Constrained geometry tetramethylcyclopentadienyl-phenoxy titanium complexes: Synthesis, structures and catalytic properties for ethylene polymerization

The synthesis of a new bidentate ligand, 1-(2-methoxyphenyl)-2,3,4,5-tetramethyl-cyclopentadiene (1), as well as its corresponding constrained geometry titanium complex, 2-tetramethylcyclopentadienyl-phenoxytitanium dichloride [(TCP)TiCl2, 2], was described. Complex 2 was synthesized by reaction of TiCl4 with the lithium salt of 1, followed by CH3Cl elimination at 65 °C. Molecular structures of 2 and a known complex, 2-tetramethylcyclopentadienyl-6-methyl-phenoxytitanium dichloride [(TCMP)TiCl2, IVd], were determined by single-crystal X-ray diffraction. The Cp(cent)–Ti–O angles of 107.4° for 2, 107.0° for IVd reveal their sterically open features as catalyst precursors. When activated with AliBu3 and Ph3C+B(C6F5)4-, complex 2 exhibits reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melting points.

Graphical abstractThe synthesis of a new bidentate ligand, 1-(2-methoxyphenyl)-2,3,4,5-tetramethyl-cyclopentadiene (1), as well as its corresponding constrained geometry titanium complex, 2-tetramethylcyclopentadienyl-phenoxytitanium dichloride [(TCP)TiCl2, 2], was described. Complex 2 was synthesized by reaction of TiCl4 with the lithium salt of 1, followed by CH3Cl elimination at 65 °C. Molecular structures of 2 and a known complex, 2-tetramethylcyclopentadienyl-6-methyl-phenoxytitanium dichloride [(TCMP)TiCl2, IVd], were determined by single-crystal X-ray diffraction. When activated with AliBu3 and Ph3C+B(C6F5)4-, complex 2 exhibits moderate catalytic properties for ethylene polymerization.Figure optionsDownload full-size imageDownload as PowerPoint slide