Preparation of urethane and urea derivatives of (NPCl2)3. Crystal structure of a spirocyclic phosphazene with a phosphacyanuric loop

Abstract

Reactions of (NPCl₂)₃ with NaNCO in the presence of aliphatic alcohols have been investigated. Using an equimolar amount of NaNCO in refluxing acetonitrile, high yields of mono(urethane) derivatives N₃P₃Cl₅(NHCO₂R) were obtained. Disubstitution is mainly non-geminal. Reactions of (NPCl₂)₃ with AgNCO and methanol in acetonitrile follow a quite different pattern and lead to the formation of three products with basically geminal structures, e.g. gem-N₃P₃Cl₄(OR)(NHCO₂R), gem-N₃P₃Cl₄(NHCO₂R)₂, and a spiro derivative (NPCl₂)₂NP[N(CO₂R)C(O)NHC(CH₃)N]. The crystal structure of the last compound (R = CH₃) has been determined. The difference between the reaction pathways observed for NaNCO and AgNCO is discussed in terms of S_N2 and S_N1 mechanisms, respectively. An improved synthesis of (NPCl₂)₂NP(NH₂)(NCO) and its reactions with alcohols and amines are described.