N,N-Di­methyl­anilinium 3-cyano-4-(di­cyano­methyl­ene)-5-oxo-4,5-di­hydro-1H-pyrrol-2-olate

In the title compound, C₈H₁₂N⁺·C₈HN₄O₂⁻, the anion and cation lie on a crystallographic mirror plane and form planar ribbons via N—H...O [N...O = 2.933 (4) Å, H...O = 2.01 Å and N—H...O = 170°] and N—H...N [N...N = 3.016 (5) Å, H...N = 2.15 Å and N—H...N = 169°] hydrogen bonds. The ribbons are further linked via weak C—H...O and C—H...N hydrogen bonds. In adjacent planes, anions lie opposite cations; π–π interactions (separation a/2 = 3.520 Å) exist between the anions and the cations, and stacks are formed, running along the a axis. The cations are disordered over two interpenetrating sites, with occupancies of 0.833 (5) and 0.167 (5).

S1. Comment

We have recently reported the synthesis and structure of the potassium salt of the title anion (Tafeenko et al., 2003). On the basis of the structural data and the calculated charge distribution on the atoms of the anion, the following types of anion–cation interaction can be postulated: (a) "Isotropic" interactions, with each outer hetero-atom of the anion taking part in the formation of a polyhedron enclosing the cation (Li, K, Na and Cs). (b) π–π stacking interactions, involving planar cations (e.g. pyridinium). (c) A transition metal–anion π-system interaction. (e.g. ferrocene). (d) Interaction of the hetero-atoms of the anion and the transition metal to form a coordination compound or chelate complex. An example of type (a) was described by Tafeenko et al. (2003). Interactions of type (b) were expected in the title compound, (I). Interactions of type (c) and (d) are the subject of further investigations.

The synthesis was carried out as shown in the scheme above. The most remarkable features of this reaction are the main roles that are played by the two elementary particles (proton and electron) supplied by the hydrogen iodide. The H atom interacts with the lone pair of the N atom of the N,N-dimethyl-N-phenilamine molecule to form a cation (the lower-right structure in the scheme), whereas the electron induces the rearrangement of the three-membered ring of 2,2,3,3-tetracyanocyclopropanecarboxylic acid to give an anion.

The title compound (Fig. 1) has all atoms of the anion and cation lying in a crystallographic mirror plane, with the exception of the methyl groups of the cation, which are located between planes and have an essential impact on the specific packing geometry. The bond lengths and angles in the anion are similar to those in the corresponding potassium salt (see above). The unique cation is disordered over two interpenetrating sites with occupancies of 0.833 (5) and 0.167 (5) (see Experimental). The methyl groups enlarge the distances (half of the a axis) between the molecular planes and also prevent the formation of a more symmetrical anion–cation stacking. The shortest distance between an anion and a cation that form a stack and lie in adjacent mirror planes is 2.45 Å [H16B···N4(1/2 − x,1 − y+,z − 1/2); Fig. 2a and Table 1; atom H16B belongs to the C16 methyl group]. Although π–π interactions exist between anion and the cation, these interactions might have been stronger if the methyl atoms located between the planes had been absent. The tendency of the anion–cation distances in the stack to decrease is reflected by the atomic displacement tensors of the atoms of the anion. The principal axes of the ellipsoids of these atoms are orthogonal to the mirror plane, but the values for those atoms that are not involved in the π–π interaction are noticeably larger. Another explanation of the enlarged atomic displacement ellipsoids of the anion is steric hindrance of the exocyclic cyano groups (Tafeenko et al., 2003).

In the mirror plane, adjacent anions are linked via N—H···N hydorgen bonds (Table 1 and Fig. 2 b); cations are linked to the resulting anion chain by N—H···O hydrogen bonds. The ribbons so formed extend in the c direction, and adjacent ribbons are linked via weak (Steiner, 1996) C—H···O and C—H···N hydrogen bonds (Fig. 2 b and Table 1).

