Tris(2-cyanoethyl) isocyanurate

The title compound, 1,3,5-tris(2-cyano­ethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, C₁₂H₁₂N₆O₃, forms a layered structure stabilized by C—H...O and C—H...N hydrogen bonds.

S1. Comment

The importance of C—H···O and C—H···N hydrogen bonds in the crystal structures of organic compounds is well known (Desiraju & Steiner, 1999). In this context, the title compound, (I), is of interest because it contains activated C—H donors and carbonyl and cyano acceptors. Furthermore, the molecule has trigonal symmetry and so its crystal structure could be relevant in the context of octupolar nonlinear optical effects (Thalladi et al., 1997). \scheme

The molecular geometry of (I) is shown in Fig. 1. Two of the cyanoethyl groups are oriented on one side of the heterocyclic ring, whilst the third points in the other direction. The crystal is centrosymmetric and the molecules form a layered structure (Fig. 2). In the (011) plane, each molecule is connected to four inversion-related molecules via C—H···O hydrogen bonds [C5—H5A···O3ⁱ, C7—H7B···O1ⁱⁱ, C8—H8B···O2ⁱⁱⁱ and C11—H11A···O3^v; see Table 1; symmetry codes: (i) 1 - x, -y, 2 - z; (ii) 1 - x, 1 - y, 2 - z; (iii) 1 - x, 1 - y, 1 - z; (v) 1 - x, -y, 1 - z]. These interactions will be referred to hereinafter as i, j, k and l, respectively. Translation-related molecules are linked via C—H···N hydrogen bonds [C8—H8A···N6ⁱⁱⁱ and C10—H10B···N4^iv; see Table 1; symmetry code: (iv) x, y, z - 1]. These interactions interactions will be referred to hereinafter as m and n, respectively.

In order to analyse the C—H···N≡C hydrogen bond directionality (φ angle) at the acceptor atom, the Cambridge Structural Database (CSD version 5.17, 197481 entries; Allen & Kennard, 1993) was searched for C—H···N≡C geometries. Ordered crystal structures of non-metal-atom-containing compounds with R < 0.075 were considered. Structures containing charged residues were excluded. In order that acceptor directionality not be biased by steric factors, only those geometries where a single C—H group approaches a cyano group were considered. In other words, geometries with bifurcated acceptors were not selected. The H-atom positions were normalized to standard neutron values, with the H···N distance allowed to lie between 1.5 and 3.0 Å and the H···N≡C angle between 40 and 180°. The mean H···N distance was found to be 2.67 Å for 249 fragments and the mean H···N≡C angle was 132.0°. The angular distribution is shown in Fig. 3. However, after cone-correction (Kroon & Kanters, 1974) it was observed that the distribution of φ angles tends strongly towards a linear geometry at the acceptor N atom. This shows that in C—H···N≡C hydrogen bonds, the main acceptor centre is the lone pair on the N atom rather than the C≡N triple bond.

S2. Experimental

Colourless crystals (m.p. 502 K) of (I), which was prepared according to the method of Frazier et al. (1960) were obtained by crystallization from dimethyl formamide.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: Xtal 3.5 (Hall et al., 1997); program(s) used to solve structure: SHELXS86 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLUTON-(C) (Spek, 1979-1997); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. An ORTEPII view (Johnson, 1976) and the atom-numbering scheme for (I). Displacement ellipsoids are drawn at the 35% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The layer structure of (I) viewed down [100]. O and N atoms are shaded. C—H···O hydrogen bonds are indicated as i, j, k and l and C—H···N hydrogen bonds are indicated m and n.
	Fig. 3. The distribution of φ angles for C—H···N≡C hydrogen bonds. The distribution is not cone-corrected and displays data from 329 non-bifurcated geometries taken from the Cambridge Structural Database (Allen & Kennard, 1993).

