5-Hydrazino-1,3-dimethyl-4-nitro-1H-pyrazole

Three distinct N—H...O,N inter­actions connect mol­ecules of the title compound, C₅H₉N₅O₂, into a supra­molecular assembly. The mol­ecules are stacked in columns along the b axis. In this arrangement, the mol­ecules are linked to each other by four two-center hydrogen bonds in an R⁴₂(12) ring motif. The N—H...O,N inter­actions have D...A distances ranging from 3.044 (2) to 3.182 (3) Å and D—H...A angles ranging from 138 (2) to 164 (2)° (where D and A are donor and acceptor, respectively).

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C)= 0.002 Å
• R factor = 0.041
• wR factor = 0.127
• Data-to-parameter ratio = 12.6

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S1. Comment

Substituted pyrazolo-1,2,4-triazines constitute an important family of heterocyclic compounds due to their possible biological activity. including antifungal, antiviral, anti-inflammatory, anticonvulsant, antidepressant, antihypertensive properties (Tewari et al., 2002; Manfredini et al., 1992; Mavel et al., 1993). A novel method for the synthesis of many substituted pyrazolo[4,3 e][1,2,4]triazines has been reported very recently (Abu-Safieh et al., 2007). This synthesis based on the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Then by using polyphosphoric acid via intramolecular oxidative cyclization the target pyrazolotriazines is obtained. In this paper, we report the crystal structure of the title compound, (I), which represents the first step product, 5-hydrazinopyrazole, of these reactions to the formation of pyrazolotriazines.

The title compound, (I), formed from the hydrazinolysis of 5-chloro-1,3-dimethyl-4-nitropyrazole in an S_N Ar addition-elimination reaction. A view of the structure of (I) and its atom-numbering scheme is shown in Fig. 1. Selected geometrical parameters are given in Table 1. The asymmetric unit of (I) is made up of one organic moiety composed of a central N-containing ring, with a methyl group connected to the 1-position of the ring, a methyl group in the 3-position of the ring, a nitro group (—NO₂) in the 4-position of the ring and a hydrazine group NH₂NH— group connected to the 5-position of the ring. The pyrazolo ring is planar, which can be attributed to a wide range of electron delocalization [maximum deviations of -0.0015 (9), -0.0014 (9) and 0.0018 (9) for N1, C4 and C5, respectively]. Compound (I) is comparable to other similar ones in Cambridge Structural Database (CSD; see for example: Yu et al., 2007; Wang et al., 2007; Xia et al., 2007a,b; Bustos et al., 2007), except that the substituents at positions 3- (—NO₂) and 4- (NH₂NH—) are of the kind that are good candidates to participate in hydrogen bonding leading to a supramolecular architecture (see hydrogen bonding discussion below).

The bond distances of similar types within the ring are not equivalent [1.309 (2) and 1.3443 (17) Å for N2—C3 and N1—C5, respectively, and 1.410 (2) and 1.419 (2) Å for C4—C5 and C3—C4, respectively]. Furthermore, the N1—C6 bond distance is different (1.453 (2) Å) and significantly longer than the N1—C5 and N2—C3 bonds, which is indicative of some multiple bond character in both N1—C5 and N2—C3 (Guzei et al., 2007; Yan, 2007; Wang et al., 2007). The sum of the angles at N1 is 360°, indicating sp² hybridization. The N1—C6 bond length is closer to the average C_ar—Nsp³ (pyramidal) value of 1.419 (17) Å than to the C_ar—Nsp² 1.353 (7) Å (Allen et al., 1987). The N1—N2 bond length is 1.3907 (18) Å, (smaller than a single bond) (1.41 Å; Burke-Laing & Laing, 1976; Guzei et al., 2007; Yan, 2007; Wang et al, 2007). The remaining bond lengths in (I) show no unusual values (Sun et al., 2007; Guzei et al., 2007; Yan, 2007; Wang et al., 2007).

