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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 18, Number 6
BKCSDE 18(6)
June 20, 1997 

Syntheses of Polysiloxane-Bridged Dinuclear Metallocenes and Their Catalytic Activities
Seok Kyun Noh, Suchan Kim, Dong-ho Lee, Keun-byoung Yoon, Hun-bong Lee
The polysiloxane-bridged dinuclear metallocenes [(SiMe2O)n-SiMe2(C5H4)2][(C9H7)ZrCl2]2 (n=1 (7), 2 (8), 3 (9)) have been generated as a model complex for the immobilized metallocene at silica surface by treating the respective disodium salts of the ligands with 2 equivalents of (C9H7)ZrCl3 in THF. All three complexes are characterized by 1H NMR and measurement of metal content through ICP-MS. It turned out that the values of Δδ=[δ d-δp], the chemical shift difference between the distal (δd) and proximal (δp) protons, for the produced dinuclear compounds (0.47 for 7, 0.49 for 8, and 0.5 for 9) were larger than the Δδ value of the known ansa-type complex holding the same ligand as a chelating one, that is just the opposite to the normal trend. In order to compare polymerization behavior of the dinuclear metallocene with the corresponding mononuclear metallocene, (Cp)(C9H7)ZrCl2 was separately prepared. To investigate the catalytic properties of the dinuclear complexes and mononuclear metallocenes ethylene polymerization has been conducted in the presence of MMAO. The polymerization results display the typical activity dependence on polymerization temperature for all complexes. The most important feature is that the polymers from the dinuclear metallocenes represent enormously improved molecular weight compared with the polymer from the corresponding mononuclear metallocene. In addition, the influence of the nature of the bridging ligand upon the reactivities of the dinuclear metallocenes has also been observed.
618 - 622
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