Non-linear optical crystals of 2,2,3-tri­methyl-3-(1H-1,2,3,4-tetrazol-5-yl)­butane­nitrile

The title compound, C₈H₁₃N₅, is a novel functionally substituted 5-alkyl­tetrazole. The substituent on the tetrazole C atom is symmetrical, with intrinsic symmetry close to m. There is intermolecular N—H...N hydrogen bonding between adjacent tetrazole rings, which is responsible for the formation of one-dimensional polymeric chains running along the c axis. The polycrystalline compound exhibits frequency doubling for incident light (λ = 1064 nm) from a YAG:Nd pulsed laser.

S1. Comment

Interest in 5-monosubstituted tetrazoles has arisen for several reasons. The N-unsubstituted tetrazolyl group –CN₄H is a non-classic isostere for the carboxylic group and hence may be a suitable substitutent for it in drug design (Herr, 2002). Moreover, 5-monosubstituted tetrazoles, since they are coordinated by diverse modes, are interesting ligands for transition metal complexes and possess some unique properties (Yelamos et al., 2001). To date, only one 5-alkyltetrazole and two functionally substituted 5-alkyltetrazoles have been structurally characterized [Cambridge Structural Database (CSD); Version 5.24 of November 2002; Allen, 2002], namely 5-methyltetrazole (Ohno et al., 1999), 5-trichloromethyltetrazole (Geisenberg et al., 1987) and zwitterionic 5-(1-piperidiniomethyl)tetrazole (Lyakhov et al., 2003). In this paper, we report the synthesis and the molecular and crystal structures of a novel representative of functionally substituted 5-alkyltetrazoles, viz. 2,2,3-trimethyl-3-(1H-1,2,3,4-tetrazol-5-yl)butanenitrile, (I) (Fig. 1).

The tetrazole ring geometry is typical of the 5-substituted tetrazoles listed in the CSD. The N2—N3 [1.285 (2) Å] and N4—C5 [1.323 (2) Å] formal double bonds are the shortest bonds in the ring, and the ring is planar within 0.001 (1) Å.

The bond distances and angles in the substitutent on the C atom of the tetrazole ring are consistent with those observed previously for similar fragments (CSD). The substitutent is almost symmetrical, with intrinsic symmetry close to m (a pseudo-mirror plane is perpendicular to the tetrazole ring plane). If the tetrazole ring was also symmetrical, the space group would be the centric Pcam group. However, the tetrazole ring H atom is unambiguosly located only at one N atom, and the tetrazole ring is non-symmetrical, so the obtained data correspond to the acentric Pca2₁ space group. These results are supported by an investigation of the optical properties of (I). The polycrystalline compound exhibits visually detected frequency doubling for an incedent pumping light (λ=1064 nm, 10 ns pulses, 100 mJ pulse⁻¹) from a YAG:Nd pulsed laser.

There are classical intermolecular N1—H1···N4(3/2 − x, y, 1/2 + z) hydrogen bonds between adjacent tetrazole rings in the structure of (I). These bonds are responsible for the formation of one-dimensional polymeric chains that extend along the c axis (Fig. 2).

S2. Experimental

The title compound was obtained unexpectedly during the cycloaddition of the azide ion to tetramethylsuccinonitrile according to the method described by Finnegan et al. (1958). Although there was a twofold excess of azide ions, only one nitrile group was involved in the reaction. A mixture of tetramethylsuccinonitrile (11.0 g, 81 mmol), sodium azide (10.5 g, 162 mmol) and ammonium chloride (8.7 g, 162 mmol) in dimethylformamide (130 ml) was stirred at 388–403 K for 40 h. The solvent was removed at reduced pressure on a steam bath, and the residue was dissolved in water (100 ml) and acidified with concentrated hydrochloric acid (15 ml). The precipitate was filtered, washed with several portions of water and dried. Crystallization from ethyl acetate gave the title compound (9.4 g, yield 65%; m.p. 462–463 K, decomposition, uncorrected). ¹H NMR (100 MHz, DMSO-d₆, p.p.m.): δ 1.29 (s, 6H, 2CH₃), 1.58 (s, 6H, 2CH₃); ¹³C NMR (25 MHz, DMSO-d₆, p.p.m.): δ 26.5 (2CH₃), 26.9 (2CH₃), 42.8 and 43.9 (2C_quaternary), 127.7 (CN), 164.0 (C_tetrazole). Single crystals were grown by recrystallization from ethyl acetate at 288–293 K.