S2. Experimental

2,2,3,3-Tetracyanocycloprpanecarboxylic acid was synthesized from α-chloro ketone and TCNE (ethylene-1,1,2,2-tetracarbonitrile). N,N,-dimethyl-N-benzenaminium 3-cyano-4-(dicyanomethylene)-5-oxo-4,5-dihydro-1H-pyrrol-2-olate was obtained by mixing N,N-dimethyl-N-phenilamine and hydrogen iodide and then adding 2,2,3,3-tetracyanocyclopropanecarboxylic acid. The reaction was carried out in aqua-1,4-dioxane (1:1) at room temperature. Yellow crystals were collected from the reaction mixture by filtration and drying.

S3. Refinement

Four different diffraction experiments were carried out using three different crystals of the title compound, with both room-temperature and 110 K data sets. For full details see the _exptl_special_details section of the archived CIF. All data sets led to the same structure and only the results from the 110 K data set are described here. All H atoms were refined as riding, with N—H distances of 0.88 and 0.93 Å, and C—H distances of 0.95 and 0.98 Å. During the refinement, difference maps showed peaks consistent with the cation atoms N5 and C10–C15 being unequally disordered over two interpenetrating sites. This disorder was allowed for by the use of appropriate SHELXL97 (Sheldrick, 1997) SAME and DFIX restraints. At convergence, the cation disorder was modelled with occupancies of 0.833 (5) and 0.167 (5). The minor-occupancy cation orientation also leads to an N51—H51···N3 hydrogen bond (Table 1). The minor-occupancy methyl C atom (C161) was constrained to have the same coordinates and anisotropic displacement parameters as the major (C16) site.

Computing details

Data collection: SMART (Bruker, 1998); cell refinement: SAINT-Plus (Bruker, 1998); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 2000) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

Figure 1. A view of the salt, with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. The cations are disordered over two interpenetrating sites with occupancies of 0.833 (5) and 0.167 (5). Figure 2a. A view almost normal to the molecular planes, showing how the cations and anions overlap to form π–π stacks along the a axis. Atoms marked with a dollar are at the equivalent position (1/2 − x, 1 − y, z − 1/2). Figure 2 b. Part of the crystal structure, showing the formation via strong hydrogen bonds (N—H···N and N—H···O) of ribbons of anions and cations along the c axis. The ribbons are connected by weak (C—H···O and C—H···N) hydrogen bonds. Atoms marked with an asterisk (*) or hash (#) are at the equivalent positions (x,y,z − 1) and (x,y + 1,z), respectively.

N,N-dimethylanilinium 3-cyano-4-(dicyanomethylene)-5-oxo-4,5-dihydro-1H-pyrrol-2-olate

Crystal data

C8H12N^+·C8HN4O2^−	Dx = 1.331 Mg m^−3
Mr = 307.31	Melting point: 221 K
Orthorhombic, Pmn21	Mo Kα radiation, λ = 0.71073 Å
a = 7.0399 (7) Å	Cell parameters from 925 reflections
b = 12.5636 (12) Å	θ = 3–30°
c = 8.6695 (8) Å	µ = 0.09 mm^−1
V = 766.79 (13) Å^3	T = 110 K
Z = 2	Prism, yellow
F(000) = 320	0.30 × 0.10 × 0.10 mm

Data collection

Bruker SMART 1000 CCD area-detector diffractometer	936 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.034
Graphite monochromator	θmax = 30.1°, θmin = 1.6°
ϕ and ω scans	h = −9→9
5974 measured reflections	k = −16→17
1283 independent 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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.112	H-atom parameters constrained
S = 1.01	w = 1/[σ^2(Fo^2) + (0.0684P)^2] where P = (Fo^2 + 2Fc^2)/3
1282 reflections	(Δ/σ)max = 0.001
153 parameters	Δρmax = 0.19 e Å^−3
19 restraints	Δρmin = −0.35 e Å^−3

Special details

Experimental. Three experiments were carried out at room temperature. (Enraf–Nonius CAD-4 diffractometer, ω – scan, Cu Kα radiation, cell parameters from 25 reflections at 293 (2) K are a=7.0544 (15), b=12.586 (2), c=8.691 (1), space group Pmn2₁) and one experiment at T = 110 K. Though in principal all four experiments delivered the same structural model, the final model is based on the low temperature data because of the larger amount of reflections with I>2σ(I).

