| Abstract
| - Steric shielding of zirconocene complexes affects the nature of reactive species formed by reagents typically used to generate zirconocenium cations.
- The sterically shielded cation rac-Me2Si(2-Me-4-t-Bu-C5H2)2ZrMe+, generated by reactionof rac-Me2Si(2-Me-4-t-Bu-C5H2)2ZrMe2 with methylalumoxane (MAO) or with dimethylanilinium or trityl perfluorotetraphenylborate, differs from other, more open zirconocenemethyl cations in that it does not form the symmetric AlMe3 adduct rac-Me2Si(2-Me-4-t-Bu-C5H2)2Zr(μ-Me)2AlMe2+. Instead, the unsymmetric ternary adduct rac-Me2Si(2-Me-4-t-Bu-C5H2)2ZrMe(μ-Me)AlMe3−NMe2Ph+ is formed in the presence of dimethylaniline andtrimethylaluminum. UV/vis and 1H NMR characteristics of hydrocarbon solutions containingrac-Me2Si(2-Me-4-t-Bu-C5H2)2ZrMe+···B(C6F5)4- or rac-Me2Si(2-Me-4-t-Bu-C5H2)2ZrMe+···MAOMe- indicate that cation−anion association in these ion pairs is unusually weak.
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