S3. Refinement

Methyl H atoms were included in calculated positions, (C—H = 0.96 Å) and refined using a riding model, with U_iso(H) values equal to 1.5U_eq of the corresponding C atom. The tetrazole H atom was localized from a ΔF map and refined using a riding model, with N—H distances of 0.86 Å and a U_iso(H) value equal to 1.2U_eq of the N atom. Because the compound contains only C, N and H atoms, absolute structure determination was not intended.

Computing details

Data collection: R3m software (Nicolet, 1980); cell refinement: R3m software (Nicolet, 1980); data reduction: R3m software (Nicolet, 1980); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997), PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

	Fig. 1. ORTEP-3 (Farrugia, 1997) plot of (I). Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as spheres of arbitrary radii.
	Fig. 2. The crystal structure of (I), viewed along the b axis. Dashed lines indicate N—H···N hydrogen bonding.

(I)

Crystal data

C8H13N5	F(000) = 384
Mr = 179.23	Dx = 1.245 Mg m^−3
Orthorhombic, Pca21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2ac	Cell parameters from 25 reflections
a = 15.070 (3) Å	θ = 17.7–22.8°
b = 6.4292 (12) Å	µ = 0.08 mm^−1
c = 9.8694 (18) Å	T = 293 K
V = 956.2 (3) Å^3	Prism, colourless
Z = 4	0.44 × 0.32 × 0.30 mm

Data collection

Nicolet R3m four-circle diffractometer	Rint = 0.028
Radiation source: fine-focus sealed tube	θmax = 30.1°, θmin = 2.7°
Graphite monochromator	h = −1→21
ω/2θ scans	k = 0→9
1571 measured reflections	l = 0→13
1475 independent reflections	3 standard reflections every 100 reflections
1309 reflections with I > 2σ(I)	intensity decay: none

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.108	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0702P)^2 + 0.0423P] where P = (Fo^2 + 2Fc^2)/3
1475 reflections	(Δ/σ)max < 0.001
122 parameters	Δρmax = 0.17 e Å^−3
1 restraint	Δρmin = −0.17 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
N1	0.75734 (10)	0.3535 (2)	0.46059 (15)	0.0322 (3)
H1	0.7471	0.3264	0.5445	0.039*
N2	0.81473 (11)	0.4977 (3)	0.41459 (17)	0.0401 (4)
N3	0.81126 (11)	0.4909 (3)	0.28457 (17)	0.0400 (4)
N4	0.75213 (11)	0.3427 (3)	0.24388 (15)	0.0346 (3)
C5	0.71891 (8)	0.25916 (19)	0.35541 (19)	0.0278 (2)
C6	0.64829 (8)	0.09268 (19)	0.36315 (19)	0.0295 (2)
C7	0.55467 (8)	0.2038 (2)	0.3643 (2)	0.0327 (3)
C8	0.48574 (10)	0.0404 (3)	0.3690 (3)	0.0458 (4)
N9	0.43087 (12)	−0.0813 (3)	0.3724 (4)	0.0774 (7)
C10	0.65740 (15)	−0.0501 (4)	0.2392 (2)	0.0437 (5)
H10A	0.6516	0.0308	0.1580	0.065*
H10B	0.6118	−0.1543	0.2417	0.065*
H10C	0.7145	−0.1161	0.2406	0.065*
C11	0.66184 (16)	−0.0389 (4)	0.4914 (2)	0.0441 (5)
H11A	0.7204	−0.0979	0.4906	0.066*
H11B	0.6186	−0.1485	0.4936	0.066*
H11C	0.6551	0.0475	0.5700	0.066*
C12	0.53751 (15)	0.3332 (4)	0.2365 (3)	0.0519 (6)
H12A	0.5437	0.2465	0.1579	0.078*
H12B	0.5796	0.4451	0.2320	0.078*
H12C	0.4785	0.3891	0.2396	0.078*
C13	0.54138 (15)	0.3413 (4)	0.4893 (2)	0.0513 (6)
H13A	0.4829	0.4005	0.4875	0.077*
H13B	0.5847	0.4508	0.4892	0.077*
H13C	0.5482	0.2588	0.5697	0.077*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0296 (6)	0.0390 (8)	0.0279 (6)	−0.0027 (6)	−0.0014 (5)	−0.0019 (5)
N2	0.0333 (7)	0.0450 (10)	0.0421 (8)	−0.0086 (7)	−0.0004 (6)	−0.0025 (7)
N3	0.0362 (8)	0.0420 (10)	0.0418 (8)	−0.0076 (7)	0.0047 (6)	0.0031 (7)
N4	0.0332 (6)	0.0415 (8)	0.0293 (6)	−0.0037 (7)	0.0017 (5)	0.0015 (6)
C5	0.0254 (4)	0.0323 (5)	0.0258 (5)	0.0018 (4)	−0.0001 (6)	−0.0007 (7)
C6	0.0302 (5)	0.0301 (5)	0.0281 (5)	−0.0016 (4)	−0.0004 (6)	−0.0024 (7)
C7	0.0277 (5)	0.0369 (6)	0.0336 (6)	−0.0033 (4)	−0.0008 (7)	0.0005 (8)
C8	0.0366 (7)	0.0574 (9)	0.0435 (9)	−0.0119 (6)	0.0016 (8)	−0.0010 (9)
N9	0.0578 (10)	0.0816 (12)	0.0927 (17)	−0.0347 (9)	0.0012 (13)	0.0014 (16)
C10	0.0493 (10)	0.0394 (11)	0.0423 (9)	−0.0006 (9)	0.0024 (8)	−0.0118 (8)
C11	0.0506 (11)	0.0416 (11)	0.0402 (9)	−0.0062 (9)	−0.0064 (8)	0.0134 (8)
C12	0.0372 (10)	0.0614 (15)	0.0570 (13)	0.0068 (10)	−0.0018 (9)	0.0198 (11)
C13	0.0379 (10)	0.0622 (15)	0.0536 (12)	0.0051 (10)	0.0044 (8)	−0.0228 (11)

