Reactions of alkali-metal azides with some halogenophosphorus compounds

Abstract

The reactions of alkali-metal (Li or Na) azides with PCl₃, PBr₃, Pl₃[PCl₄][SbCl₆], and [N(n-C₅H₁₁)₄][PCl₆] in solution in suitable organic solvents have been investigated by means of ³¹P n.m.r. spectroscopy. Both substitution and decomposition (with loss of N₂) reactions have been observed; the decomposition products are polymeric cyclic or acyclic phosphazenes, depending on the starting material. This has been confirmed for the cyclic trimers and tetramers by direct substitution of azide into (NPCl₂)₃, (NPCl₂)₄, and their bromo-analogues. For the six-co-ordinate anions [PCl_6–n(N₃)_n]^–(2 ⩽n⩽ 4), where isomerism is possible, one isomer appears to form preferentially in each instance. Structural assignments have been made on the basis of pairwise interactions. Isolation of the products has not in general been attempted because of the hazards involved.