tris-(2-cyanoethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione

Crystal data

C12H12N6O3	F(000) = 600
Mr = 288.28	Dx = 1.435 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.727 (2) Å	Cell parameters from 25 reflections
b = 13.781 (2) Å	θ = 9–11°
c = 9.956 (2) Å	µ = 0.11 mm^−1
β = 90.46 (2)°	T = 293 K
V = 1334.6 (4) Å^3	Needle, colourless
Z = 4	0.60 × 0.48 × 0.20 mm

Data collection

Enraf-Nonius CAD4 diffractometer	Rint = 0.009
Radiation source: fine-focus sealed tube	θmax = 30.0°, θmin = 2.5°
Graphite monochromator	h = 0→13
ω scan	k = 0→19
4071 measured reflections	l = −13→13
3877 independent reflections	3 standard reflections every 100 reflections
2466 reflections with I > 2σ(I)	intensity decay: <2%

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)] = 0.063	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.190	All H-atom parameters refined
S = 1.07	Calculated w = 1/[σ^2(Fo^2) + (0.1131P)^2] where P = (Fo^2 + 2Fc^2)/3
3877 reflections	(Δ/σ)max = 0.001
239 parameters	Δρmax = 0.42 e Å^−3
0 restraints	Δρmin = −0.35 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 on F² for ALL reflections except for 0 with very negative F² or flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The observed criterion of F² > σ(F²) is used only for calculating R-factor-obs 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	0.52324 (13)	0.21961 (9)	0.88234 (12)	0.0320 (3)
N2	0.57008 (13)	0.36854 (10)	0.77997 (12)	0.0335 (3)
N3	0.58906 (14)	0.22449 (10)	0.65698 (12)	0.0329 (3)
N4	0.7529 (2)	0.2362 (2)	1.2025 (2)	0.0735 (6)
N5	0.2423 (2)	0.50605 (15)	0.8464 (2)	0.0688 (6)
N6	0.3507 (2)	0.2616 (2)	0.3405 (2)	0.0736 (6)
O1	0.4922 (2)	0.36075 (10)	0.99425 (12)	0.0500 (4)
O2	0.6370 (2)	0.37115 (10)	0.56279 (12)	0.0502 (4)
O3	0.55985 (14)	0.08116 (9)	0.76524 (12)	0.0471 (4)
C1	0.5252 (2)	0.31962 (12)	0.89298 (14)	0.0329 (3)
C2	0.6009 (2)	0.32434 (12)	0.65919 (15)	0.0339 (3)
C3	0.5580 (2)	0.16932 (12)	0.76809 (14)	0.0331 (3)
C4	0.4777 (2)	0.16261 (14)	0.9982 (2)	0.0398 (4)
H4A	0.412 (2)	0.117 (2)	0.967 (2)	0.061 (6)*
H4B	0.4286 (19)	0.2021 (15)	1.0545 (18)	0.036 (5)*
C5	0.5962 (2)	0.11570 (15)	1.0735 (2)	0.0476 (5)
H5A	0.562 (2)	0.0703 (17)	1.138 (2)	0.056 (6)*
H5B	0.651 (2)	0.0825 (16)	1.0157 (19)	0.045 (5)*
C6	0.6837 (2)	0.1845 (2)	1.1450 (2)	0.0495 (5)
