Donor-Stabilized Cations and Imine Transfer from N-Silylphosphoranimines

A series of donor-stabilized N-silylphosphoranimine salts [DMAP·PCl₂NSiMe₃]⁺X^- (DMAP = 4-(dimethylamino)pyridine) were prepared by the reaction of Cl₃PNSiMe₃ with DMAP in the presence of silver salts AgX (X = OSO₂CF₃, BF₄, and SbF₆). Repeating the reaction in the absence of AgX gave the chloride salt [DMAP·PCl₂NSiMe₃]Cl which has been shown to be in equilibrium with free DMAP and Cl₃PNSiMe₃. Attempts to stabilize a N-silylphosphoranimine cation with phosphine donors led to unexpected imine transfer chemistry. For example, Cl₃PNSiMe₃ reacts with phosphines, R₃P (R = ⁿBu and Ph), to produce the metathesis products PCl₃ and R₃PNSiMe₃ which subsequently react together to afford the N-phosphinophosphoranimines R₃PN−PCl₂ and ClSiMe₃ as a byproduct.