Syntheses, reactions, and ethylenepolymerization of titanium complexes with [N,N,S] ligands

Abstract

Tridentate dianionic arylsulfide free ligands [ArNHCH₂C₆H₄NHC₆H₄-2-SPh] (Ar = Ph (3a); Ar = 2,4,6-trimethylphenyl (3b); Ar = 2,6-diisopropylphenyl (3c)) have been prepared by reduction of the corresponding imine compounds [ArNCHC₆H₄NHC₆H₄-2-SPh] (Ar = Ph (2a); Ar = 2,4,6-trimethylphenyl (2b); Ar = 2,6-diisopropylphenyl (2c)) with LiAlH₄ in high yields. Reactions of TiCl₄ with the tridentate dianionic arylsulfide free ligands (3a–3c) afford five-coordinate and four-coordinate titanium complexes [κS, κ²N-(ArNHCH₂C₆H₄NHC₆H₄-2-SPh)TiCl₂] (Ar = Ph (4a); Ar = 2,4,6-trimethylphenyl (4b)] and [κ²N-(ArNHCH₂C₆H₄NHC₆H₄-2-SPh)TiCl₂] (Ar = 2,6-diisopropylphenyl (4c)], respectively. The molecular structures of compounds 2b, 2c, 3b and 3c·HCl have been characterized by single crystal X-ray diffraction analyses. Complexes 2a–4c are characterized by IR,¹H-NMR spectra, and elemental analysis. EXAFS spectroscopy performed on complexes 4b and 4c reveals the expected different coordination geometry due to steric hindrance effect. When activated by excess methylaluminoxane (MAO), 4a–4c can be used as catalysts for ethylene polymerization and exhibit moderate to good activities.