One-Step Simple Preparation of Catalytic Initiators for Catalyst-Transfer Kumada Polymerization: Synthesis of Defect-Free Polythiophenes

Abstract

Externally initiated living catalyst-transfer polymerization based on Ni(II)-catalyzed Kumada coupling of aromatic halogen-substituted Grignard monomers is an established and highly efficient method for the controlled preparation of conjugated polymers such as polythiophenes and poly(p-phenylenes). In this contribution, we report a simple preparation of external catalytic initiators for such a polymerization based on oxidative addition between a readily available Ni(0) complex Ni(dppp)2 (where dppp is 1,3-bis(diphenylphosphino)propane) and various aryl halides. As a direct challenge to previous reports and established opinion that such a reaction would be impossible, this clean and efficient oxidative addition enables simple preparation of highly reactive catalytic initiators for the catalyst-transfer polymerization. In particular, we demonstrated that polymerization of 5-halo-2-thienylmagnesium monomers initiated by these catalysts produced highly regioregular, defect-free polythiophenes and block copoly...