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)
O1	0.5000	0.11422 (17)	0.3697 (3)	0.0623 (7)
O2	0.5000	0.4752 (2)	0.3956 (3)	0.0994 (13)
N1	0.5000	0.2962 (2)	0.3428 (3)	0.0617 (8)
H1	0.5000	0.2988	0.2413	0.074*
N2	0.5000	0.3371 (3)	1.0000 (4)	0.0721 (10)
N3	0.5000	0.6137 (3)	0.6991 (5)	0.1011 (16)
N4	0.5000	0.0834 (2)	0.7873 (4)	0.0569 (7)
C2	0.5000	0.2032 (2)	0.4266 (4)	0.0468 (7)
C3	0.5000	0.2325 (2)	0.5876 (3)	0.0378 (6)
C4	0.5000	0.3428 (2)	0.5998 (3)	0.0410 (7)
C5	0.5000	0.3840 (3)	0.4354 (4)	0.0588 (10)
C6	0.5000	0.4110 (2)	0.7236 (3)	0.0478 (8)
C7	0.5000	0.5236 (3)	0.7070 (4)	0.0664 (11)
C8	0.5000	0.3713 (3)	0.8772 (4)	0.0518 (8)
C9	0.5000	0.1527 (2)	0.7012 (4)	0.0411 (6)
N5	0.5000	0.8927 (3)	0.4766 (3)	0.0413 (8)	0.833 (5)
H5	0.5000	0.9652	0.4548	0.050*	0.833 (5)
C10	0.5000	0.8365 (3)	0.3260 (4)	0.0381 (9)	0.833 (5)
C11	0.5000	0.8970 (3)	0.1941 (5)	0.0434 (10)	0.833 (5)
H11	0.5000	0.9725	0.1998	0.052*	0.833 (5)
C12	0.5000	0.8458 (4)	0.0520 (5)	0.0518 (13)	0.833 (5)
H12	0.5000	0.8864	−0.0405	0.062*	0.833 (5)
C13	0.5000	0.7366 (4)	0.0451 (5)	0.0538 (14)	0.833 (5)
H13	0.5000	0.7019	−0.0522	0.065*	0.833 (5)
C14	0.5000	0.6769 (4)	0.1787 (6)	0.0546 (13)	0.833 (5)
H14	0.5000	0.6014	0.1730	0.066*	0.833 (5)
C15	0.5000	0.7266 (3)	0.3204 (5)	0.0497 (11)	0.833 (5)
H15	0.5000	0.6860	0.4127	0.060*	0.833 (5)
C16	0.3262 (3)	0.8711 (2)	0.5681 (3)	0.0581 (6)	0.83
H16A	0.3214	0.7954	0.5950	0.087*	0.83
H16B	0.2138	0.8897	0.5071	0.087*	0.83
H16C	0.3284	0.9138	0.6626	0.087*	0.83
N51	0.5000	0.8200 (17)	0.5085 (19)	0.053 (3)*	0.167 (5)
H51	0.5000	0.7530	0.5540	0.063*	0.167 (5)
C101	0.5000	0.7975 (19)	0.339 (2)	0.053 (3)*	0.167 (5)
C111	0.5000	0.6980 (19)	0.282 (3)	0.053 (3)*	0.167 (5)
H111	0.5000	0.6383	0.3495	0.063*	0.167 (5)
C121	0.5000	0.684 (2)	0.126 (3)	0.053 (3)*	0.167 (5)
H121	0.5000	0.6142	0.0845	0.063*	0.167 (5)
C131	0.5000	0.768 (2)	0.028 (3)	0.053 (3)*	0.167 (5)
H131	0.5000	0.7573	−0.0801	0.063*	0.167 (5)
C141	0.5000	0.870 (2)	0.088 (3)	0.053 (3)*	0.167 (5)
H141	0.5000	0.9296	0.0206	0.063*	0.167 (5)
C151	0.5000	0.884 (2)	0.244 (3)	0.053 (3)*	0.167 (5)
H151	0.5000	0.9539	0.2858	0.063*	0.167 (5)
C161	0.3262 (3)	0.8711 (2)	0.5681 (3)	0.0581 (6)	0.17
H16D	0.2144	0.8361	0.5236	0.087*	0.17
H16E	0.3259	0.9465	0.5395	0.087*	0.17
H16F	0.3226	0.8645	0.6807	0.087*	0.17

