The control of the stereochemistry in the palladium-catalyzed alternating styrene/carbon monoxide copolymerization: effect of the chirality of the ligand and of the ligand-to-palladium ratio.

Diaquapalladium(2+) trifluoromethanesulfonates modified with (4R,4'S)- or (4S,4'S)-2,2'-bis(4-benzyl-4,5-dihydrooxazole) (Cs- and C2-ligands) produce isotactic poly(1-oxo-2-phenylpropane-1,3-diyl) through copolymerization of styrene with carbon monoxide. However, the same meso-catalyst in the presence of the free ligand leads to prevailingly syndiotactic growth of the copolymer, whereas the optically active catalyst, when used in the presence of the free enantiomeric ligand, gives an atactic copolymer.