organic compounds
N-[3-(2,6-Dimethylanilino)-1-methylbut-2-enylidene]-2,6-dimethylanilinium chloride†
aFacultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, Av. Pedro de Alba s/n, 66451 San Nicolás de los Garza, N. L., Mexico, and bCINVESTAV-Monterrey, Vía del conocimiento 201, PIIT. Autopista al Aeropuerto Km. 9.5, Apodaca, N. L. Mexico
*Correspondence e-mail: vjimenez@fcq.uanl.mx
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); Park (2007); Bourget-Merle et al. (2002); Nagendran & Roesky (2008); Holland & Tolman (2000); Stender et al. (2001); Carey et al., 2003. For W-shaped cations related to the title compound, see: Brownstein et al. (1983); Kuhn et al. (2000); Lesikar & Richards (2006).
Experimental
Crystal data
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Refinement
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Data collection: XSCANS (Siemens, 1996); cell XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97.
Supporting information
10.1107/S1600536809020571/fl2243sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809020571/fl2243Isup2.hkl
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).
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.
Data collection: XSCANS (Siemens, 1996); cell
XSCANS (Siemens, 1996); data reduction: XSCANS (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).C21H27N2+·Cl− | Dx = 1.094 Mg m−3 |
Mr = 342.90 | Mo Kα radiation, λ = 0.71073 Å |
Tetragonal, I41/a | Cell parameters from 77 reflections |
Hall symbol: -I 4ad | θ = 4.6–12.3° |
a = 28.639 (5) Å | µ = 0.19 mm−1 |
c = 10.150 (3) Å | T = 298 K |
V = 8325 (3) Å3 | Prism, colorless |
Z = 16 | 0.50 × 0.36 × 0.22 mm |
F(000) = 2944 |
Bruker P4 diffractometer | 1541 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.049 |
Graphite monochromator | θmax = 25.1°, θmin = 2.0° |
ω scans | h = −34→13 |
Absorption correction: ψ scan XSCANS (Siemens, 1996) | k = −34→1 |
Tmin = 0.854, Tmax = 0.959 | l = −12→12 |
7193 measured reflections | 3 standard reflections every 97 reflections |
3671 independent reflections | intensity decay: 1.5% |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.062 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.171 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.12 | w = 1/[σ2(Fo2) + (0.06P)2] where P = (Fo2 + 2Fc2)/3 |
3671 reflections | (Δ/σ)max < 0.001 |
229 parameters | Δρmax = 0.43 e Å−3 |
0 restraints | Δρmin = −0.32 e Å−3 |
0 constraints |
C21H27N2+·Cl− | Z = 16 |
Mr = 342.90 | Mo Kα radiation |
Tetragonal, I41/a | µ = 0.19 mm−1 |
a = 28.639 (5) Å | T = 298 K |
c = 10.150 (3) Å | 0.50 × 0.36 × 0.22 mm |
V = 8325 (3) Å3 |
Bruker P4 diffractometer | 1541 reflections with I > 2σ(I) |
