Zur Reaktion von 2,3-Dihydroimidazol-2-ylidenen mit Pentafluorpyridin: Carbene als Reaktionspartner in der nucleophilen aromatischen Substitution/ On the Reaction of 2,3-Dihydroimidazol-2-ylidenes with Pentafluoropyridine: Carbenes as Reactants in Nucleophilic Aromatic Substitution

The 2,3-dihydro-1,3,4,5-tetraalkylimidazol-2-ylidenes 3 (R = Me, iso-Pr) react immediately with pentafluoropyridine to form the 2-tetrafluoropyridylimidazolium salts 4 in good yields. In contrast with the tetramethyl derivative 4a, alkyl fluoride is eliminated from the isopropyl salt 4b to give 1 -isopropyl-4,5-dimethyl-2-tetrafluoropyridylimidazole, which dimerises via hydrogen bridges in the solid state (7). The X-ray structures of 1,3-diisopropyl-4,5-dimethyl-2-tetrafluoropyridylimidazolium chloride (5) and 7 are reported.