Stereospecific post-metallocene polymerization catalysts: The example of isospecific styrene polymerization

In the context of developing single-site stereoselective post-metallocene catalysts, the case for isospecific styrene polymerization catalysts based on methylaluminoxane-activated group 4 metal bis(phenolato) complexes is summarized. In the context of developing single-site stereoselective post-metallocene catalysts, the case for isospecific styrene polymerization catalysts based on methylaluminoxane-activated group 4 metal bis(phenolato) complexes is summarized. Ligands derived from the 1,4-dithiabutanediyl-linked bis(phenol)s have been found to induce stereochemical rigidity by the presence of the hemi-labile sulfide donor functions. Isospecific styrene polymerization was achieved using easily accessible catalyst precursors of the type [MX 2(OC6H2-tBu2-4,6) 2S(CH2)2S] (M = Ti, Zr, Hf; X = Cl, O iPr, CH2Ph). Activating the dibenzyl titanium complex [Ti(CH2Ph)2(OC6H2- tBu2-4,6)2S(CH2)2S] with B(C6F5)3 and AliBu3, controlled isotactic polymerization became possible at lower temperatures. A remarkable dependence of both the activity and stereoselectivity on the ligand substitution pattern was observed. Analogous precursors with the 1,5-dithiapentanediyl-linked bis(phenolato) ligand gave syndiotactic polystyrene with lower activity. © 2004 Elsevier B.V. All rights reserved.