Absorption correction: ψ scan XSCANS (Siemens, 1996) | Rint = 0.049 |
Tmin = 0.854, Tmax = 0.959 | 3 standard reflections every 97 reflections |
7193 measured reflections | intensity decay: 1.5% |
3671 independent reflections |
R[F2 > 2σ(F2)] = 0.062 | 0 restraints |
wR(F2) = 0.171 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.12 | Δρmax = 0.43 e Å−3 |
3671 reflections | Δρmin = −0.32 e Å−3 |
229 parameters |
x | y | z | Uiso*/Ueq | ||
Cl1 | 0.89962 (3) | 0.22980 (3) | 0.87464 (9) | 0.0839 (4) | |
C1 | 0.84317 (12) | 0.14527 (11) | 0.1392 (5) | 0.0623 (9) | |
C2 | 0.79611 (13) | 0.15570 (13) | 0.1335 (6) | 0.0824 (11) | |
C3 | 0.76486 (14) | 0.11910 (17) | 0.1272 (7) | 0.1044 (14) | |
H3A | 0.7330 | 0.1251 | 0.1223 | 0.125* | |
C4 | 0.78047 (16) | 0.07434 (16) | 0.1282 (8) | 0.1031 (13) | |
H4A | 0.7591 | 0.0499 | 0.1251 | 0.124* | |
C5 | 0.82605 (17) | 0.06477 (14) | 0.1334 (7) | 0.1001 (13) | |
H5A | 0.8360 | 0.0339 | 0.1322 | 0.120* | |
C6 | 0.85857 (13) | 0.10015 (13) | 0.1404 (6) | 0.0800 (12) | |
N7 | 0.87572 (10) | 0.18264 (10) | 0.1423 (4) | 0.0623 (8) | |
H7 | 0.8870 (13) | 0.1961 (13) | 0.057 (3) | 0.075* | |
C8 | 0.89275 (12) | 0.20174 (12) | 0.2519 (3) | 0.0528 (9) | |
C9 | 0.87894 (9) | 0.18619 (10) | 0.3745 (3) | 0.0565 (8) | |
H9A | 0.8571 | 0.1622 | 0.3753 | 0.068* | |
C10 | 0.89372 (12) | 0.20212 (12) | 0.4965 (3) | 0.0527 (9) | |
N11 | 0.87729 (10) | 0.18288 (10) | 0.6051 (3) | 0.0592 (8) | |
H11 | 0.8875 (13) | 0.1952 (12) | 0.693 (3) | 0.071* | |
C12 | 0.84451 (12) | 0.14556 (11) | 0.6106 (5) | 0.0589 (9) | |
C13 | 0.79765 (13) | 0.15614 (12) | 0.6194 (7) | 0.0801 (10) | |
C14 | 0.76658 (13) | 0.11931 (15) | 0.6254 (7) | 0.1053 (13) | |
H14A | 0.7347 | 0.1253 | 0.6284 | 0.126* | |
C15 | 0.78209 (15) | 0.07445 (14) | 0.6271 (7) | 0.0982 (12) | |
H15A | 0.7607 | 0.0501 | 0.6335 | 0.118* | |
C16 | 0.82809 (16) | 0.06482 (12) | 0.6197 (6) | 0.0886 (11) | |
H16A | 0.8380 | 0.0339 | 0.6192 | 0.106* | |
C17 | 0.86083 (12) | 0.10022 (12) | 0.6127 (6) | 0.0725 (10) | |
C18 | 0.78029 (14) | 0.20557 (14) | 0.1303 (8) | 0.144 (2) | |
H18A | 0.7929 | 0.2219 | 0.2049 | 0.217* | |
H18B | 0.7468 | 0.2067 | 0.1336 | 0.217* | |
H18C | 0.7910 | 0.2201 | 0.0506 | 0.217* | |
C19 | 0.90988 (14) | 0.08956 (14) | 0.1468 (7) | 0.130 (2) | |
H19A | 0.9144 | 0.0564 | 0.1496 | 0.195* | |
H19B | 0.9230 | 0.1035 | 0.2245 | 0.195* | |
H19C | 0.9251 | 0.1021 | 0.0702 | 0.195* | |
C20 | 0.92742 (11) | 0.23930 (11) | 0.2268 (3) | 0.0681 (10) | |
H20A | 0.9303 | 0.2443 | 0.1336 | 0.102* | |
H20B | 0.9572 | 0.2303 | 0.2622 | 0.102* | |
H20C | 0.9172 | 0.2676 | 0.2683 | 0.102* | |
C21 | 0.92784 (11) | 0.23993 (11) | 0.5203 (3) | 0.0685 (10) | |
H21A | 0.9306 | 0.2454 | 0.6134 | 0.103* | |
H21B | 0.9174 | 0.2680 | 0.4777 | 0.103* | |
