Ligand effect in olefin polymerization catalyzed by (cyclopentadienyl)(aryloxy) titanium(IV) complexes, Cp′TiCl 2(OAr)–MAO system. : Ethylene/1-hexene copolymerization by (1,3- tBu 2C 5H 3)TiCl 2(O-2,6- iPr 2C 6H 3)–MAO catalyst system

Abstract

Effect of substituents on cyclopentadienyl group for catalytic activity in 1-hexene and 1-octene polymerization with the series of Cp′TiCl 2(O-2,6- iPr 2C 6H 3) [Cp′=Cp ( 1a), tBuC 5H 4 ( 2a), 1,3-Me 2C 5H 3 ( 3a), 1,3- tBu 2C 5H 3 ( 4a), and C 5Me 5 ( 5a)]–methylaluminoxane (MAO) catalysts have been explored, and the activity increased in the order: 4a (26 kg polymer/mol Ti·h)< 1a (63)< 2a (89)< 3a (184)< 5a (728). The catalytic activity in 1-hexene polymerization with the series of Cp*TiCl 2(OAr) [OAr=2,6- iPr 2C 6H 3 ( 5a), 2,4,6-Me 3C 6H 2 ( 5b), 2,6-Me 2C 6H 3 ( 5c), 2- tBu-4,6-Me 2C 6H 2 ( 5d), 4-MeC 6H 4 ( 5e)]–MAO catalysts increased in the order: 5a (728 kg polymer/mol Ti·h)> 5d (694)> 5c (76)> 5e (48)> 5b (39). These orders are somewhat different from those in ethylene polymerization, and these differences observed here would be due to the steric bulk of monomer used as well as of substituents on both cyclopentadienyl and aryloxy groups. Although (1,3- tBu 2C 5H 3)TiCl 2(O-2,6- iPr 2C 6H 3) ( 4a) showed the lowest catalytic activity for polymerization of both 1-hexene and 1-octene, 4a exhibited the significant activity for copolymerization of ethylene with 1-hexene, resulting in obtaining copolymer with relatively high 1-hexene contents (20.2–36.5 mol%) with relatively narrow molecular weight distributions.