Syntheses, reactions, and ethylenepolymerization of half-sandwich titanium complexes containing salicylbenzoxazole and salicylbenzothiazole ligands

Abstract

Half-sandwich titanium salicylbenzoxazole complexes CpTiLCl₂2a–2c [L = R-2-(benzo[d]xazol-2-yl)phenol (R = H (2a), R = 6-CH₃ (2b), R = 4-CH₃-6-^tBu (2c)] and salicylbenzothiazole complexes CpTiLCl₂2d–2g [L = R-2-(benzo[d]thiazol-2-yl)phenol (R = H (2d), R = 6-CH₃ (2e), R = 6-^tBu (2f), R = 4-Cl (2g)] were synthesized by the reaction of CpTiCl₃ with the sodium salts of their corresponding precursors. Complexes 2a–2g were fully characterized by ¹H and ¹³C NMR spectra and elemental analyses. The molecular structures of 2a and 2b were determined by single crystal X-ray diffraction methods. When activated by excess methylaluminoxane (MAO) these half-sandwich titanium complexes showed moderate to high activities for ethylene polymerization and produced high molecular weight polyethylenes. The half-sandwich titanium salicylbenzoxazole complexes (2a–2c) exhibited higher activities, of up to 1.23 × 10⁶ g PE mol Ti⁻¹ h⁻¹ for the 2b/MAO system, than those of their analogues, half-sandwich titanium salicylbenzothiazole complexes (2d–2g).