A new class of mono- And tetra-nuclear titanatranes: Synthesis, structure, and ethylene polymerization studies. Role of single-sited active species?

Mono- and tetranuclear titanatranes bearing the C3-symmetric aminotriol ligand N(CH2-CHPhOH)3 were synthesized. The structure of the tetratitanium compound was determined by single-crystal X-ray crystallography. The new titanatrane derivative included four aminotriols ligated to four titanium atoms, forming a tetranuclear unit with μ 2-O and μ3-O bridges. The mono- and tetranuclear titanatranes were capable of polymerizing ethylene with a turnover frequency of up to 375 kg of PE/((mol of catalyst) h bar). The polymers obtained had T m % 133°C, indicative of linear polyethylene, and were further characterized by NMR. The ethylene polymerization activities of mono- and tetranuclear titanium catalysts were related by a factor of 4, indicating possibly the formation of a common single-site active species.