N,N′-Bis(3-chloro-2-fluoro­benzyl­idene)ethane-1,2-diamine

The mol­ecule of the title centrosymmetric Schiff base compound, C₁₆H₁₂Cl₂F₂N₂, adopts an E configuration with respect to the azomethine C=N bond. The imino groups are coplanar with the aromatic rings. Within the mol­ecule, the planar units are parallel, but extend in opposite directions from the dimethyl­ene bridge. An inter­esting feature of the crystal structure is the short inter­molecular Cl...F [3.1747 (5) Å] inter­actions, which are shorter than the sum of the van der Waals radii of these atoms. These inter­actions link neighbouring mol­ecules along the b axis. The crystal structure is further stabilized by π–π inter­actions, with a centroid–centroid distance of 3.5244 (4) Å.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.001 Å
• R factor = 0.030
• wR factor = 0.089
• Data-to-parameter ratio = 38.2

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT431_ALERT_2_C Short Inter HL..A Contact  Cl1    ..  F1      ..       3.17 Ang.
PLAT153_ALERT_1_C The su's on the Cell Axes   are Equal (x 100000)         20 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   2 ALERT level C = Check and explain
   0 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

---

S1. Comment

Schiff bases are among the most prevalent mixed-donor ligands in the field of coordination chemistry in which there has been growing interest, mainly because of their wide application in areas such as biochemistry, synthesis, and catalysis (Pal et al., 2005; Hou et al., 2001; Ren et al., 2002). Many Schiff base complexes have been structurally characterized, but only a relatively small number of free Schiff bases have had their X-ray structures reported (Calligaris & Randaccio, 1987). As an extension of our work (Fun, Kargar & Kia 2008; Fun, Kia & Kargar 2008) on the structural characterization of Schiff base ligands, the title compound (I), is reported here.

The molecule of the title compound (Fig. 1), adopts an E configuration with respect to the azomethine C═N bond. The bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable with the values found in related structures (Fun & Kia 2008a,b; Fun, Kargar & Kia 2008; Fun, Kia & Kargar 2008). The two planar units are parallel but extend in opposite directions from the dimethylene bridge. The interesting feature of the crystal structure is the short intermolecular Cl···F interactions [symmetry code: x, -1/2 - y, -1/2 + z] with a distance of 3.1747 (5) Å, which is shorter than the sum of the van der Waals radii of these atoms. These interactions link neighbouring molecules along the b-axis. The crystal structure is further stabilized by π–π interactions with a centroid to centroid distance of 3.5244 (4) Å [Cg1–Cg1; symmetry code, 2 - x, -y, -z; Cg1 is the centroid of the C1–C6 benzene ring].

Related literature

For bond-length data, see Allen et al. (1987). For related structures, see, for example: Fun & Kia (2008a,b): Fun, Kargar & Kia (2008); Fun, Kia & Kargar (2008). For information on Schiff base complexes and their applications, see, for example: Pal et al. (2005); Calligaris & Randaccio (1987); Hou et al. (2001); Ren et al. (2002). For hydrogen-bonding motifs, see: Bernstein et al. (1995).

S2. Experimental

The synthetic method has been described earlier (Fun, Kargar & Kia, 2008). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

S3. Refinement

All of the hydrogen atoms were positioned geometrically with C—H = 0.95 or 0.99 Å and refined in riding mode with U_iso (H) = 1.2 U_eq (C).

Computing details

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).

Figures

	Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms. The suffix A corresponds to symmetry code (-x + 2, -y, -z + 1).
	Fig. 2. The crystal packing of (I), viewed approximately down the a-axis, showing the linking of the molecules by Cl···F contacts along the b-axis. Intermolecular interactions are shown as dashed lines.

N,N'-Bis(3-chloro-2-fluorobenzylidene)ethane-1,2-diamine

Crystal data

C16H12Cl2F2N2	F(000) = 348
Mr = 341.18	Dx = 1.556 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8904 reflections
a = 7.2249 (2) Å	θ = 2.9–41.0°
b = 11.3676 (2) Å	µ = 0.46 mm^−1
c = 10.3368 (2) Å	T = 100 K
β = 120.906 (1)°	Block, colourless
V = 728.42 (3) Å^3	0.52 × 0.41 × 0.29 mm
Z = 2

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	3821 independent reflections
Radiation source: fine-focus sealed tube	3403 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
ϕ and ω scans	θmax = 37.5°, θmin = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −11→12
Tmin = 0.794, Tmax = 0.878	k = −19→19
16842 measured reflections	l = −17→17

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.088	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0499P)^2 + 0.131P] where P = (Fo^2 + 2Fc^2)/3
3821 reflections	(Δ/σ)max = 0.001
100 parameters	Δρmax = 0.45 e Å^−3
0 restraints	Δρmin = −0.35 e Å^−3

