0.9300
C2—C181.499 (5)C16—C171.383 (4)
C3—C41.358 (5)C16—H16A0.9300
C3—H3A0.9300C17—C231.497 (4)
C4—C51.335 (5)C18—H18A0.9600
C4—H4A0.9300C18—H18B0.9600
C5—C61.378 (5)C18—H18C0.9600
C5—H5A0.9300C19—H19A0.9600
C6—C191.502 (5)C19—H19B0.9600
N7—C81.332 (4)C19—H19C0.9600
N7—H71.00 (3)C20—H20A0.9600
C8—C91.379 (4)C20—H20B0.9600
C8—C201.486 (4)C20—H20C0.9600
C9—C101.386 (4)C21—H21A0.9600
C9—H9A0.9300C21—H21B0.9600
C10—N111.319 (4)C21—H21C0.9600
C10—C211.479 (4)C22—H22A0.9600
N11—C121.424 (4)C22—H22B0.9600
N11—H111.01 (3)C22—H22C0.9600
C12—C131.379 (4)C23—H23A0.9600
C12—C171.380 (4)C23—H23B0.9600
C13—C141.381 (5)C23—H23C0.9600
C13—C221.505 (5)
C6—C1—C2121.3 (3)C14—C15—H15A119.6
C6—C1—N7120.1 (3)C15—C16—C17121.0 (4)
C2—C1—N7118.6 (3)C15—C16—H16A119.5
C3—C2—C1118.1 (3)C17—C16—H16A119.5
C3—C2—C18121.8 (4)C12—C17—C16117.4 (3)
C1—C2—C18120.1 (3)C12—C17—C23121.2 (3)
C4—C3—C2120.2 (4)C16—C17—C23121.4 (3)
C4—C3—H3A119.9C2—C18—H18A109.5
C2—C3—H3A119.9C2—C18—H18B109.5
C5—C4—C3121.1 (4)H18A—C18—H18B109.5
C5—C4—H4A119.5C2—C18—H18C109.5
C3—C4—H4A119.5H18A—C18—H18C109.5
C4—C5—C6120.8 (4)H18B—C18—H18C109.5
C4—C5—H5A119.6C6—C19—H19A109.5
C6—C5—H5A119.6C6—C19—H19B109.5
C1—C6—C5118.5 (4)H19A—C19—H19B109.5
C1—C6—C19120.5 (3)C6—C19—H19C109.5
C5—C6—C19121.0 (4)H19A—C19—H19C109.5
C8—N7—C1124.6 (4)H19B—C19—H19C109.5
C8—N7—H7117 (2)C8—C20—H20A109.5
C1—N7—H7119 (2)C8—C20—H20B109.5
N7—C8—C9121.0 (3)H20A—C20—H20B109.5
N7—C8—C20113.5 (3)C8—C20—H20C109.5
C9—C8—C20125.5 (3)H20A—C20—H20C109.5
C8—C9—C10127.7 (3)H20B—C20—H20C109.5
C8—C9—H9A116.1C10—C21—H21A109.5
C10—C9—H9A116.1C10—C21—H21B109.5
N11—C10—C9120.0 (3)H21A—C21—H21B109.5
N11—C10—C21113.9 (3)C10—C21—H21C109.5
C9—C10—C21126.1 (3)H21A—C21—H21C109.5
C10—N11—C12125.6 (4)H21B—C21—H21C109.5
C10—N11—H11120 (2)C13—C22—H22A109.5
C12—N11—H11115 (2)C13—C22—H22B109.5
C13—C12—C17122.4 (3)H22A—C22—H22B109.5
C13—C12—N11118.6 (3)C13—C22—H22C109.5
C17—C12—N11118.9 (3)H22A—C22—H22C109.5
C12—C13—C14117.5 (3)H22B—C22—H22C109.5
C12—C13—C22120.4 (3)C17—C23—H23A109.5
C14—C13—C22122.1 (4)C17—C23—H23B109.5
C15—C14—C13120.8 (4)H23A—C23—H23B109.5
C15—C14—H14A119.6C17—C23—H23C109.5
C13—C14—H14A119.6H23A—C23—H23C109.5
C16—C15—C14120.8 (4)H23B—C23—H23C109.5
C16—C15—H15A119.6
C6—C1—C2—C3−0.9 (11)C8—C9—C10—N11−179.2 (3)
N7—C1—C2—C3178.4 (6)C8—C9—C10—C210.3 (5)
C6—C1—C2—C18−179.1 (6)C9—C10—N11—C120.3 (5)
N7—C1—C2—C180.2 (11)C21—C10—N11—C12−179.3 (3)
C1—C2—C3—C40.7 (12)C10—N11—C12—C13−92.5 (6)
C18—C2—C3—C4178.9 (8)C10—N11—C12—C1790.3 (6)
C2—C3—C4—C5−0.9 (14)C17—C12—C13—C14−2.5 (11)
C3—C4—C5—C61.2 (15)N11—C12—C13—C14−179.6 (6)
C2—C1—C6—C51.2 (10)C17—C12—C13—C22178.9 (6)
N7—C1—C6—C5−178.1 (6)N11—C12—C13—C221.8 (10)
C2—C1—C6—C19−179.9 (6)C12—C13—C14—C152.2 (12)
N7—C1—C6—C190.8 (10)C22—C13—C14—C15−179.3 (8)
C4—C5—C6—C1−1.4 (12)C13—C14—C15—C16−1.6 (14)
C4—C5—C6—C19179.8 (8)C14—C15—C16—C171.2 (14)
C6—C1—N7—C8−88.2 (6)C13—C12—C17—C162.1 (10)
C2—C1—N7—C892.5 (6)N11—C12—C17—C16179.2 (6)
C1—N7—C8—C9−0.8 (5)C13—C12—C17—C23−178.5 (6)
C1—N7—C8—C20178.1 (3)N11—C12—C17—C23−1.4 (9)
N7—C8—C9—C10179.4 (3)C15—C16—C17—C12−1.4 (11)
C20—C8—C9—C100.6 (5)C15—C16—C17—C23179.2 (7)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N11—H11···Cl11.01 (3)2.12 (3)3.115 (3)170 (3)
N7—H7···Cl1i1.00 (3)2.12 (3)3.110 (4)170 (3)

Symmetry codes: (i) x, y, z−1.

Footnotes

1This paper is dedicated to Professor Dr Dr mult. h.c. Herbert W. Roesky.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: FL2243).

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