A New Route to the Phosphazene Polymerization Precursors, Cl₃PNSiMe₃ and (NPCl₂)₃

An improved synthesis of the phosphazene polymerization precursors, hexachlorocyclotriphosphazene, (NPCl2)3 (1), and Cl3PNSiMe3 (2) is reported. The addition of PCl5 to N(SiMe3)3 in methylene chloride at 40 °C produced a mixture of phosphazenes which contained 76% of 1. However, the addition of N(SiMe3)3 to PCl5 in methylene chloride at 0 °C, followed by the addition of hexane, provided 2 in 40% yield. The mechanism of the reaction is discussed.