2-(7-Iso­propyl-2-methyl­cyclo­hepta­[b]­thio­phen-8-yl­idene)­propane­di­nitrile

The exocyclic double-bond length of the title compound, C₁₆H₁₄N₂S, is 1.366 (4) Å. The planarity of the seven-membered ring is decreased by the iso­propyl group and the thio­phene ring. The di­cyano­methyl­ene group intersects the seven-membered ring at an angle of 45.9 (2)°.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.052
• wR factor = 0.143
• Data-to-parameter ratio = 16.7

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level C:



PLAT_371  Alert C Long   C(sp2)-C(sp1) Bond  C(8)   -   C(9)   =       1.44 Ang.

PLAT_371  Alert C Long   C(sp2)-C(sp1) Bond  C(8)   -   C(10)  =       1.44 Ang.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 2 Alert Level C = Please check

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S1. Comment

8,8-Dicyanoheptafulvene (DCH), a non-benzenoid aromatic compound, has a brilliant red color and a large dipole moment (7.49 D; Shimanouchi et al., 1966). The introduction of substituent groups to the seven-membered ring causes the color to change. For example, the crystal colors of 1,6-dimethyl-8,8-dicyanoheptafulvene (DMDCH; Shimanouchi et al., 1974a) and 1-isopropyl-8,8-dicyanoheptafulvene (IPDCH; Shimanouchi et al., 1974b) are yellow. It is observed by the X-ray crystallographic analyses of DMDCH and IPDCH that the conjugation between the exocyclic double bond and the seven-membered ring is largely hindered by the substituent at the neighboring position. We now report the structure of the title compound, (I), which has a yellow color, with the aim of contributing to a deeper understanding of the relationships between the 8,8-dicyanoheptafulvene moiety and neighboring substituents.

The seven-membered ring in (I) has a twisted conformation; the intersection angles between the least-squares planes A (defined by C1/C2/C7) and B (defined by C2/C3/C6/C7), and between the least-squares planes B and C (defined by C3–C6) are 45.2 (3) and 22.2 (2)°, respectively. The deviations of each atom from the seven-membered ring are -0.39 Å for C1, 0.12 Å for C2, 0.22 Å for C3, 0.18 Å for C4, -0.24 Å for C5, -0.18 Å for C6 and 0.22 Å for C7, resulting from the intramolecular steric hindance between the isopropyl and the cyano groups. The dicyanomethylene group is inclined to the seven-membered ring (defined by C1–C7) at an angle of 45.9 (2)°, which is distinct from that (4.8°) of DCH (Shimanouchi et al., 1966), similar to that (47.5°) of DMDCH (Shimanouchi et al., 1974a), and larger than that (39.2°) of IPDCH (Shimanouchi et al., 1974b). These observations result from the intramolecular steric hindrance between the thiophene ring and the cyano groups in addition to the steric hindrance between the isopropyl and the cyano groups. The dihedral angle between thiophene ring and the least-squares plane B is 22.2 (1)°. The deviations of each atom from the thiophene ring plane are within 0.02 Å. It is interesting that the exocyclic C1═C8 bond length [1.366 (4) Å] of (I) is shorter than that (1.422 Å) of DCH, and similar to those (1.361 and 1.367 Å) of DMDCH and IPDCH (Shimanouchi et al., 1974a,b).

S2. Experimental

Compound (I) was prepared from 7-isopropyl-2-methylcyclohepta[b]thiophen-8-one (Ikeda et al., 1994) and malononitrile by reflux in acetic anhydride. Single crystals of (I) were obtained by recrystallization from chloroform.

S3. Refinement

All H atoms were located at ideal positions and constrained with U_iso held fixed to 1.2 or 1.5 times (H₂O) U_eq of the parent atoms.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SIR97 (Altomare et al., 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Xtal_GX (Hall & du Boulay, 1995); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. The molecular structure of (I) showing 50% probability displacement ellipsoids.