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.111 (2)	0.0367 (12)	0.0389 (13)	0.000	0.000	−0.0094 (11)
O2	0.226 (4)	0.0340 (14)	0.0382 (13)	0.000	0.000	0.0064 (11)
N1	0.120 (2)	0.0401 (16)	0.0250 (12)	0.000	0.000	0.0027 (12)
N2	0.125 (3)	0.061 (2)	0.0298 (15)	0.000	0.000	0.0013 (15)
N3	0.213 (5)	0.0407 (18)	0.050 (2)	0.000	0.000	−0.0057 (19)
N4	0.0887 (19)	0.0410 (14)	0.0410 (14)	0.000	0.000	0.0074 (13)
C2	0.076 (2)	0.0345 (16)	0.0297 (15)	0.000	0.000	−0.0029 (12)
C3	0.0587 (17)	0.0295 (15)	0.0254 (12)	0.000	0.000	−0.0002 (11)
C4	0.0641 (18)	0.0330 (16)	0.0261 (13)	0.000	0.000	0.0010 (11)
C5	0.113 (3)	0.0382 (18)	0.0250 (13)	0.000	0.000	0.0043 (14)
C6	0.083 (2)	0.0351 (16)	0.0253 (14)	0.000	0.000	−0.0027 (12)
C7	0.130 (4)	0.0399 (17)	0.0295 (16)	0.000	0.000	−0.0076 (14)
C8	0.087 (2)	0.0384 (17)	0.0299 (15)	0.000	0.000	−0.0039 (14)
C9	0.0594 (17)	0.0314 (13)	0.0324 (14)	0.000	0.000	−0.0020 (12)
N5	0.0623 (19)	0.0310 (18)	0.0307 (15)	0.000	0.000	−0.0011 (12)
C10	0.0569 (19)	0.032 (2)	0.0256 (18)	0.000	0.000	−0.0054 (17)
C11	0.065 (2)	0.033 (2)	0.032 (2)	0.000	0.000	−0.0013 (17)
C12	0.074 (2)	0.052 (4)	0.029 (2)	0.000	0.000	0.0001 (19)
C13	0.080 (3)	0.051 (3)	0.030 (2)	0.000	0.000	−0.011 (2)
C14	0.083 (3)	0.0337 (19)	0.047 (3)	0.000	0.000	−0.009 (2)
C15	0.082 (3)	0.033 (2)	0.034 (2)	0.000	0.000	0.0023 (17)
C16	0.0669 (13)	0.0662 (17)	0.0412 (12)	−0.0016 (11)	0.0063 (11)	−0.0105 (11)
C161	0.0669 (13)	0.0662 (17)	0.0412 (12)	−0.0016 (11)	0.0063 (11)	−0.0105 (11)

Geometric parameters (Å, º)

