Complexes of titanium and zirconium containing a tridentate linked amido-cyclopentadienyl ligand with a soft donor group: synthesis, structure, and ethylene polymerization catalysis

摘要

Group 4 metal complexes M(#eta#~5:#eta#~1-C_5R_4SiMe_2NCH_2CH_2SMe)Cl_2 (R = H, M = Ti; R = Me, M = Ti, Zr) containing the thioether-functionalized linked amido-cyclopentadienyl ligand were synthesized and characterized by ~1H- and ~(13)C-NMR spectroscopy, mass spectrometry, and elemental analysis. The crystal structures of the complexes Ti(#eta#~5:#eta#~1-C_5H_4SiMe_2NCH_2CH_2SMe)Cl_2 and Zr(#eta#~5:#eta#~1:#eta#~1-C_5MeSiMe_2NCH_2CH_2SMe)Cl_2 were determined by single-crystal X-ray diffraction studies. The titanium complex is a conventional three-legged piano-stool molecule without an intramolecular interaction between the sulfur donor group and the titanium center, whereas the zirconium complex adopts a trigonal bipyramidal structure, with the five-membered ring and the coordinating methylthio group in the apical positions. Reaction between the titanium dibenzyl Ti(#eta#~5:#eta#~1-C_5Me_4ZNCH_2CH_2SMe)(CH_2Ph)_2 (Z = SiMe_2, CH_2SiMe_2) and B(C_6F_5)_3 in C_6D_5Br resulted in the clean formation of the solvent-separated ion pair [Ti(#eta#~5:#eta#~1-C_5Me_2ZNCH_2CH_2CH_2SMe)(#eta#~2-CH_2Ph)]~+[(PhCH_2)B(C_6F_5)_3]~-. The dichloro complexes M(#eta#~5:#eta#~1-C_5Me_4SiMe_2NCH_2CH_2SMe)Cl_2, when activated with methylaluminoxane, catalyzed the polymerization of ethylene with moderate activities. The phosphino-functionalized ligand C_5Me_4SiMe_2NC_6H_4(PPh_2)-2 was also coordinated at titanium and zirconium centers; NMR spectroscopic data inferred an intramolecular metal-phosphine interaction for these M{#eta#~5:#eta#~1-C_5Me_4SiMe_2NC_6H_4(PPh_2)-2}Cl_2 complexes.