Synthesis and Catalytic Applications of Heterobimetallic Carbene Complexes Obtained via Sequential Metalation of Two Bisazolium Salts

A simple sequential metalation approach starting from the imidazolium/benzimidazolium salt 4(I)2 yielded the heterobimetallic RhIII/M (M = PdII, IrI, AuI, RuII) complexes [6]–[9]. Alternatively, a symmetrical 1,3-imidazolium substituted benzene was used for the preparation of the heterobimetallic M′/PdII (M′ = RhIII, IrIII) complexes [12] and [13]. The versatile stepwise approach used for the preparation of complexes [6]–[9] involved the deprotonation reaction of the bisazolium salt 4(I)2 in the presence of [RhCp*(Cl)2]2 to afford the monometallic complex [5]I featuring a chelating coordinated bidentate CNHC^Cphenyl ligand. Complex [5]I was reacted with Ag2O to give a nonisolated RhIII/AgI complex which in a subsequent transmetalation reaction yielded the heterobimetallic RhIII/M bis-NHC complexes (M = PdII [6], IrI [7], AuI [8], RuII [9]). Similarly, heterobimetallic M′/PdII bis-NHC complexes [12] (M′ = RhIII) and [13] (M′ = IrIII) have been prepared from a symmetrical bisazolium salt by generating first...