| Abstract: | The syndiotactic polymerization of styrene (St) and the copolymerization of St with ethylene (E) were carried out by using a series of chiral half-sandwich rare-earth metal dialkyl complexes (Cpx*) as the catalysts.The complexes are Ln(CH2SiMe3)2(THF) (1-4∶ Ln =Sc (1),Ln =Lu (2),Ln =Y (3),Ln =Dy (4)) bearing chiral cyclopentadienyl ligand containing bulky cylcohexane derivatives in thepresence of activator and AliBu3.For the St polymerization,a high activity up to 3.1 × 106 g of polymer mo1Ln-1·h-1 and a high syndiotactic selectivity more than 99％ were achieved.The resulting syndiotactic polystyrenes (sPSs) have the molecular weights (Mn) ranging from 3700 g·mol-1 to 6400 g·mol-1 and the molecular weight distributions (Mw/Mn) from 1.40 to 5.03.As for the copolymerization of St and E,the activity was up to 2.4 × 106 g of copolymer molsc-1·h-1·MPa-1,giving random St-E copolymers containing syndiotactic polystyrene sequences with different St content in the range of 15 mo1％-58 mol％.These results demonstrate that the bulky cyclopentadienyl ligands of the chiral half-sandwich rare-earth metal complexes effectively inhibit the continued insertion of St monomers into the (co)polymer chain to some extent in comparison with the known half-sandwich rare-earth metal complexes. |
