Bis(chalcogenones) as pincer ligands: isolation and Heck activity of the selone-ligated unsymmetrical C,C,Se-Pd pincer complex

The reaction of meta-phenylene-bis(1-methyl-1H-imidazole-2(3H)-selone) with [Pd-2(mu-Cl)(2)(2-C6H4CH2NMe2)(2)] in dry benzene and glacial acetic acid resulted in the formation of an unsymmetrical 5,6-membered C,C,Se-Pd(II) pincer complex through C-H bond activation and extrusion of one selenium. This is the first example of a C,C,Se-Pd(II) complex wherein the central Pd(II) is simultaneously coordinated to a selone and an N-heterocyclic carbene. The chelated complex of the type [PdL2](2+)2[PF6](L = bis(selone)) was isolated from the reaction of the bis(selone) with [PdCl2(PhCN)(2)] and NH4PF6. The unsymmetrical pincer complex was studied for Heck activity revealing its application as an acceptable catalyst in coupling of iodobenzene with acrylates and styrene.