The Effect of SiMe3 and SiEt3 Para Substituents for High Activity and Introduction of a Hydroxy Group in Ethylene Copolymerization Catalyzed by Phenoxide-Modified Half-Titanocenes

Abstract

Remarkable effects of SiMe₃ and SiEt₃ para-substituents in the phenoxide-modified half-titanocenes, Cp*TiCl₂ (O-2,6-ⁱ Pr₂ -4-R-C₆ H₂ ) [R=SiMe₃ (6), SiEt₃ (7)], toward the catalytic activities in ethylene copolymerizations with 2-methyl-1-pentene, 1-decene, 1-dodecene and with 9-decen-1-ol (DC-OH) have been demonstrated. The activities by 6, 7 at 50 °C showed higher than those conducted at 25 °C in all cases in the presence of MAO cocatalyst. Efficient synthesis of high-molecular-weight (HMW) ethylene copolymers incorporating DC-OH (or 5-hexen-1-ol, HX-OH) has been attained in the copolymerization by 7, which showed better DC-OH (HX-OH) incorporation at 50 °C to afford the HMW copolymers, poly(ethylene-co-DC-OH)s, with high activities (activity 1.21-3.81×10⁵ kg-polymer mol^-1 -Ti h, M_n =6.55-10.0×10⁴ , DC-OH 2.3-3.6 mol %).

Keywords: ethylene copolymerization; half-titanocenes; ligand effect; polyolefin-containing polar groups; titanium catalyst.