Ethylene polymerization and ethylene/1-octene copolymerization with a titanium complex supported by a bis(indolyl) ligand

Abstract

The synthesis of bis(diethylamido){di(3-methylindol-2-yl)phenylmethane}titanium (1) was achieved in high yield (85%) by the treatment of 2,2′-di(3-methylindolyl)phenylmethane with Ti(NEt2)4 in toluene at reflux for 18 h. The ethylene polymerization activity of the 1/modified methylaluminoxane (MMAO) catalyst system was low (16.3 kg of polyethylene (PE)/mol of Ti•h), but pretreatment of 1 with ClSiMe3 followed by activation with MMAO improved the activity up to 154 kg of PE/mol of Ti•h. An NMR-scale reaction of 1 with ClSiMe3 in C6D6 at 80 °C for 22 h indicated the generation of an amido chlorido complex together with the formation of Et2N–SiMe3. Partial chlorination would facilitate methylation by MMAO. The polyethylenes obtained in this study are all monomodal by size exclusion chromatography and have linear structures by NMR spectroscopy. The catalyst system was also found to be active for ethylene/1-octene copolymerization (90 kg of copolymer/mol of Ti•h). Ethylene polymerization with bis(diethylamido){di(3-methylindol-2-yl)phenylmethane}titanium (1) was examined using modified methylaluminoxane (MMAO) as an activator. The activity of the 1/MMAO catalyst system was low (16.3 kg of polyethylene (PE)/mol of Ti•h), but pretreatment of 1 with ClSiMe3 followed by activation with MMAO improved the activity up to 154 kg of PE/mol of Ti•h. The obtained PEs are all monomodal by size exclusion chromatography and have linear structures by NMR spectroscopy. The 1/ClSiMe3/MMAO catalyst system was also active for ethylene/1-octene copolymerization (90 kg of copolymer/mol of Ti•h).