Benzenimidazole-functionalized imidazolium-based N-heterocyclic carbene complexes of silver(I) and Palladium(II):: Isolation of a Ag3 intermediate toward a facile transmetalation and Suzuki coupling

A new benzenimidazole-functionalized imidazolium-based N-heterocyclic carbene complex of Pd(II) has been prepared from facile transmetalation via a Ag(I) precursor. The latter was obtained from a condensation reaction between Ag2O and benzenimidazolium salt. Single-crystal X-ray crystallography revealed an unusual trinuclear Ag3Cl2(mu-Cl)(mu-N-C)(2) (N-C = 3-methyl-1-(1-ethyl-2-methylbenzoyl)imidazolin-2-ylidene) intermediate in which the central carbene-supported Ag(I) is flanked by two imidazolecoordinated Ag(I). The hybrid ligand (N-C), carrying two heterodonors of benzenimidazole and carbene, is bridging in Ag(l) but chelating in Pd(II). The latter mononuclear PdCl2(eta-N-C) is active toward Suzuki-Miyaura coupling of aryl bromides and boronic acids, giving a TON up to 11750 within 4 h at rt.