2,2-Di­methyl-1-(2,4,6-tri­nitro­phenyl)­hydrazine

The title mol­ecule (DMPH-H), C₈H₉N₅O₆, was investigated to provide comparison with 2,2-di­phenyl-1-picryl­hydrazine, which unlike DMPH-H is readily oxidizable to form a well known stable free radical (DPPH). The structure shows essential differences in the configuration of the hydrazine-N atoms, the ortho-nitro group orientations and the crystal packing. The bond angles of the di­methyl­amino N atom [107.90 (13), 108.96 (12) and 112.21 (13)°] are consistent with a tetrahedral N atom and sp³ hybridization.

S1. Comment

2,2-Dimethyl-1-picrylhydrazine (DMPH-H) reported herein is the latest member of a series of closely related picrylhydrazines being investigated in an on-going study of their internal rotations (conformerizations), as well as the acidity and oxidizability of the hydrazinic moiety (e.g. Brown et al., 1999; Tyson & Weil, 1990). Comparisons of the molecular structures, pseudo-thermodynamic conformerization activation parameters, chemical properties, and the results of molecular-orbital computations have been a vital component of this work (Brown et al., 1999; Wang et al., 1991).

DMPH-H was reported earlier as not being oxidizable to the corresponding hydrazyl radical (Poirier & Benington, 1954). We have confirmed this observation, of interest since 2,2-diphenyl-1-picrylhydrazine (DPPH-H) forms a very stable free radical (DPPH). The bond angles for N7 of DMPH-H [107.90 (13), 108.96 (12) and 112.21 (13)°] are consistent with a tetrahedral nitrogen atom and sp³ hybridization, compared to the equivalent nitrogen atom in DPPH-H which is sp² hybridized (with some sp³ character) (Wang et al., 1991). Thus, the structural differences (e.g. of the π-electron systems) elucidate the chemical differences.

The structure of DMPH-H has an intra-molecular hydrogen bond between the hydrogen H1 on N1 and one of the oxygen atoms on N2 (O21) [or N6 (O61)] to form a six-membered ring (Fig. 1), a structure found in all of the picryl hydrazines (Brown et al., 1999; Wang et al., 1991). The result is to put the plane of the N2 nitro group fairly close [22.62 (6)°] to the plane of the picryl ring [whereas the plane of the N6 nitro group adopts a conformation highly twisted [52.74 (6)° relative to the plane of the picryl ring due to the proximity of atom N7] unlike the coplanar situation in DPPH-H (Wang et al., 1991).

There are no solvent molecules trapped in the DMPH-H structure and no large cavities in the lattice, unlike DPPH-H which crystallizes with interstitial clathrate solvent molecules (Wang et al., 1991).

Atom H1 forms a short intramolecular hydrogen bond with an ortho nitro group (as in DPPH-H) but also forms a long intermolecular hydrogen bond to atom O22 on an adjacent molecule (1/2 + x, 1/2 − y, 1 − z).

Dynamic NMR and self-consistent field molecular orbital studies of DMPH-H are under way.

S2. Experimental

A mixture of picryl chloride (2.48 g, 10 mmol) and K₂CO₃ (1.65 g, 12 mmol) was dissolved in 1:1 MeOH-H₂O (50 ml). To this solution, cooled to 273 K, was added dropwise a solution of 1,1-dimethylhydrazine (720 mg, 12 mmol) dissolved in MeOH (5 ml). After the addition was complete, the resulting deep red-colored solution was stirred for 1 h. The reaction mixture was evaporated to the point of turbidity, warmed gently to afford a homogenous solution and allowed to cool down slowly to afford a yellow solid. Filtration and recrystallization from absolute EtOH gave 2.2 g (82% yield) of the title compound [m.p. 411–413 K (literature 409–411 K; Latham et al., 1976)]; IR (KBr) ν_max: 3270 (m, N—H str), 3093 (m, C—H str), 1620 (s), 1590 (m), 1512 (s), 1456 (m), 1333 (s), 1301 (m), 1087 (m), 724 (m) cm⁻¹; ¹H NMR (300 MHz, CDCl₃, p.p.m.) δ: 2.59 (s, 6H), 8.30 (bs, 1H), 8.98 (s, exch, 1H), 9.16 (bs, 1H); ¹H NMR (300 MHz, DMSO-d₆, p.p.m.) δ: 2.57 (s, 6H), 8.81 (s, 2H), 9.73 (s, exch, 1H); ¹³C NMR (75 MHz, (CD₃)₂CO, p.p.m.) δ: 45.3 (q, CH₃), 123.9 (s, Ar—C), 124.8 (s, Ar—C), 133.8 (d, Ar—CH), 141.1 (d, Ar—CH); EI—MS m/z (relative intensity): Calculated for C₈H₉N₅O₆ 271.0553. Found 271.0550 (M+, 37), 254.0529 (100), 209 (15), 179 (11), 149 (17).

