Type of Publication: | Journal article |
URI (citable link): | http://nbn-resolving.de/urn:nbn:de:bsz:352-239201 |
Author: | Beck, Stefan; Prosenc, Marc-Heinrich; Brintzinger, Hans-Herbert; Goretzki, Ralf; Herfert, Norbert; Fink, Gerhard |
Year of publication: | 1996 |
Published in: | Journal of Molecular Catalysis A: Chemical ; 111 (1996), 1-2. - pp. 67-79. - ISSN 1381-1169 |
DOI (citable link): | https://dx.doi.org/10.1016/1381-1169(96)00168-9 |
Summary: |
Binuclear zirconocene cations are observed by 1H-NMR in C6D6 solutions containing B(C6F5)3 and an excess of a zirconocene dimethyl complex. The CH3-bridged cation [((C5H5)2ZrCH3)2(μ-CH3)]+, solvent-separated from the anion H3CB(C6F5)−3, is present in equilibrium with (C5H5)2Zr(CH3)2 and the mononuclear ion pair [(C5H5)2ZrCH+3***H3CB(C6F5)−3]; in more concentrated solutions, a binuclear ion pair [((C5H5)2ZrCH3)2(μ-CH3)+***H3CB(C6F5)−3] is the dominant species. Similar equilibria are observed in C6D6 solutions containing B(C6F5)3 and (CH3)4C2(C5H4)2Zr(CH3)2, (CH3)2Si(C5H4)2Zr(CH3)2 or rac-(CH3)2Si(indenyl)2Zr(CH3)2. Complexes with sterically more demanding ligands, such as (C5(CH3)5)2Zr(CH3)2 or rac-(CH3)2Si(2-methyl-benz[e]indenyl)2Zr(CH3)2 do not form any binuclear species under these conditions. In the catalyst system rac-(CH3)2Si(indenyl)2Zr(CH3)2Bu3NH+B(C6F5)−4, activities for the polymerization of propene increase with excess of the dimethyl zirconocene complex. This effect is due in part to a sacrifice of some dimethyl zirconocene for the removal of impurities from the catalyst system and in part to a stabilization of the catalyst in the form of the binuclear cation [((CH3)2Si(indenyl)2ZrCH3)2(μ-CH3)]+. The latter appears to act, in the presence of propene, as a source of the mononuclear cation [(CH3)2Si(indenyl)2ZrCH3(C3H6)]+, rather than as a polymerization catalyst by itself.
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Subject (DDC): | 540 Chemistry |
Keywords: | NMR, Ziegler-Natta, zirconocene |
Link to License: | In Copyright |
BECK, Stefan, Marc-Heinrich PROSENC, Hans-Herbert BRINTZINGER, Ralf GORETZKI, Norbert HERFERT, Gerhard FINK, 1996. Binuclear zirconocene cations with μ-CH3-bridges in homogeneous Ziegler-Natta catalyst systems. In: Journal of Molecular Catalysis A: Chemical. 111(1-2), pp. 67-79. ISSN 1381-1169. Available under: doi: 10.1016/1381-1169(96)00168-9
@article{Beck1996Binuc-23920, title={Binuclear zirconocene cations with μ-CH3-bridges in homogeneous Ziegler-Natta catalyst systems}, year={1996}, doi={10.1016/1381-1169(96)00168-9}, number={1-2}, volume={111}, issn={1381-1169}, journal={Journal of Molecular Catalysis A: Chemical}, pages={67--79}, author={Beck, Stefan and Prosenc, Marc-Heinrich and Brintzinger, Hans-Herbert and Goretzki, Ralf and Herfert, Norbert and Fink, Gerhard} }
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