(E)-4-Bromo-N-{(E)-3-[(4-bromo-2-methyl­phen­yl)imino]­butan-2-yl­idene}-2-methyl­aniline

The title compound, C₁₈H₁₈Br₂N₂, is centrosymmetric with the mid-point of the central C-C bond of the butyl group located on an inversion center. The terminal benzene ring is approximately perpendicular to the central butyl plane [dihedral angle = 71.9 (8)°]. No hydrogen bonding or aromatic stacking is observed in the crystal.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.009 Å
• R factor = 0.052
• wR factor = 0.113
• Data-to-parameter ratio = 15.0

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT029_ALERT_3_C _diffrn_measured_fraction_theta_full Low .......      0.974
PLAT341_ALERT_3_C Low Bond Precision on  C-C Bonds ...............     0.0093 Ang
PLAT905_ALERT_3_C Negative K value in the Analysis of Variance ...     -4.996
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         33

Alert level G
PLAT005_ALERT_5_G No _iucr_refine_instructions_details  in the CIF          ?
PLAT083_ALERT_2_G SHELXL Second Parameter in WGHT Unusually Large.       5.90
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        293 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        293 K

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   5 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   4 ALERT level G = General information/check it is not something unexpected

   2 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
   5 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

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S1. Comment

There is a considerable interest in the development of new late transition metal catalysts for the polymerization of α-olefins since Brookhart discovered highly active α-diimine nickel catalysts (Johnson et al., 1995; Killian et al., 1996). It is well known that the ligand structure had significant influence on the product properties and polymerization activities (Popeney & Guan, 2010; Popeney et al., 2011; Yuan et al., 2005).

In this study, we designed and synthesized the title compound as a bidentate ligand, and its molecular structure was characterized by X-ray diffraction. In the solid state, the ligand exhibits a -1 symmetry. The single bond of 1,4-diazabutadiene fragment is (E)-configured. The dihedral angle between the benzene ring and 1,4-diazabutadiene plane is 71.9 (8)°, similar to that found in a related compound (Zhang et al., 2013). In the crystal packing, there is no hydrogen-bond between the molecules.

Related literature

For applications of diimine-metal catalysts, see: Johnson et al. (1995); Killian et al. (1996); Popeney & Guan (2010); Popeney et al. (2011); Yuan et al. (2005). For a related structure, see: Zhang et al. (2013).

S2. Experimental

Formic acid (0.5 ml) was added to a stirred solution of 2,3-butanedione (0.103 g, 1.2 mmol) and 4-bromo-2-methylaniline (0.447 g, 2.4 mmol) in methanol (25 ml). The mixture was refluxed for 24 h, then cooled and the precipitate was separated by filtration. The solid was recrystallized from dichloromethane/cyclohexane (v/v = 6:1), washed with cold ethanol and dried under vacuum to give the title ligand 0.37 g (87%). Anal. Calcd. for C₁₈H₁₈Br₂N₂: C, 51.21; H, 4.30; N, 6.64. Found: C, 51.18; H, 4.29; N, 6.68. Crystals suitable for X-ray structure determination were grown from a solution of the title compound in a mixture of cyclohexane/dichloromethane (1:4, v/v).

S3. Refinement

All hydrogen atoms were placed in calculated positions with C—H distances of 0.93 and 0.96 Å for aryl and methyl type H-atoms. They were included in the refinement in a riding model approximation, respectively. The H-atoms were assigned U_iso = 1.2 times U_eq of the aryl C atoms and 1.5 times U_eq of the methyl C atoms.

Computing details

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); 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).

Figures

Fig. 1. Molecular structure of the title compound, using 30% probability level ellipsoids.

(E)-4-Bromo-N-{(E)-3-[(4-bromo-2- methylphenyl)imino]butan-2-ylidene}-2-methylaniline

Crystal data

C18H18Br2N2	F(000) = 840
Mr = 422.16	Dx = 1.612 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 951 reflections
a = 13.625 (13) Å	θ = 2.8–20.3°
b = 7.495 (7) Å	µ = 4.66 mm^−1
c = 17.029 (17) Å	T = 293 K
V = 1739 (3) Å^3	Block, yellow
Z = 4	0.21 × 0.20 × 0.15 mm

Data collection

Bruker APEXII CCD diffractometer	1541 independent reflections
Radiation source: fine-focus sealed tube	847 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.104
ϕ and ω scans	θmax = 25.3°, θmin = 2.8°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −15→15
Tmin = 0.441, Tmax = 0.542	k = −9→5
6368 measured reflections	l = −20→18

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.052	H-atom parameters constrained
wR(F^2) = 0.113	w = 1/[σ^2(Fo^2) + (0.0106P)^2 + 5.9013P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
1541 reflections	Δρmax = 0.70 e Å^−3
103 parameters	Δρmin = −0.85 e Å^−3
0 restraints	Extinction correction: SHELXTL (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0038 (5)

