Bifunctional Fluorophosphonium Triflates as Intramolecular Frustrated Lewis Pairs: Reversible CO₂ Sequestration and Binding of Carbonyls, Nitriles and Acetylenes

Abstract

Abstract Electrophilic fluorophosphonium triflates bearing pyridyl ( 3 [OTf]) or imidazolyl ( 4 [OTf])‐substituents act as intramolecular frustrated Lewis pairs (FLPs) and reversibly form 1 : 1 adducts with CO 2 ( 5 + and 6 + ). An unusual and labile spirocyclic tetrahedral intermediate ( 7 2+ ) is observed in CO 2 ‐pressurized (0.5–2.0 bar) solutions of cation 4 + at low temperatures, as demonstrated by variable‐temperature NMR studies, which were confirmed crystallographically. In addition, cations 3 + and 4 + actively bind carbonyls, nitriles and acetylenes by 1,3‐dipolar cycloaddition, as shown by selected examples.