Cyclic phosphazenes

(NPCl₂)_n, where n = 3, 4, 5

structures determined by X-ray crystallography

hexachlorotricyclophosphazene, (NPCl₂)₃
Wikipedia: Hexachlorophosphazene
Acta Cryst. (2006) B62, 321–329


octachlorotetracyclophosphazene, (NPCl₂)₄
stable T form: chair conformation
Acta Cryst. (1968) B24, 707–713


metastable K form: boat conformation
Acta Cryst. (1962) 15, 539–543


decachloropentacyclophosphazene, (NPCl₂)₅
J. Chem. Soc. A (1968), 2317–2325