Synthesis, Structures, and Catalytic Properties of Constrained Geometry Cyclopentadienyl-phenoxytitanium Dichlorides

Abstract

The synthesis of four new bidentate ligands, 2-(3,4-diphenylcyclopentadienyl)-6-phenylphenol ((DCPP)H2, 7), 2-(3,4-diphenylcyclopentadienyl)-6-tert-butylphenol ((DCBP)H2, 8), 2-(3,4-diphenylcyclopentadienyl)-4, 6-di-tert-butylphenol (DCDBP)H2, 9), and 2-(3,4-diphenylcyclopentadienyl)-6-methylphenol ((DCMP)H2, 10), as well as their corresponding constrained geometry cyclopentadienyl-phenoxytitanium dichlorides ((DCPP)TiCl2 (11), (DCBP)TiCl2 (12), (DCDBP)TiCl2 (13), and (DCMP)TiCl2 (14)), are described. Complexes 11−14 were synthesized from the reaction of TiCl4 with the corresponding dilithio salt of the ligand. Molecular structures of 11 and 12 were determined by single-crystal X-ray diffraction studies. The Cp(cent)−Ti−O angles of 107.4° for 11 and 106.7° for 12 reveal their sterically open features as catalyst precursors. When activated with iBu3Al and Ph3C+B(C6F5)4-, complexes 11−14 exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melt transition temperatures. Compounds 12 and 13 show good catalytic activity for copolymerization of ethylene with 1-hexene.