Half-Titanocence Anilide Complexes Cp′TiCl2[N(2,6-R21C6H3)R2]: Synthesis, Structures and Catalytic Properties for Ethylene Polymerization and Copolymerization with 1-Hexene

A number of new half-sandwich titanium(IV) complexes of the type [Cp'TiCl2{N(2,6-(R2C6H3)-C-1)R-2}] [R-1 = iPr (1, 2, 4), Me (3, 5); R-2 = Me (1, 3, 4, 5), Bn (2); Cp' = Cp (1, 2, 3), Cp* (4, 5)] have been synthesized by the reaction of [Cp'TiCl3] with the lithium salts of the corresponding anilide in toluene or diethyl ether. All titanium complexes were characterized by H-1 and C-13 NMR spectroscopy and elemental analyses. The molecular structures of complexes 1, 4, and 5 were determined by single-crystal X-ray diffraction analysis. When activated with AliBu(3) and Ph3CB(C6F5)(4), complexes 1-5 exhibited reasonable catalytic activity in ethylene polymerization, producing high-or ultra-high-molecular-weight polyethylene. It was found that complex 4 shows the highest catalytic activity in ethylene polymerization and complexes 1-3 pro-duced ultra-high-molecular-weight (M-n > 3 x 10(6) g mol(-1), viscosity-average molecular weight) polyethylene. The copolymerization of ethylene with 1-hexene catalyzed by these complexes in the presence of AliBu(3)/Ph3CB(C6F5)(4) was also investigated. Complexes 4 and 5 with the pentamethylcyclopentadienyl ligand were found to show higher catalytic activity in ethylene/1-hexene copolymerization and produced poly(ethylene-co-1-hexene)s with much higher molecular weights and co-monomer incorporation than their cyclopentadienyl analogues 1-3 under similar conditions. The comonomer incorporation abilities of complexes 4 and 5 are relatively high in comparison with other half-sandwich titanium catalyst systems.