Phosphine-mediated dehalogenation reactions of trichloro(N-silyl)phosphoranimines

The reaction of N-(trimethylsilyl)phosphoranimine Cl3P=NSiMe3 (1) with nBu3P or Ph3P yields the N-(dichlorophosphino)phosphoranimines nBu3P=NPCl2 (4a) or Ph3P=NPCl2 (4b), respectively. Detailed studies of this reaction indicate a mechanism that involves the reductive dechlorination of 1 by the tertiary phosphine to yield nBu3PCl2 (5a) or Ph3PCl2 (5b) with the apparent formation of the transient chlorophosphinimine ClP=NSiMe3 (6), followed by condensation of 5a or 5b with 1 to form 4a or 4b and Me3SiCl. Convincing evidence for the proposed mechanism was revealed by studies of the analogous reaction between the N-(triphenylsilyl)phosphoranimine Cl3P=NSiPh3 (8) with nBu3P and Ph3P. These reactions quantitatively generated 5a and 5b and also allowed the correspondingly more stable chlorophosphinimine ClP=NSiPh3 (10) to be identified.