3-(Dicyano­methyl­idene)-6,6-dimethyl­cyclo­hexa-1,4-diene

In the title compound, C₁₁H₁₀N₂, the six-membered ring is planar (r.m.s.d. 0.013 Å). Mol­ecules are linked by weak C—H...N inter­actions into chains parallel to [201], which lie in planes parallel to (02).

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.051
• wR factor = 0.132
• Data-to-parameter ratio = 18.4

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT230_ALERT_2_C Hirshfeld Test Diff for    C7     -   C9      ..       5.49 su
PLAT371_ALERT_2_C Long   C(sp2)-C(sp1) Bond  C7     -   C8     ...       1.43 Ang.
PLAT371_ALERT_2_C Long   C(sp2)-C(sp1) Bond  C7     -   C9     ...       1.43 Ang.
PLAT480_ALERT_4_C Long H...A H-Bond Reported H5     ..  N1      ..       2.65 Ang.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   5 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
   3 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
   2 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

In our studies of the preparation and properties of novel cross-conjugated π-electron systems (Hopf, 1984, 2001; Hopf et al., 2002), we needed the structure of the title compound 3 for comparison; see Fig. 1.

The molecular dimensions (Table 1) accord with expectation. The six-membered ring is planar (r.m.s. deviation 0.013 Å), with the dicyanomethylidene group bent out of the plane by up to 0.179 (3) Å for N2.

The packing involves chains of molecules parallel to (201), linked via the weak hydrogen bond H5···N1 (Table 2). This interaction might be better considered as an H···π interaction to the midpoint of C8≡N1, which is slightly more linear (H···midpoint 2.76 Å, angle 148°). The chains lie in planes parallel to 102 (Fig. 2).

Related literature

For related literature, see: Hopf (1984, 2001); Hopf et al. (2002); Yanagita et al. (1951).

S2. Experimental

The preparation of (3) was achieved by Knoevenagel condensation of 4,4-dimethylcyclohexa-2,5-dione (1) (Yaganita et al., 1951) with malonodinitrile (2). 10 mg β-alanine and 0.2 ml glacial acetic acid were added to a mixture of 0.49 g (4.0 mmol) 1 and 0.26 g (4.0 mmol) of freshly distilled 2 in 8 ml anhydrous ethanol. After stirring for several days (TLC monitoring), 40 ml dichloromethane were added and the reaction mixture filtered through a short silica gel column. The solvent was removed by rotary evaporation and the remaining solid purified by plate chromatography (silica gel, dichloromethane): 0.20 g (30%) 3, colourless needles, m.p. 94°C. Single crystals were obtained from dichloromethane.

¹H-NMR: δ = 1.25 (s, 6H, CH₃), 6.67 (d, J = 9.9 Hz, 2H, 1- and 5-H), 6.82 (d, J = 9.9 Hz, 2- and 4-H); ¹³C-NMR: δ = 26.6 (CH₃), 39.8 (C6), 76.5 (C7), 112.9 (C≡N), 120.5 (C2,C4), 154.5 (C1,C5), 157.0 (C3); IR (KBr): ¯ν = 1972 (m), 2935 (m), 2219 (s), 1650 (s), 1641 (s), 1525 (s), 1474 (m), 924 (w), 825 (s), 690 (w) cm^-1; UV (acetonitrile): λ_max (log ε) = 322 nm (4.40); MS (EI, 70 eV): m/z = 170 (31) [M⁺], 156 (11), 155 (100), 143 (15), 128 (35), 115 (12), 105 (23), 101 (19), 91 (14); elemental analysis: C₁₁H₁₀N₂ (170.23): calcd C 77.62, H 5.92, N 16.46; found C 77.31, H 5.94, N 16.40.

S3. Refinement

Methyl H atoms were identified in difference syntheses, idealized and then refined using rigid methyl groups (C—H 0.98 Å, H—C—H 109.5°) allowed to rotate but not tip. Other H atoms were included using a riding model with C—H 0.95 Å. U(H) values were fixed at n × U(eq) of the parent atom, with n = 1.5 for methyl H, 1.2 for other H.

Computing details

Data collection: XSCANS (Fait, 1991); cell refinement: XSCANS (Fait, 1991); data reduction: XSCANS (Fait, 1991); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP5 (Siemens, 1994); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. The molecule of the title compound in the crystal. Ellipsoids represent 30% probability levels.
	Fig. 2. Packing diagram of the title compound viewed perpendicular to the plane 102.
	Fig. 3. The preparation.

