Crystal structure of sodium 4-azido-1,2,3-triazolide monohydrate, Na(N3C2HN3) · H2O

Abstract

C 2 H 3 N 6 NaO, monoclinic, P 12 1 / m 1(no. 11), a =3.6146(8) Å, b =7.146(1) Å, c =11.258(2) Å, =92.02(1)°, V =290.6 Å 3 , Z =2, R gt (F) =0.042, wR ref (F 2 ) =0.110, T =233 K. Source of materialThe sodium salt of 4-azido-1,2,3-triazole [1,2] was obtained as ah ydrate by refluxing perfluoroallylbenzene with an excess of sodium azide in moist acetone. Crystals of this unexpected product were collected in low yield after filtration and evaporization of the solvent. This compound is certainly an energetic material, but no hazard assessment has been conducted so far. Experimental detailsThin plate with thickness of 0.01 mm and its small X-ray scattering power led to areduced number of observed reflections and a low N gt / N param ratio. Hydrogen atom at C1 (or C1A) could not be found from Fourier difference map because of the overlying with N3 from the disordered azido group. Therefore, it was calculated geometrically. The water hydrogen atom (with O1 in aspecial position) was found and refined with an isotropic displacement parameter and an O-H bond restraint of 0.85 Å. DiscussionThe title compound crystallizes centrosymmetrically with apositional disorder of the azido group N3-N4-N5 by amirror plane through the atoms O1, Na1, N1 and N5. The nitrogen atoms N3 and N4 in general positions were refined with an occupancy of 0.5. In the figure the disordered azido group at C1A and the disordered hydrogen atom at C1 were omitted for clarity. The azido group is not linear with an N3-N4-N5 angle of 172.5°(maybe an indication that the nitrogen atom N5 lies not exactly on the mirror plane), and it is tilted slightly out of the ring plane. Hydrogen bridges are observed between the water molecule and the azido group with d (O1-H···N3 )=2.009 Å. The sodium ion has adistorted octahedral coordination by four nitrogen atoms from different azolide rings and two oxygen atoms from water molecules with distances between 2.347 Å-2.721 Åand deviations from the right angle of ± 10°. By the coordination of the sodium ion a monolayer is formed and the azido groups penetrate into the adjacent layers which are stacked along the c axis.Z. Kristallogr. NCS 220 (2005) 575-576 575