There are three strong interactions (Table 2) of two types (N—H···O and N—H···N). These hydrogen bonds link molecules into two-dimensional corrugated sheets (Fig. 2) stacked along the b axis (Fig. 3). The significance of the hydrogen bonds is represented by relatively short D···A distances and D—H···A angles spanning 138 (2) to 164 (2)° (Table 2). These hydrogen bonds link the molecules to each other by four two-center N—H···O hydrogen bonds, in which the N—H and H₂N species of the hydrazino group lead to a number of intra- and intermolecular hydrogen bonds (Table 2). The NH₂ group of the H₂NH— species at (x, y, z) participitate in two N—H···O—NO hydrogen bonds [N4—H4A···O1 (x - 1/2, -y + 3/2, -z + 1) and N4—H4B···O2 (-x + 1/2, y - 1/2, z)], forming a centrosymmetric R⁴₂(12) ring (Bernstein et al., 1995), Fig. 3. In addition to these hydrogen bonds occurring between the molecules in the inversion related columns, there are also N—H···N hydrogen bonds [N3—H3···N2 (x, -y + 3/2, z - 1/2)].

As can be seen from the packing diagram (Fig. 3), the intermolecular hydrogen bonds (Table 2) and other less significant hydrogen bond interactions (longer interactions) cause to the formation of a three-dimensional supramolecular architecture, in which they may be effective in the stabilization of the crystal structure. Dipole-dipole and van der Waals interactions are also effective in the molecular packing.

Related literature

For related literature, see: Abu-Safieh et al. (2007); Allen et al. (1987); Bernstein et al. (1995); Burke-Laing & Laing (1976); Bustos et al. (2007); Guzei et al. (2007); Manfredini et al. (1992); Mavel et al. (1993); Sun et al. (2007); Tewari et al. (2002); Wang et al. (2007); Xia et al. (2007a,b); Yu et al. (2007).

For related literature, see: Yan (2007).

S2. Experimental

The title compound (I), prepared according to the following method (Abu-Safieh et al., 2007). H₂NNH₂·H₂O (85%, 8 ml, 160 mmol) was added dropwise to a stirred solution of 5-chloro-1,3-dimethyl-4-nitropyrazole (88 mg, 5 mmol) dissolved in 30 ml absolute ethanol. After stirring for ca 15 min at ambient temperature, the mixture was refluxed (water bath) for ca 2 h. The solvent was removed in vacuo to dryness. The resulting residual solid, recrystallized from ethanol yielded X-ray quality yellow crystals (m.p. 452–453 K). Yield = 0.59 g (69%). ¹H NMR (300 MHz, CDCl₃): δ 2.39 (s, 3H, CH₃—C(3)), 3.92 (br s,, 2H, N(4)H₂), 3.95 (s, 3H, N(1)—CH₃), 8.07 (br s, 1H, N(3)H); ¹³C NMR (75 MHz, CDCl₃): δ 14.4 (C(7)), 39.3 (C(6)), 118.1 (C(3)), 145.0 (C(4)), 147.6 (C(5)); IR (cm^-1): 3339 (υ(N—H)), 2970 (υ(C—H)), 1664 (υ(C═N)), 1582, 1367 (υ(NO₂)).

S3. Refinement

All H atoms were located in the difference map and refined independently with isotropic thermal displacement coefficients.

Computing details

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: HELENA (Spek, 1996); program(s) used to solve structure: XS in SHELXTL (Bruker, 2003); program(s) used to refine structure: XL in SHELXTL; molecular graphics: XP in SHELXTL; software used to prepare material for publication: XCIF in SHELXTL.

Figures

	Fig. 1. A molecular drawing of (I) shown with 50% probability ellipsoids.
	Fig. 2. Packing diagram of (I), shows the corrugated sheets of molecules. All hydrogen atoms not involved in hydrogen bonding were omitted for clarity. Hydrogen bonds are shown with dashed lines.
	Fig. 3. Packing diagram of (I) shown along the a axis. All hydrogen atoms not involved in hydrogen bonding were omitted for clarity. Hydrogen bonds are shown with dashed lines. [Symmetry codes: (i) x - 1/2, -y + 3/2, -z + 1; (ii) -x + 1/2, y - 1/2, z; (iv) -x, -y + 1, -z + 1; (v) x + 1/2, -y + 3/2, -z + 1; (vi) -x + 1, -y + 2, -z + 1; (vii) -x + 1/2, y + 1/2, z].
	Fig. 4. The formation of the title compound.

