دورية
Activation of Racemic Ethylene-Bridged Bis(indenyl)-Type Siloxy-Substituted Zirconocenes with Methylaluminoxane. A Combined UV/vis Spectroscopic and ab Initio Hartree−Fock Study
| العنوان: | Activation of Racemic Ethylene-Bridged Bis(indenyl)-Type Siloxy-Substituted Zirconocenes with Methylaluminoxane. A Combined UV/vis Spectroscopic and ab Initio Hartree−Fock Study |
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| المؤلفون: | Makela, N. I., Knuuttila, H. R., Linnolahti, M., Pakkanen, T. A., Leskela, M. A. |
| المصدر: | Macromolecules; April 2002, Vol. 35 Issue: 9 p3395-3401, 7p |
| مستخلص: | Lowest energy ligand-to-metal charge-transfer (LMCT) transitions of racemic siloxy-substituted ethylene-bridged bis(indenyl)-type zirconocenes reacted with methylaluminoxane (MAO) were studied using UV/vis spectroscopy in combination with the ab initio Hartree−Fock method. The LMCT absorptions were recorded at various [Al]/[Zr] ratios, representing dichloride, methylated, and cationic forms of the zirconocenes. The experimental LMCT absorption energies of each intermediate were compared to the calculated energies of the indenyl ligand-based HOMO and the zirconium-based LUMO. The lowest energy LMCT absorptions were directly proportional to the calculated LUMO−HOMO energy gaps. Furthermore, the LMCT absorption energies were demonstrated to correlate with ethylene polymerization activity of the siloxy-substituted complexes. This correlation was clarified by a frontier orbital analysis, suggesting that decreasing absorption energy is related to the feasibility of the activation of the catalyst. |
| قاعدة البيانات: | Supplemental Index |
Find this issue from the American Chemical Society | تدمد: | 00249297 15205835 |
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| DOI: | 10.1021/ma012127u |