Synthesis and use of mono- or bisxylyl linked bis(benzimidazolium) bromides as carbene precursors for C–C bond formation reactions

Two benzimidazolium moieties linked by one or two xylyls (m- and p-) have been synthesized, characterized and then they were used for Heck coupling reactions as in situ formed catalysts. Mono bridged salts are more efficient as compared to bisbridged salts. In addition, mono bridged salts were converted to Rh–NHC complexes which were tested as catalysts for the arylation of aldehydes.