(1)

Crystal data

C16H14N2S	Dx = 1.247 Mg m^−3
Mr = 266.35	Melting point = 107–108 K
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
a = 17.174 (5) Å	Cell parameters from 20 reflections
b = 7.380 (5) Å	θ = 10.1–18.0°
c = 11.393 (5) Å	µ = 0.22 mm^−1
β = 100.647 (5)°	T = 296 K
V = 1419.1 (12) Å^3	Prism, red
Z = 4	0.27 × 0.27 × 0.23 mm
F(000) = 560

Data collection

Enraf-Nonius FR590 diffractometer	1396 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.039
Graphite monochromator	θmax = 26.3°, θmin = 2.7°
ω–2θ scans	h = −21→21
Absorption correction: ψ scan (North et al., 1968)	k = −9→0
Tmin = 0.959, Tmax = 1.000	l = −14→0
3016 measured reflections	3 standard reflections every 120 min
2871 independent reflections	intensity decay: 0.5%

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)] = 0.052	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.143	H-atom parameters constrained
S = 0.99	w = 1/[σ^2(Fo^2) + (0.058P)^2 + 0.0071P] where P = (Fo^2 + 2Fc^2)/3
2871 reflections	(Δ/σ)max < 0.001
172 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.29 e Å^−3

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
S1	0.54532 (5)	0.19535 (14)	0.38292 (8)	0.0499 (3)
N1	0.44857 (17)	0.4131 (4)	0.1162 (3)	0.0595 (9)
N2	0.56520 (17)	0.0975 (4)	−0.1129 (3)	0.0531 (8)
C1	0.62781 (16)	0.1698 (4)	0.1956 (3)	0.0339 (7)
C2	0.62663 (18)	0.2272 (4)	0.3161 (3)	0.0372 (8)
C3	0.68670 (19)	0.3169 (4)	0.3920 (3)	0.0429 (8)
C4	0.7619 (2)	0.3647 (5)	0.3615 (3)	0.0556 (10)
H4	0.7886	0.4624	0.4021	0.067*
C5	0.7970 (2)	0.2827 (5)	0.2808 (4)	0.0580 (10)
H5	0.8433	0.3353	0.2653	0.070*
C6	0.77017 (19)	0.1209 (5)	0.2156 (3)	0.0466 (9)
H6	0.8101	0.0499	0.1945	0.056*
C7	0.69612 (18)	0.0557 (5)	0.1802 (3)	0.0397 (8)
C8	0.56826 (17)	0.2091 (4)	0.1019 (3)	0.0336 (7)
C9	0.50189 (19)	0.3232 (5)	0.1128 (3)	0.0408 (8)
C10	0.56775 (17)	0.1473 (4)	−0.0182 (3)	0.0377 (8)
C11	0.5902 (2)	0.3035 (5)	0.5113 (3)	0.0510 (9)
C12	0.6629 (2)	0.3626 (5)	0.5015 (3)	0.0537 (10)
