Preparation, crystal structure, thermal decomposition, and explosive properties of [Cd(en)(N₃)₂]_n

A new multi-ligand coordination polymer of cadmium(II) ethylenediamine azide, [Cd(en)(N₃)₂]_n (en=ethylenediamine), was synthesized and characterized by using elemental analysis and FT-IR spectrum. Its crystal structure was determined by means of X-ray single crystal diffraction. The obtained results show that this crystal belongs to monoclinic, P2₁/n space group, a=0.6548(1) nm, b=1.0170(2) nm, c=1.2246(2) nm, β=90.23(1)°, V=0.8156(2) nm³, D_c=2.090 g·cm^-3, Z=4, R₁=0.024, wR₂ (I>2σ(I))=0.0416 and S=0.998. The Cd(II) ion is six-coordinated with four azido ligands by μ-1, 1 azido bridges, and two ethylenediamine molecules which serve as bidentate ligands through the nitrogen atoms. The thermal decomposition mechanism of the title complex was studied by using differential scanning calorimetry (DSC) and thermogravimetry-differential thermogravimetry (TG-DTG) techniques. Under nitrogen atmosphere with a heating rate of 10 K·min^-1, the thermal decomposition of the complex contains two main successive exothermic processes between 519 and 701 K in the DSC curve, and the final decomposed residue at 725 K is Cd. The non-isothermal kinetics parameters were calculated by using the Kissinger's method, Ozawa-Doyle's method, pervasive integration method, and differential method, respectively. The sensitivity properties of [Cd(en)(N₃)₂]_n were also determined with standard methods.