Note: In an alternative preparation, using a reported method (Nelsen & Weisman, 1973) based on reductive alkylation of hydrazines, a mixture of picryl hydrazine (2.43 g, 10 mmol), aq. HCHO (37%, 8 ml), and NaBH₃CN (230 mg, 4 mmol) in 50 ml MeOH was stirred at ambient temperature for 2 h. Usual workup, e.g., extraction with EtOAc, washing with 10% NaHCO₃ and water, and evaporation of the organic extracts gave a yellow solid that was purified by crystallization (EtOH) to afford 1.6 g (58% yield) of the title compound with physical and spectroscopic characteristics essentially identical to the ones reported above.

S3. Refinement

The molecule exhibits no optical activity but crystallizes in the acentric space group P2₁2₁2₁. The intermolecular hydrogen bonding described in Table 1 produces continuous spirals of molecules, resulting in the non-centrosymetric space group. Using Mo radiation, and in the absence of any atom with more electrons than oxygen, it is not possible to determine with certainty if the crystal used is all of one hand or is a racemic twin. During refinement, the structure was treated as a racemic twin.

All hydrogen atoms were placed in calculated positions on the corresponding carbon atoms (C—H = 0.98 Å on aliphatic carbons, 0.95 Å on aromatic carbons) and 0.88 Å on nitrogen and were not refined. The U_iso of each hydrogen atom was assigned as equal to 1.2 times the U_eq of the attached atom.

The ω-scan width was (0.65 + 0.72 tanθ)° with a ω-scan rate of 0.69–3.35° min⁻¹. The scan angle was extended 25% on each side of each peak for background measurement.

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1992); cell refinement: CAD-4 EXPRESS; data reduction: DIFDAT_SORTRF_ADDREF in Xtal (Hall et al., 1997); program(s) used to solve structure: Xtal; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Xtal; software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. A general ORTEPII (Johnson, 1976) view of the title compound with non-hydrogen displacement ellipsoids drawn at the 50% probability level. For clarity, the H atoms are drawn as small spheres of arbitrary size.

2,2-dimethyl-1-(2,4,6-trinitro)phenylhydrazine

Crystal data

C8H9N5O6	Dx = 1.631 Mg m^−3
Mr = 271.20	Melting point = 138–140 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 25 reflections
a = 6.5156 (7) Å	θ = 10.4–18.5°
b = 8.2006 (11) Å	µ = 0.14 mm^−1
c = 20.6704 (14) Å	T = 123 K
V = 1104.5 (2) Å^3	Prism, orange
Z = 4	0.42 × 0.30 × 0.25 mm
F(000) = 560

Data collection

Nonius CAD-4 diffractometer	2171 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.044
Graphite monochromator	θmax = 33.5°, θmin = 2.7°
ω scan b/P/b	h = 0→10
Absorption correction: ψ scan (North et al., 1968)	k = 0→12
Tmin = 0.88, Tmax = 0.96	l = 0→32
2553 measured reflections	3 standard reflections every 200 reflections
2479 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.100	w = 1/[σ^2(Fo^2) + (0.0563P)^2 + 0.2264P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max < 0.001
2479 reflections	Δρmax = 0.43 e Å^−3
175 parameters	Δρmin = −0.35 e Å^−3
0 restraints	Absolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.0 (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.

Refinement was by full-matrix least-squares methods.

