Bis(4-maleimido­phenyl)­methane

In the crystal structure of the title compound, C₂₁H₁₄N₂O₄, the asymmetric unit contains one-half of the mol­ecule, with the other half generated by a crystallographic twofold axis; the central C atom lies on the twofold axis. The dihedral angle between the substituted phenyl and pyrrole rings is 52.1 (1)°. The molecular packing in the crystal is stabilized by π–π-stacking interactions and weak C—H...π interactions.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.032
• wR factor = 0.091
• Data-to-parameter ratio = 9.3

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry

General Notes



REFLT_03
         From the CIF: _diffrn_reflns_theta_max           28.28
         From the CIF: _reflns_number_total               1133
         Count of symmetry unique reflns         1133
         Completeness (_total/calc)            100.00%
         TEST3: Check Friedels for noncentro structure
         Estimate of Friedel pairs measured         0
         Fraction of Friedel pairs measured     0.000
         Are heavy atom types Z>Si present           no
          Please check that the estimate of the number of Friedel pairs is
          correct. If it is not, please give the correct count in the
          _publ_section_exptl_refinement section of the submitted CIF.

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S1. Comment

The title compound, (I), is the first and primary kind of bismaleimide (BMI). As a classical high-performance thermosetting polyimide, BMI resins have been widely studied. BMI resins are attractive because of their high chemical, corrosion, radiation resistance, as well as their attrition-enduring, insulating, and mechanical properties (Jin et al., 2001; Glatz & Mulhaupt, 1993; Gawdzik et al., 2001). However, the most attractive property is that they have excellent hot/wet stability up to 573–623 K (Gawdzik et al., 2001). Therefore, BMI resins have been widely used for advanced composite materials, multi-layered lamination materials, abrasive materials, sealing materials, molding materials, powder coating, adhesives, etc (Jin et al., 2001; Glatz & Mulhaupt, 1993; Gawdzik et al., 2001). We report here the crystal structure of (I).

The asymmetric unit of (I) contains one-half of the molecule (Fig. 1), with the other half generated by a crystallographic twofold axis passing through atom C11. The bond lengths and angles of the phenylmaleimide moiety are comparable with those observed in N-(4-hydroxyphenyl)maleimide (Rodriguez et al., 2002). The dihedral angle between the phenyl ring and pyrrole ring is 52.1 (1)°. The torsion angles C4—N1—C5—C6 and C1—N1—C5—C10 are −53.4 (3) and −51.4 (3)°, respectively. Atom O1 lies on the pyrrole plane whereas O2 deviates from it by 0.027 (2)°. In the molecule, the dihedral angle between the symmetry-related phenyl rings bridged by C11 is 76.59 (4)°. The symmetry-related pyrrole rings are nearly orthogonal, with a dihedral angle of 83.74 (6)°. The end-to-end distance of the molecule is 13.54 Å.

The molecular packing in the crystal is stabilized by π–π-stacking interactions and C—H···π interactions. The maleimide moiety and phenyl ring of the symmetry-related molecule at (y, 1/2 − x, 1/4 + z) are stacked with their centroids separated by a distance of 3.484 (1) Å. A weak C—H···π interaction involving C9 and the maleimide moiety is observed, such that H9···Cg = 3.01 Å, C9···Cg = 3.750 (2) Å and C9—H9···Cg = 138°, where Cg is the centre of gravity of the pyrrole ring at (−1/2 + x, 1/2 − y, z).

S2. Experimental

An acetone solution (15 ml) of maleic anhydride (2 mmol, 196 mg) and 4,4'-diaminophenylmethane (1 mmol, 198 mg) were stirred for 1 h, then acetic anhydride (5 ml), anhydrous magnesium acetate (0.2 g) and triethylamine (5 ml) were added. The resultant solution was heated to 353 K and kept for 1 h. The above solution was then cooled to room temperature. With water added, shiny yellow crystals were deposited, filtered and washed with water and acetone in turn. Recrystallization was carried out using an ethanol solution and dried in a vacuum desiccator under CaCl₂ (yield 82%). Analysis calculated for the title complex: C 70.39, H 3.94, N 7.82%; found: C 70.15, H 4.00, N 7.68%.

S3. Refinement

All H atoms, except H11, were positioned geometrically and treated as riding atoms, with U_iso(H) = 1.2U_eq(C). H11 was located from a difference Fourier map and it was allowed to ride on the attached atom during the final cycles of refinement. Due to the absence of any significant anomalous scatters, the 631 Friedel opposites were merged and an arbitrary choice of enantiomer has been made.

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL, PARST (Nardelli, 1995) and PLATON (Spek, 1990).

