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

Abstract

Group 4 metal complexes M(η 5 :η 1 -C 5 R 4 SiMe 2 NCH 2 CH 2 SMe)Cl 2 (R=H, M=Ti; R=Me, M=Ti, Zr) containing the thioether-functionalized linked amido–cyclopentadienyl ligand were synthesized and characterized by 1 H- and 13 C-NMR spectroscopy, mass spectrometry, and elemental analysis. The crystal structures of the complexes Ti(η 5 :η 1 -C 5 H 4 SiMe 2 NCH 2 CH 2 SMe)Cl 2 and Zr(η 5 :η 1 :η 1 -C 5 Me 4 SiMe 2 NCH 2 CH 2 SMe)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(η 5 :η 1 -C 5 Me 4 ZNCH 2 CH 2 SMe)(CH 2 Ph) 2 (Z=SiMe 2 , CH 2 SiMe 2 ) and B(C 6 F 5 ) 3 in C 6 D 5 Br resulted in the clean formation of the solvent-separated ion pair [Ti(η 5 :η 1 -C 5 Me 4 ZNCH 2 CH 2 SMe)(η 2 -CH 2 Ph)] + [(PhCH 2 )B(C 6 F 5 ) 3 ] − . The dichloro complexes M(η 5 :η 1 -C 5 Me 4 SiMe 2 NCH 2 CH 2 SMe)Cl 2 , when activated with methylaluminoxane, catalyzed the polymerization of ethylene with moderate activities. The phosphino-functionalized ligand C 5 Me 4 SiMe 2 NC 6 H 4 (PPh 2 )-2 was also coordinated at titanium and zirconium centers; NMR spectroscopic data inferred an intramolecular metal–phosphine interaction for these M{η 5 :η 1 -C 5 Me 4 SiMe 2 NC 6 H 4 (PPh 2 )-2}Cl 2 complexes.