Toward the synthesis of a catalytic conducting metallopolymer for cross-coupling reactions

The thiophene-based metallopolymer provides a great template for redox-active catalysts. Chemical or electrochemical doping of the metallopolymer can generate charged species within the polymer backbone thereby tuning the electronic nature of the bound metals. The metal-ligand bond strength and the catalytic activity in such a conducting metallopolymer can be tuned directly by applying different potential to the material. Thiophene-functionalized N-heterocyclic carbene (NHC) based palladium complexes are believed to be catalytically active for cross-coupling reactions and electropolymerizable into the metallopolymer. The tenability of the resulting metallopolymers as cross-coupling reaction catalysts can be evaluated by their catalytic performances under different applied voltages. Two thiophene-functionalized benzimidazolium chloride molecules (DThBMesHCl and DThBAdHCl) were synthesized as precursors for NHC ligands. Their metalation with Pd and Ag precursors failed to generate desired metal complexes. The results were analyzed by comparison with the literature examples and the Ag metalation of non-thiophene version of the benzimidazolium chloride molecule. The major obstacles for the metalation were concluded to be the steric hindrance from the bulky N-substituent and/or the lack of acidity of the imidazolium moiety.