Figures

Fig. 1. The structure of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme for one asymmetric unit. The other half of the molecule is generated by a twofold axis through C11.

[Bis(4-maleimidophenyl)]methane

Crystal data

C21H14N2O4	Dx = 1.347 Mg m^−3
Mr = 358.34	Melting point: 429(1) K K
Tetragonal, I41cd	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: I 4bw -2c	Cell parameters from 7096 reflections
a = 12.9880 (4) Å	θ = 3.0–28.3°
c = 20.9435 (12) Å	µ = 0.10 mm^−1
V = 3532.9 (3) Å^3	T = 293 K
Z = 8	Block, yellow
F(000) = 1488	0.50 × 0.50 × 0.44 mm

Data collection

Siemens SMART CCD area-detector diffractometer	1133 independent reflections
Radiation source: fine-focus sealed tube	1074 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.019
Detector resolution: 8.33 pixels mm^-1	θmax = 28.3°, θmin = 3.0°
ω scans	h = −16→17
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	k = −17→16
Tmin = 0.917, Tmax = 0.959	l = −27→17
10396 measured reflections

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)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.092	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0615P)^2 + 0.5468P] where P = (Fo^2 + 2Fc^2)/3
1133 reflections	(Δ/σ)max < 0.001
122 parameters	Δρmax = 0.20 e Å^−3
1 restraint	Δρmin = −0.18 e Å^−3

Special details

Experimental. The data collection covered over a hemisphere of reciprocal space by a combination of three sets of exposures; each set had a different ϕ angle (0, 88 and 180°) for the crystal and each exposure of 30 s covered 0.3° in ω. The crystal-to-detector distance was 5 cm and the detector swing angle was −35°. Crystal decay was monitored by repeating fifty initial frames at the end of data collection and analysing the intensity of duplicate reflections, and was found to be negligible.

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
O1	0.13504 (13)	0.44916 (11)	0.33818 (8)	0.0571 (4)
O2	0.33293 (14)	0.20193 (12)	0.43277 (9)	0.0601 (4)
N1	0.21972 (12)	0.30366 (11)	0.37498 (8)	0.0404 (3)
C1	0.19960 (15)	0.40975 (13)	0.37131 (9)	0.0424 (4)
C2	0.27430 (17)	0.45966 (15)	0.41584 (9)	0.0488 (4)
H2	0.2792	0.5300	0.4235	0.059*
C3	0.33187 (16)	0.38877 (15)	0.44252 (10)	0.0470 (4)
H3	0.3844	0.4008	0.4717	0.056*
C4	0.29940 (14)	0.28556 (14)	0.41842 (9)	0.0428 (4)
C5	0.16504 (13)	0.22650 (13)	0.34007 (9)	0.0378 (4)
C6	0.21903 (14)	0.15502 (14)	0.30377 (9)	0.0404 (4)
H6	0.2906	0.1569	0.3025	0.049*
C7	0.16548 (14)	0.08081 (14)	0.26945 (9)	0.0412 (4)
H7	0.2018	0.0322	0.2459	0.049*
C8	0.05871 (14)	0.07800 (13)	0.26966 (8)	0.0389 (3)
C9	0.00563 (15)	0.15057 (15)	0.30645 (9)	0.0461 (4)
H9	−0.0660	0.1495	0.3072	0.055*
C10	0.05793 (14)	0.22407 (15)	0.34180 (9)	0.0453 (4)
H10	0.0218	0.2714	0.3665	0.054*
C11	0.0000	0.0000	0.22962 (11)	0.0437 (5)
H11	−0.0491	0.0392	0.2019	0.052*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0666 (9)	0.0414 (7)	0.0634 (9)	0.0043 (6)	−0.0127 (8)	0.0009 (6)
O2	0.0624 (9)	0.0455 (8)	0.0723 (10)	0.0088 (7)	−0.0122 (8)	0.0002 (7)
N1	0.0448 (7)	0.0327 (7)	0.0437 (8)	−0.0013 (5)	−0.0003 (6)	−0.0034 (6)
C1	0.0506 (9)	0.0341 (8)	0.0424 (8)	−0.0023 (7)	0.0050 (7)	−0.0022 (7)
C2	0.0622 (11)	0.0385 (8)	0.0457 (9)	−0.0094 (8)	0.0026 (8)	−0.0049 (7)
C3	0.0518 (10)	0.0457 (9)	0.0435 (9)	−0.0094 (8)	0.0007 (7)	−0.0048 (7)
C4	0.0424 (8)	0.0415 (8)	0.0446 (9)	−0.0006 (7)	0.0037 (7)	−0.0017 (7)
C5	0.0427 (8)	0.0320 (7)	0.0387 (8)	−0.0037 (6)	0.0040 (7)	−0.0005 (6)
C6	0.0397 (8)	0.0355 (8)	0.0461 (9)	0.0019 (6)	0.0024 (7)	−0.0013 (6)
C7	0.0490 (9)	0.0330 (7)	0.0415 (8)	0.0046 (6)	0.0029 (7)	−0.0032 (6)
C8	0.0485 (9)	0.0327 (7)	0.0356 (7)	−0.0069 (6)	0.0035 (7)	0.0027 (6)
C9	0.0396 (8)	0.0492 (9)	0.0496 (9)	−0.0089 (8)	0.0098 (8)	−0.0060 (8)
C10	0.0455 (10)	0.0438 (8)	0.0467 (9)	−0.0040 (7)	0.0128 (8)	−0.0093 (7)
C11	0.0544 (13)	0.0402 (11)	0.0366 (11)	−0.0101 (11)	0.000	0.000

