Synthesis of Pincer-Type Bis(benzimidazolin-2-ylidene) Palladium Complexes and Their Application in C−C Coupling Reactions

Reaction of the xylene-bridged bisbenzimidazolium salts 2,6-bis( N -alkyl- N ‘-methylenebenzimidazolium)-1-bromophenylene dibromide ( 1, alkyl = ethyl; 2, alkyl = n -propyl; 3, alkyl = n -butyl) with [Pd 2 (dba) 3 ] yields the palladium pincer complexes of type [Pd(L)Br], 4 − 6 (L = 2,6-bis( N -alkyl- N ‘-methylenebenzimidazolin-2-ylidene)phenylene). Pincer complexes 4 − 6 have been tested as precatalysts in Heck and Suzuki coupling reactions of various aryl bromides with styrene and phenylboronic acid, respectively.