A new precursor for the synthesis of porphyrazine: 2,3-bis(4-methyl­phenyl)­maleo­nitrile

The structure of the title compound consists of discrete C₁₈H₁₄N₂ mol­ecules in a cis configuration. The mol­ecules are distorted from planarity.

S1. Comment

It has been shown that both maleonitrile and fumaronitrile compounds can be cyclized into porphyrazine macrocyles, but in very low yields when using the fumaronitrile isomer (Fitzgerald et al., 1991). The fumaronitriles must first be thermally isomerized to the maleonitrile cis-isomer before cyclization can occur. It has been reported that dialkyl or alkyl/aryl mixed fumaronitriles can be photoisomerized to the maleonitrile form (Fitzgerald et al., 1991). Diarylfumaronitriles on the contrary have been shown to be unable to be photoisomerized (Sargent & Timmons, 1963). We had set out to prepare the porphyrazine precursor molecule 2,3-di-(4-methylphenyl)maleonitrile but in several reports, each using different synthetic conditions, only the fumaronitrile isomer was isolated (Chatterjea et al., 1966; Ogata & Nagura, 1974; Pochat, 1978; Kurihara et al., 1987). Using a previously reported procedure (Baumann et al., 1997) for the oxidative coupling of para-substituted benzyl cyanides, we have isolated not only the trans, (I), but also the cis isomer, 2,3-di-(4-methylphenyl)maleonitrile, (II), and characterized them by several methods including X-ray crystallography. Due to the relative high yields of their syntheses, these latter compounds are therefore of interest for the preparation of porphyrazines. \sch

Although the structure of the trans isomer, (I), has been determined, it will be not presented in this article because of its low quality, mainly due to the thin, needle-shaped crystals and the poor diffracting power of the samples. The molecule of the title compound, (II), is not planar: it is distorted from planarity along the C═C bond. This is evident as shown by the torsion angles along the C═C bond (Table 1) and with the values of the angles between the planes defined by C1, C3, C5 and C2, C4, C12 [10.6 (1)°] and those defined by C1, C2, C5, C12 and C1, C2, C3, C4 [7.43 (2)°].

Such non-planarity was also observed in the trans-α,β-dicyanostilbene (Wallwork, 1961), which is the only aryl-containing disubstituted dinitrile compound reported so far in the Cambridge Structural Database. Since the accuracy of its structural determination is not comparable to the present one, no comparison will be undertaken. The p-methylphenyl groups are twisted about the C5—C8 and C12—C15 axes and forms an angle of 37.54 (6) and 43.88 (6)° with the mean-plane built around the C═C bond (least-square plane through atoms C1, C2, C3, C4, C5 and C12). The angle between the two p-methylphenyl group planes is 56.95 (6)°.

S2. Experimental

Compound (I) (pale yellow needles) was synthesized in 43% yield using procedures similar to that found for the coupling of related benzyl cyanide compounds (Baumann et al., 1997). Elemental and melting point analyses were in agreement with that previously reported for this compound (Pochat, 1978; Chatterjea et al., 1966). Compound (II) was obtained in 15% yield from the filtrate of (I) after the filtrate was placed in a freezer at 253 K for 3 d. Well formed, yellow hexagonal plates crystallized, were filtered, washed with MeOH and dried under vacuum (m.p. 432–433 K uncorrected). Elemental analysis: found, C 83.31, H 5.30, N 10.68%; calculated for C₁₈H₁₄N₂, C 83.69, H 5.46, N 10.84%. IR (KBr): 3033, 2923 (CH), 2216 (CN), 1654 (C═C) cm^-1.

S3. Refinement

H atoms on the phenyl groups were placed geometrically at 0.95 Å and riding the adjacent C atom with an isotropic displacement parameter 20% higher than the one of the adjacent C atom. H atoms of the methyl groups were treated as idealized disordered (two positions rotated from 60° from each other) with an isotropic displacement parameter 20% higher than the one of the adjacent C atom and the C—H distance free to vary.

Computing details

Data collection: IPDS Software (Stoe & Cie, 1996); cell refinement: IPDS Software; data reduction: X-RED (Stoe & Cie, 1996); program(s) used to solve structure: SHELXS86 (Sheldrick, 1986); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

Fig. 1. The molecular structure of (II), showing 30% probability displacement ellipsoids and the atom-numbering scheme. H atoms have been omitted for clarity.

cis-α,α'-Dicyan-4,4'-dimethyl-stilben

Crystal data

C18H14N2	F(000) = 544
Mr = 258.31	Dx = 1.192 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 8.5424 (8) Å	Cell parameters from 5000 reflections
b = 18.089 (2) Å	θ = 2.2–26.1°
c = 9.3202 (9) Å	µ = 0.07 mm^−1
β = 90.898 (11)°	T = 160 K
V = 1440.0 (3) Å^3	Plate, yellow
Z = 4	0.40 × 0.23 × 0.08 mm