O1—C2	1.222 (4)	C12—H12	0.9500
O2—C5	1.197 (4)	C13—C14	1.379 (6)
N1—C5	1.364 (4)	C13—H13	0.9500
N1—C2	1.376 (4)	C14—C15	1.378 (6)
N1—H1	0.8800	C14—H14	0.9500
N2—C8	1.148 (4)	C15—H15	0.9500
N3—C7	1.134 (4)	C16—H16A	0.9800
N4—C9	1.147 (4)	C16—H16B	0.9800
C2—C3	1.444 (4)	C16—H16C	0.9800
C3—C4	1.390 (4)	N51—C161^i	1.475 (10)
C3—C9	1.405 (4)	N51—C101	1.494 (16)
C4—C6	1.373 (4)	N51—H51	0.9300
C4—C5	1.516 (4)	C101—C111	1.344 (17)
C6—C8	1.421 (4)	C101—C151	1.367 (18)
C6—C7	1.422 (5)	C111—C121	1.369 (18)
N5—C16^i	1.484 (3)	C111—H111	0.9500
N5—C16	1.484 (3)	C121—C131	1.35 (2)
N5—C10	1.485 (4)	C121—H121	0.9500
N5—H5	0.9300	C131—C141	1.376 (19)
C10—C11	1.373 (5)	C131—H131	0.9500
C10—C15	1.381 (6)	C141—C151	1.364 (19)
C11—C12	1.389 (6)	C141—H141	0.9500
C11—H11	0.9500	C151—H151	0.9500
C12—C13	1.374 (8)
C5—N1—C2	112.1 (3)	C12—C13—C14	120.4 (4)
C5—N1—H1	124.0	C12—C13—H13	119.8
C2—N1—H1	124.0	C14—C13—H13	119.8
O1—C2—N1	124.3 (3)	C15—C14—C13	120.1 (4)
O1—C2—C3	128.6 (3)	C15—C14—H14	119.9
N1—C2—C3	107.1 (3)	C13—C14—H14	119.9
C4—C3—C9	131.2 (3)	C14—C15—C10	119.0 (4)
C4—C3—C2	109.1 (3)	C14—C15—H15	120.5
C9—C3—C2	119.7 (3)	C10—C15—H15	120.5
C6—C4—C3	132.9 (3)	N5—C16—H16A	109.5
C6—C4—C5	121.5 (3)	N5—C16—H16B	109.5
C3—C4—C5	105.6 (3)	H16A—C16—H16B	109.5
O2—C5—N1	127.2 (3)	N5—C16—H16C	109.5
O2—C5—C4	126.7 (3)	H16A—C16—H16C	109.5
N1—C5—C4	106.2 (3)	H16B—C16—H16C	109.5
C4—C6—C8	120.9 (3)	C161^i—N51—C101	115.2 (8)
C4—C6—C7	122.8 (3)	C161^i—N51—H51	104.2
C8—C6—C7	116.3 (3)	C101—N51—H51	104.2
N3—C7—C6	177.7 (4)	C111—C101—C151	121.1 (17)
N2—C8—C6	178.5 (4)	C111—C101—N51	123 (2)
N4—C9—C3	176.1 (3)	C151—C101—N51	116.4 (18)
C16^i—N5—C16	111.1 (3)	C101—C111—C121	119 (2)
C16^i—N5—C10	112.51 (18)	C101—C111—H111	120.6
C16—N5—C10	112.51 (18)	C121—C111—H111	120.6
C16^i—N5—H5	106.7	C131—C121—C111	121 (2)
C16—N5—H5	106.7	C131—C121—H121	119.3
C10—N5—H5	106.7	C111—C121—H121	119.3
C11—C10—C15	121.6 (3)	C121—C131—C141	119 (2)
C11—C10—N5	117.9 (3)	C121—C131—H131	120.3
C15—C10—N5	120.5 (4)	C141—C131—H131	120.3
C10—C11—C12	118.8 (4)	C151—C141—C131	120 (2)
C10—C11—H11	120.6	C151—C141—H141	120.2
C12—C11—H11	120.6	C131—C141—H141	120.2
C13—C12—C11	120.1 (4)	C141—C151—C101	120 (2)
C13—C12—H12	120.0	C141—C151—H151	120.1
C11—C12—H12	120.0	C101—C151—H151	120.1
C16^i—N5—C10—C11	−116.8 (2)	C16—N5—C10—C15	−63.2 (2)
C16—N5—C10—C11	116.8 (2)	C161^i—N51—C101—C111	113.5 (12)
C16^i—N5—C10—C15	63.2 (2)	C161^i—N51—C101—C151	−66.5 (12)

Symmetry code: (i) −x+1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···N2^ii	0.88	2.15	3.016 (5)	169
N5—H5···O1^iii	0.93	2.01	2.933 (4)	170
N51—H51···N3	0.93	2.16	3.07 (2)	169
C11—H11···O1^iii	0.95	2.31	3.125 (5)	143
C13—H13···N3^ii	0.95	2.42	3.374 (6)	180
C14—H14···O2	0.95	2.50	3.156 (6)	126
C15—H15···O2	0.95	2.65	3.226 (5)	119
C16—H16B···N4^iv	0.98	2.45	3.394 (3)	161

Symmetry codes: (ii) x, y, z−1; (iii) x, y+1, z; (iv) −x+1/2, −y+1, z−1/2.