H21C | 0.9577 | 0.2310 | 0.4854 | 0.103* | |
C22 | 0.78164 (14) | 0.20619 (14) | 0.6190 (8) | 0.1295 (17) | |
H22A | 0.7974 | 0.2230 | 0.6876 | 0.194* | |
H22B | 0.7486 | 0.2073 | 0.6338 | 0.194* | |
H22C | 0.7887 | 0.2201 | 0.5354 | 0.194* | |
C23 | 0.91199 (13) | 0.08983 (13) | 0.6062 (7) | 0.1174 (17) | |
H23A | 0.9168 | 0.0567 | 0.6127 | 0.176* | |
H23B | 0.9277 | 0.1052 | 0.6778 | 0.176* | |
H23C | 0.9244 | 0.1009 | 0.5241 | 0.176* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cl1 | 0.1080 (7) | 0.1037 (7) | 0.0400 (4) | −0.0103 (5) | −0.0002 (6) | 0.0004 (6) |
C1 | 0.077 (2) | 0.063 (2) | 0.047 (2) | −0.0056 (19) | −0.003 (2) | −0.007 (2) |
C2 | 0.084 (3) | 0.076 (2) | 0.087 (3) | −0.002 (2) | −0.023 (4) | −0.011 (4) |
C3 | 0.081 (3) | 0.119 (3) | 0.113 (3) | −0.013 (3) | −0.034 (5) | 0.002 (7) |
C4 | 0.106 (3) | 0.098 (3) | 0.105 (3) | −0.028 (3) | 0.000 (6) | 0.001 (6) |
C5 | 0.121 (3) | 0.075 (3) | 0.105 (3) | −0.007 (3) | 0.000 (5) | −0.023 (4) |
C6 | 0.089 (3) | 0.068 (2) | 0.083 (3) | −0.009 (2) | −0.006 (3) | −0.003 (3) |
N7 | 0.0791 (19) | 0.0624 (17) | 0.045 (2) | −0.0064 (15) | −0.0018 (18) | −0.0033 (18) |
C8 | 0.062 (2) | 0.054 (2) | 0.0422 (19) | 0.0017 (18) | −0.0027 (17) | −0.0015 (17) |
C9 | 0.0653 (18) | 0.0616 (18) | 0.0426 (15) | −0.0103 (14) | −0.0007 (19) | −0.0040 (19) |
C10 | 0.060 (2) | 0.052 (2) | 0.045 (2) | −0.0028 (17) | −0.0009 (17) | −0.0006 (17) |
N11 | 0.0787 (18) | 0.0613 (17) | 0.038 (2) | −0.0112 (14) | −0.0008 (17) | 0.0027 (16) |
C12 | 0.073 (2) | 0.064 (2) | 0.040 (2) | −0.0079 (19) | 0.006 (2) | 0.004 (2) |
C13 | 0.085 (3) | 0.072 (2) | 0.082 (3) | −0.009 (2) | 0.011 (4) | −0.001 (4) |
C14 | 0.078 (3) | 0.106 (3) | 0.132 (4) | −0.013 (3) | 0.007 (5) | 0.015 (7) |
C15 | 0.105 (3) | 0.082 (3) | 0.107 (3) | −0.021 (2) | 0.025 (5) | 0.011 (5) |
C16 | 0.118 (3) | 0.068 (2) | 0.079 (3) | −0.007 (2) | 0.009 (5) | −0.005 (4) |
C17 | 0.084 (2) | 0.066 (2) | 0.067 (3) | −0.007 (2) | −0.006 (3) | 0.011 (3) |
C18 | 0.108 (3) | 0.104 (3) | 0.221 (6) | 0.025 (3) | −0.046 (7) | −0.006 (7) |
C19 | 0.103 (3) | 0.092 (3) | 0.194 (6) | 0.016 (2) | −0.004 (5) | −0.012 (5) |
C20 | 0.087 (2) | 0.070 (2) | 0.0476 (18) | −0.017 (2) | 0.010 (2) | 0.0013 (17) |
C21 | 0.083 (2) | 0.072 (2) | 0.0499 (19) | −0.013 (2) | −0.006 (2) | 0.0015 (18) |
C22 | 0.103 (3) | 0.095 (3) | 0.190 (5) | 0.017 (2) | 0.028 (7) | −0.001 (6) |
C23 | 0.096 (3) | 0.092 (3) | 0.164 (5) | 0.013 (2) | −0.022 (4) | 0.006 (4) |
C1—C6 | 1.366 (4) | C14—C15 | 1.360 (5) |
C1—C2 | 1.382 (5) | C14—H14A | 0.9300 |
C1—N7 | 1.419 (4) | C15—C16 | 1.348 (5) |
C2—C3 | 1.380 (5) | C15—H15A | 0.9300 |
C2—C18 | 1.499 (5) | C16—C17 | 1.383 (4) |
C3—C4 | 1.358 (5) | C16—H16A | 0.9300 |