Data collection

STOE Imaging Plate Diffraction System diffractometer	1754 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.054
Graphite monochromator	θmax = 26.1°, θmin = 2.3°
ϕ scan	h = −10→10
11258 measured reflections	k = −22→22
2795 independent reflections	l = −11→11

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.100	H atoms treated by a mixture of independent and constrained refinement
S = 0.95	Calculated w = 1/[σ^2(Fo^2) + (0.0551P)^2] where P = (Fo^2 + 2Fc^2)/3
2795 reflections	(Δ/σ)max = 0.013
185 parameters	Δρmax = 0.15 e Å^−3
0 restraints	Δρmin = −0.15 e Å^−3

Special details

Experimental. The data were collected on a Stoe Imaging Plate Diffraction System (IPDS) equipped with an Oxford Cryosystems cooler device. The crystal-to-detector distance was 70 mm. 154 exposures (5 min per exposure) were obtained with 0 < ϕ < 200° and with the crystals rotated through 1.3° in ϕ. Coverage of the unique set was close to 99%. Crystal decay was monitored by measuring 200 reflections per image.

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	Occ. (<1)
C1	0.47115 (16)	0.19171 (8)	0.24459 (17)	0.0312 (4)
C2	0.47219 (16)	0.11648 (8)	0.24911 (17)	0.0300 (3)
C3	0.59308 (19)	0.22740 (8)	0.16402 (19)	0.0386 (4)
C4	0.57971 (17)	0.07937 (8)	0.15590 (18)	0.0328 (4)
C5	0.35478 (16)	0.24199 (8)	0.30717 (17)	0.0307 (3)
C6	0.39837 (17)	0.31218 (8)	0.35387 (18)	0.0343 (4)
H6	0.5045	0.3273	0.3474	0.041*
C7	0.28962 (18)	0.35972 (8)	0.40915 (18)	0.0381 (4)
H7	0.3221	0.4071	0.4420	0.046*
C8	0.13319 (19)	0.33991 (8)	0.41792 (19)	0.0394 (4)
C9	0.08933 (19)	0.27076 (9)	0.3675 (2)	0.0442 (4)
H9	−0.0175	0.2564	0.3710	0.053*
C10	0.19770 (18)	0.22244 (8)	0.3123 (2)	0.0397 (4)
H10	0.1648	0.1755	0.2777	0.048*
C11	0.0151 (2)	0.39230 (11)	0.4794 (2)	0.0573 (5)
H11A	0.062 (2)	0.4431 (9)	0.487 (5)	0.069*	0.50
H11B	−0.016 (4)	0.3747 (15)	0.577 (2)	0.069*	0.50
H11C	−0.080 (3)	0.394 (2)	0.415 (3)	0.069*	0.50
H11D	−0.085 (2)	0.3648 (7)	0.499 (5)	0.069*	0.50
H11E	−0.007 (4)	0.4332 (15)	0.409 (2)	0.069*	0.50
H11F	0.058 (2)	0.414 (2)	0.571 (3)	0.069*	0.50
C12	0.37592 (15)	0.06696 (8)	0.33801 (17)	0.0293 (3)
C13	0.34716 (17)	0.08246 (8)	0.48101 (18)	0.0338 (4)
H13	0.3850	0.1271	0.5225	0.041*
C14	0.26364 (17)	0.03309 (8)	0.56332 (18)	0.0359 (4)
H14	0.2445	0.0445	0.6610	0.043*
C15	0.20717 (16)	−0.03286 (8)	0.50625 (18)	0.0345 (4)
C16	0.23710 (17)	−0.04807 (8)	0.36377 (19)	0.0377 (4)
H16	0.1990	−0.0928	0.3226	0.045*
C17	0.32123 (17)	0.00041 (8)	0.28002 (19)	0.0349 (4)
H17	0.3419	−0.0116	0.1829	0.042*
C18	0.11612 (19)	−0.08676 (10)	0.5952 (2)	0.0450 (4)
H18A	0.065 (4)	−0.0596 (5)	0.677 (3)	0.054*	0.50
H18B	0.1895 (11)	−0.1256 (13)	0.636 (3)	0.054*	0.50
H18C	0.033 (3)	−0.1113 (15)	0.5332 (12)	0.054*	0.50
H18D	0.127 (4)	−0.1381 (7)	0.554 (2)	0.054*	0.50
H18E	0.0020 (16)	−0.0720 (12)	0.595 (3)	0.054*	0.50
H18F	0.158 (3)	−0.0864 (15)	0.6972 (15)	0.054*	0.50
N1	0.68911 (19)	0.25669 (8)	0.1013 (2)	0.0576 (5)
N2	0.66194 (16)	0.04879 (7)	0.08024 (16)	0.0411 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0305 (7)	0.0287 (8)	0.0345 (10)	−0.0028 (6)	0.0024 (6)	−0.0006 (7)
C2	0.0295 (7)	0.0283 (8)	0.0321 (9)	−0.0003 (6)	0.0017 (6)	−0.0024 (6)
C3	0.0409 (9)	0.0287 (8)	0.0464 (11)	−0.0020 (7)	0.0090 (8)	−0.0024 (7)
C4	0.0343 (8)	0.0277 (8)	0.0367 (10)	−0.0017 (6)	0.0043 (7)	0.0012 (7)
C5	0.0344 (8)	0.0255 (7)	0.0324 (9)	0.0003 (6)	0.0021 (6)	0.0002 (6)
C6	0.0375 (8)	0.0267 (8)	0.0387 (10)	−0.0032 (6)	−0.0013 (7)	0.0003 (7)
C7	0.0505 (9)	0.0244 (8)	0.0393 (11)	0.0015 (7)	−0.0020 (7)	−0.0023 (7)
C8	0.0495 (9)	0.0327 (9)	0.0360 (10)	0.0111 (7)	0.0041 (7)	0.0016 (7)
C9	0.0338 (8)	0.0365 (9)	0.0623 (13)	0.0034 (7)	0.0059 (8)	0.0001 (8)
C10	0.0370 (8)	0.0276 (8)	0.0545 (12)	−0.0016 (6)	0.0040 (7)	−0.0051 (7)
C11	0.0629 (12)	0.0476 (11)	0.0616 (14)	0.0204 (9)	0.0071 (10)	−0.0054 (10)
C12	0.0301 (7)	0.0244 (7)	0.0334 (10)	0.0017 (6)	0.0013 (6)	−0.0001 (6)
C13	0.0383 (8)	0.0289 (8)	0.0341 (10)	−0.0007 (6)	0.0003 (7)	−0.0028 (7)
C14	0.0405 (8)	0.0373 (9)	0.0300 (10)	0.0039 (7)	0.0033 (7)	−0.0001 (7)
C15	0.0307 (7)	0.0348 (8)	0.0380 (11)	0.0013 (6)	0.0006 (6)	0.0066 (7)
C16	0.0405 (9)	0.0303 (8)	0.0424 (11)	−0.0051 (6)	0.0011 (7)	−0.0008 (7)
C17	0.0418 (8)	0.0298 (8)	0.0331 (10)	−0.0009 (6)	0.0051 (7)	−0.0051 (7)
C18	0.0409 (9)	0.0462 (10)	0.0480 (12)	−0.0051 (7)	0.0028 (8)	0.0115 (8)
N1	0.0565 (9)	0.0416 (8)	0.0753 (13)	−0.0106 (7)	0.0237 (9)	−0.0012 (8)
N2	0.0447 (7)	0.0342 (7)	0.0448 (10)	−0.0006 (6)	0.0106 (7)	−0.0025 (6)

