In contrast to the simple and straightforward generation of pyridinium cations, the P-alkylation of the heavier homolog λ3σ2-phosphinines is more challenging due to their weak nucleophilicity, as demonstrated only by a handful of examples. The previously reported methods to such species either apply multistep syntheses or make use of extreme electrophiles. As a consequence, detailed studies on their reactivity are underexplored due to their limited synthetic availability. Herein, it is reported that the labile Lewis pair of 3,5-bis(trimethylsilyl)-phosphinine and B(C6F5)3 serves as a platform for the facile generation of 1-R-phosphininium salts, utilizing esters or iso(thio)cyanates as alkylating reagents. With this new approach in hand, the reactivity of 1-R-phosphininium salts toward isolobal and valence-isoelectronic substrates exhibiting C≡C, C≡N, or C≡P multiple bonds has been explored systematically. To gain a deeper understanding of reactivity trends, the stability of the newly accessed phosphininium cations and the mechanisms of their follow-up reactions are explored using density functional theory (DFT) calculations.
