Binuclear Pd-methyl complexes of N,N′-{1, n}-alkanediyl-bis(pyridinyl-2-methanimine) ligands (n = 5, 8, 9, 10 and 12): Evaluation as catalysts precursors for phenylacetylene polymerization

A series of bifunctional ligands of the type N,N′-{1, n}-alkanediyl-bis(pyridinyl-2-methanimine) {n = 5, 8, 9, 10, 12}(L1–L5) were synthesized and fully characterized by IR, 1H NMR, and 13C NMR spectroscopy. Binuclear palladium-methylchloride complexes C1–C5 were formed by reacting the ligands with [(COD)Pd(CH3)Cl]. The formed complexes were fully characterized by IR, 1H NMR, 13C NMR, spectroscopy, electrospray ionization mass spectrometry and elemental analysis. The synthesized complexes were evaluated as catalyst precursors for phenylacetylene polymerization after activation with AgBF4, AgBPh4 and NaB(Arf)4 (Sodium tetrakis[(3.5-trifluoromethyl)phenyl]borate) under various reaction conditions (solvent ratio, catalyst type, monomer/catalyst ratio, reaction time and nature of counterion). The cationic palladium-methyl catalyst precursors C1a–C5a were found to be active catalysts for phenylacetylene polymerization. The obtained polyphenylacetylene were analyzed by IR, 1H NMR and 13C NMR spectroscopy and gel permeation chromatography (GPC) and found to be largely cis-transoidal in nature.