Halogen azides, structure

The crystal structure of iodine azide is polymeric with longer N-I distances than in the gas phase, becanse the IN3 units are connected by hnear coordinated iodine atoms. Structural data of the halogen azides are suimnarized in... 

Table 38 Structural data of halogen azides compared to HN3...

Covalent non-metal azides include the halogen azides N3X (X = F, Cl, Br, I), silyl azide, H3SiN3, and organic azides. Cyanuric andp-nitrophenyl azides have been studied in the crystalline state and methyl azide in the vapour state (e.d.). The structures of the last two are shown at (b) and (c). 

However, some investigators have shown that aryl azides that possess a perfluori-nated ring structure or are substituted completely with halogen atoms are quite efficient at forming the desired nitrene intermediate (Soundararajan et al., 1993 Keana... 

Compounds, such as the polyhalides and polysulphides, formally also the azides, could be regarded as produced by the attachment of one or more neutral non-polar halogen, sulphur or nitrogen molecules to a halogen, sulphide or nitride ion. With the last one this way of representation is definitely incorrect the azide-ion N3 is linear in contrast to the triangular structure to be expected for ionic bonding. 

The azide ion has not been observed in nature as an isolated species. It is, however, readily stabilized by a lattice or solution environment. Many of the ion s properties tend to be similar to those of halogen ions when it is ionically bonded or in solution. Indeed, X-ray structural data on NaNa and KN3 reveal that the ion is a compact prolate spheroid (see Chapter 3) comparable in volume to Br its electron affinity (see below) is also close to that of Br . 

Attack on Nitrogen, Chalcogen, or Halogen.- Some tertiary alkyl azides and tris(dimethylamino)phosphine gave thermally stable phosphazides (24), allowing the X-ray crystal structure of one to be determined. ... 

Very recently, Wu et al. developed an eflhcient Fe/Cu relay-catalyzed domino protocol for the synthesis of pharmaceutically significant 2-phenylquinazoIin-4-amines 67 from commercially available ortlzo-halogenated benzonitriles, aldehydes, and sodium azide (Scheme 7.47) [115]. This elegant domino reaction involved consecutive iron-mediated [3 + 2] cycloaddition, copper-catalyzed SNAr, reduction, cyclization, oxidation, and copper-catalyzed denitrogenation sequences. The structure constructed by this protocol is the privileged core in drugs and bioactive molecules. 

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