Synthesis and characterization of titanium and zirconium complexes with silicone-bridged phenoxycyclopentadienyl ligands

Dimethylsilyl(2,3,4,5-tetramethylcyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titanium dichloride (1a), a useful catalyst precursor for olefin copolymerization, was synthesized at high yield starting from allyl-protected phenolic ligand 3a,which was first treated with 2 equiv. of n-BuLi to selectively give the dilithium salt of 3a along with 1-heptene, a coupling product of a protected allyl ether moiety and butyl anion. Addition of TiCl4 to the resulting dilithium salt of 3a in toluene afforded 1a in 50% isolated yield. This methodology could be applied to the preparation of related titanium and zirconoium complexes 1b–1d, 8 with silicone-bridged Cp-phenoxy ligands, whereas the reaction starting from methyl-protected precursor 2a did not produce the zirconium complex 8. Copolymerization of ethylene and 1-hexene with the newly prepared complexes was also investigated.

Graphical abstractSiMe2-bridged Cp-phenoxy titanium and zirconium complexes 1a–1d, 8 were synthesized in high yields starting from allyl-protected phenolic ligands 3a–3d, which were first treated with 2 equiv. of n-BuLi to selectively give the dilithium salt of the ligands along with 1-heptene, a coupling product of a protected allyl ether moiety and butyl anion. Addition of TiCl4 to the resulting dilithium salts of the ligands in toluene afforded the complexes in good yields.Figure optionsDownload full-size imageDownload as PowerPoint slide