6533b837fe1ef96bd12a2619

RESEARCH PRODUCT

Syntheses, Structure, and Reactivity of Chiral Titanium Compounds: Procatalysts for Olefin Polymerization

subject

description

Titanium complexes with chelating alkoxo ligands have been synthesised with the aim to investigate titanium active centres in catalytic ethylene polymerisation. The titanium complexes cis-[TiCl2(η2-maltolato)2] (1, 89 %), and cis-[TiCl2(η2-guaiacolato)2] (2, 80 %) were prepared by direct reaction of TiCl4 with maltol and guaiacol in toluene. The addition of maltol to [Ti(OiPr)4] in THF results in the formation of species [Ti(OiPr)2(maltolato)2] (3, 82 %). The titanium compound cis-[Ti(OEt)2(η2-maltolato)2] (4, 74 %) was obtained by the transesterification reaction of species 3 with CH3CO2Et. When compound 4 is dissolved in THF a dinuclear species [Ti2(μ-OEt)2(OEt)4(η2-maltolato)2] (5, 45 %) is formed. Reaction of [Ti(OiPr)4] with crude guaiacol in THF yields a solid, which after recrystallisation from acetonitrile gives [Ti4(μ-O)4(η2-guaiacolato)8]⋅4 CH3CN (6, 55 %). In contrast, reaction of TiCl4 with crude guaiacol in tetrahydrofuran affords [Ti2(μ-O)Cl2(η2-guaiacolato)4] (7, 82 %). Crystallographic and electrochemical analyses of these complexes demonstrate that maltolato and guaiacolato ligands can be used as a valuable alternative for the cyclopentadienyl ring. These complexes have been shown to be active catalysts upon combination with the appropriate activator.