Syntheses, characterization and ethylene polymerization of half-sandwich group IV metal complexes with tridentate [O,N,S] ligands

A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O^?NS] ligand [2-Bu ^t 4-Me-6-((2-(SC₆H₅)C₆H₄N=CHC₆H₂O)]^? (La) and dianionic phenoxy-amine arylsulfide [O^?N^?S] ligand [2-Bu ^t 4-Me-6-((2-(SC₆H₅)C₆H₄N-CH₂C₆H₂O)]^2? (Lb) have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH₄ in cool diethyl ether. Half-sandwich Group IV metal complexes CpTi[O^?NS]Cl₂ (1a), CpZr[O^?NS]Cl₂ (1b), CpTi[O^?N^?S]Cl (2a), CpZr[O^?N^?S]Cl (2b) and Cp*Zr[O^?N^?S]Cl (2c) were synthesized by the reactions of La and Lb with CpTiCl₃, CpZrCl₃ and Cp*ZrCl₃, and characterized by IR, ¹H-NMR, ¹³C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane (MAO) as co-catalyst up to 1.58 × 10⁷ g-PE·mol-Zr^?1·^?1. The good catalytic activities can be maintained even at high temperatures such as 100 °C exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.