Polymerization of Substituted Acetylenes by Well-defined Palladium Complex Catalysts

This article overviews our recent research on the polymerization of substituted acetylenes by well-defined Pd catalysts. The authors synthesized a series of well-defined phosphine-ligated Pd complexes to polymerize substituted acetylene monomers. [(dppf)PdBr(R)]-type complexes [dppf = 1,1'-bis(diphenylphosphino)ferrocene; R = o-tolyl(1a), mesityl(1b), triphenylvinyl(1c), o-hydroxymethylphenyl(1d), p-cyanophenyl(1e) and p-nitrophenyl(1f) in combination with silver trifluoromethanesulfonate (AgOTf) were active for the polymerization of monosubstituted polar and apolar acetylene monomers [HC CPh(2), HC CCONHC4H9(3), HC CCO2C8H17(4), HC CCH2OCONHC6H13(5), HC CCH2OCO2C6H13(6) and HC CCH(CH3)OH(7)]. MALDI-TOF mass spectrometric and IR spectroscopic analyses of poly(2)-poly(7) confirmed the end-functionalization of the formed polymers by the "R" groups in the Pd catalysts. The polymerization of a disubstituted acetylene was achieved by bulky monophosphine-ligated Pd catalysts for the first time. The Pd catalysts were demonstrated to polymerize mono- and disubstituted acetylenes through an insertion mechanism.