The Crystal Structure of Hydrazinium Trinitromethide,

The crystal structure of hydrazinium trinitromethide $$ has been determined using 1914 x-ray data collected photographically from a single crystal held at ~ - 160 °C. The unit cell at ~ - 160°C is a = 7.91(2). b = 11.77(2), c = 13.98(2) Å, β = 104.9(3)°. and contains eight formula weights in space group P2₁/n. The calculated density is 1.93 g · cm^-3. The structure has been refined isotropically to R = 0.10 by full-matrix least-squares procedures. The two crystallographically independent trinitromethide anions are propeller shaped, with angles of 41°, 7°, 8°, and 74°. 5°, 4°, respectively, between the NO₂ and CN₃ plane normals. The central CN₃ part of each anion is almost planar. In one anion, the C atom is 0.008 Å out of the N₃ plane; in the other, the C atom is 0.033 Å out of the N₃ plane. Hydrogen atoms have been located approximately in an electron density difference synthesis. Their positions agree with those obtained from independent calculations involving the minimization of a function which is a first approximation to the electrostatic hydrogen bonding energy. These analyses provide evidence that one hydrazinium ion is eclipsed and the other is staggered.