AB- Versus AA+BB-Suzuki Polycondensation: A Palladium/Tris(tert-butyl)phosphine Catalyst Can Outperform Conventional Catalysts

Abstract

A Pd/Pt-Bu₃ catalyst having bulky, electron-rich ligands significantly outperforms conventional "step-growth catalysts" Pd(PPh₃ )₄ and Pd(Po-Tol₃ )₃ in the Suzuki polycondensation of the AB-type arylene-based monomers, such as some of the substituted fluorenes, carbazoles, and phenylenes. In the AA+BB polycondensation, Pd/Pt-Bu₃ also performs better under homogeneous reaction conditions, in combination with the organic base Et₄ NOH. The superior performance of Pd/Pt-Bu₃ is discussed in terms of its higher reactivity in the oxidative addition step and inherent advantages of the intramolecular catalyst transfer, which is a key step joining catalytic cycles of the AB-polycondensation. These findings are applied to the synthesis of a carbazole-based copolymer designed for the use as a hole conductor in solution-processed organic light-emitting diodes.

Keywords: Suzuki polycondensation; conjugated polymers; palladium catalysts.