Phosphazenes

This chapter summarizes the chemistry of phosphazenes in the calendar year 2018. The topics covered are acyclic phosphazenes, cyclophosphazenes and polyphosphazenes. The preparative aspects of these compounds, their structures and their reactivity studies are covered. Acyclic phosphazenes have been of interest from various points of view including their ability to function as strong bases and as ligands towards transition-, lanthanide- and main-group metal ions. Some of these complexes also find applications in catalysis. The multi-functional reactivity of cyclophosphazenes to form dendrimer-like structures is discussed. Also, the reactions of cyclophosphazenes with difunctional reagents has been discussed. Phosphazene polymers, including polyphosphazenes and hybrid polymers have also been covered.