C3—H3A | 0.9300 | C17—C23 | 1.497 (4) |
C4—C5 | 1.335 (5) | C18—H18A | 0.9600 |
C4—H4A | 0.9300 | C18—H18B | 0.9600 |
C5—C6 | 1.378 (5) | C18—H18C | 0.9600 |
C5—H5A | 0.9300 | C19—H19A | 0.9600 |
C6—C19 | 1.502 (5) | C19—H19B | 0.9600 |
N7—C8 | 1.332 (4) | C19—H19C | 0.9600 |
N7—H7 | 1.00 (3) | C20—H20A | 0.9600 |
C8—C9 | 1.379 (4) | C20—H20B | 0.9600 |
C8—C20 | 1.486 (4) | C20—H20C | 0.9600 |
C9—C10 | 1.386 (4) | C21—H21A | 0.9600 |
C9—H9A | 0.9300 | C21—H21B | 0.9600 |
C10—N11 | 1.319 (4) | C21—H21C | 0.9600 |
C10—C21 | 1.479 (4) | C22—H22A | 0.9600 |
N11—C12 | 1.424 (4) | C22—H22B | 0.9600 |
N11—H11 | 1.01 (3) | C22—H22C | 0.9600 |
C12—C13 | 1.379 (4) | C23—H23A | 0.9600 |
C12—C17 | 1.380 (4) | C23—H23B | 0.9600 |
C13—C14 | 1.381 (5) | C23—H23C | 0.9600 |
C13—C22 | 1.505 (5) | ||
C6—C1—C2 | 121.3 (3) | C14—C15—H15A | 119.6 |
C6—C1—N7 | 120.1 (3) | C15—C16—C17 | 121.0 (4) |
C2—C1—N7 | 118.6 (3) | C15—C16—H16A | 119.5 |
C3—C2—C1 | 118.1 (3) | C17—C16—H16A | 119.5 |
C3—C2—C18 | 121.8 (4) | C12—C17—C16 | 117.4 (3) |
C1—C2—C18 | 120.1 (3) | C12—C17—C23 | 121.2 (3) |
C4—C3—C2 | 120.2 (4) | C16—C17—C23 | 121.4 (3) |
C4—C3—H3A | 119.9 | C2—C18—H18A | 109.5 |
C2—C3—H3A | 119.9 | C2—C18—H18B | 109.5 |
C5—C4—C3 | 121.1 (4) | H18A—C18—H18B | 109.5 |
C5—C4—H4A | 119.5 | C2—C18—H18C | 109.5 |
C3—C4—H4A | 119.5 | H18A—C18—H18C | 109.5 |
C4—C5—C6 | 120.8 (4) | H18B—C18—H18C | 109.5 |
C4—C5—H5A | 119.6 | C6—C19—H19A | 109.5 |
C6—C5—H5A | 119.6 | C6—C19—H19B | 109.5 |
C1—C6—C5 | 118.5 (4) | H19A—C19—H19B | 109.5 |
C1—C6—C19 | 120.5 (3) | C6—C19—H19C | 109.5 |
C5—C6—C19 | 121.0 (4) | H19A—C19—H19C | 109.5 |
C8—N7—C1 | 124.6 (4) | H19B—C19—H19C | 109.5 |
C8—N7—H7 | 117 (2) | C8—C20—H20A | 109.5 |
C1—N7—H7 | 119 (2) | C8—C20—H20B | 109.5 |
N7—C8—C9 | 121.0 (3) | H20A—C20—H20B | 109.5 |
N7—C8—C20 | 113.5 (3) | C8—C20—H20C | 109.5 |
C9—C8—C20 | 125.5 (3) | H20A—C20—H20C | 109.5 |
C8—C9—C10 | 127.7 (3) | H20B—C20—H20C | 109.5 |
C8—C9—H9A | 116.1 | C10—C21—H21A | 109.5 |
C10—C9—H9A | 116.1 | C10—C21—H21B | 109.5 |
N11—C10—C9 | 120.0 (3) | H21A—C21—H21B | 109.5 |
N11—C10—C21 | 113.9 (3) | C10—C21—H21C | 109.5 |
C9—C10—C21 | 126.1 (3) | H21A—C21—H21C | 109.5 |
C10—N11—C12 | 125.6 (4) | H21B—C21—H21C | 109.5 |
C10—N11—H11 | 120 (2) | C13—C22—H22A | 109.5 |
C12—N11—H11 | 115 (2) | C13—C22—H22B | 109.5 |
C13—C12—C17 | 122.4 (3) | H22A—C22—H22B | 109.5 |
C13—C12—N11 | 118.6 (3) | C13—C22—H22C | 109.5 |
C17—C12—N11 | 118.9 (3) | H22A—C22—H22C | 109.5 |
C12—C13—C14 | 117.5 (3) | H22B—C22—H22C | 109.5 |
C12—C13—C22 | 120.4 (3) | C17—C23—H23A | 109.5 |
C14—C13—C22 | 122.1 (4) | C17—C23—H23B | 109.5 |
C15—C14—C13 | 120.8 (4) | H23A—C23—H23B | 109.5 |
C15—C14—H14A | 119.6 | C17—C23—H23C | 109.5 |
C13—C14—H14A | 119.6 | H23A—C23—H23C | 109.5 |
