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

Abstract

The synthesis of four new bidentate ligands, 2-(tetramethylcyclopentadienyl)-4,6-di-tert-butylphenol ((TCDBP)H2, 5), 2-(tetramethylcyclopentadienyl)-6-tert-butylphenol ((TCBP)H2, 6), 2-(tetramethylcyclopentadienyl)-6-phenylphenol ((TCPP)H2, 7), and 2-(tetramethylcyclopentadienyl)-6-methylphenol ((TCMP)H2, 8), as well as their corresponding constrained geometry tetramethylcyclopentadienyl-phenoxytitanium dichlorides (TCDBP)TiCl2 (9), (TCBP)TiCl2 (10), (TCPP)TiCl2 (11), and (TCMP)TiCl2 (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 iBu3Al and Ph3C+B(C6F5)4-, complexes 9−12 exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melting points.