| Abstract
| - Lowest energy ligand-to-metal charge-transfer (LMCT) transitions of racemic siloxy-substituted ethylene-bridged bis(indenyl)-type zirconocenes reacted with methylaluminoxane (MAO) werestudied using UV/vis spectroscopy in combination with the ab initio Hartree−Fock method. The LMCTabsorptions were recorded at various [Al]/[Zr] ratios, representing dichloride, methylated, and cationicforms of the zirconocenes. The experimental LMCT absorption energies of each intermediate werecompared 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 energygaps. Furthermore, the LMCT absorption energies were demonstrated to correlate with ethylenepolymerization activity of the siloxy-substituted complexes. This correlation was clarified by a frontierorbital analysis, suggesting that decreasing absorption energy is related to the feasibility of the activationof the catalyst.
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