Geometric parameters (Å, º)

O1—C1	1.203 (2)	C6—C7	1.389 (3)
O2—C4	1.208 (2)	C6—H6	0.93
N1—C4	1.398 (2)	C7—C8	1.387 (3)
N1—C1	1.405 (2)	C7—H7	0.93
N1—C5	1.429 (2)	C8—C9	1.399 (2)
C1—C2	1.494 (3)	C8—C11	1.520 (2)
C2—C3	1.311 (3)	C9—C10	1.386 (2)
C2—H2	0.93	C9—H9	0.93
C3—C4	1.493 (3)	C10—H10	0.93
C3—H3	0.93	C11—C8^i	1.520 (2)
C5—C6	1.390 (2)	C11—H11	1.00
C5—C10	1.392 (2)
C4—N1—C1	109.78 (15)	C7—C6—C5	119.59 (16)
C4—N1—C5	125.65 (15)	C7—C6—H6	120.2
C1—N1—C5	124.56 (16)	C5—C6—H6	120.2
O1—C1—N1	125.37 (17)	C8—C7—C6	121.15 (17)
O1—C1—C2	128.92 (17)	C8—C7—H7	119.4
N1—C1—C2	105.70 (16)	C6—C7—H7	119.4
C3—C2—C1	109.38 (17)	C7—C8—C9	118.46 (16)
C3—C2—H2	125.3	C7—C8—C11	121.15 (15)
C1—C2—H2	125.3	C9—C8—C11	120.37 (15)
C2—C3—C4	108.99 (18)	C10—C9—C8	121.11 (17)
C2—C3—H3	125.5	C10—C9—H9	119.4
C4—C3—H3	125.5	C8—C9—H9	119.4
O2—C4—N1	125.45 (18)	C9—C10—C5	119.44 (16)
O2—C4—C3	128.41 (19)	C9—C10—H10	120.3
N1—C4—C3	106.14 (15)	C5—C10—H10	120.3
C6—C5—C10	120.22 (16)	C8^i—C11—C8	113.04 (19)
C6—C5—N1	119.83 (16)	C8^i—C11—H11	109.8
C10—C5—N1	119.95 (15)	C8—C11—H11	107.5
C4—N1—C1—O1	−179.74 (19)	C4—N1—C5—C10	127.46 (19)
C5—N1—C1—O1	−0.7 (3)	C1—N1—C5—C10	−51.4 (3)
C4—N1—C1—C2	0.6 (2)	C10—C5—C6—C7	−0.3 (3)
C5—N1—C1—C2	179.61 (16)	N1—C5—C6—C7	−179.39 (16)
O1—C1—C2—C3	−179.6 (2)	C5—C6—C7—C8	1.4 (3)
N1—C1—C2—C3	0.0 (2)	C6—C7—C8—C9	−1.3 (3)
C1—C2—C3—C4	−0.6 (2)	C6—C7—C8—C11	177.06 (16)
C1—N1—C4—O2	178.6 (2)	C7—C8—C9—C10	0.3 (3)
C5—N1—C4—O2	−0.4 (3)	C11—C8—C9—C10	−178.15 (17)
C1—N1—C4—C3	−1.0 (2)	C8—C9—C10—C5	0.8 (3)
C5—N1—C4—C3	−179.93 (16)	C6—C5—C10—C9	−0.7 (3)
C2—C3—C4—O2	−178.6 (2)	N1—C5—C10—C9	178.34 (17)
C2—C3—C4—N1	1.0 (2)	C7—C8—C11—C8^i	113.84 (18)
C4—N1—C5—C6	−53.4 (3)	C9—C8—C11—C8^i	−67.81 (15)
C1—N1—C5—C6	127.72 (19)

Symmetry code: (i) −x, −y, z.