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

	x	y	z	Uiso*/Ueq
C1	0.1670 (2)	0.29234 (17)	0.37985 (7)	0.0122 (3)
C2	0.1438 (2)	0.40131 (18)	0.43288 (7)	0.0126 (3)
C3	−0.0218 (2)	0.50554 (17)	0.43987 (7)	0.0138 (3)
H3	−0.0306	0.5768	0.4760	0.017*
C4	−0.1734 (2)	0.50403 (19)	0.39351 (7)	0.0135 (3)
C5	−0.1581 (2)	0.40465 (19)	0.33881 (7)	0.0137 (3)
H5	−0.2627	0.4053	0.3068	0.016*
C6	0.0100 (2)	0.30665 (17)	0.33228 (7)	0.0120 (3)
C71	0.4635 (3)	−0.0231 (2)	0.31116 (8)	0.0174 (3)
H71A	0.5069	0.0555	0.2782	0.026*
H71B	0.4412	−0.1298	0.2909	0.026*
H71C	0.5702	−0.0325	0.3443	0.026*
C72	0.1869 (3)	−0.0885 (2)	0.38630 (8)	0.0187 (3)
H72A	0.2890	−0.1140	0.4196	0.028*
H72B	0.1515	−0.1881	0.3626	0.028*
H72C	0.0634	−0.0440	0.4068	0.028*
N1	0.3153 (2)	0.17874 (17)	0.37546 (7)	0.0156 (3)
H1	0.4360	0.1945	0.3935	0.019*
N2	0.2872 (2)	0.39574 (16)	0.48659 (6)	0.0143 (2)
N4	−0.3534 (2)	0.60611 (18)	0.40141 (7)	0.0171 (3)
N6	0.0318 (2)	0.22711 (16)	0.26857 (6)	0.0139 (2)
N7	0.2723 (2)	0.03271 (16)	0.34104 (6)	0.0138 (2)
O21	0.4622 (2)	0.34351 (15)	0.47657 (6)	0.0180 (2)
O22	0.2284 (2)	0.44183 (17)	0.54008 (6)	0.0232 (3)
O41	−0.3559 (2)	0.70268 (17)	0.44722 (7)	0.0285 (3)
O42	−0.4949 (2)	0.58919 (15)	0.36294 (6)	0.0208 (3)
O61	0.1907 (2)	0.25165 (15)	0.23855 (6)	0.0191 (2)
O62	−0.1155 (2)	0.15051 (17)	0.24792 (6)	0.0220 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0121 (6)	0.0101 (6)	0.0144 (6)	0.0013 (5)	0.0018 (5)	0.0016 (5)
C2	0.0130 (6)	0.0106 (5)	0.0143 (6)	0.0002 (5)	0.0001 (5)	0.0007 (5)
C3	0.0160 (6)	0.0100 (5)	0.0154 (6)	0.0014 (5)	0.0025 (6)	−0.0001 (5)
C4	0.0136 (6)	0.0108 (6)	0.0162 (6)	0.0042 (5)	0.0036 (5)	0.0026 (5)
C5	0.0142 (6)	0.0125 (6)	0.0144 (6)	0.0020 (6)	0.0009 (5)	0.0017 (5)
C6	0.0137 (6)	0.0106 (5)	0.0118 (6)	0.0003 (5)	0.0015 (5)	0.0001 (5)
C71	0.0146 (6)	0.0201 (7)	0.0176 (7)	0.0050 (6)	0.0023 (5)	−0.0030 (6)
C72	0.0213 (8)	0.0158 (6)	0.0192 (7)	0.0020 (7)	0.0040 (6)	0.0006 (6)
N1	0.0127 (5)	0.0150 (5)	0.0193 (6)	0.0041 (5)	−0.0032 (5)	−0.0044 (5)
N2	0.0158 (6)	0.0112 (5)	0.0159 (5)	−0.0014 (5)	−0.0012 (5)	−0.0004 (5)
N4	0.0172 (6)	0.0144 (6)	0.0198 (6)	0.0055 (6)	0.0039 (5)	0.0026 (5)
N6	0.0156 (6)	0.0131 (5)	0.0132 (5)	0.0030 (5)	0.0004 (5)	0.0002 (5)
N7	0.0145 (6)	0.0106 (5)	0.0162 (5)	0.0031 (5)	0.0013 (5)	−0.0023 (5)
O21	0.0153 (5)	0.0179 (5)	0.0209 (5)	0.0025 (5)	−0.0039 (4)	0.0004 (5)
O22	0.0243 (6)	0.0297 (7)	0.0156 (5)	−0.0024 (6)	−0.0009 (5)	−0.0067 (5)
O41	0.0309 (7)	0.0243 (6)	0.0302 (7)	0.0144 (6)	0.0014 (6)	−0.0092 (5)
O42	0.0161 (5)	0.0220 (5)	0.0242 (6)	0.0062 (5)	0.0002 (5)	0.0029 (5)
O61	0.0202 (6)	0.0205 (5)	0.0166 (5)	−0.0008 (5)	0.0066 (5)	0.0003 (5)
O62	0.0177 (5)	0.0244 (6)	0.0237 (6)	−0.0015 (5)	−0.0018 (5)	−0.0087 (5)

Geometric parameters (Å, º)

