Constrained Geometry Tetramethylcyclopentadienyl-phenoxytitanium Dichlorides: Template Synthesis, Structures, and Catalytic Properties for Ethylene Polymerization

The synthesis of four new bidentate ligands, 2-(tetramethylcyclopentadienyl)-4,6-di- tert -butylphenol ((TCDBP)H 2, 5 ), 2-(tetramethylcyclopentadienyl)-6- tert -butylphenol ((TCBP)H 2, 6 ), 2-(tetramethylcyclopentadienyl)-6-phenylphenol ((TCPP)H 2, 7 ), and 2-(tetramethylcyclopentadienyl)-6-methylphenol ((TCMP)H 2, 8 ), as well as their corresponding constrained geometry tetramethylcyclopentadienyl-phenoxytitanium dichlorides (TCDBP)TiCl 2 ( 9 ), (TCBP)TiCl 2 ( 10 ), (TCPP)TiCl 2 ( 11 ), and (TCMP)TiCl 2 ( 12 ) are described. A new method for the synthesis of complexes 9 − 12 was developed. Molecular structures of 9, 10, and 11 were determined by single-crystal X-ray diffraction. The Cp(cent)−Ti−O angles of 106.8° for 9, 107.1° for 10, and 107.3° for 11 reveal their sterically open features as catalyst precursors. When activated with i Bu 3 Al and Ph 3 C + B(C 6 F 5 ) 4 -, complexes 9 − 12 exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melting points.