5-Hydrazino-1,3-dimethyl-4-nitro-1H-pyrazole

Crystal data

C5H9N5O2	F(000) = 720
Mr = 171.17	Dx = 1.482 Mg m^−3
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 1846 reflections
a = 8.3129 (3) Å	θ = 2.1–28.0°
b = 14.340 (3) Å	µ = 0.12 mm^−1
c = 12.869 (4) Å	T = 298 K
V = 1534.1 (6) Å^3	Block, yellow
Z = 8	0.55 × 0.35 × 0.35 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	1233 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.027
Graphite monochromator	θmax = 28.0°, θmin = 3.2°
ω scans	h = −1→11
Absorption correction: numerical (Shape Tracing Software; Rigaku, 2003)	k = −1→18
Tmin = 0.945, Tmax = 0.967	l = −16→16
4386 measured reflections	3 standard reflections every 400 reflections
1846 independent reflections	intensity decay: 3%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.042	All H-atom parameters refined
wR(F^2) = 0.127	w = 1/[σ^2(Fo^2) + (0.0736P)^2 + 0.0821P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
1846 reflections	Δρmax = 0.26 e Å^−3
146 parameters	Δρmin = −0.16 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0061 (18)

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
O1	0.21521 (17)	0.87426 (10)	0.56075 (8)	0.0607 (4)
N1	0.05276 (17)	0.72636 (9)	0.80896 (9)	0.0422 (4)
O2	0.32124 (19)	0.96616 (9)	0.67586 (10)	0.0670 (4)
N2	0.11316 (18)	0.78454 (9)	0.88612 (9)	0.0464 (4)
N3	0.05167 (19)	0.71807 (10)	0.62276 (11)	0.0485 (4)
H3	0.087 (2)	0.7452 (13)	0.5686 (13)	0.050 (5)*
C3	0.1893 (2)	0.85253 (11)	0.83932 (11)	0.0420 (4)
N4	−0.0454 (2)	0.63832 (13)	0.61765 (12)	0.0563 (4)
H4A	−0.108 (3)	0.6468 (16)	0.5671 (19)	0.074 (7)*
H4B	0.010 (3)	0.5904 (19)	0.598 (2)	0.095 (10)*
C4	0.17954 (19)	0.83961 (10)	0.73019 (11)	0.0383 (4)
N5	0.24162 (16)	0.89595 (10)	0.65299 (11)	0.0446 (4)
C5	0.08993 (18)	0.75750 (11)	0.71340 (10)	0.0378 (4)
C6	−0.0289 (3)	0.64202 (16)	0.84255 (17)	0.0608 (6)
H6C	−0.137 (4)	0.647 (2)	0.830 (2)	0.130 (11)*
C7	0.2681 (3)	0.92806 (15)	0.89924 (15)	0.0574 (5)
H7C	0.239 (3)	0.9836 (17)	0.8771 (18)	0.077 (7)*
H7A	0.234 (3)	0.9278 (17)	0.972 (2)	0.084 (7)*
H7B	0.388 (3)	0.9269 (19)	0.888 (2)	0.101 (9)*
H6A	−0.003 (4)	0.631 (2)	0.905 (3)	0.109 (9)*
H6B	0.010 (4)	0.592 (3)	0.810 (3)	0.149 (15)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0709 (9)	0.0775 (9)	0.0338 (6)	−0.0148 (7)	0.0073 (6)	0.0072 (6)
N1	0.0459 (8)	0.0492 (7)	0.0315 (6)	0.0003 (6)	0.0011 (5)	0.0045 (5)
O2	0.0827 (10)	0.0577 (8)	0.0607 (8)	−0.0225 (8)	0.0039 (7)	0.0039 (6)
N2	0.0558 (9)	0.0531 (8)	0.0302 (6)	0.0059 (7)	−0.0001 (6)	0.0000 (5)
N3	0.0568 (9)	0.0576 (8)	0.0311 (6)	−0.0131 (7)	0.0003 (6)	0.0011 (6)
C3	0.0471 (9)	0.0447 (8)	0.0340 (7)	0.0098 (7)	−0.0015 (7)	−0.0002 (6)
N4	0.0603 (10)	0.0643 (10)	0.0443 (8)	−0.0149 (9)	−0.0077 (8)	−0.0001 (7)
C4	0.0412 (8)	0.0419 (7)	0.0318 (7)	0.0056 (7)	0.0018 (6)	0.0017 (6)
N5	0.0461 (8)	0.0486 (8)	0.0392 (7)	−0.0007 (7)	0.0045 (6)	0.0049 (6)
C5	0.0363 (8)	0.0462 (8)	0.0308 (7)	0.0066 (7)	0.0023 (6)	0.0038 (6)
C6	0.0703 (14)	0.0654 (12)	0.0469 (10)	−0.0140 (11)	0.0002 (10)	0.0173 (9)
C7	0.0729 (15)	0.0538 (11)	0.0456 (10)	0.0033 (10)	−0.0042 (9)	−0.0093 (8)