C1—N1	1.3451 (19)	C71—H71B	0.9800
C1—C2	1.422 (2)	C71—H71C	0.9800
C1—C6	1.423 (2)	C72—N7	1.474 (2)
C2—C3	1.384 (2)	C72—H72A	0.9800
C2—N2	1.452 (2)	C72—H72B	0.9800
C3—C4	1.376 (2)	C72—H72C	0.9800
C3—H3	0.9500	N1—N7	1.4207 (18)
C4—C5	1.397 (2)	N1—H1	0.8800
C4—N4	1.450 (2)	N2—O22	1.2297 (18)
C5—C6	1.366 (2)	N2—O21	1.2354 (18)
C5—H5	0.9500	N4—O42	1.226 (2)
C6—N6	1.4764 (19)	N4—O41	1.2346 (19)
C71—N7	1.464 (2)	N6—O62	1.2236 (19)
C71—H71A	0.9800	N6—O61	1.2237 (18)
N1—C1—C2	124.30 (14)	H71B—C71—H71C	109.5
N1—C1—C6	121.77 (14)	N7—C72—H72A	109.5
C2—C1—C6	113.84 (13)	N7—C72—H72B	109.5
C3—C2—C1	123.47 (14)	H72A—C72—H72B	109.5
C3—C2—N2	116.19 (13)	N7—C72—H72C	109.5
C1—C2—N2	120.07 (13)	H72A—C72—H72C	109.5
C4—C3—C2	118.76 (14)	H72B—C72—H72C	109.5
C4—C3—H3	120.6	C1—N1—N7	118.43 (13)
C2—C3—H3	120.6	C1—N1—H1	120.8
C3—C4—C5	121.18 (14)	N7—N1—H1	120.8
C3—C4—N4	119.79 (14)	O22—N2—O21	123.00 (14)
C5—C4—N4	119.03 (14)	O22—N2—C2	118.52 (14)
C6—C5—C4	118.70 (14)	O21—N2—C2	118.48 (13)
C6—C5—H5	120.6	O42—N4—O41	124.08 (14)
C4—C5—H5	120.6	O42—N4—C4	118.05 (14)
C5—C6—C1	123.83 (13)	O41—N4—C4	117.86 (14)
C5—C6—N6	115.16 (13)	O62—N6—O61	124.81 (14)
C1—C6—N6	120.72 (13)	O62—N6—C6	117.57 (13)
N7—C71—H71A	109.5	O61—N6—C6	117.43 (13)
N7—C71—H71B	109.5	N1—N7—C71	107.90 (13)
H71A—C71—H71B	109.5	N1—N7—C72	108.96 (12)
N7—C71—H71C	109.5	C71—N7—C72	112.21 (13)
H71A—C71—H71C	109.5
N1—C1—C2—C3	−172.91 (15)	C2—C1—N1—N7	149.55 (15)
C6—C1—C2—C3	3.5 (2)	C6—C1—N1—N7	−26.6 (2)
N1—C1—C2—N2	0.8 (2)	C3—C2—N2—O22	20.8 (2)
C6—C1—C2—N2	177.25 (13)	C1—C2—N2—O22	−153.42 (15)
C1—C2—C3—C4	0.4 (2)	C3—C2—N2—O21	−159.87 (13)
N2—C2—C3—C4	−173.61 (13)	C1—C2—N2—O21	25.9 (2)
C2—C3—C4—C5	−2.6 (2)	C3—C4—N4—O42	−172.42 (14)
C2—C3—C4—N4	176.90 (14)	C5—C4—N4—O42	7.1 (2)
C3—C4—C5—C6	0.7 (2)	C3—C4—N4—O41	6.3 (2)
N4—C4—C5—C6	−178.82 (14)	C5—C4—N4—O41	−174.13 (15)
C4—C5—C6—C1	3.7 (2)	C5—C6—N6—O62	−52.43 (18)
C4—C5—C6—N6	−170.10 (13)	C1—C6—N6—O62	133.60 (15)
N1—C1—C6—C5	170.95 (15)	C5—C6—N6—O61	122.90 (15)
C2—C1—C6—C5	−5.6 (2)	C1—C6—N6—O61	−51.08 (19)
N1—C1—C6—N6	−15.6 (2)	C1—N1—N7—C71	148.03 (14)
C2—C1—C6—N6	167.86 (13)	C1—N1—N7—C72	−89.89 (16)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O21	0.88	2.11	2.6666 (18)	120
N1—H1···O22^i	0.88	2.60	3.358 (2)	145

Symmetry code: (i) x+1/2, −y+1/2, −z+1.