(E,E)-N ¹,N ²-Bis(2,6-difluoro­benzyl­idene)ethane-1,2-diamine

Abstract

The asymmetric unit of the title compound, C₁₆H₁₂F₄N₂, comprises half of the potentially bidentate Schiff base ligand, with an inversion centre located at the mid-point of the central C—C bond. The crystal packing is stabilized by inter­molecular C—H⋯N and π–π inter­actions [centroid–centroid distance = 3.6793 (12) Å and inter­planar spacing = 3.4999 (7) Å].

Related literature

For background to the synthesis and structural variations of Schiff base ligands and their complexes, see: Granovski et al. (1993 ▶); Elmali et al. (2000 ▶).

Experimental

Crystal data

• C₁₆H₁₂F₄N₂

• M _r = 308.28

• Monoclinic,

• a = 7.3304 (10) Å

• b = 10.5414 (15) Å

• c = 9.2106 (13) Å

• β = 105.487 (2)°

• V = 685.89 (17) ų

• Z = 2

• Mo Kα radiation

• μ = 0.13 mm⁻¹

• T = 150 K

• 0.34 × 0.30 × 0.10 mm

Data collection

• Bruker SMART 1K CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.958, T _max = 0.987

• 4573 measured reflections

• 1203 independent reflections

• 1057 reflections with I > 2σ(I)

• R _int = 0.031

Refinement

• R[F ² > 2σ(F ²)] = 0.043

• wR(F ²) = 0.124

• S = 1.15

• 1203 reflections

• 100 parameters

• H-atom parameters constrained

• Δρ_max = 0.27 e Å⁻³

• Δρ_min = −0.23 e Å⁻³

Data collection: SMART (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); 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: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Supplementary material file. DOI: 10.1107/S1600536811044692/su2335Isup3.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
C5—H5⋯N1i	0.95	2.53	3.471 (2)	171

Symmetry code: (i) .

supplementary crystallographic information

Comment

Schiff base ligands are among the most prevalent ligands in the field of coordination chemistry. Metal derivatives of Schiff bases have been studied extensively, and Ni^II and Cu^II complexes play a major role in both synthetic and structural research (Elmali et al., 2000; Granovski et al., 1993).

The asymmetric unit of the title compound comprises half of the potentially bidentate Schiff base ligand; an inversion centre is located in the middle of the central C—C bond (Fig. 1). Each half of the molecule is essentially planar, the imine segment (C1—N1═C2—C3) being rotated only 7.36 (10)° out of the plane of the benzene ring. The two halves are parallel by inversion symmetry, but not coplanar, the CH₂CH₂ linker unit forming a step between them.

The crystal packing is stabilized by intermolecular C—H···N interactions (see Table 1), which generate sheets parallel to (1 0 -1), and by intermolecular π-π interactions [centroid-centroid distance = 3.6793 (12) Å, interplanar separation = 3.4999 (7) Å, the two planes are strictly parallel by inversion symmetry].

Experimental

The title compound was synthesized by mixing 2,4-difluorobenzaldehyde (4 mmol) and ethylenediamine (2 mmol) in chloroform (20 ml). After stirring for 2 h, the solution was filtered and the resulting yellow solid was crystallized from ethanol, giving single crystals suitable for X-ray diffraction.

Refinement

All H atoms were positioned geometrically and constrained to ride on the parent atoms, with C—H = 0.95–0.99Å and U_iso(H) = 1.2 U_eq(C).

Figures

Fig. 1.

The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering. Symmetry code for suffix A: -x + 1, -y + 1, -z + 2.

Fig. 2.

The crystal packing, viewed down the a axis, showing linking of molecules through the intermolecular C—H···N hydrogen bonds to form sheets in the (1 0 - 1) plane. The dashed lines represent these intermolecular interactions.

Crystal data

C16H12F4N2	F(000) = 316
Mr = 308.28	Dx = 1.493 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 4055 reflections
a = 7.3304 (10) Å	θ = 2.9–28.3°
b = 10.5414 (15) Å	µ = 0.13 mm−1
c = 9.2106 (13) Å	T = 150 K
β = 105.487 (2)°	Plate, yellow
V = 685.89 (17) Å3	0.34 × 0.30 × 0.10 mm
Z = 2

Data collection

Bruker SMART 1K CCD area-detector diffractometer	1203 independent reflections
Radiation source: fine-focus sealed tube	1057 reflections with I > 2σ(I)
graphite	Rint = 0.031
Detector resolution: 8.33 pixels mm-1	θmax = 25.0°, θmin = 3.0°
ω scans	h = −8→8
Absorption correction: multi-scan (SADABS; Bruker, 2005)	k = −12→12
Tmin = 0.958, Tmax = 0.987	l = −10→10
4573 measured reflections

Refinement

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)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.124	H-atom parameters constrained
S = 1.15	w = 1/[σ2(Fo2) + (0.0646P)2 + 0.2701P] where P = (Fo2 + 2Fc2)/3
1203 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.27 e Å−3
0 restraints	Δρmin = −0.23 e Å−3

Special details

Experimental. The low-temperature data were collected with the Oxford Cyrosystems Cryostream low-temperature attachment.

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.