3-(Dicyanomethylidene)-6,6-dimethylcyclohexa-1,4-diene

Crystal data

C11H10N2	F(000) = 360
Mr = 170.21	Dx = 1.159 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.8978 (8) Å	Cell parameters from 62 reflections
b = 18.534 (2) Å	θ = 5–12.5°
c = 6.8486 (6) Å	µ = 0.07 mm^−1
β = 103.232 (8)°	T = 173 K
V = 975.88 (17) Å^3	Block, colourless
Z = 4	0.6 × 0.6 × 0.6 mm

Data collection

Siemens P4 diffractometer	Rint = 0.013
Radiation source: fine-focus sealed tube	θmax = 27.5°, θmin = 3.3°
Graphite monochromator	h = −10→9
ω scans	k = −6→24
3180 measured reflections	l = 0→8
2226 independent reflections	3 standard reflections every 247 reflections
1716 reflections with I > 2σ(I)	intensity decay: none

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)] = 0.051	H-atom parameters constrained
wR(F^2) = 0.132	w = 1/[σ^2(Fo^2) + (0.0892P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
2226 reflections	Δρmax = 0.50 e Å^−3
121 parameters	Δρmin = −0.41 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.34 (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.

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

- 4.0384 (0.0036) x + 0.2071 (0.0092) y + 6.5304 (0.0014) z = 0.0741 (0.0061)

* 0.0103 (0.0009) C1 * 0.0083 (0.0008) C2 * -0.0187 (0.0008) C3 * 0.0093 (0.0009) C4 * 0.0093 (0.0010) C5 * -0.0185 (0.0009) C6 - 0.0826 (0.0017) C7 - 0.1204 (0.0022) C8 - 0.1269 (0.0022) C9 - 0.1396 (0.0028) N1 - 0.1789 (0.0026) N2

Rms deviation of fitted atoms = 0.0132

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
N1	1.01120 (16)	0.68467 (7)	0.5936 (2)	0.0572 (4)
N2	0.68155 (18)	0.86921 (6)	0.37784 (19)	0.0547 (4)
C1	0.46171 (16)	0.56316 (6)	0.28058 (18)	0.0369 (3)
H1	0.4818	0.5128	0.2978	0.044*
C2	0.59169 (15)	0.60762 (6)	0.35924 (17)	0.0343 (3)
H2	0.6999	0.5882	0.4293	0.041*
C3	0.57112 (15)	0.68519 (6)	0.33993 (16)	0.0320 (3)
C4	0.40267 (16)	0.71260 (6)	0.23917 (18)	0.0396 (3)
H4	0.3838	0.7632	0.2287	0.048*
C5	0.27336 (17)	0.66755 (7)	0.1606 (2)	0.0460 (4)
H5	0.1648	0.6881	0.0958	0.055*
C6	0.28664 (15)	0.58718 (7)	0.1671 (2)	0.0418 (3)
C7	0.70796 (15)	0.73089 (6)	0.41331 (16)	0.0338 (3)
C8	0.87590 (16)	0.70475 (7)	0.51221 (18)	0.0398 (3)
C9	0.69184 (17)	0.80778 (7)	0.39413 (18)	0.0391 (3)
C10	0.2557 (2)	0.55870 (7)	−0.0502 (2)	0.0539 (4)
H10A	0.1400	0.5735	−0.1254	0.081*
H10B	0.2634	0.5059	−0.0484	0.081*
H10C	0.3442	0.5786	−0.1146	0.081*
C11	0.14710 (19)	0.55525 (9)	0.2676 (3)	0.0624 (5)
H11A	0.0315	0.5708	0.1938	0.094*
H11B	0.1675	0.5723	0.4065	0.094*
H11C	0.1537	0.5025	0.2663	0.094*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0466 (7)	0.0505 (7)	0.0686 (8)	−0.0086 (5)	0.0015 (6)	0.0017 (6)
N2	0.0815 (9)	0.0309 (6)	0.0557 (7)	−0.0078 (5)	0.0242 (6)	−0.0056 (5)
C1	0.0433 (7)	0.0250 (5)	0.0409 (6)	0.0024 (4)	0.0068 (5)	0.0015 (5)
C2	0.0383 (6)	0.0269 (6)	0.0358 (6)	0.0040 (4)	0.0047 (5)	0.0030 (4)
C3	0.0422 (6)	0.0260 (5)	0.0280 (5)	0.0003 (4)	0.0086 (4)	−0.0009 (4)
C4	0.0472 (7)	0.0241 (5)	0.0447 (6)	0.0064 (5)	0.0045 (5)	−0.0019 (5)
C5	0.0408 (7)	0.0318 (6)	0.0593 (8)	0.0091 (5)	−0.0013 (6)	−0.0033 (6)
C6	0.0389 (7)	0.0291 (6)	0.0531 (7)	0.0001 (5)	0.0018 (5)	−0.0038 (5)
C7	0.0451 (6)	0.0281 (6)	0.0292 (5)	−0.0028 (4)	0.0103 (4)	−0.0011 (4)
C8	0.0436 (7)	0.0352 (6)	0.0399 (6)	−0.0100 (5)	0.0083 (5)	−0.0017 (5)
C9	0.0529 (7)	0.0314 (6)	0.0350 (6)	−0.0066 (5)	0.0146 (5)	−0.0045 (5)
C10	0.0612 (9)	0.0363 (7)	0.0545 (8)	−0.0005 (6)	−0.0070 (7)	−0.0055 (6)
C11	0.0453 (8)	0.0536 (9)	0.0890 (12)	−0.0061 (7)	0.0170 (8)	−0.0039 (8)

