Two types of pyrazole-based palladium complexes were used to catalyze the polymerization of phenylacetylene. Catalysts with electron-withdrawing linkers, [{1,3-(3,5-R 2 pzCO) 2 C 6 H 4 }Pd 2 Cl 2 (μ-Cl) 2 ] (R= t Bu (1), Ph (2), Me (3), [{2,6-(3,5-R 2 pzCO) 2 C 5 H 3 N)}PdCl 2 ] (R= t Bu (4), Me (5)), show high conversion; whilst those with simple pyrazole ligands, [(3,5-R 2 pz) 2 PdCl 2 ] (R=H (6), Me (7), t Bu (8)), [(3,5- t Bu 2 pz) 2 PdCl(Me)] (9), have much lower conversions. Conversion greatly improved when 9 was used to catalyze the co-polymerization of sulfur dioxide and phenylacetylene. Both types of catalysts produce predominantly trans–cisoidal polyphenylacetylene.