Stabilised phosphazides

The Staudinger reaction between phosphines and azides provides a straightforward route to azaylides. Until the 1980s, it was thought that the putative intermediates of this reaction, namely phosphazides, were merely transient species that could be detected only by spectroscopic methods. This review summarises the achievements reported over the last 25 years on the preparation, structure and properties of phosphazides stabilised by substitution effects and/or coordination to transition metals or main group elements. Relevant computational studies on the Staudinger reaction are included.