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 (Ų)

	x	y	z	Uiso*/Ueq
F1	0.24616 (17)	0.28505 (10)	0.59397 (12)	0.0409 (4)
F2	0.29841 (19)	0.71120 (10)	0.45850 (14)	0.0434 (4)
N1	0.4481 (2)	0.46153 (14)	0.79618 (16)	0.0297 (4)
C1	0.5503 (3)	0.51558 (19)	0.9411 (2)	0.0334 (5)
H1A	0.5590	0.6088	0.9317	0.040*
H1B	0.6805	0.4809	0.9717	0.040*
C2	0.3868 (2)	0.53796 (16)	0.6894 (2)	0.0277 (4)
H2	0.4123	0.6256	0.7087	0.033*
C3	0.2783 (2)	0.50109 (15)	0.53673 (18)	0.0244 (4)
C4	0.2091 (2)	0.37948 (16)	0.49141 (19)	0.0272 (4)
C5	0.1031 (2)	0.35046 (18)	0.3480 (2)	0.0311 (5)
H5	0.0594	0.2664	0.3225	0.037*
C6	0.0615 (3)	0.44634 (19)	0.2419 (2)	0.0332 (5)
H6	−0.0123	0.4279	0.1426	0.040*
C7	0.1257 (3)	0.56853 (19)	0.2780 (2)	0.0330 (5)
H7	0.0974	0.6345	0.2052	0.040*
C8	0.2317 (2)	0.59168 (16)	0.4228 (2)	0.0287 (4)

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
F1	0.0569 (8)	0.0217 (6)	0.0346 (6)	−0.0067 (5)	−0.0046 (5)	0.0054 (4)
F2	0.0677 (8)	0.0190 (6)	0.0419 (7)	0.0003 (5)	0.0118 (6)	0.0036 (5)
N1	0.0339 (8)	0.0273 (8)	0.0247 (8)	0.0032 (6)	0.0022 (6)	−0.0038 (6)
C1	0.0331 (10)	0.0355 (10)	0.0280 (10)	−0.0021 (8)	0.0020 (8)	−0.0042 (8)
C2	0.0331 (9)	0.0210 (9)	0.0287 (9)	−0.0031 (7)	0.0077 (7)	−0.0021 (7)
C3	0.0259 (8)	0.0230 (9)	0.0248 (9)	0.0035 (7)	0.0075 (7)	−0.0012 (7)
C4	0.0306 (9)	0.0228 (9)	0.0271 (9)	0.0030 (7)	0.0059 (7)	0.0027 (7)
C5	0.0312 (9)	0.0292 (10)	0.0308 (10)	−0.0017 (7)	0.0044 (8)	−0.0059 (7)
C6	0.0300 (9)	0.0421 (11)	0.0251 (9)	0.0044 (8)	0.0032 (7)	−0.0014 (8)
C7	0.0370 (10)	0.0349 (10)	0.0278 (10)	0.0101 (8)	0.0098 (8)	0.0082 (8)
C8	0.0357 (10)	0.0198 (9)	0.0324 (10)	0.0042 (7)	0.0124 (8)	0.0007 (7)

Geometric parameters (Å, °)

F1—C4	1.349 (2)	C3—C8	1.392 (2)
F2—C8	1.360 (2)	C3—C4	1.401 (3)
N1—C2	1.258 (2)	C4—C5	1.376 (3)
N1—C1	1.461 (2)	C5—C6	1.382 (3)
C1—C1i	1.502 (4)	C5—H5	0.950
C1—H1A	0.990	C6—C7	1.381 (3)
C1—H1B	0.990	C6—H6	0.950
C2—C3	1.471 (2)	C7—C8	1.374 (3)
C2—H2	0.950	C7—H7	0.950
C2—N1—C1	116.98 (16)	F1—C4—C3	118.52 (15)
N1—C1—C1i	110.12 (19)	C5—C4—C3	123.79 (16)
N1—C1—H1A	109.6	C4—C5—C6	118.53 (17)
C1i—C1—H1A	109.6	C4—C5—H5	120.7
N1—C1—H1B	109.6	C6—C5—H5	120.7
C1i—C1—H1B	109.6	C7—C6—C5	120.98 (17)
H1A—C1—H1B	108.1	C7—C6—H6	119.5
N1—C2—C3	124.56 (16)	C5—C6—H6	119.5
N1—C2—H2	117.7	C8—C7—C6	117.89 (18)
C3—C2—H2	117.7	C8—C7—H7	121.1
C8—C3—C4	114.00 (15)	C6—C7—H7	121.1
C8—C3—C2	120.03 (15)	F2—C8—C7	118.23 (17)
C4—C3—C2	125.95 (15)	F2—C8—C3	116.95 (16)
F1—C4—C5	117.69 (16)	C7—C8—C3	124.81 (17)
C2—N1—C1—C1i	119.1 (2)	C3—C4—C5—C6	−0.1 (3)
C1—N1—C2—C3	−178.90 (15)	C4—C5—C6—C7	0.4 (3)
N1—C2—C3—C8	−174.14 (17)	C5—C6—C7—C8	−0.1 (3)
N1—C2—C3—C4	7.6 (3)	C6—C7—C8—F2	178.75 (15)
C8—C3—C4—F1	−179.76 (15)	C6—C7—C8—C3	−0.6 (3)
C2—C3—C4—F1	−1.4 (3)	C4—C3—C8—F2	−178.50 (14)
C8—C3—C4—C5	−0.5 (3)	C2—C3—C8—F2	3.0 (2)
C2—C3—C4—C5	177.93 (16)	C4—C3—C8—C7	0.8 (3)
F1—C4—C5—C6	179.17 (15)	C2—C3—C8—C7	−177.67 (16)

Symmetry codes: (i) −x+1, −y+1, −z+2.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···N1ii	0.95	2.53	3.471 (2)	171

Symmetry codes: (ii) x−1/2, −y+1/2, z−1/2.