Di­cyano­durene–p-tetra­fluoro­di­iodo­benzene (1/1)

In the crystal structure of the 1:1 complex between di­cyano­durene (2,3,5,6-tetra­methyl-1,4-benzodicarbo­nitrile) and p-tetra­fluoro­di­iodo­benzene (2,3,5,6-tetra­fluoro-1,4-di­iodo­ben­zene), C₁₂H₁₂N₂·C₆F₄I₂, there are two major types of intermolecular interaction. The planar mol­ecules are stacked alternately in the common charge-transfer arrangement with mol­ecules 3.53 (3) Å apart. In addition, the mol­ecules form linear chains, driven by CN...I interactions, with a distance of 3.061 (3) Å. The di­cyano­durene and tetra­fluoro­di­iodo­benzene mol­ecules lie on centers of symmetry.

Key indicators

• Single-crystal X-ray study
• T = 173 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.026
• wR factor = 0.073
• Data-to-parameter ratio = 18.6

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(11)  -   C(21)  =       1.44 Ang.


 0 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

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S1. Comment

Significant intermolecular CN···I—C interactions are well known. In the earliest work on ICN (Ketelaar & Zwartsenberg, 1939) and ICCCN (Borgen et al., 1962), the CN···I distances are less than 3.0 Å. In p-iodobenzonitrile (Schlemper & Britton, 1965; see also Desiraju & Harlow, 1989) and similar compounds with aromatic rings between the I and the CN [for a summary, see Table 4 in Ojala et al. (1999)], the distances are nearer 3.2 Å, which is still shorter than the expected van der Waals distance of about 3.4 Å.

It was conjectured that p-dicyanobenzene and p-diiodobenzene might form a solid-state complex with similar interactions, but attempts in this laboratory to prepare crystals of such a complex by evaporating solutions that were equimolar in the two components produced only a mixture of crystals of the starting materials. The recent results of Cardillo et al. (2000), which showed that fluorinated diiodides interact strongly with a number of dibasic nitrogen compounds suggested that replacing the p-diiodobenzene with p-tetrafluorodiiodobenzene would give a better chance of success. However, attempts to prepare a complex of p-tetrafluorodiiodobenzene and p-dicyanobenzene again led to mixtures of the two starting materials.

As Cardillo et al. (2000) have shown, replacement of H with F in the diiodides makes the I atoms stronger Lewis acids. In a similar fashion, replacement of H with CH₃ in the dicyanides should make the cyanide groups stronger Lewis bases. Accordingly, the preparation of the title compound, (I), was attempted and was successful. The structure of (I) is reported here.

The bond lengths and angles are normal. Fig. 1 shows one CN···I interaction. Since both molecules lie on centers of symmetry, these interactions lead to chains of molecules lying along the [102] direction. Adjacent molecules in these chains are tilted 2.1 (2)° away from being parallel to each other. The metric parameters of the CN···I interaction are: CN···I 143.4 (4)°, N···I 3.061 (3)° and N···I—C 172.6 (3)°.

The π–π interactions between molecules in adjacent chains are also significant. Fig. 2 shows the overlap between molecules viewed perpendicular to the plane of the diiodide molecule. The perpendicular distance between the ring atoms in the molecules is 3.53 (3) Å. This is consistent with the findings of Dahl (1971, 1972, 1975) that complexes of hexafluorobenzene with p-xylene, mesitylene, durene, and hexamethylbenzene had inter-ring distances of 3.55, 3.56, 3.51 and 3.56 Å, respectively.

The combination of the CN···I and π–π interactions lead to layers of molecules perpendicular to the b axis as shown in Fig. 3. I atoms in adjacent chains make van der Waals contacts of 4.247 (2) Å.

S2. Experimental

The diiodide was obtained from Aldrich Chemical Co. Inc. The dicyanodurene was prepared as described in Britton & van Rij (1991). The crystals grew as plates from acetonitrile,

S3. Refinement

All of the peaks higher than 0.5 e Å⁻³ in the final difference Fourier map lie about 1 Å from the I atom. The methyl H atoms were included at idealized positions with the methyl groups allowed to rotate around the C—C bonds.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); 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.

Figures

	Fig. 1. The title complex, with displacement ellipsoids shown at the 50% probability level. Unlabelled atoms are related to the labelled atoms by centers of symmetry. The dotted line shows the short CN···I contact.
	Fig. 2. The π-π overlap between the molecules, viewed normal to the plane of the C6F4I2 molecule.
	Fig. 3. View along b, showing one layer formed by the combined CN···I and π–π interactions.

2,3,5,6-tetramethyl-1,4-benzodicarbonitrile–2,3,5,6-tetrafluoro-1,4- diiodobenzene (1/1)

Crystal data

C12H12N2·C6F4I2	F(000) = 552
Mr = 586.10	Dx = 1.990 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2326 reflections
a = 7.447 (2) Å	θ = 3.0–27.4°
b = 13.657 (4) Å	µ = 3.26 mm^−1
c = 9.642 (2) Å	T = 173 K
β = 94.19 (1)°	Plate, colorless
V = 978.0 (4) Å^3	0.50 × 0.20 × 0.05 mm
Z = 2

Data collection

Siemens SMART area-detector diffractometer	2234 independent reflections
Radiation source: fine-focus sealed tube	1903 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
ω scans	θmax = 27.5°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.50, Tmax = 0.85	k = −17→17
9767 measured reflections	l = −11→12

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)] = 0.026	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.073	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.041P)^2 + 0.663P] where P = (Fo^2 + 2Fc^2)/3
2234 reflections	(Δ/σ)max = 0.009
120 parameters	Δρmax = 1.18 e Å^−3
0 restraints	Δρmin = −0.49 e Å^−3