Geometric parameters (Å, º)

O1—N5	1.2467 (18)	N4—H4A	0.84 (3)
N1—C5	1.3443 (17)	N4—H4B	0.87 (3)
N1—N2	1.3907 (18)	C4—N5	1.3805 (19)
N1—C6	1.453 (2)	C4—C5	1.410 (2)
O2—N5	1.2404 (18)	C6—H6C	0.92 (3)
N2—C3	1.309 (2)	C6—H6A	0.84 (3)
N3—C5	1.3347 (19)	C6—H6B	0.90 (4)
N3—N4	1.401 (2)	C7—H7C	0.88 (3)
N3—H3	0.851 (18)	C7—H7A	0.98 (3)
C3—C4	1.419 (2)	C7—H7B	1.01 (3)
C3—C7	1.482 (3)
C5—N1—N2	111.77 (13)	O2—N5—C4	120.25 (14)
C5—N1—C6	131.00 (15)	O1—N5—C4	118.26 (14)
N2—N1—C6	117.12 (13)	N3—C5—N1	127.16 (15)
C3—N2—N1	107.03 (12)	N3—C5—C4	127.85 (13)
C5—N3—N4	121.60 (14)	N1—C5—C4	104.99 (12)
C5—N3—H3	116.1 (12)	N1—C6—H6C	110 (2)
N4—N3—H3	122.3 (12)	N1—C6—H6A	108 (2)
N2—C3—C4	109.31 (14)	H6C—C6—H6A	116 (3)
N2—C3—C7	121.23 (15)	N1—C6—H6B	111 (2)
C4—C3—C7	129.46 (16)	H6C—C6—H6B	110 (3)
N3—N4—H4A	105.9 (16)	H6A—C6—H6B	102 (3)
N3—N4—H4B	110.6 (18)	C3—C7—H7C	112.0 (15)
H4A—N4—H4B	102 (2)	C3—C7—H7A	111.6 (15)
N5—C4—C5	125.16 (13)	H7C—C7—H7A	104 (2)
N5—C4—C3	127.92 (15)	C3—C7—H7B	110.7 (15)
C5—C4—C3	106.90 (13)	H7C—C7—H7B	104 (2)
O2—N5—O1	121.49 (13)	H7A—C7—H7B	115 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N4—H4A···O1^i	0.84 (3)	2.23 (3)	3.044 (2)	164 (2)
N4—H4B···O2^ii	0.87 (3)	2.48 (3)	3.182 (3)	138 (2)
N3—H3···N2^iii	0.851 (18)	2.396 (17)	3.088 (2)	138.8 (16)

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