A Pd^II complex bearing a benzimidazole-derived ligand with potentially "mesoionic and remote" character and its catalytic activity

The oxidative addition of palladium(0) to the C2-protected 5-bromo-2-methylbenzimidazolium tetrafluoroborate 3 affords the complex trans-[PdBr(bimy)(PPh₃)₂]BF₄ (4), which is the first complex of an unprecedented benzimidazole-derived ligand (bimy) with a potentially "mesoionic and remote" character. DFT calculations revealed that the bimy ligand bridges the gap between the mesoionic pyrazolin-4-ylidene and the anionic phenyl ligand. A preliminary catalytic study revealed the promising activity of 4 in the Sonogashira coupling of aryl bromides with phenylacetylene. The oxidative addition of Pd⁰ to a C2-protected 5-bromobenzimidazolium salt affords a complex of an unprecedented and formally neutral benzimidazole-derived ligand (bimy). DFT calculations indicate that the bimy ligand bridges the gap between neutral mesoionic and anionic aryl ligands. The catalytic activity of the complex in the Sonogashira reaction has been studied.