Facile and efficient olefination of aryl halides catalyzed by a palladium complex containing a heteroarene-functionalized N-heterocyclic carbene

[Ag-4(L)(4)](PF6)(4) and [Pd(L)(2)](PF6)(2) (L = 3-(2,4-dimethyl-1,8-naphthyrid-7-yl)-l-picolylimidazolylidene) have been prepared and fully characterized. The silver compound consists of a Ag-4 ring with short Ag-Ag contacts displaying a butterfly conformation. The palladium complex exhibits a helical structure with palladium located in a square-planar environment with two carbene ligands and two pyridines in a cis arrangement. The palladium complex has proven to be a highly efficient catalyst for Heck coupling reactions of aryl bromides with n-butyl acrylate. TON values up to 10(6) and TOF values up to 5 x 10(5) h(-1) can be achieved.