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

Abstract

The reaction of meta-phenylene-bis(1-methyl-1H-imidazole-2(3H)-selone) with [Pd₂(μ-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.