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

摘要

Tridentate dianionic arylsulfide free ligands [ArNHCH_2C _6H_4NHC_6H_4-2-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 [ArNCHC_6H _4NHC_6H_4-2-SPh] (Ar = Ph (2a); Ar = 2,4,6-trimethylphenyl (2b); Ar = 2,6-diisopropylphenyl (2c)) with LiAlH _4 in high yields. Reactions of TiCl_4 with the tridentate dianionic arylsulfide free ligands (3a-3c) afford five-coordinate and four-coordinate titanium complexes [κS, κ~2N-(ArNHCH _2C_6H_4NHC_6H_4-2-SPh) TiCl_2] (Ar = Ph (4a); Ar = 2,4,6-trimethylphenyl (4b)] and [κ~2N-(ArNHCH_2C_6H_4NHC _6H_4-2-SPh)TiCl_2] (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.