N,N′-Bis-(2,4-dichloro­benzyl­idene)-2,2-dimethyl­propane-1,3-diamine

The mol­ecule of the title Schiff base compound, C₁₉H₁₈Cl₄N₂, has crystallographic twofold rotation symmetry, with one C atom lying on the rotation axis. The dihedral angle between the two symmetry-related benzene rings is 84.70 (2)°. The plane of the –C=N—C– group is twisted away from the benzene ring by 7.5 (1)°. In the crystal structure, weak inter­molecular Cl...Cl [3.4851 (3) Å] contacts link neighbouring mol­ecules into a two-dimensional network parallel to the bc plane.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.001 Å
• R factor = 0.030
• wR factor = 0.099
• Data-to-parameter ratio = 43.4

checkCIF/PLATON results

No syntax errors found



Alert level C
            Value of measurement temperature given =   100.000
            Value of melting point given =     0.000
PLAT143_ALERT_4_C su on c - Axis Small or Missing (x 100000) .....         10 Ang.

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

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 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
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

Schiff bases are one of most prevalent mixed-donor ligands in the field of coordination chemistry. They play an important role in the development of coordination chemistry related to catalysis and enzymatic reactions, magnetism, and supramolecular architectures. Crystal structures of Schiff bases derived from substituted benzaldehydes and closely related to the title compound have been reported earlier (Li et al., 2005; Bomfim et al., 2005; Glidewell et al., 2005, 2006; Sun et al., 2004; Fun et al., 2008).

The molecule of the title Schiff base compound has crystallographic twofold rotation symmetry (Fig. 1). Bond lengths are within normal ranges (Allen et al., 1987). The plane of the –C═N—C– group is twisted away from the benzene ring by 7.5 (1)°.

In the crystal structure, weak intermolecular Cl···Cl contacts [Cl1···Cl2(x,1 - y,-1/2 + z) = 3.4851 (3) Å] link neighbouring molecules into a two-dimensional network parallel to the bc plane (Fig.2).

Related literature

For bond-length data, see: Allen et al. (1987). For related structures, see: Li et al. (2005); Bomfim et al. (2005); Glidewell et al. (2005, 2006); Sun et al. (2004); Fun et al. (2008).

S2. Experimental

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

S3. Refinement

H atoms were positioned geometrically and refined using a riding model, with C—H = 0.93 Å for aromatic and 0.97 Å for methylene and 0.96 Å for methyl H atoms.

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 the title compound, with atom labels and 50% probability ellipsoids for non-H atoms. Atoms labelled with the suffix A are generated by the symmetry operation (1/2 - x, 2 - y, z).
	Fig. 2. Part of the crystal structure of the title compound, viewed down the b-axis. Dashed lines indicate intermolecular Cl···Cl interactions.

N,N'-Bis-(2,4-dichlorobenzylidene)-2,2-dimethylpropane-1,3-diamine

Crystal data

C19H18Cl4N2	F(000) = 856
Mr = 416.15	Dx = 1.452 Mg m^−3
Orthorhombic, Pcca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2a 2ac	Cell parameters from 9929 reflections
a = 30.7633 (4) Å	θ = 3.6–41.1°
b = 5.4012 (1) Å	µ = 0.63 mm^−1
c = 11.4532 (1) Å	T = 100 K
V = 1903.05 (5) Å^3	Block, colourless
Z = 4	0.43 × 0.25 × 0.23 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	6565 independent reflections
Radiation source: fine-focus sealed tube	5678 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.028
ϕ and ω scans	θmax = 42.5°, θmin = 1.3°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −52→57
Tmin = 0.774, Tmax = 0.872	k = −9→10
86683 measured reflections	l = −20→20