H12	0.6950	0.4281	0.5614	0.064*
C13	0.5474 (3)	0.3181 (6)	0.6143 (3)	0.0746 (13)
H13A	0.4963	0.2620	0.5933	0.112*
H13B	0.5410	0.4435	0.6327	0.112*
H13C	0.5775	0.2581	0.6827	0.112*
C14	0.6780 (2)	−0.1343 (5)	0.1325 (3)	0.0519 (10)
H14	0.6393	−0.1243	0.0580	0.062*
C15	0.6399 (2)	−0.2411 (5)	0.2199 (4)	0.0700 (12)
H15A	0.6279	−0.3612	0.1895	0.105*
H15B	0.5918	−0.1821	0.2305	0.105*
H15C	0.6756	−0.2480	0.2953	0.105*
C16	0.7498 (3)	−0.2352 (6)	0.1047 (4)	0.0858 (14)
H16A	0.7729	−0.1667	0.0482	0.129*
H16B	0.7335	−0.3517	0.0714	0.129*
H16C	0.7881	−0.2507	0.1768	0.129*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0486 (5)	0.0622 (6)	0.0414 (5)	−0.0025 (5)	0.0148 (4)	−0.0051 (5)
N1	0.0468 (18)	0.067 (2)	0.066 (2)	0.0139 (17)	0.0140 (16)	−0.0020 (18)
N2	0.059 (2)	0.065 (2)	0.0351 (17)	−0.0014 (16)	0.0070 (14)	0.0021 (16)
C1	0.0281 (16)	0.0355 (18)	0.0383 (17)	−0.0053 (14)	0.0066 (14)	0.0011 (15)
C2	0.0386 (18)	0.0382 (18)	0.0345 (17)	0.0034 (15)	0.0059 (14)	0.0000 (15)
C3	0.0451 (19)	0.041 (2)	0.0395 (18)	0.0013 (17)	−0.0013 (15)	0.0010 (17)
C4	0.047 (2)	0.049 (2)	0.063 (3)	−0.0168 (19)	−0.0068 (19)	0.0000 (19)
C5	0.034 (2)	0.069 (3)	0.070 (3)	−0.009 (2)	0.0083 (19)	0.007 (2)
C6	0.038 (2)	0.055 (2)	0.047 (2)	0.0081 (17)	0.0102 (16)	0.0075 (18)
C7	0.0332 (18)	0.052 (2)	0.0341 (18)	0.0040 (17)	0.0058 (15)	0.0033 (16)
C8	0.0284 (16)	0.0376 (18)	0.0355 (17)	−0.0024 (15)	0.0076 (13)	−0.0012 (15)
C9	0.0363 (19)	0.045 (2)	0.0404 (18)	0.0005 (17)	0.0060 (15)	−0.0024 (17)
C10	0.0299 (17)	0.042 (2)	0.039 (2)	0.0012 (15)	0.0003 (15)	0.0062 (16)
C11	0.066 (2)	0.051 (2)	0.0363 (19)	0.010 (2)	0.0099 (17)	−0.0021 (18)
C12	0.070 (3)	0.047 (2)	0.038 (2)	0.005 (2)	−0.0076 (18)	−0.0050 (17)
C13	0.103 (3)	0.084 (3)	0.042 (2)	0.010 (3)	0.028 (2)	−0.003 (2)
C14	0.053 (2)	0.053 (2)	0.047 (2)	0.0159 (19)	−0.0002 (18)	−0.0060 (18)
C15	0.064 (3)	0.044 (2)	0.102 (3)	−0.003 (2)	0.013 (3)	−0.001 (2)
C16	0.096 (4)	0.071 (3)	0.098 (3)	0.030 (3)	0.038 (3)	−0.016 (3)

Geometric parameters (Å, º)

