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The title mol­ecule, C20H24N2, is centrosymmetric, crystallizing with the –N=C(CH3)—C(CH3)=N– diimino group in a trans configuration. The crystal structure is stabilized by an intra­molecular C—H...N hydrogen-bonding inter­action.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807049367/om2165sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807049367/om2165Isup2.hkl
Contains datablock I

CCDC reference: 672819

Key indicators

  • Single-crystal X-ray study
  • T = 295 K
  • Mean [sigma](C-C)= 0.002 Å
  • R factor = 0.042
  • wR factor = 0.131
  • Data-to-parameter ratio = 15.1

checkCIF/PLATON results

No syntax errors found


No errors found in this datablock

Comment top

Coordinated 1,4-diaza-1,3-butadiene groups have attracted much interest in relation to their electron donor and acceptor properties (Van Koten & Vrieze, 1982; Vrieze et al., 1987) and, more recently, due to their application to olefin homo- and co- polymerizations [Brookhart et al., 2000].

The present communication describes the chief characteristics of 2,3-bis(2-ethylphenylimino)butane, Scheme 1. The molecule is centrosymmetric, crystallizing with the diimino group –N=C(CH3)-C(CH3)=N– in a trans configuration, Fig. 1.

The carbon and nitrogen atoms in the –N=C(CH3)-C(CH3)=N– moiety present bond lengths of 1.2780 (16) Å for C9=N1, 1.4279 (17) Å for C8—N1, and 1.514 (2) Å for C9—C9i [Symmetry code: (i)= -x,-y + 1,-z]. These values are in good agreement with the distances found in the recently reported crystalline structure of the compound 2,3-bis(2-trifluoromethyl- phenylimino)butane in which the following bond lengths were observed: 1.423 (3) Å for C—N, 1.280 (3) Å for C=N, and 1.513 (4) Å for C—C (Bomfim et al., 2007). The isolated molecules show intramolecular non-classical hydrogen bonds including the nitrogen atom (N1) of the –N=C(CH3)-C(CH3)=N– moiety as acceptor, (Fig. 1). The C9—H9B···N1 distance is 2.885 (2) Å and the angle is 102° (Spek, 2003).

The observed torsion angles are -4.4 (2)° for C10—C9—N1—C8, -9.0 (2)° for N1—C8—C3—C2, 115.32 (15)° for C9—N1—C8—C3, and -86.88 (19)° for C8—C3—C2—C1. These values can be considered as consequence of the intramolecular interaction described above. The observed deviations between the C8/N1/C9/C10 and C3/C4/C5/C6/C7/C8 planes [70,8(1)°] can be related to steric factors because the presence of the ethyl groups in the phenyl rings. This kind of deviation was also observed in the crystalline structure of the similar compound 2,3-bis(2-tert-butylphenylimino)butane, 69.6 (1)° (Ferreira et al., 2006).

Related literature top

For related literature, see: Brookhart et al. (2000); Bomfim et al.. (2007); Ferreira et al. (2006); Van Koten & Vrieze (1982); Vrieze et al. (1987). Hydrogen-bond calculations were carried out using PLATON (Spek, 2003).

Experimental top

To a solution of 3.72 g (40 mmol) of aniline in 40 ml of dichloromethane, were added 1.29 g (15 mmol) of 2,3-butanedione and a catalytic amount of p-toluene sulfonic acid. The mixture was heated under reflux for 24 h, after which the reaction mixture was cooled to room temperature and filtered. After removing the solvent under reduced pressure, the product was precipitated with cold methanol. The product was filtered and washed with cold ethanol (5 x 10 ml). X-ray diffraction quality crystals were obtained by recrystallization from a methanol/ethanol (1:1) mixture. The diimine was obtained as yellow crystals. Yield: 70%; Mp: 367 K; The compound was characterized by 1H, 13C NMR spectroscopy and infrared spectroscopy.

Refinement top

The hydrogen atoms were fixed geometrically and allowed to ride on their parent atoms; the carbon rings and their respective atoms have been refined with C—H of 0.93 Å and Uiso(H) = 1.2 Ueq(Csp2)·The hydrogen atoms of the methyl group hydrogen atoms were fixed geometrically at a distance of 0.96 Å and refined with Uiso(H) = 1.5Ueq(Csp3).

