Nucleophilicity of Alkyl Zirconocene and Titanocene Precatalysts,and Kinetics of Activation by Carbenium Ions and by B(C6F5)3 |
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| Authors: | Dr. Guillaume Berionni Dr. Hiroaki Kurouchi Lucien Eisenburger Prof. Dr. Herbert Mayr |
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| Affiliation: | 1. http://www.cup.uni‐muenchen.de/oc/mayr/ 0000-0002-5422-9113 Department Chemie, Ludwig-Maximilians-Universit?t München, München, Germany;2. Department Chemie, Ludwig-Maximilians-Universit?t München, München, Germany |
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| Abstract: | Kinetics of activation of methyl and benzyl metallocene precatalysts by benzhydrylium ions, tritylium ions, and triarylborane B(C6F5)3 were measured spectrophotometrically. The rate constants correlate linearly with the electrophilicity parameter E of the benzhydrylium and tritylium ions employed, allowing us to determine the σ‐nucleophilicities of the metal–carbon bond of several zirconocenes and titanocenes. Bridging, substitution, metal, and ligand effects on the rates of metal–alkyl bond cleavage (M=Zr, Ti) were studied and structure–reactivity correlations were used to predict the kinetics of generation of metallocenium ions pairs, which are active catalysts in polymerization reactions and are highly electrophilic Lewis acids in frustrated Lewis pair catalysis. |
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| Keywords: | catalyst activation kinetics metallocenes nucleophilicity polymerization catalysts |
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