Special details

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
Br1	0.30195 (6)	0.23158 (11)	0.40014 (4)	0.0631 (4)
C1	0.4677 (5)	0.4420 (8)	0.2188 (4)	0.0398 (17)
H1	0.5330	0.4728	0.2107	0.048*
C2	0.4386 (5)	0.3772 (9)	0.2914 (4)	0.0444 (19)
H2	0.4836	0.3653	0.3321	0.053*
C3	0.3421 (5)	0.3308 (8)	0.3021 (4)	0.0374 (17)
C4	0.2742 (5)	0.3508 (7)	0.2429 (4)	0.0341 (16)
H4	0.2092	0.3188	0.2518	0.041*
C5	0.3017 (5)	0.4189 (7)	0.1692 (3)	0.0277 (14)
C6	0.3998 (4)	0.4617 (7)	0.1574 (4)	0.0299 (15)
C7	0.4845 (4)	0.4520 (8)	0.0370 (4)	0.0307 (15)
C8	0.5198 (5)	0.2627 (8)	0.0474 (4)	0.0451 (17)
H8A	0.4765	0.2006	0.0825	0.068*
H8B	0.5850	0.2636	0.0689	0.068*
H8C	0.5205	0.2035	−0.0026	0.068*
C9	0.2258 (4)	0.4423 (8)	0.1053 (4)	0.0452 (18)
H9A	0.2541	0.5074	0.0623	0.068*
H9B	0.1706	0.5071	0.1257	0.068*
H9C	0.2045	0.3273	0.0872	0.068*
N1	0.4299 (4)	0.5380 (6)	0.0839 (3)	0.0331 (13)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0619 (6)	0.0768 (6)	0.0505 (5)	0.0068 (5)	0.0143 (4)	0.0208 (5)
C1	0.017 (4)	0.044 (4)	0.058 (5)	−0.003 (3)	0.004 (3)	0.006 (4)
C2	0.040 (5)	0.048 (5)	0.045 (4)	−0.005 (4)	−0.007 (3)	0.004 (4)
C3	0.033 (4)	0.031 (4)	0.048 (4)	0.001 (3)	0.003 (4)	0.000 (3)
C4	0.021 (4)	0.030 (3)	0.051 (4)	−0.001 (3)	0.009 (3)	−0.002 (3)
C5	0.024 (4)	0.019 (3)	0.041 (4)	−0.001 (3)	0.002 (3)	−0.001 (3)
C6	0.027 (4)	0.021 (3)	0.042 (4)	0.001 (3)	0.012 (3)	0.000 (3)
C7	0.012 (3)	0.028 (4)	0.052 (4)	−0.005 (3)	0.004 (3)	0.008 (3)
C8	0.043 (4)	0.033 (4)	0.060 (4)	0.012 (4)	0.015 (4)	0.012 (3)
C9	0.033 (5)	0.043 (4)	0.059 (5)	−0.002 (3)	0.003 (4)	0.003 (4)
N1	0.021 (3)	0.030 (3)	0.048 (4)	0.000 (3)	0.006 (3)	0.006 (3)

Geometric parameters (Å, º)

Br1—C3	1.908 (7)	C6—N1	1.436 (7)
C1—C2	1.386 (9)	C7—N1	1.268 (7)
C1—C6	1.403 (8)	C7—C8	1.509 (8)
C1—H1	0.9300	C7—C7^i	1.510 (11)
C2—C3	1.372 (9)	C8—H8A	0.9600
C2—H2	0.9300	C8—H8B	0.9600
C3—C4	1.375 (9)	C8—H8C	0.9600
C4—C5	1.406 (8)	C9—H9A	0.9600
C4—H4	0.9300	C9—H9B	0.9600
C5—C6	1.390 (8)	C9—H9C	0.9600
C5—C9	1.512 (8)
C2—C1—C6	120.8 (6)	C1—C6—N1	120.2 (5)
C2—C1—H1	119.6	N1—C7—C8	126.2 (5)
C6—C1—H1	119.6	N1—C7—C7^i	116.6 (7)
C3—C2—C1	118.8 (6)	C8—C7—C7^i	117.2 (7)
C3—C2—H2	120.6	C7—C8—H8A	109.5
C1—C2—H2	120.6	C7—C8—H8B	109.5
C2—C3—C4	121.3 (6)	H8A—C8—H8B	109.5
C2—C3—Br1	119.3 (5)	C7—C8—H8C	109.5
C4—C3—Br1	119.4 (5)	H8A—C8—H8C	109.5
C3—C4—C5	120.9 (6)	H8B—C8—H8C	109.5
C3—C4—H4	119.5	C5—C9—H9A	109.5
C5—C4—H4	119.5	C5—C9—H9B	109.5
C6—C5—C4	118.0 (6)	H9A—C9—H9B	109.5
C6—C5—C9	121.8 (6)	C5—C9—H9C	109.5
C4—C5—C9	120.2 (6)	H9A—C9—H9C	109.5
C5—C6—C1	120.1 (6)	H9B—C9—H9C	109.5
C5—C6—N1	119.5 (6)	C7—N1—C6	120.9 (5)
C6—C1—C2—C3	0.6 (10)	C4—C5—C6—N1	−177.6 (5)
C1—C2—C3—C4	−1.3 (10)	C9—C5—C6—N1	2.9 (8)
C1—C2—C3—Br1	177.3 (5)	C2—C1—C6—C5	1.1 (9)
C2—C3—C4—C5	0.3 (9)	C2—C1—C6—N1	176.6 (5)
Br1—C3—C4—C5	−178.3 (4)	C8—C7—N1—C6	3.9 (10)
C3—C4—C5—C6	1.4 (8)	C7^i—C7—N1—C6	−177.3 (6)
C3—C4—C5—C9	−179.2 (6)	C5—C6—N1—C7	−112.5 (7)
C4—C5—C6—C1	−2.0 (8)	C1—C6—N1—C7	71.9 (8)
C9—C5—C6—C1	178.5 (5)

Symmetry code: (i) −x+1, −y+1, −z.