C7	0.5907 (2)	0.47405 (13)	0.7898 (2)	0.0405 (4)
H7A	0.671 (2)	0.4873 (16)	0.7477 (19)	0.048 (5)*
H7B	0.6016 (18)	0.4867 (14)	0.8848 (18)	0.036 (5)*
C8	0.4743 (2)	0.53229 (15)	0.7274 (2)	0.0473 (5)
H8A	0.497 (3)	0.599 (2)	0.731 (2)	0.078 (8)*
H8B	0.469 (2)	0.5156 (16)	0.638 (2)	0.049 (5)*
C9	0.3432 (2)	0.51787 (13)	0.7938 (2)	0.0452 (4)
C10	0.6230 (2)	0.17185 (14)	0.5334 (2)	0.0400 (4)
H10A	0.688 (2)	0.1216 (17)	0.5600 (19)	0.051 (6)*
H10B	0.673 (2)	0.2129 (16)	0.4688 (19)	0.050 (6)*
C11	0.4950 (2)	0.13159 (14)	0.4639 (2)	0.0418 (4)
H11A	0.527 (2)	0.0910 (17)	0.396 (2)	0.051 (6)*
H11B	0.437 (2)	0.0977 (17)	0.5282 (19)	0.051 (6)*
C12	0.4141 (2)	0.2050 (2)	0.3958 (2)	0.0444 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0347 (7)	0.0256 (7)	0.0356 (6)	0.0001 (5)	−0.0032 (5)	0.0017 (5)
N2	0.0373 (7)	0.0240 (6)	0.0391 (6)	0.0001 (5)	−0.0007 (5)	−0.0005 (5)
N3	0.0356 (7)	0.0287 (7)	0.0344 (6)	0.0042 (5)	−0.0025 (5)	−0.0026 (5)
N4	0.0726 (14)	0.0678 (14)	0.0795 (13)	−0.0155 (11)	−0.0278 (11)	0.0092 (11)
N6	0.0470 (10)	0.078 (2)	0.0955 (14)	−0.0081 (10)	−0.0211 (10)	0.0330 (12)
N5	0.0531 (11)	0.0471 (12)	0.106 (2)	0.0000 (9)	0.0066 (10)	0.0051 (11)
O1	0.0720 (9)	0.0343 (7)	0.0436 (6)	0.0008 (6)	0.0076 (6)	−0.0059 (5)
O2	0.0635 (9)	0.0401 (8)	0.0471 (6)	0.0018 (6)	0.0111 (6)	0.0079 (6)
O3	0.0642 (9)	0.0245 (6)	0.0524 (7)	0.0004 (6)	−0.0071 (6)	−0.0031 (5)
C1	0.0347 (7)	0.0270 (8)	0.0370 (7)	0.0004 (6)	−0.0033 (6)	−0.0005 (6)
C2	0.0318 (7)	0.0308 (8)	0.0390 (7)	0.0038 (6)	−0.0012 (6)	0.0004 (6)
C3	0.0334 (7)	0.0267 (8)	0.0392 (7)	0.0012 (6)	−0.0083 (6)	−0.0027 (6)
C4	0.0428 (9)	0.0352 (9)	0.0415 (8)	−0.0078 (8)	0.0032 (7)	0.0037 (7)
C5	0.0659 (13)	0.0322 (9)	0.0446 (9)	−0.0010 (9)	−0.0041 (8)	0.0096 (8)
C6	0.0536 (11)	0.0455 (11)	0.0492 (9)	−0.0006 (9)	−0.0070 (8)	0.0127 (8)
C7	0.0431 (9)	0.0288 (8)	0.0497 (9)	−0.0071 (7)	0.0030 (7)	−0.0017 (7)
C8	0.0646 (12)	0.0275 (9)	0.0500 (9)	0.0025 (8)	0.0054 (8)	0.0068 (7)
C9	0.0528 (11)	0.0220 (8)	0.0605 (10)	0.0019 (7)	−0.0051 (8)	−0.0011 (7)
C10	0.0396 (9)	0.0414 (10)	0.0389 (8)	0.0109 (8)	−0.0006 (6)	−0.0060 (7)
C11	0.0544 (11)	0.0298 (9)	0.0413 (8)	−0.0012 (8)	−0.0030 (7)	−0.0053 (7)
C12	0.0386 (9)	0.0474 (11)	0.0472 (9)	−0.0097 (8)	−0.0057 (7)	0.0045 (8)

Geometric parameters (Å, º)