Geometric parameters (Å, º)

C1—C2	1.362 (2)	C8—C9	1.386 (2)
C1—C3	1.446 (2)	C8—C11	1.504 (2)
C1—C5	1.474 (2)	C9—C10	1.378 (2)
C2—C4	1.440 (2)	C12—C13	1.388 (2)
C2—C12	1.479 (2)	C12—C17	1.397 (2)
C3—N1	1.145 (2)	C13—C14	1.383 (2)
C4—N2	1.146 (2)	C14—C15	1.389 (2)
C5—C10	1.389 (2)	C15—C16	1.384 (2)
C5—C6	1.391 (2)	C15—C18	1.505 (2)
C6—C7	1.372 (2)	C16—C17	1.383 (2)
C7—C8	1.387 (2)
C2—C1—C3	117.26 (13)	C9—C8—C11	121.23 (15)
C2—C1—C5	127.47 (14)	C7—C8—C11	120.81 (15)
C3—C1—C5	115.20 (12)	C10—C9—C8	121.28 (15)
C1—C2—C4	116.81 (13)	C9—C10—C5	120.41 (14)
C1—C2—C12	128.27 (14)	C13—C12—C17	118.85 (14)
C4—C2—C12	114.91 (12)	C13—C12—C2	121.61 (13)
N1—C3—C1	178.93 (17)	C17—C12—C2	119.39 (15)
N2—C4—C2	178.16 (16)	C14—C13—C12	120.20 (14)
C10—C5—C6	118.39 (13)	C13—C14—C15	121.41 (16)
C10—C5—C1	120.95 (13)	C16—C15—C14	118.03 (14)
C6—C5—C1	120.52 (13)	C16—C15—C18	120.32 (15)
C7—C6—C5	120.66 (14)	C14—C15—C18	121.65 (16)
C6—C7—C8	121.24 (14)	C17—C16—C15	121.39 (15)
C9—C8—C7	117.96 (14)	C16—C17—C12	120.12 (16)
C3—C1—C2—C4	−9.1 (2)	C3—C1—C2—C12	171.1 (2)
C5—C1—C2—C4	167.7 (2)	C5—C1—C2—C12	−12.1 (3)