(E,E)-N1,N2-Bis(2,6-difluoro­benzyl­idene)ethane-1,2-diamine

Khaledi Sardashti, M.; Kia, R.; Clegg, W.; Harrington, R.W.

doi:10.1107/S1600536811044692

organic compounds

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ISSN: 2056-9890

Volume 67| Part 11| November 2011| Page o3107

doi:10.1107/S1600536811044692

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(E,E)-N¹,N²-Bis(2,6-difluorobenzylidene)ethane-1,2-diamine

Mohammad Khaledi Sardashti,^a ^* Reza Kia,^b William Clegg ^c and Ross W. Harrington ^c

^aDepartment of Chemistry, Faculty of Science, Islamic Azad University, Shahrekord Branch, Box 166, Tehran, Iran, ^bDepartment of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran, and ^cSchool of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, England
^*Correspondence e-mail: khaledi1974@yahoo.com

(Received 24 October 2011; accepted 25 October 2011; online 29 October 2011)

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, P 2₁ /n
a = 7.3304 (10) Å
b = 10.5414 (15) Å
c = 9.2106 (13) Å
β = 105.487 (2)°
V = 685.89 (17) Å³
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[F² > 2σ(F²)] = 0.043
wR(F²) = 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

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) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

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 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811044692/su2335sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811044692/su2335Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811044692/su2335Isup3.cml

checkCIF report

Comment top

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].

Related literature top

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 top

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.

Computing details top

Data collection: SMART (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); 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 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	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.

(E,E)-N¹,N²-Bis(2,6- difluorobenzylidene)ethane-1,2-diamine top

Crystal data top

C₁₆H₁₂F₄N₂	F(000) = 316
M_r = 308.28	D_x = 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 top

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

Refinement top

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(F_o²) + (0.0646P)² + 0.2701P] where P = (F_o² + 2F_c²)/3
1203 reflections	(Δ/σ)_max < 0.001
100 parameters	Δρ_max = 0.27 e Å⁻³
0 restraints	Δρ_min = −0.23 e Å⁻³

Crystal data top

C₁₆H₁₂F₄N₂	V = 685.89 (17) Å³
M_r = 308.28	Z = 2
Monoclinic, P2₁/n	Mo Kα radiation
a = 7.3304 (10) Å	µ = 0.13 mm⁻¹
b = 10.5414 (15) Å	T = 150 K
c = 9.2106 (13) Å	0.34 × 0.30 × 0.10 mm
β = 105.487 (2)°

Data collection top

Bruker SMART 1K CCD area-detector diffractometer	1203 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2005)	1057 reflections with I > 2σ(I)
T_min = 0.958, T_max = 0.987	R_int = 0.031
4573 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.043	0 restraints
wR(F²) = 0.124	H-atom parameters constrained
S = 1.15	Δρ_max = 0.27 e Å⁻³
1203 reflections	Δρ_min = −0.23 e Å⁻³
100 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
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 (Å²) top

	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, º) top

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 code: (i) −x+1, −y+1, −z+2.

Hydrogen-bond geometry (Å, º) top

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

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

Experimental details

Crystal data
Chemical formula	C₁₆H₁₂F₄N₂
M_r	308.28
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	150
a, b, c (Å)	7.3304 (10), 10.5414 (15), 9.2106 (13)
β (°)	105.487 (2)
V (Å³)	685.89 (17)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.13
Crystal size (mm)	0.34 × 0.30 × 0.10

Data collection
Diffractometer	Bruker SMART 1K CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2005)
T_min, T_max	0.958, 0.987
No. of measured, independent and observed [I > 2σ(I)] reflections	4573, 1203, 1057
R_int	0.031
(sin θ/λ)_max (Å⁻¹)	0.594

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.043, 0.124, 1.15
No. of reflections	1203
No. of parameters	100
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.27, −0.23

Computer programs: SMART (Bruker, 2005), SAINT (Bruker, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

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) x−1/2, −y+1/2, z−1/2.

Acknowledgements

MK thanks the Islamic Azad University, Shahrkord Branch, for support of this work. WC and RWH thank the EPSRC (UK) for equipment funding.

References

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