Phenoxide-Modified Half-Titanocenes Supported on Star-Shaped ROMP Polymers as Catalyst Precursors for Ethylene Copolymerization
Zelin Sun, Palawat Unruean, Hirotaka Aoki, Boonyarach Kitiyanan, Kotohiro Nomura
Abstract
The synthesis and identification of half-titanocenes containing an aryloxide ligand supported at the chain end (surface) of soluble star-shaped polymers, by adopting sequential one-pot living ring-opening metathesis polymerizations (ROMP) of norbornene (NBE) and a cross-linking reagent using a molybdenum alkylidene catalyst, have been explored. The Ti K-edge XANES spectra (in toluene at 25 °C) indicate that the basic geometry and electronic nature of the original complex, Cp*TiMe2(O-iPr2C6H3) (1), were preserved in the supported catalyst on the star-shaped ROMP polymers. The supported catalyst showed high catalytic activities for ethylene polymerization, which are lower than that by 1 but higher than that by the supported catalyst at the linear ROMP polymer chain end; efficient 1-hexene incorporation in the ethylene/1-hexene copolymerization has also been demonstrated in this star-shaped supported catalyst.