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

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 CO2 (5 + and 6 +). An unusual and labile spirocyclic tetrahedral intermediate (7 2+) is observed in CO2‐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.