SYNTHESIS OF POLY(ARYLENE ETHYNE)S VIA PALLADIUM-CATALYZED CROSS-COUPLING REACTIONS WITH CU AND SN REAGENTS

Comparative studies have been carried out of the effectiveness of two organometallic coupling reagents for the synthesis of poly (alkynylarene) s via palladium catalyzed cross-coupling reactions of dialkynes with organic dibromides. In comparison to copper reagents, monomeric difunctional trialkyltin acetylides show increased thermal stability which allows reactions to be performed at higher temperatures; they give oligomeric and polymeric materials of improved molecular weight. By contrast, the inferior solubility of copper acetylides limits chain growth, and above 140-degrees-C the Pd/CuI system is prone to homopolymerization of the dialkyne. The coupling reactions are solvent-dependent but not strongly influenced by the nature of the palladium precursor complex or the phosphine ligand.