Synthesis of polyfluorene containing simple functional end group with aryl palladium(II) complexes as initiators

Abstract

A series of aryl Pd(II) complexes of the formula PdL2(Ar)Br (L = PPh3, 1–8; L = PCy3, 9–11; L = PEt3, 12) and [Pd(P(o-tol)3)(Ar)(μ-Br)]2 (13–18; Ar = substituted phenyl with simple functional group, Cy = cyclohexyl, o-tol = o-tolyl) has been synthesized by direct oxidative addition of Pd(0) precursor and excess aryl bromide. In contrast, the corresponding Pd(II) bromide coordinated with partly aryl-aryl exchanged phosphine was isolated for the bidentate 1,2-bis(diphenylphosphino)ethane (dppe) or 1,3-bis(diphenylphosphino)propane (dppp) ligand, indicating that the aryl-aryl exchange occurs more easily probably because of the chelate effect of the bidentate ligand and the intramolecular π-π interaction between neighboring phenyl rings. Suzuki-Miyaura coupling polymerization of AB-type fluorene monomer with these Pd(II) complexes as initiators was carried out. The aryl Pd(II) complexes with P(o-tol)3 exhibit the catalyst-transfer polymerization at room temperature. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) characterization and end group analysis reveal that the functional group is anchored at the end of polymer backbone. Furthermore, the groups can be transferred to other more useful active groups via simple organic reaction.