Half‐Titanocence Anilide Complexes Cp′TiCl 2 [N(2,6‐R 1 2 C 6 H 3 )R 2 ]: 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′TiCl 2 {N(2,6‐R 1 2 C 6 H 3 )R 2 }] [R 1 = i Pr ( 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′TiCl 3 ] with the lithium salts of the corresponding anilide in toluene or diethyl ether. All titanium complexes were characterized by 1 H and 13 C 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 Al i Bu 3 and Ph 3 CB(C 6 F 5 ) 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 ( M η > 3 × 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 Al i Bu 3 /Ph 3 CB(C 6 F 5 ) 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.