Synthesis of head-to-tail-type poly(1,3-phenylene) with high degrees of polymerization catalyzed by Nickel(II)-(N-heterocyclic Carbene) complex

Poly(1,3-phenylene)s with high degree of polymerization were synthesized in a regioregular manner. The reaction of 2-bromo-4-chloro-hexyloxybenzene with a Grignard reagent and following cross-coupling catalyzed by a nickel(II) complex underwent polymerization in good to excellent yields. The use of bidentate phosphines as a ligand, which were shown to be suitable for poly(1,4-phenylene) synthesis, only afforded the polymer with relatively low degree of polymerization (DP), while the polymerization with N-heterocyclic carbene as a ligand showed a high degree of polymerization (DP) of up to >100 in excellent yield.