Synthesis and characterization of mixed-substituent N-silylphosphoranimines

The preparation of a large series of new N-silyl-P-alkylphosphoranimines and their (silylamino)phosphine precursors is reported. Oxidative bromination of the P-functional (silylamino)phosphines, (Me₃Si)₂NP(R)X [R = n-Pr, n-Bu, i-Pr, t-Bu; X = Br, OR′ (R′ = CH₂CF₃, Ph)], occurred smoothly at 0 °C and afforded the desired P-bromophosphoranimines, Me₃SiN=P(R)(X)Br. Nucleophilic substitution reactions of the P-dibromo members of this series with LiOR′ gave the corresponding P-trifluoroethoxy- and P-phenoxyphosphoranimines, Me₃SiN=P(R)-(OR′)₂ (R′ = CH₂CF₃, Ph). All of these N-silylphosphoranimines, which are potential precursors to new cyclic and/or polymeric phosphazenes, were obtained as thermally stable, distillable liquids and were characterized by NMR (¹H, ¹³C, and ³¹P) spectroscopy and elemental analysis.