Novel palladium complexes bearing a di-tert-butyl(4-substituted phenyl)phosphine ligand were synthesized and employed as catalysts for the polymerization of 1-chloro-2-(4-tert-butylphenyl)acetylene. Polymers were obtained as THF-soluble (weight-average molecular weights: 5100-59800) and insoluble parts, which were considered to be lower and higher molecular weight polyacetylenes. The catalytic activity increased as increasing the electron-withdrawing character of the substituent on the phosphine ligand.