Low-melting dialkyl- and bis(polyfluoroalkyl)-substituted 1,1 '-methylenebis(imidazolium) and 1,1 '-methylenebis(1,2,4-triazolium) bis(trifluoromethanesulfonyl)amides: Ionic liquids leading to bis(N-heterocyclic carbene) complexes of palladium

摘要

Ionic liquids with pincer dicationic nuclei, 2a-6a and 2b-6b, were prepared from either 1,1'-methylenebis(imidazole) or 1,1'-methylenebis(1,2,4-triazole) via quaternization with alkyl or polyfluoroalkyl halides under classical or microwave irradiation conditions. Palladium-catalyzed Heck cross-coupling reactions were performed successfully in the ionic liquid 3a. A single-crystal X-ray structure of a bis(N-heterocyclic carbene) complex of palladium (7) formed in the ionic liquid catalyst system supports its likelihood as the active catalyst.