From Unstable to Stable: Half-Metallocene Catalysts for Olefin Polymerization

The reaction of LAlMeOH [L = CH(N(Ar)(CMe))2, Ar = 2,6-i-Pr2C6H3] with CpTiMe3, Cp*TiMe3, and Cp*ZrMe3 was investigated to yield LAlMe(μ-O)TiMe2Cp (2), LAlMe(μ-O)TiMe2Cp* (3), and LAlMe(μ-O)ZrMe2Cp* (4), respectively. The resulting compounds 2−4 are stable at elevated temperatures, in contrast to their precursors such as CpTiMe3 and Cp*ZrMe3, which already decompose below room temperature. Compounds 2−4 were characterized by single-crystal X-ray structural analysis. Compounds 2 and 3 were tested for ethylene polymerization in the presence of methylaluminoxane. The half-metallocene complex 3 has higher activity compared to 2. The polydispersities are in the range from 2.8 to 4.2. A copolymerization with styrene was not observed.