Dimeric palladium 1,2,3-triazol-5-ylidene complexes – synthesis, structure, reactivity and catalytic properties in Suzuki coupling

Abstract

New dimeric palladium 1,2,3-triazol-5-ylidene complexes of the general formula [{Pd(μ-Cl)Cl(tzNHC)}₂] (tzNHC = 1-mesityl-3-methyl-4-phenyl-1H-1,2,3-triazol-5-ylidene; 1-hexyl-3-methyl-4-phenyl-1H-1,2,3-triazol-5-ylidene and 1-butyl-3-methyl-4-phenyl-1H-1,2,3-triazol-5-ylidene) were synthesized and characterized by spectroscopic methods, X-ray analysis and DFT calculations. For the mesityl substituted complex, the crystallographic structures of both the cisoidal and transoidal isomer were obtained. In the presence of an excess of 4-tolylboronic acid, the loss of the tzNHC ligand from the palladium coordination sphere as a 5-tolyltriazolium salt was observed. The complexes are precursors of palladium species catalytically active in the coupling of arylboronic acids with aryl bromides.