Phosphazides as ligands in coordination chemistry

Phosphazides (R 3 P=N–N=N–R') are intermediates in the Staudinger reaction (R 3 P + N 3 –R' → R 3 P=N–R'), which is commonly employed to prepare iminophosphoranes/phosphinimines (R 3 P=N–R'). Phosphazides are rarely isolated due to their propensity to decompose via loss of dinitrogen (N 2 ), along with concomitant generation of a phosphinimine. While phosphinimines are commonplace in multidentate ligand frameworks, phosphazides have been largely overlooked as a viable functional group in coordination chemistry, despite their diverse coordination behavior. This review provides a comprehensive accounting of phosphazides coordinated to metal centres and describes their potential to stabilize metal complexes that exhibit novel reaction chemistry.