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Synthesis, characterization, and reactivities of the polysiloxane-bridged binuclear metallocenes tetramethyldisiloxanediylbis(cyclopentadienyltitanium trichloride) and hexamethyltrisiloxanediylbis(cyclopentadienyltitanium trichloride)

1996; Elsevier BV; Volume: 518; Issue: 1-2 Linguagem: Inglês

10.1016/0022-328x(96)06128-1

1872-8561

Seok Kyun Noh, Gyu‐gum Byun, Chul-Soo Lee, Dong‐Ho Lee, Keun‐byung Yoon, Kyoung Seok Kang,

Silicone and Siloxane Chemistry

The reaction of dithallium salts of tetramethyldisiloxanediylbis(cyclopentadienyl), 3, and hexamethyltrisiloxanediylbis(cyclopentadienyl), 4, with two equivalents of TiCl4 gives the title compounds tetramethyldisiloxanediylbis(cyclopentadienyltitanium trichloride), 5 and hexamethyltrisiloxanediylbis(cyclopentadienyltitanium trichloride), 6 respectively. The stoichiometric reaction of 5 and 6 with water results in the formation of new oxygen-bridged metallocenes [(TiCl2)2(μ2-O)-(η5-C5H4)2-μ2-(SiMe2)2O], 7, and [(TiCl2)2(μ2-O)-(η5-C5H4)2-μ2-(SiMe2)3O2}], 8. In addition, further reaction of 7 and 8 with another one equivalent of water or the treatment of 5 and 6 with an excess amount of water gives rise to the formation of the metallocene compounds having Ti4O4 rings [(TiCl)2(μ2-O)-(η5-C5H4)2-μ2-(SiMe2)2O]2(μ2-O)2, 9, and [(TiCl)2(μ2-O)-(η5-C5H4)2-μ2-(SiMe2)3O2]2 (μ2-O)2, 10. All the new kinds of metalocenes prepared have been characterized by IR, NMR, mass spectrometry, or elemental analysis. Especially an investigation of the Δδ values in 1H NMR and a comparison between the theoretical and observed isotopic ratio in a mass spectra among the synthesized bridged compounds have been very conveniently utilized to study their structures. Polymerization experiments with the dinuclear complexes in the presence of methylaluminoxane as a cocatalyst indicate that the compounds 5 and 6 do exhibit catalytic activity for syndiotactic polymerization of styrene.