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) = 0.099	H-atom parameters constrained
S = 1.19	w = 1/[σ^2(Fo^2) + (0.0454P)^2 + 0.5965P] where P = (Fo^2 + 2Fc^2)/3
4992 reflections	(Δ/σ)max = 0.001
115 parameters	Δρmax = 0.51 e Å^−3
0 restraints	Δρmin = −0.30 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	0.053693 (7)	1.12278 (4)	0.346996 (17)	0.01671 (5)
Cl2	0.046757 (8)	0.37440 (4)	0.653936 (18)	0.02040 (6)
N1	0.19231 (2)	0.96758 (14)	0.31674 (6)	0.01660 (12)
C1	0.08049 (2)	0.88739 (14)	0.42126 (6)	0.01301 (12)
C2	0.05625 (3)	0.74765 (14)	0.49989 (6)	0.01467 (12)
H2A	0.0270	0.7822	0.5127	0.018*
C3	0.07667 (3)	0.55568 (15)	0.55865 (7)	0.01504 (12)
C4	0.12041 (3)	0.50138 (16)	0.54095 (7)	0.01807 (13)
H4A	0.1336	0.3713	0.5807	0.022*
C5	0.14395 (3)	0.64492 (16)	0.46298 (8)	0.01748 (13)
H5A	0.1732	0.6098	0.4510	0.021*
C6	0.12480 (2)	0.84188 (14)	0.40166 (7)	0.01397 (12)
C7	0.15133 (2)	0.99635 (15)	0.32244 (7)	0.01527 (12)
H7A	0.1379	1.1157	0.2763	0.018*
C8	0.21668 (3)	1.13674 (14)	0.24238 (7)	0.01553 (13)
H8A	0.2317	1.2566	0.2909	0.019*
H8B	0.1966	1.2262	0.1925	0.019*
C9	0.2500	1.0000	0.16598 (9)	0.01351 (16)
C18	0.22667 (3)	0.81059 (16)	0.08866 (7)	0.01774 (13)
H18A	0.2044	0.8922	0.0443	0.027*
H18B	0.2138	0.6850	0.1368	0.027*
H18C	0.2472	0.7358	0.0364	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.01438 (9)	0.01789 (9)	0.01786 (9)	0.00404 (6)	0.00073 (5)	0.00121 (5)
Cl2	0.02045 (10)	0.02338 (10)	0.01738 (9)	−0.00623 (7)	0.00240 (6)	0.00349 (6)
N1	0.0117 (3)	0.0205 (3)	0.0176 (3)	−0.0015 (2)	0.0016 (2)	0.0025 (2)
C1	0.0116 (3)	0.0143 (3)	0.0131 (3)	0.0006 (2)	0.0001 (2)	−0.0008 (2)
C2	0.0117 (3)	0.0175 (3)	0.0149 (3)	−0.0002 (2)	0.0016 (2)	−0.0010 (2)
C3	0.0143 (3)	0.0170 (3)	0.0139 (3)	−0.0031 (2)	0.0004 (2)	0.0006 (2)
C4	0.0136 (3)	0.0197 (3)	0.0209 (3)	−0.0004 (2)	−0.0016 (2)	0.0046 (3)
C5	0.0108 (3)	0.0207 (3)	0.0209 (3)	0.0005 (2)	−0.0002 (2)	0.0044 (3)
C6	0.0102 (3)	0.0168 (3)	0.0149 (3)	−0.0004 (2)	0.0005 (2)	0.0009 (2)
C7	0.0120 (3)	0.0178 (3)	0.0160 (3)	−0.0004 (2)	0.0010 (2)	0.0015 (2)
C8	0.0120 (3)	0.0163 (3)	0.0183 (3)	−0.0012 (2)	0.0021 (2)	0.0009 (2)
C9	0.0113 (4)	0.0144 (4)	0.0148 (4)	−0.0023 (3)	0.000	0.000
C18	0.0169 (3)	0.0176 (3)	0.0187 (3)	−0.0033 (3)	−0.0036 (2)	−0.0008 (2)

Geometric parameters (Å, º)

Cl1—C1	1.7376 (8)	C5—H5A	0.93
Cl2—C3	1.7311 (8)	C6—C7	1.4783 (11)
N1—C7	1.2720 (10)	C7—H7A	0.93
N1—C8	1.4566 (10)	C8—C9	1.5369 (10)
C1—C2	1.3917 (11)	C8—H8A	0.97
C1—C6	1.4033 (11)	C8—H8B	0.97
C2—C3	1.3866 (11)	C9—C18	1.5316 (10)
C2—H2A	0.93	C9—C18^i	1.5316 (10)
C3—C4	1.3917 (11)	C9—C8^i	1.5369 (10)
C4—C5	1.3869 (12)	C18—H18A	0.96
C4—H4A	0.93	C18—H18B	0.96
C5—C6	1.4043 (11)	C18—H18C	0.96
C7—N1—C8	117.61 (7)	N1—C7—H7A	119.7
C2—C1—C6	121.94 (7)	C6—C7—H7A	119.7
C2—C1—Cl1	117.35 (6)	N1—C8—C9	112.00 (6)
C6—C1—Cl1	120.71 (6)	N1—C8—H8A	109.2
C3—C2—C1	118.49 (7)	C9—C8—H8A	109.2
C3—C2—H2A	120.8	N1—C8—H8B	109.2
C1—C2—H2A	120.8	C9—C8—H8B	109.2
C2—C3—C4	121.66 (7)	H8A—C8—H8B	107.9
C2—C3—Cl2	119.21 (6)	C18—C9—C18^i	109.36 (9)
C4—C3—Cl2	119.12 (6)	C18—C9—C8^i	108.71 (4)
C5—C4—C3	118.74 (8)	C18^i—C9—C8^i	109.73 (4)
C5—C4—H4A	120.6	C18—C9—C8	109.73 (4)
C3—C4—H4A	120.6	C18^i—C9—C8	108.71 (4)
C4—C5—C6	121.76 (7)	C8^i—C9—C8	110.59 (9)
C4—C5—H5A	119.1	C9—C18—H18A	109.5
C6—C5—H5A	119.1	C9—C18—H18B	109.5
C1—C6—C5	117.40 (7)	H18A—C18—H18B	109.5
C1—C6—C7	122.39 (7)	C9—C18—H18C	109.5
C5—C6—C7	120.19 (7)	H18A—C18—H18C	109.5
N1—C7—C6	120.65 (7)	H18B—C18—H18C	109.5
C6—C1—C2—C3	−1.08 (11)	Cl1—C1—C6—C7	2.99 (11)
Cl1—C1—C2—C3	178.81 (6)	C4—C5—C6—C1	−0.64 (13)
C1—C2—C3—C4	0.20 (12)	C4—C5—C6—C7	177.81 (8)
C1—C2—C3—Cl2	−178.30 (6)	C8—N1—C7—C6	−176.18 (7)
C2—C3—C4—C5	0.42 (13)	C1—C6—C7—N1	172.02 (8)
Cl2—C3—C4—C5	178.92 (7)	C5—C6—C7—N1	−6.36 (12)
C3—C4—C5—C6	−0.19 (13)	C7—N1—C8—C9	−134.46 (8)
C2—C1—C6—C5	1.29 (11)	N1—C8—C9—C18	59.07 (9)
Cl1—C1—C6—C5	−178.59 (6)	N1—C8—C9—C18^i	178.63 (7)
C2—C1—C6—C7	−177.13 (7)	N1—C8—C9—C8^i	−60.85 (5)

Symmetry code: (i) −x+1/2, −y+2, z.