Poly(ionic liquid)s-Supported N-Heterocyclic Carbene Silver Complexes for the Cycloaddition of CO₂ with Epoxides

Abstract: A series of poly(ionic liquid)s-supported N-heterocyclic carbene silver complexes (Poly(NHC-Ag/IL)s), poly(ionic liquid)s (PILs) and poly(N-heterocyclic carbene silver complexes) (Poly(NHC-Ag)s) were prepared through radical co-polymerization of N-vinylimidazolium ionic liquids, NHC-Ag monomers and divinylbenzene, respectively. These polymers were applied to catalyze the cycloaddition reaction of carbon dioxide and epoxides without any co-catalyst. Poly(NHC-Ag/IL)s exhibited higher activities than the corresponding PILs and Poly(NHC-Ag)s, which was attributed to the synergistic effect of NHC-Ag and bromide. Furthermore, Poly(NHC-Ag/IL)s could be easily recycled five times without significant loss of catalytic activity. Graphic Abstract: Multi-functional poly(ionic liquid)s-supported N-heterocyclic carbene silver complexes (Poly(NHC-Ag/IL)s) were synthesized by radical co-polymerization of N-vinylimidazolium ionic liquids, NHC-Ag monomers and DVB. Poly(NHC-Ag/IL)s exhibited high activities for cycloaddition reaction of carbon dioxide and epoxides due to their multi-functional groups including Lewis acidic silver and a bromine anion.