Geometry of diazo and azido groups

This section is primarily concerned with the geometrical characteristics of the diazo group obtained by X-ray diffraction studies of benzenediazonium compounds (1), a-diazoketones (resonance hybrids 2a,b,c) and diazoalkanes (3a,b). The section concludes with some geometrical details for the analogous azido group (4a,b). There are 50 crystal- 

TABLE 11. Diazo and azido compounds Mean geometrical parameters for 1-4  

FIGURE 5. Plot of the N=N bond length versus the C—N bond length for diazo compounds 

FIGURE 6. Plot of the N1N2 bond length versus the N2N3 bond length for azido compounds 

The MO calculations of Csizmadia and coworkers agree well with these experimental observations. We may conclude that resonance hybrid 2a plays a major role in a-diazoketone structures with contributions from 2b and, to a much smaller extent, 2c. 

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