N,N-Bis(cyanomethyl)nitrous amide

In the title compound, C4H4N4O, both H atoms bonded to one methylene C atom are involved in C—H⋯N hydrogen-bonding interactions; one of the interactions results in dimers of the title molecule lying about inversion centers in R 2 2(12) motifs and the other forms chains of molecules lying along the c axis.

In the title compound, C 4 H 4 N 4 O, both H atoms bonded to one methylene C atom are involved in C-HÁ Á ÁN hydrogenbonding interactions; one of the interactions results in dimers of the title molecule lying about inversion centers in R 2 2 (12) motifs and the other forms chains of molecules lying along the c axis.

Comment
At present, much attention in the field of ferroelectric materials is focused on developing ferroelectric organic or inorganic compounds (Haertling et al., 1999;Homes et al., 2001). It has been reported that N,N-bis(cyanomethyl)nitramide crystallizes in space group (C 2) at room temperature (Adolf et al., 1996), a noncentrosymmetric space group is required for ferroelectric behavior. Its ferroelectric property still needs to be further confirmed by many experiments, such as dielectric measurements and DSC to varify the permittivity anomaly, phase transition, etc. For this reason, we have synthesized the title compound to investigate its physical properties. The dielectric constant of the title compound as a function of temperature indicates that the permittivity is basically temperature-independent (dielectric constant = 3.2 to 5.6), suggesting that this compound should not be a real ferroelectric or there may be no distinct phase transition within the measured temperature range. Similarly, below the melting point (308 K) of the compound, the dielectric constant as a function of temperature also goes smoothly, and there is no dielectric anomaly observed. Herein, we report the synthesis and crystal structure of the title compound.
The bond distances and bond angles in the title compound agree very well with the corresponding distances and angles reported for a closely related compound (Kaida et al., 1990); both cyanic groups are linear (Fig. 1). It is interesting to note that both H-atoms bonded to only one methylene carbon (C3) are involved in hydrogen bonding interactions of the type C-H···N, C3-H3B···N2 hydrogen bonds result in dimers of the title molecule lying about inversion centers in R 2 2 (12) motifs in graph set notation (Bernstein et al., 1994) while C3-H3C···N1 interactions result in chains of molecules lying along the c-axis (Tab. 1, Fig. 2). Dipole-dipole and van der Waals interactions are effective in the molecular packing.

Experimental
A solution of sodium nitrite (2.3 g, 33 mmoles) in water (10 ml) was added at 291-293 K to a solution of 2,2'-azanediyldiacetonitrile hydrochloride (1.7 g, 28 mmoles) in water (30 ml). The mixture was heated for 1.5 h at 313-323 K and allowed to stand for 12 h at 293 K. The title compound as nitroso derivative, was extracted with ether, the ether solution was evaporated. Single crystals suitable for X-ray diffraction analysis were obtained from slow evaporation of an ethyl acetate solution of the title compound.

Refinement
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.97 Å and U iso (H) = 1.2U eq (C).
supplementary materials sup-2 Figures   Fig. 1. Perspective drawing of the title compound with displacement ellipsoids drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 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 (Å 2 )