Abstract
AbstractActivation of the metallocene complexes (n‐C4H9‐(η5‐C5H4))2ZrCl2 (BuCp2ZrCl2) and rac‐1,2‐ethylenebis(1‐η5‐C9H6)ZrCl2 (EBIZrCl2) using methylaluminoxane (MAO) was investigated by electrospray ionization mass spectrometry (ESI‐MS). Formation of dinuclear complexes at low Al : Zr ratios, which is accompanied by catalyst deactivation, occurs in the former case. In contrast, this behavior was not observed at similar Al : Zr ratios in the case of the EBIZrCl2 complex. Both active [BuCp2ZrMe2AlMe2][MAO(Me)] 3 and deactivated [(BuCp2Zr)2(μ‐CH2)μ‐Cl][MAO(Me)] 9 complexes were detected in leaching experiments using a SiO2‐MAO‐supported BuCp2ZrCl2 catalyst and excess MAO. DFT studies of the structure and UV‐Vis spectra calculated for the dinuclear cations 9 detected by ESI‐MS suggest that these species may account for long‐wavelength absorption seen in experimental spectra of complexes like BuCp2ZrCl2 upon activation with MAO.
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