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
I1	0.67123 (3)	0.539275 (16)	0.84228 (2)	0.03787 (10)
F2	0.5820 (3)	0.34337 (14)	0.6655 (2)	0.0502 (5)
F3	0.4433 (3)	0.31441 (14)	0.4064 (2)	0.0490 (5)
C1	0.5721 (4)	0.5154 (2)	0.6379 (3)	0.0313 (6)
C2	0.5418 (4)	0.4216 (2)	0.5846 (3)	0.0341 (7)
C3	0.4706 (4)	0.4076 (2)	0.4512 (3)	0.0325 (7)
C11	0.9304 (4)	0.5359 (2)	1.3749 (3)	0.0269 (6)
C12	0.9926 (4)	0.60287 (19)	1.4780 (3)	0.0284 (6)
C13	1.0645 (4)	0.5671 (2)	1.6059 (3)	0.0266 (6)
C21	0.8572 (4)	0.5727 (2)	1.2430 (3)	0.0346 (7)
C22	0.9829 (5)	0.7115 (2)	1.4509 (4)	0.0455 (8)
H22A	0.9278	0.7233	1.3570	0.068*
H22B	1.1047	0.7392	1.4591	0.068*
H22C	0.9100	0.7427	1.5191	0.068*
C23	1.1325 (5)	0.6352 (2)	1.7205 (3)	0.0365 (7)
H23A	1.1990	0.5976	1.7940	0.055*
H23B	1.0304	0.6683	1.7588	0.055*
H23C	1.2125	0.6840	1.6832	0.055*
N21	0.7986 (4)	0.6015 (2)	1.1382 (3)	0.0501 (8)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.03722 (15)	0.05128 (15)	0.02497 (14)	0.00091 (9)	0.00133 (9)	−0.00511 (8)
F2	0.0740 (15)	0.0398 (10)	0.0360 (11)	0.0040 (10)	−0.0014 (10)	0.0063 (8)
F3	0.0698 (14)	0.0334 (10)	0.0435 (12)	−0.0058 (9)	0.0015 (10)	−0.0100 (8)
C1	0.0294 (15)	0.0397 (16)	0.0253 (16)	−0.0019 (12)	0.0046 (12)	−0.0055 (12)
C2	0.0374 (17)	0.0333 (14)	0.0323 (17)	0.0012 (13)	0.0073 (13)	0.0031 (13)
C3	0.0389 (17)	0.0317 (15)	0.0275 (16)	−0.0032 (12)	0.0069 (13)	−0.0066 (11)
C11	0.0256 (14)	0.0308 (13)	0.0236 (14)	−0.0003 (10)	−0.0023 (11)	0.0013 (11)
C12	0.0283 (14)	0.0272 (13)	0.0295 (15)	0.0003 (11)	0.0000 (11)	−0.0003 (11)
C13	0.0256 (14)	0.0273 (12)	0.0267 (15)	−0.0014 (11)	−0.0002 (11)	−0.0032 (11)
C21	0.0365 (17)	0.0358 (14)	0.0302 (17)	−0.0019 (13)	−0.0051 (13)	0.0005 (13)
C22	0.061 (2)	0.0292 (15)	0.044 (2)	−0.0006 (15)	−0.0112 (17)	0.0024 (13)
C23	0.0391 (18)	0.0360 (16)	0.0331 (17)	−0.0015 (13)	−0.0057 (13)	−0.0079 (13)
N21	0.060 (2)	0.0512 (18)	0.0367 (18)	0.0018 (14)	−0.0134 (15)	0.0061 (13)

Geometric parameters (Å, º)

I1—C1	2.079 (3)	C12—C22	1.507 (4)
F2—C2	1.344 (4)	C13—C11^ii	1.418 (4)
F3—C3	1.355 (3)	C13—C23	1.504 (4)
C1—C3^i	1.380 (5)	C21—N21	1.141 (4)
C1—C2	1.392 (5)	C22—H22A	0.9800
C2—C3	1.368 (4)	C22—H22B	0.9800
C3—C1^i	1.380 (5)	C22—H22C	0.9800
C11—C12	1.405 (4)	C23—H23A	0.9800
C11—C13^ii	1.418 (4)	C23—H23B	0.9800
C11—C21	1.438 (4)	C23—H23C	0.9800
C12—C13	1.396 (4)
C3^i—C1—C2	116.5 (3)	C12—C13—C23	121.3 (3)
C3^i—C1—I1	121.4 (2)	C11^ii—C13—C23	120.9 (3)
C2—C1—I1	122.1 (2)	N21—C21—C11	179.6 (4)
F2—C2—C3	119.3 (3)	C12—C22—H22A	109.5
F2—C2—C1	119.6 (3)	C12—C22—H22B	109.5
C3—C2—C1	121.1 (3)	H22A—C22—H22B	109.5
F3—C3—C2	118.0 (3)	C12—C22—H22C	109.5
F3—C3—C1^i	119.6 (3)	H22A—C22—H22C	109.5
C2—C3—C1^i	122.3 (3)	H22B—C22—H22C	109.5
C12—C11—C13^ii	123.3 (3)	C13—C23—H23A	109.5
C12—C11—C21	118.8 (3)	C13—C23—H23B	109.5
C13^ii—C11—C21	117.9 (3)	H23A—C23—H23B	109.5
C13—C12—C11	118.8 (3)	C13—C23—H23C	109.5
C13—C12—C22	120.6 (3)	H23A—C23—H23C	109.5
C11—C12—C22	120.6 (3)	H23B—C23—H23C	109.5
C12—C13—C11^ii	117.9 (3)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) −x+2, −y+1, −z+3.