Unprecedented Regioregular Poly(1,4‐arylene)s Prepared by Nickel(II)‐Catalyzed Cross‐Coupling Polymerization of 2,5‐Disubstituted Bromo(chloro)arylene

Abstract

The unprecedented synthesis of regioregular head‐to‐tail‐type poly(1,4‐arylene)s bearing different substituents at the 2‐ and 5‐positions is described. They were prepared by the polymerization of 2,5‐disubstituted bromo(chloro)arylenes by selective halogen–metal exchange with a Grignard reagent and subsequent cross‐coupling polymerization with a nickel catalyst [NiCl2(dppp)]. Formation of the regioregular poly(1,4‐arylene)s were confirmed by NMR spectroscopy, and showed remarkable differences to those polymers having uncontrolled regioregularity. Polymerization of bromo(chloro)arylenes with a chiral alkoxy substituent also led to the regioregular head‐to‐tail‐type polyarylene, which demonstrated circular dichroism, thus suggesting formation of a structure with higher‐order regularity.

Nickel(II) Thiocyanate Complex as a Catalyst for Cross-Coupling Reactions

“…A precipitate formed after stirring for 12 hours, and complex 2 was isolated in 74% yield. Polymerization of 1-bromo-4-chloro-2,5-bis(hexyloxy)benzene ( 3 ) 16 was then carried out with the nickel complex 2 as a catalyst (Scheme 2 ). Treatment of 3 with i -PrMgCl·LiCl at 60 °C for one hour in THF resulted in halogen–metal exchange at the carbon–bromine bond.…”

“…13–15 We have also shown that a related nickel(II) catalyst can be used in the syntheses of poly-1,4-arylenes from dibromoarenes or bromo(chloro)arenes. 16–18 Our interest in the application of the nickel complex of Ni(NCS) 2 turned to the use of nickel complex 2 for the cross-coupling polymerization of thiophenes and phenylenes.…”