Special details

Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra 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
Cl1	0.65534 (3)	−0.131316 (15)	−0.342553 (18)	0.01852 (5)
F1	0.71054 (8)	−0.18319 (4)	−0.04997 (5)	0.01952 (9)
N1	0.83760 (10)	0.03597 (6)	0.29627 (6)	0.01620 (10)
C1	0.72180 (10)	−0.06703 (6)	−0.07109 (7)	0.01350 (10)
C2	0.69340 (10)	−0.02919 (6)	−0.20779 (7)	0.01388 (10)
C3	0.70125 (11)	0.09019 (6)	−0.23283 (7)	0.01577 (11)
H3	0.6802	0.1170	−0.3265	0.019*
C4	0.74016 (11)	0.17052 (6)	−0.11975 (8)	0.01704 (11)
H4	0.7457	0.2523	−0.1363	0.020*
C5	0.77080 (11)	0.13130 (6)	0.01692 (8)	0.01554 (11)
H5	0.7977	0.1868	0.0934	0.019*
C6	0.76267 (10)	0.01123 (6)	0.04403 (7)	0.01320 (10)
C7	0.80350 (10)	−0.03353 (6)	0.19019 (7)	0.01486 (11)
H7	0.8043	−0.1160	0.2053	0.018*
C8	0.88630 (11)	−0.01757 (7)	0.43842 (7)	0.01710 (11)
H8A	0.8762	−0.1043	0.4279	0.021*
H8B	0.7805	0.0092	0.4659	0.021*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.02300 (8)	0.01901 (9)	0.01500 (8)	−0.00281 (5)	0.01081 (6)	−0.00347 (5)
F1	0.0292 (2)	0.01227 (18)	0.01890 (19)	−0.00308 (15)	0.01361 (17)	0.00007 (14)
N1	0.0180 (2)	0.0181 (2)	0.0121 (2)	0.00091 (18)	0.00742 (18)	0.00082 (17)
C1	0.0142 (2)	0.0125 (2)	0.0135 (2)	−0.00087 (18)	0.00691 (18)	0.00018 (18)
C2	0.0139 (2)	0.0153 (3)	0.0124 (2)	−0.00011 (18)	0.00672 (18)	−0.00027 (18)
C3	0.0166 (2)	0.0165 (3)	0.0141 (2)	0.0015 (2)	0.0079 (2)	0.00275 (19)
C4	0.0201 (3)	0.0140 (3)	0.0170 (2)	0.0024 (2)	0.0096 (2)	0.0025 (2)
C5	0.0183 (3)	0.0131 (3)	0.0151 (2)	0.00170 (19)	0.0085 (2)	0.00006 (18)
C6	0.0133 (2)	0.0140 (2)	0.0121 (2)	0.00054 (18)	0.00633 (18)	0.00056 (18)
C7	0.0158 (2)	0.0161 (3)	0.0122 (2)	−0.00085 (19)	0.00683 (19)	0.00053 (19)
C8	0.0178 (2)	0.0212 (3)	0.0122 (2)	−0.0012 (2)	0.0076 (2)	0.0008 (2)

Geometric parameters (Å, º)

Cl1—C2	1.7235 (7)	C4—C5	1.3865 (10)
F1—C1	1.3476 (8)	C4—H4	0.9500
N1—C7	1.2687 (9)	C5—C6	1.4007 (9)
N1—C8	1.4568 (9)	C5—H5	0.9500
C1—C2	1.3878 (9)	C6—C7	1.4733 (9)
C1—C6	1.3906 (9)	C7—H7	0.9500
C2—C3	1.3882 (9)	C8—C8^i	1.5267 (13)
C3—C4	1.3934 (10)	C8—H8A	0.9900
C3—H3	0.9500	C8—H8B	0.9900
C7—N1—C8	116.79 (6)	C4—C5—H5	119.5
F1—C1—C2	118.62 (6)	C6—C5—H5	119.5
F1—C1—C6	119.48 (6)	C1—C6—C5	117.68 (6)
C2—C1—C6	121.90 (6)	C1—C6—C7	119.95 (6)
C1—C2—C3	119.61 (6)	C5—C6—C7	122.33 (6)
C1—C2—Cl1	119.54 (5)	N1—C7—C6	121.26 (6)
C3—C2—Cl1	120.84 (5)	N1—C7—H7	119.4
C2—C3—C4	119.62 (6)	C6—C7—H7	119.4
C2—C3—H3	120.2	N1—C8—C8^i	109.32 (7)
C4—C3—H3	120.2	N1—C8—H8A	109.8
C5—C4—C3	120.12 (6)	C8^i—C8—H8A	109.8
C5—C4—H4	119.9	N1—C8—H8B	109.8
C3—C4—H4	119.9	C8^i—C8—H8B	109.8
C4—C5—C6	121.07 (6)	H8A—C8—H8B	108.3
F1—C1—C2—C3	179.08 (6)	C2—C1—C6—C5	1.11 (9)
C6—C1—C2—C3	−1.35 (10)	F1—C1—C6—C7	2.90 (9)
F1—C1—C2—Cl1	−2.49 (8)	C2—C1—C6—C7	−176.66 (6)
C6—C1—C2—Cl1	177.08 (5)	C4—C5—C6—C1	−0.31 (10)
C1—C2—C3—C4	0.78 (10)	C4—C5—C6—C7	177.39 (6)
Cl1—C2—C3—C4	−177.63 (5)	C8—N1—C7—C6	−177.18 (6)
C2—C3—C4—C5	−0.01 (10)	C1—C6—C7—N1	−178.79 (6)
C3—C4—C5—C6	−0.22 (11)	C5—C6—C7—N1	3.55 (10)
F1—C1—C6—C5	−179.33 (6)	C7—N1—C8—C8^i	117.01 (8)

Symmetry code: (i) −x+2, −y, −z+1.