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: PHICHI (Duisenberg et al., 2000); data reduction: DIRAX (Duisenberg, 1992); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. ORTEP of the title compound with thermal parameters at a level of 50% probability. [Symmetry code: (i) = -x, -y + 1, -z]. In addition, intramolecular interactions are shown.
2,3-Bis(2-ethylphenylimino)butane top
Crystal data top
C20H24N2Z = 2
Mr = 292.41F(000) = 316
Monoclinic, P21/nDx = 1.106 Mg m3
Hall symbol: -P 2ynMo Kα radiation, λ = 0.71073 Å
a = 7.1898 (14) Åθ = 1–27.5°
b = 8.3807 (17) ŵ = 0.07 mm1
c = 14.784 (3) ÅT = 295 K
β = 99.76 (3)°Block, yellow
V = 877.9 (3) Å30.59 × 0.42 × 0.20 mm
Data collection top
Nonius KappaCCD
diffractometer
1295 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.032
Graphite monochromatorθmax = 25.0°, θmin = 2.8°
ϕ scans, and ω scans with κh = 88
14591 measured reflectionsk = 99
1541 independent reflectionsl = 1717
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.042Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.131H-atom parameters constrained
S = 1.11 w = 1/[σ2(Fo2) + (0.0709P)2 + 0.1453P]
where P = (Fo2 + 2Fc2)/3
1541 reflections(Δ/σ)max < 0.001
102 parametersΔρmax = 0.17 e Å3
0 restraintsΔρmin = 0.15 e Å3
Crystal data top
C20H24N2V = 877.9 (3) Å3
Mr = 292.41Z = 2
Monoclinic, P21/nMo Kα radiation
a = 7.1898 (14) ŵ = 0.07 mm1
b = 8.3807 (17) ÅT = 295 K
c = 14.784 (3) Å0.59 × 0.42 × 0.20 mm
β = 99.76 (3)°
Data collection top
Nonius KappaCCD
diffractometer
1295 reflections with I > 2σ(I)
14591 measured reflectionsRint = 0.032
1541 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0420 restraints
wR(F2) = 0.131H-atom parameters constrained
S = 1.11Δρmax = 0.17 e Å3
1541 reflectionsΔρmin = 0.15 e Å3
102 parameters
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

- 4.2173 (0.0061) x + 6.2054 (0.0072) y - 3.3116 (0.0107) z = 3.1390 (0.0047)

* -0.0075 (0.0003) C1 * 0.0171 (0.0008) N1 * -0.0170 (0.0008) C7 * 0.0074 (0.0003) C8

Rms deviation of fitted atoms = 0.0132

4.1020 (0.0043) x + 6.1247 (0.0048) y - 6.8890 (0.0086) z = 2.4256 (0.0042)

Angle to previous plane (with approximate e.s.d.) = 70.77 (0.06)

* 0.0027 (0.0010) C1 * -0.0047 (0.0010) C2 * 0.0029 (0.0010) C3 * 0.0010 (0.0011) C4 * -0.0031 (0.0011) C5 * 0.0012 (0.0011) C6

Rms deviation of fitted atoms = 0.0029

- 2.2590 (0.0157) x + 5.3706 (0.0113) y + 10.9924 (0.0126) z = 6.6238 (0.0055)

Angle to previous plane (with approximate e.s.d.) = 88.48 (0.10)