C16—C15—C14 | 120.8 (4) | H23B—C23—H23C | 109.5 |
C16—C15—H15A | 119.6 | ||
C6—C1—C2—C3 | −0.9 (11) | C8—C9—C10—N11 | −179.2 (3) |
N7—C1—C2—C3 | 178.4 (6) | C8—C9—C10—C21 | 0.3 (5) |
C6—C1—C2—C18 | −179.1 (6) | C9—C10—N11—C12 | 0.3 (5) |
N7—C1—C2—C18 | 0.2 (11) | C21—C10—N11—C12 | −179.3 (3) |
C1—C2—C3—C4 | 0.7 (12) | C10—N11—C12—C13 | −92.5 (6) |
C18—C2—C3—C4 | 178.9 (8) | C10—N11—C12—C17 | 90.3 (6) |
C2—C3—C4—C5 | −0.9 (14) | C17—C12—C13—C14 | −2.5 (11) |
C3—C4—C5—C6 | 1.2 (15) | N11—C12—C13—C14 | −179.6 (6) |
C2—C1—C6—C5 | 1.2 (10) | C17—C12—C13—C22 | 178.9 (6) |
N7—C1—C6—C5 | −178.1 (6) | N11—C12—C13—C22 | 1.8 (10) |
C2—C1—C6—C19 | −179.9 (6) | C12—C13—C14—C15 | 2.2 (12) |
N7—C1—C6—C19 | 0.8 (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—C19 | 179.8 (8) | C14—C15—C16—C17 | 1.2 (14) |
C6—C1—N7—C8 | −88.2 (6) | C13—C12—C17—C16 | 2.1 (10) |
C2—C1—N7—C8 | 92.5 (6) | N11—C12—C17—C16 | 179.2 (6) |
C1—N7—C8—C9 | −0.8 (5) | C13—C12—C17—C23 | −178.5 (6) |
C1—N7—C8—C20 | 178.1 (3) | N11—C12—C17—C23 | −1.4 (9) |
N7—C8—C9—C10 | 179.4 (3) | C15—C16—C17—C12 | −1.4 (11) |
C20—C8—C9—C10 | 0.6 (5) | C15—C16—C17—C23 | 179.2 (7) |
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11···Cl1 | 1.01 (3) | 2.12 (3) | 3.115 (3) | 170 (3) |
N7—H7···Cl1i | 1.00 (3) | 2.12 (3) | 3.110 (4) | 170 (3) |
Symmetry code: (i) x, y, z−1. |
Experimental details
Crystal data | |
Chemical formula | C21H27N2+·Cl− |
Mr | 342.90 |
Crystal system, space group | Tetragonal, I41/a |
Temperature (K) | 298 |
a, c (Å) | 28.639 (5), 10.150 (3) |
V (Å3) | 8325 (3) |
Z | 16 |
Radiation type | Mo Kα |
µ (mm−1) | 0.19 |
Crystal size (mm) | 0.50 × 0.36 × 0.22 |
Data collection | |
Diffractometer | Bruker P4 diffractometer |
Absorption correction | ψ scan XSCANS (Siemens, 1996) |
Tmin, Tmax | 0.854, 0.959 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7193, 3671, 1541 |
Rint | 0.049 |
(sin θ/λ)max (Å−1) | 0.596 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.062, 0.171, 1.12 |
No. of reflections | 3671 |
No. of parameters | 229 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.43, −0.32 |
Computer programs: XSCANS (Siemens, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2006).
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11···Cl1 | 1.01 (3) | 2.12 (3) | 3.115 (3) | 170 (3) |
N7—H7···Cl1i | 1.00 (3) | 2.12 (3) | 3.110 (4) | 170 (3) |
Symmetry code: (i) x, y, z−1. |
Footnotes
†This paper is dedicated to Professor Dr Dr mult. h.c. Herbert W. Roesky.
Acknowledgements
This work was supported by PROMEP (Programa de Mejoramiento del Profesorado), grant No. 103.5/08/3125.
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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.