Geometric parameters (Å, º)

N1—C8	1.1481 (17)	C5—H5	0.9500
N2—C9	1.1451 (17)	C6—C11	1.544 (2)
C1—C2	1.3303 (17)	C6—C10	1.5451 (19)
C1—C6	1.4905 (17)	C7—C8	1.4288 (18)
C1—H1	0.9500	C7—C9	1.4341 (16)
C2—C3	1.4495 (15)	C10—H10A	0.9800
C2—H2	0.9500	C10—H10B	0.9800
C3—C7	1.3745 (16)	C10—H10C	0.9800
C3—C4	1.4436 (16)	C11—H11A	0.9800
C4—C5	1.3334 (18)	C11—H11B	0.9800
C4—H4	0.9500	C11—H11C	0.9800
C5—C6	1.4933 (17)
C2—C1—C6	124.33 (10)	C5—C6—C10	108.51 (11)
C2—C1—H1	117.8	C11—C6—C10	109.07 (12)
C6—C1—H1	117.8	C3—C7—C8	122.10 (10)
C1—C2—C3	121.16 (10)	C3—C7—C9	122.20 (11)
C1—C2—H2	119.4	C8—C7—C9	115.70 (10)
C3—C2—H2	119.4	N1—C8—C7	178.94 (14)
C7—C3—C4	121.29 (10)	N2—C9—C7	178.86 (14)
C7—C3—C2	121.03 (10)	C6—C10—H10A	109.5
C4—C3—C2	117.67 (10)	C6—C10—H10B	109.5
C5—C4—C3	120.62 (11)	H10A—C10—H10B	109.5
C5—C4—H4	119.7	C6—C10—H10C	109.5
C3—C4—H4	119.7	H10A—C10—H10C	109.5
C4—C5—C6	124.79 (11)	H10B—C10—H10C	109.5
C4—C5—H5	117.6	C6—C11—H11A	109.5
C6—C5—H5	117.6	C6—C11—H11B	109.5
C1—C6—C5	111.34 (10)	H11A—C11—H11B	109.5
C1—C6—C11	108.95 (12)	C6—C11—H11C	109.5
C5—C6—C11	110.07 (11)	H11A—C11—H11C	109.5
C1—C6—C10	108.86 (11)	H11B—C11—H11C	109.5
C6—C1—C2—C3	0.20 (19)	C2—C1—C6—C10	117.14 (14)
C1—C2—C3—C7	−176.99 (11)	C4—C5—C6—C1	2.35 (19)
C1—C2—C3—C4	2.36 (16)	C4—C5—C6—C11	123.28 (15)
C7—C3—C4—C5	176.90 (12)	C4—C5—C6—C10	−117.44 (15)
C2—C3—C4—C5	−2.44 (17)	C4—C3—C7—C8	−179.56 (11)
C3—C4—C5—C6	0.0 (2)	C2—C3—C7—C8	−0.24 (16)
C2—C1—C6—C5	−2.44 (18)	C4—C3—C7—C9	−0.09 (16)
C2—C1—C6—C11	−124.02 (14)	C2—C3—C7—C9	179.23 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5···N1^i	0.95	2.65	3.4007 (17)	136

Symmetry code: (i) x−1, −y+3/2, z−1/2.