Synthesis and characterization of titanium ketimide complexes Ti(NCtBu2)nCl4−n (n = 1, 2): Ethylene polymerization studies

Compounds [Ti(NCtBu2)Cl3]2, 1, [Ti(NCtBu2)2Cl2]2, 2, [Ti(NCtBu2)(CH2Ph)3], 3, [Ti(NCtBu2)2(CH2Ph)2], 4, [Ti(NCtBu2)(CH2Ph)2(μ-CH2PhB(C6F5)3], 5 and [Ti(NCtBu2)2(CH2Ph) (μ-CH2PhB(C6F5)3], 6, are described. 1 was obtained from the reaction of TiCl4 and Me3SiNCtBu2 and used as starting material for the preparation of 2 and 3. Complex 4 was obtained by reaction of 2 with PhCH2MgCl. Complexes 5 and 6 were prepared by addition of B(C6F5)3 to 3 and 4, respectively. The NMR spectra of 5 and 6 reveal that these complexes exist in solution as zwitterions with one benzyl ligand bridging the titanium and boron centres. Complexes 1 and 2 are ethylene polymerization catalysts when activated with MAO, displaying activities of 217.1 and 794.6 kg/(mol(Ti[E]) h), respectively.