Covalent Inorganic Azides

The chemistry of covalent inorganic azides originated with the synthesis of aqueous HN₃ solutions by Tony Curtis in 1890. A little later, in 1900, it proved possible to prepare iodine azide, IN₃, as the first member of the meanwhile complete series of halogen azides. Since then it has been possible to synthesize, in addition to HN₃ and the stable salt H₂NSbF, azide compounds of elements from Groups 13 to 17. In these compounds the N₃ moiety acts as a pseudohalogen and is primarily covalently coordinated to the nonmetal. Only a few organic azides, however, as well as HN₃, H₂N, and all halogen azides have been thoroughly studied with respect to structure and bonding. The combined application of diffraction methods (X-ray and electron diffraction) and microwave spectroscopy together with quantum chemical approaches such as ab initio SCF and density functional calculations have led in the last few years to an improved understanding of the molecular properties of numerous nonmetal azides, almost all of which are explosive. This interaction of theory and experiment has greatly enhanced the development of azide chemistry and has led to realistic expectations for the synthesis of as yet unknown nonmetal azides.