Synthesis and Characterization of New Nitrogen-Donor-Stabilized N-Silylphosphoranimine Cations

The phosphoranimine Br(CF3CH2O)2P=NSiMe3 (12) reacts quantitatively with nitrogen bases pyridine, 4,4'-bipyridine, and quinuclidine (quin) to form the N-donor stabilized phosphoranimine cations [N-donor.P(OCH2CF3)2=NSiMe3] ([15]+) in the presence of the halide abstractor AgOTf. In contrast to quinuclidine, in the absence of a halide abstractor, the weak bases pyridine and 4,4'-bipyridine do not undergo reactions with 12 or with the phosphoranimine Cl3P=NSiMe3 (7). Furthermore, unlike the weaker bases, quinuclidine also reacts with 7 to form the expected quinuclidine-stabilized phosphoranimine cation [quin.PCl2=NSiMe3]+ ([16]+) in the presence of AgOTf. However, in the absence of AgOTf, quinuclidine reacts with 7 to presumably yield the salt [16]Cl, which then undergoes a further quinuclidine ring-opening reaction to yield the cationic piperidyl-substituted phosphoranimine [(quin)CH2CH2C5H9N-PCl2=NSiMe3]Cl ([19]Cl). Reactions involving 7 and 12 with other halide abstraction reagents, such as GaCl3, are also described.