Simple preparations of new monomeric trihalogenophosphine imides

Abstract

The oxidation of halogeno(2,4,6-tri-tert-butylphenylimino)phosphines [(2,4,6-Bu^t₃C₆H₂)NPX, X = Cl, Br or I] with dihalogens (Cl₂, Br₂ or I₂) resulted in the formation of trihalogeno(N-2,4,6-tri-tert-butylphenyl)phosphine imides. The imides (2,4,6-Bu^t₃C₆H₂)NPCl₃ and (2,4,6-Bu^t₃C₆H₂)NPBr₃ were obtained quantitatively from the corresponding halogenoiminophosphine with PhlCl₂ and Br₂, respectively, and were crystallographically characterized [(2,4,6-Bu^t₃C₆H₂)NPCl₃; Cm, a= 11.960(3), b= 14.696(2), c= 5.954(2)Å, β= 97.71 (2)°, Z= 2, R= 0.036, R′= 0.047; (2,4,6-Bu^t₃C₆H₂)NPBr₃; P2,/c, a= 18.841(8), b= 9.480(4), c= 12.186(5)Å, β= 98.00(3)°, Z= 4, R= 0.068, R′= 0.074]. Reactions involving a halogenoiminophosphine and a different halogen are accompanied by halide exchange and give mixtures of products, most of which can be assigned and include the mixed trihalides, (2,4,6-Bu^t₃C₆H₂)NPX₂X′. No reaction is observed between (2,4,6-Bu^t₃C₆H₂)NPI and I₂, but one iodo derivative has been isolated and characterized spectroscopically and by X-ray crystallography as (2,4,6-Bu^t₃C₆H₂)NPCl₂I₂ which is formed in the disproportionation reaction of (2,4,6-Bu^t₃C₆H₂)NPCl and I₂. The trihalides are monomeric in the solid state and exhibit extremely short N–P bonds with large angles at the nitrogen centres.