N1—C1	1.382 (2)	C7—C8	1.517 (3)
N1—C3	1.377 (2)	C8—C9	1.455 (3)
N1—C4	1.467 (2)	C10—C11	1.524 (3)
N2—C1	1.385 (2)	C11—C12	1.447 (3)
N2—C2	1.383 (2)	C4—H4A	0.95 (2)
N2—C7	1.471 (2)	C4—H4B	0.92 (2)
N3—C2	1.381 (2)	C5—H5A	0.96 (2)
N3—C3	1.378 (2)	C5—H5B	0.91 (2)
N3—C10	1.468 (2)	C7—H7A	0.91 (2)
N4—C6	1.133 (3)	C7—H7B	0.97 (2)
N5—C9	1.128 (3)	C8—H8A	0.94 (3)
N6—C12	1.134 (3)	C8—H8B	0.92 (2)
O1—C1	1.203 (2)	C10—H10A	0.97 (2)
O2—C2	1.211 (2)	C10—H10B	0.99 (2)
O3—C3	1.215 (2)	C11—H11A	0.93 (2)
C4—C5	1.515 (3)	C11—H11B	0.98 (2)
C5—C6	1.455 (3)
C1—N1—C3	124.18 (13)	C5—C4—H4A	113.0 (15)
C1—N1—C4	118.53 (13)	C5—C4—H4B	110.4 (12)
C3—N1—C4	117.27 (14)	H4A—C4—H4B	103.8 (18)
C1—N2—C2	124.32 (14)	C4—C5—H5A	110.2 (14)
C1—N2—C7	118.07 (13)	C4—C5—H5B	110.4 (13)
C2—N2—C7	117.58 (13)	C6—C5—H5A	107.5 (13)
C2—N3—C3	123.77 (13)	C6—C5—H5B	107.0 (14)
C2—N3—C10	119.10 (13)	H5A—C5—H5B	107.7 (19)
C3—N3—C10	116.89 (14)	N2—C7—H7A	106.5 (14)
O1—C1—N1	122.04 (14)	N2—C7—H7B	104.9 (11)
O1—C1—N2	122.7 (2)	C8—C7—H7A	110.3 (13)
N1—C1—N2	115.29 (13)	C8—C7—H7B	112.4 (11)
O2—C2—N2	121.4 (2)	H7A—C7—H7B	109.1 (17)
O2—C2—N3	122.89 (15)	C7—C8—H8A	109.1 (17)
N2—C2—N3	115.72 (13)	C7—C8—H8B	107.6 (13)
O3—C3—N1	121.75 (14)	C9—C8—H8A	108.6 (15)
O3—C3—N3	121.98 (14)	C9—C8—H8B	111.1 (13)
N1—C3—N3	116.27 (14)	H8A—C8—H8B	106.9 (19)
N1—C4—C5	112.59 (15)	N3—C10—H10A	105.9 (12)
C4—C5—C6	113.8 (2)	N3—C10—H10B	112.2 (12)
N4—C6—C5	178.3 (2)	C11—C10—H10A	113.0 (13)
N2—C7—C8	113.3 (2)	C11—C10—H10B	108.6 (12)
C9—C8—C7	113.3 (2)	H10A—C10—H10B	105.1 (17)
N5—C9—C8	179.2 (2)	C10—C11—H11A	105.6 (14)
N3—C10—C11	111.83 (14)	C10—C11—H11B	110.6 (12)
C10—C11—C12	113.4 (2)	C12—C11—H11A	105.4 (13)
N6—C12—C11	178.8 (2)	C12—C11—H11B	108.9 (13)
N1—C4—H4A	107.7 (7)	H11A—C11—H11B	112.9 (19)
N1—C4—H4B	108.9 (12)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C5—H5A···O3^i	0.96 (2)	2.59 (2)	3.504 (2)	160 (2)
C7—H7B···O1^ii	0.97 (2)	2.59 (2)	3.238 (2)	124 (1)
C8—H8A···N6^iii	0.95 (3)	2.53 (3)	3.382 (3)	150 (2)
C8—H8B···O2^iii	0.92 (2)	2.73 (2)	3.353 (2)	126 (2)
C10—H10B···N4^iv	0.99 (2)	2.79 (2)	3.647 (3)	146 (2)
C11—H11A···O3^v	0.93 (2)	2.98 (2)	3.750 (2)	141 (2)

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