Half‐Titanocence Anilide Complexes Cp′TiCl2[N(2,6‐R12C6H3)R2]: Synthesis, Structures and Catalytic Properties for Ethylene Polymerization and Copolymerization with 1‐Hexene

Abstract

AbstractA number of new half‐sandwich titanium(IV) complexes of the type [Cp′TiCl2{N(2,6‐R12C6H3)R2}] [R1 = iPr (1, 2, 4), Me (3, 5); R2 = 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 1H and 13C 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 AliBu3 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 produced ultra‐high‐molecular‐weight (Mη > 3 × 106 g mol–1, viscosity‐average molecular weight) polyethylene. The copolymerization of ethylene with 1‐hexene catalyzed by these complexes in the presence of AliBu3/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 co‐monomer incorporation abilities of complexes 4 and 5 are relatively high in comparison with other half‐sandwich titanium catalyst systems.