Hexanitrohexaazaisowurtzitane (HNIW) was synthesized by a three-step reaction: condensation of benzylamine with glyoxal, debenzylation of condensation product, and nitrolysis of debenzylation product. The obtained nitrolysis product is α-HNIW which was identified by IR, ^1H NMR, ^1^3C NMR, MS(CI) and elemental analysis. Dissolving the α -HNIW in an appropriate solvent followed by evaporating the solvent slowly to a certain extent at a fixed temperature gave single crystals of γ-HNIW (identified by FTIR, FIR and LR spectra). HNIW consists of a rigid isowurtzitane cage with a nitro group attached to each of the six bridging nitrogens within the cage. This cage polycyclic nitramine is characterized by high strain, high enthalpy of formation and high density. The crystal structure was determined by X-ray diffractomer. The crystal belongs to monoclinic system and space group P2~1/n with parameters: a=1.3213(11)nm, b=0.8161(6)nm, c=1.4898(4)nm; β=109.168(9)ⅲ; Z=4; V=1.5175(4)nm^3. Dc=1.918g/cm^3, Dm=1.92g/cm^3. Final R=0.0360mm^-^1; S=0.938; (Δρ)max=344e/nm^3, (Δ ρ )min=-193e/nm^3. In this paper, the configuration of γ-HNIW and its cell paking are shown, and the isotropic thermal parameters, bond lengths and bond angles of HNIW are reported.

Key words: CRYSTAL STRUCTURE, NITROGEN HETEROCYCLICS, X-RAY DIFFRACTION ANALYSIS