3,5-Dimethyl-4-nitroso-1H-pyrazole

Inna Safyanova; Nikolay M Dudarenko; Vadim A Pavlenko; Turganbay S Iskenderov; Matti Haukka

doi:10.1107/S1600536811033794

. 2011 Aug 31;67(Pt 9):o2520–o2521. doi: 10.1107/S1600536811033794

3,5-Dimethyl-4-nitroso-1H-pyrazole

Inna Safyanova ^a,^*, Nikolay M Dudarenko ^a, Vadim A Pavlenko ^a, Turganbay S Iskenderov ^a, Matti Haukka ^b

PMCID: PMC3200577 PMID: 22059058

Abstract

In the unit cell of the title compound, C₅H₇N₃O, there are two conformers (A and B) which differ in the position of the oxime group with respect to the protonated pyrazole nitrogen (trans in the A conformer and cis in the B conformer) and in the geometric parameters. The oxime group exists in the nitroso form in both conformers. In the crystal, molecules are linked by intermolecular N—H⋯O and N—H⋯N hydrogen bonds into zigzag-like chains along the b axis.

Related literature

For the use of pyrazole-based ligands, see: Mullins & Pecoraro (2008 ▶); Mukhopadhyay et al. (2004 ▶). For the magnetic properties of pyrazolate complexes, see: Aromi & Brechin (2006 ▶); Gatteschi et al. (2006 ▶). For the use of oxime substituents in the synthesis of polynuclear ligands, see: Petrusenko et al. (1997 ▶); Kanderal et al. (2005 ▶); Sachse et al. (2008 ▶); Moroz et al. (2010 ▶). For the use of 4-nitropyrazoles as ligands, see: Halcrow (2005 ▶). For related structures, see: Fletcher et al. (1997 ▶); Kovbasyuk et al. (2004 ▶); Mokhir et al. (2002 ▶); Sliva et al. (1997 ▶); Wörl, Fritsky et al. (2005 ▶); Wörl, Pritzkow et al. (2005 ▶). For the synthesis of the title compound, see: Cameron et al. (1996 ▶).

Experimental

Crystal data

C₅H₇N₃O
M _r = 125.14
Monoclinic,
a = 4.0268 (2) Å
b = 15.3793 (7) Å
c = 19.6627 (9) Å
β = 94.613 (3)°
V = 1213.75 (10) Å³
Z = 8
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 120 K
0.46 × 0.33 × 0.13 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997 ▶) T _min = 0.955, T _max = 0.987
9003 measured reflections
2747 independent reflections
1866 reflections with I > 2σ(I)
R _int = 0.040

Refinement

R[F ² > 2σ(F ²)] = 0.041
wR(F ²) = 0.109
S = 1.03
2747 reflections
175 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.23 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Data collection: COLLECT (Nonius, 2000 ▶); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR2004 (Burla et al., 2005 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2008 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811033794/jh2317sup1.cif

e-67-o2520-sup1.cif^{(17.4KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811033794/jh2317Isup2.hkl

e-67-o2520-Isup2.hkl^{(134.9KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811033794/jh2317Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1B—H1B⋯O1Aⁱ	0.954 (18)	1.802 (18)	2.7526 (16)	174.0 (15)
N1A—H1A⋯N2Bⁱⁱ	0.915 (19)	1.95 (2)	2.8544 (18)	171.5 (16)

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

Financial support from the State Fund for Fundamental Research of Ukraine (grant No. F40.3/041) and the Swedish Institute (Visby Program) is gratefully acknowledged.

supplementary crystallographic information

Comment

Pyrazole-based ligands are widely used in bioinorganic chemistry, molecular magnetism and supramolecular chemistry, as they are able to form different architectures, ranging from polynuclear clusters to metallocycles (Mullins, et al., 2008; Mukhopadhyay, et al., 2004). In addition to the ability to bridge two or more metal ions, pyrazole ligands also provide an effective magnetic exchange pathway between them (Aromi et al. 2006; Gatteschi, et al., 2006). The incorporation of other coordinating groups to the pyrazole ring can increase the variety of polynuclear compounds that can be formed. For example, introduction of the potentially bridging oxime group in the molecules of the ligands already having bridging moieties (such as pyrazolates) can lead to increase of nuclearity and complexity of the metal complexes on their basis (Petrusenko et al., 1997; Kanderal et al., 2005; Sachse et al., 2008; Moroz et al., 2010). In this work, we report the crystal structure of the title compound which contains the oxime group in the 4-position of the pyrazole ring. Unlike 4-nitropyrazoles which have been widely used for preparation of oligonuclear metal complexes (Halcrow et al., 2005), 4-nitrosopyrazoles have never been studied as ligands, and no metal complexes based on this type of ligands have been reported up to date. Crystal and molecular structures of only two 4-nitrosopyrazoles have been reported before (Cameron et al., 1996; Fletcher et al., 1997).

In the unit cell there are two types of conformers (A and B) of the title compound which differs significantly by the geometrical parameters and by the position of the oxime group with respect to the protonated pyrazole nitrogen (Fig. 1). In the conformer A, the oxime group is trans- with respect to the pyrazole hydrogen, while in the conformer B the oxime-group is cis-situated. In the conformers A and B the bond lengths markedly differs, first of all it is noticeable upon comparing the interatomic distances within the oxime groups. In the conformer B, the difference in bond lengths between C—N (1.3902 (19) Å) and N=O (1.2412 (16) Å) bonds of the oxime groups is quite large (ca 0.15 Å) while in the conformer A (C—N 1.3553 (19) Å and N=O 1.2701 (16) Å) it is much less pronounced (less than 0.08 Å). This clearly indicates that the CNO moiety in both conformers exists in the nitroso-form (Sliva et al. (1997); Mokhir et al., 2002), however, in the conformer A there is a noticeable contribution of the isonitroso-form. Such a difference can be a consequence of the involvement of the oxime oxygen O1A in formation of the intermolecular H-bond, while O1B does not participate in any H-bond (Table 1).

The differences in geometrical and electronic structure of the oxime groups significantly influence on the C—C, C—N, N—N bond lengths within the pyrazole rings which are deviated from normal values (Kovbasyuk et al., 2004; Wörl, Fritsky et al., 2005; Wörl, Pritzkow et al., 2005). Thus, there are signs of conjugation of the C(3B)—C(4B) bond with the O(1B)—N(3B) bond which results in noticeable shortening of the former (1.405 (2) Å) as compare to that observed in the conformer A, C(3)—C(4) = 1.442 (2) Å.

In the crystal, the molecules are linked by intermolecular N—H···O and N—H···N hydrogen bonds building zigzag chains along the b axis (Fig.2, Table 1). The translational along a axis chains form walls which are united into the crystal by van der Waals interactions.

Experimental

3,5-dimethyl-4-nitrozo-1H-pyrazole was synthesized by using a literature procedure (Cameron et al., 1996) from acetylacetone, sodium nitrite and hydrazine hydrate in aqueous hydrochloric acid. The crude product was collected by filtration and purified by recrystallization from benzene. Colorless crystals suitable for the X-ray diffraction were obtained after several hours (yield 78%).