In situ formation of mixed phosphine-imidazolylidene palladium complexes in room-temperature ionic liquids

The in situ formation of a mixed phosphine-imidazolylidene palladium complex, 3, in the room-temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) has been observed under conditions employed in many palladium-catalyzed coupling reactions. This paper highlights the noninnocent nature of imidazolium-based ionic liquids and the implications of this for ionic liquid mediated palladium catalysis.