Geometric parameters (Å, º)

N1—C5	1.334 (2)	C8—N9	1.139 (2)
N1—N2	1.347 (2)	C10—H10A	0.9600
N1—H1	0.8600	C10—H10B	0.9600
N2—N3	1.285 (2)	C10—H10C	0.9600
N3—N4	1.365 (2)	C11—H11A	0.9600
N4—C5	1.323 (2)	C11—H11B	0.9600
C5—C6	1.5113 (16)	C11—H11C	0.9600
C6—C10	1.535 (3)	C12—H12A	0.9600
C6—C11	1.536 (3)	C12—H12B	0.9600
C6—C7	1.5817 (17)	C12—H12C	0.9600
C7—C8	1.4784 (19)	C13—H13A	0.9600
C7—C13	1.531 (3)	C13—H13B	0.9600
C7—C12	1.532 (3)	C13—H13C	0.9600
C5—N1—N2	109.23 (15)	C6—C10—H10B	109.5
C5—N1—H1	125.4	H10A—C10—H10B	109.5
N2—N1—H1	125.4	C6—C10—H10C	109.5
N3—N2—N1	106.69 (17)	H10A—C10—H10C	109.5
N2—N3—N4	110.12 (17)	H10B—C10—H10C	109.5
C5—N4—N3	106.59 (15)	C6—C11—H11A	109.5
N4—C5—N1	107.37 (11)	C6—C11—H11B	109.5
N4—C5—C6	126.58 (17)	H11A—C11—H11B	109.5
N1—C5—C6	126.02 (16)	C6—C11—H11C	109.5
C5—C6—C10	108.68 (15)	H11A—C11—H11C	109.5
C5—C6—C11	109.76 (15)	H11B—C11—H11C	109.5
C10—C6—C11	108.36 (12)	C7—C12—H12A	109.5
C5—C6—C7	107.96 (10)	C7—C12—H12B	109.5
C10—C6—C7	110.82 (14)	H12A—C12—H12B	109.5
C11—C6—C7	111.21 (15)	C7—C12—H12C	109.5
C8—C7—C13	107.03 (17)	H12A—C12—H12C	109.5
C8—C7—C12	107.06 (18)	H12B—C12—H12C	109.5
C13—C7—C12	109.15 (14)	C7—C13—H13A	109.5
C8—C7—C6	107.80 (12)	C7—C13—H13B	109.5
C13—C7—C6	112.52 (15)	H13A—C13—H13B	109.5
C12—C7—C6	112.96 (15)	C7—C13—H13C	109.5
N9—C8—C7	178.1 (2)	H13A—C13—H13C	109.5
C6—C10—H10A	109.5	H13B—C13—H13C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···N4^i	0.86	1.97	2.8004 (18)	162

Symmetry code: (i) −x+3/2, y, z+1/2.