* 0.0000 (0.0000) C2 * 0.0000 (0.0000) C9 * 0.0000 (0.0000) C10

Rms deviation of fitted atoms = 0.0000

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C10.00541 (18)0.61257 (16)0.19534 (8)0.0418 (3)
C20.11601 (18)0.72533 (17)0.22436 (9)0.0453 (4)
C30.0656 (2)0.79142 (18)0.31205 (9)0.0525 (4)
H30.14390.86730.33200.063*
C40.0974 (2)0.74664 (19)0.36952 (9)0.0574 (4)
H40.12800.79170.42760.069*
C50.2150 (2)0.6345 (2)0.34047 (10)0.0606 (4)
H50.32480.60360.37920.073*
C60.1701 (2)0.56783 (19)0.25387 (10)0.0542 (4)
H60.25030.49280.23460.065*
C70.03553 (16)0.54972 (15)0.04211 (8)0.0388 (3)
C80.1974 (2)0.6616 (2)0.03814 (10)0.0566 (4)
H8A0.21240.73170.09020.085*
H8B0.17210.72330.01730.085*
H8C0.31110.60110.03900.085*
C90.2913 (2)0.7804 (2)0.16144 (12)0.0681 (5)
H9A0.38510.81220.19790.082*
H9B0.34290.69230.12250.082*
C100.2522 (3)0.9194 (3)0.10155 (13)0.0905 (7)
H10A0.20311.00750.13980.136*
H10B0.36720.95090.06280.136*
H10C0.16160.88770.06420.136*
N10.05162 (15)0.53221 (14)0.10996 (7)0.0434 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0463 (7)0.0458 (7)0.0351 (7)0.0058 (5)0.0123 (5)0.0023 (5)
C20.0473 (7)0.0491 (8)0.0422 (7)0.0015 (6)0.0155 (6)0.0036 (6)
C30.0656 (9)0.0501 (8)0.0455 (8)0.0015 (7)0.0205 (7)0.0081 (6)
C40.0792 (10)0.0572 (9)0.0364 (7)0.0109 (8)0.0112 (7)0.0061 (6)
C50.0645 (9)0.0701 (10)0.0435 (8)0.0023 (8)0.0013 (7)0.0013 (7)
C60.0555 (8)0.0607 (9)0.0465 (8)0.0102 (7)0.0087 (6)0.0034 (7)
C70.0390 (6)0.0410 (7)0.0370 (6)0.0026 (5)0.0076 (5)0.0020 (5)
C80.0607 (9)0.0634 (9)0.0480 (8)0.0185 (7)0.0155 (6)0.0104 (7)
C90.0516 (8)0.0871 (12)0.0645 (10)0.0169 (8)0.0069 (7)0.0202 (9)
C100.1110 (16)0.0836 (14)0.0669 (11)0.0429 (12)0.0134 (11)0.0018 (10)
N10.0452 (6)0.0483 (7)0.0382 (6)0.0015 (5)0.0112 (5)0.0064 (5)
Geometric parameters (Å, º) top
C1—C61.394 (2)C7—N11.2780 (16)
C1—C21.4023 (19)C7—C81.5032 (19)
C1—N11.4280 (16)C7—C7i1.513 (2)
C2—C31.3998 (19)C8—H8A0.9600
C2—C91.506 (2)C8—H8B0.9600
C3—C41.378 (2)C8—H8C0.9600
C3—H30.9300C9—C101.518 (3)
C4—C51.381 (2)C9—H9A0.9700
C4—H40.9300C9—H9B0.9700
C5—C61.384 (2)C10—H10A0.9600
C5—H50.9300C10—H10B0.9600
C6—H60.9300C10—H10C0.9600
C6—C1—C2119.91 (12)C8—C7—C7i117.84 (13)
C6—C1—N1120.54 (12)C7—C8—H8A109.5
C2—C1—N1119.20 (12)C7—C8—H8B109.5
C3—C2—C1118.23 (13)H8A—C8—H8B109.5
C3—C2—C9120.60 (13)C7—C8—H8C109.5
C1—C2—C9121.10 (12)H8A—C8—H8C109.5
C4—C3—C2121.54 (14)H8B—C8—H8C109.5
C4—C3—H3119.2C2—C9—C10112.15 (15)
C2—C3—H3119.2C2—C9—H9A109.2
C3—C4—C5119.69 (13)C10—C9—H9A109.2
C3—C4—H4120.2C2—C9—H9B109.2
C5—C4—H4120.2C10—C9—H9B109.2
C4—C5—C6120.22 (14)H9A—C9—H9B107.9
C4—C5—H5119.9C9—C10—H10A109.5
C6—C5—H5119.9C9—C10—H10B109.5
C5—C6—C1120.39 (14)H10A—C10—H10B109.5
C5—C6—H6119.8C9—C10—H10C109.5
C1—C6—H6119.8H10A—C10—H10C109.5
N1—C7—C8126.02 (12)H10B—C10—H10C109.5
N1—C7—C7i116.13 (13)C7—N1—C1122.28 (11)
C6—C1—C2—C30.8 (2)C2—C1—C6—C50.2 (2)
N1—C1—C2—C3173.99 (12)N1—C1—C6—C5173.36 (13)
C6—C1—C2—C9177.77 (14)C3—C2—C9—C1090.00 (18)
N1—C1—C2—C99.0 (2)C1—C2—C9—C1086.93 (19)
C1—C2—C3—C40.8 (2)C8—C7—N1—C14.4 (2)
C9—C2—C3—C4177.81 (14)C7i—C7—N1—C1176.99 (13)
C2—C3—C4—C50.3 (2)C6—C1—N1—C771.49 (18)
C3—C4—C5—C60.3 (2)C2—C1—N1—C7115.32 (14)
C4—C5—C6—C10.3 (2)
Symmetry code: (i) x, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C9—H9B···N10.972.522.885 (2)102

Experimental details

Crystal data
Chemical formulaC20H24N2
Mr292.41
Crystal system, space groupMonoclinic, P21/n
Temperature (K)295
a, b, c (Å)7.1898 (14), 8.3807 (17), 14.784 (3)
β (°) 99.76 (3)
V3)877.9 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.07
Crystal size (mm)0.59 × 0.42 × 0.20
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
14591, 1541, 1295
Rint0.032
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.131, 1.11
No. of reflections1541
No. of parameters102
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.17, 0.15

Computer programs: COLLECT (Nonius, 1998), PHICHI (Duisenberg et al., 2000), DIRAX (Duisenberg, 1992), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C9—H9B···N10.972.522.885 (2)102
 

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