Heck Reaction in Ionic Liquids and the in Situ Identification of N-Heterocyclic Carbene Complexes of Palladium

摘要: The Heck reaction was found to proceed markedly more efficiently in the ionic liquid 1-butyl-3-methylimidazolium bromide ([bmim][Br]) than analogous tetrafluoroborate salt ([bmim][BF4]). In relation this observation, 1-butyl-3-methylimidazol-2-ylidene (bmiy) complexes of palladium [PdBr(μ-Br)(bmiy)]2 (1) and [PdBr2(bmiy)2] (2) have been isolated [bmim][Br] but not [bmim][BF4] under conditions similar those employed for reaction. both molecular solvents, complex 2 formed via intermediate 1. has shown be active much less so due transformation by latter into species.