S1—C11	1.719 (4)	C8—C10	1.441 (4)
S1—C2	1.725 (3)	C8—C9	1.441 (5)
N1—C9	1.137 (4)	C11—C12	1.346 (5)
N2—C10	1.133 (4)	C11—C13	1.499 (5)
C1—C8	1.366 (4)	C12—H12	0.930
C1—C2	1.441 (4)	C13—H13A	0.960
C1—C7	1.480 (4)	C13—H13B	0.960
C2—C3	1.386 (4)	C13—H13C	0.960
C3—C12	1.422 (5)	C14—C15	1.512 (5)
C3—C4	1.442 (5)	C14—C16	1.522 (5)
C4—C5	1.334 (5)	C14—H14	0.980
C4—H4	0.930	C15—H15A	0.960
C5—C6	1.436 (5)	C15—H15B	0.960
C5—H5	0.930	C15—H15C	0.960
C6—C7	1.350 (4)	C16—H16A	0.960
C6—H6	0.930	C16—H16B	0.960
C7—C14	1.515 (5)	C16—H16C	0.960
C11—S1—C2	92.27 (17)	C13—C11—S1	119.4 (3)
C8—C1—C2	122.8 (3)	C11—C12—C3	114.7 (3)
C8—C1—C7	121.6 (3)	C11—C12—H12	122.7
C2—C1—C7	115.5 (3)	C3—C12—H12	122.7
C3—C2—C1	126.5 (3)	C11—C13—H13A	109.5
C3—C2—S1	111.1 (2)	C11—C13—H13B	109.5
C1—C2—S1	122.4 (2)	H13A—C13—H13B	109.5
C2—C3—C12	111.0 (3)	C11—C13—H13C	109.5
C2—C3—C4	124.3 (3)	H13A—C13—H13C	109.5
C12—C3—C4	124.6 (3)	H13B—C13—H13C	109.5
C5—C4—C3	126.4 (3)	C15—C14—C7	109.3 (3)
C5—C4—H4	116.8	C15—C14—C16	110.4 (3)
C3—C4—H4	116.8	C7—C14—C16	114.0 (3)
C4—C5—C6	126.2 (3)	C15—C14—H14	107.6
C4—C5—H5	116.9	C7—C14—H14	107.6
C6—C5—H5	116.9	C16—C14—H14	107.6
C7—C6—C5	130.2 (3)	C14—C15—H15A	109.5
C7—C6—H6	114.9	C14—C15—H15B	109.5
C5—C6—H6	114.9	H15A—C15—H15B	109.5
C6—C7—C1	119.0 (3)	C14—C15—H15C	109.5
C6—C7—C14	123.8 (3)	H15A—C15—H15C	109.5
C1—C7—C14	117.0 (3)	H15B—C15—H15C	109.5
C1—C8—C10	123.2 (3)	C14—C16—H16A	109.5
C1—C8—C9	123.2 (3)	C14—C16—H16B	109.5
C10—C8—C9	113.6 (3)	H16A—C16—H16B	109.5
N1—C9—C8	177.1 (4)	C14—C16—H16C	109.5
N2—C10—C8	178.1 (3)	H16A—C16—H16C	109.5
C12—C11—C13	129.7 (4)	H16B—C16—H16C	109.5
C12—C11—S1	110.9 (3)
C8—C1—C2—C3	−129.2 (4)	C2—C1—C7—C6	−57.8 (4)
C7—C1—C2—C3	54.0 (4)	C8—C1—C7—C14	−58.6 (4)
C8—C1—C2—S1	48.9 (4)	C2—C1—C7—C14	118.2 (3)
C7—C1—C2—S1	−127.8 (3)	C2—C1—C8—C10	−178.0 (3)
C11—S1—C2—C3	0.7 (3)	C7—C1—C8—C10	−1.4 (5)
C11—S1—C2—C1	−177.7 (3)	C2—C1—C8—C9	5.0 (5)
C1—C2—C3—C12	176.2 (3)	C7—C1—C8—C9	−178.4 (3)
S1—C2—C3—C12	−2.1 (4)	C2—S1—C11—C12	1.0 (3)
C1—C2—C3—C4	−1.1 (5)	C2—S1—C11—C13	−178.4 (3)
S1—C2—C3—C4	−179.4 (3)	C13—C11—C12—C3	176.8 (4)
C2—C3—C4—C5	−25.1 (6)	S1—C11—C12—C3	−2.4 (4)
C12—C3—C4—C5	158.0 (4)	C2—C3—C12—C11	3.0 (4)
C3—C4—C5—C6	−5.8 (6)	C4—C3—C12—C11	−179.7 (3)
C4—C5—C6—C7	29.9 (6)	C6—C7—C14—C15	112.8 (4)
C5—C6—C7—C1	7.8 (5)	C1—C7—C14—C15	−63.0 (4)
C5—C6—C7—C14	−167.9 (3)	C6—C7—C14—C16	−11.3 (5)
C8—C1—C7—C6	125.4 (3)	C1—C7—C14—C16	172.9 (3)