title: Nucleophilicity of Alkyl Zirconocene and Titanocene Precatalysts, and Kinetics of Activation by Carbenium Ions and by B(C6 F5 )3.
abstract: Kinetics of activation of methyl and benzyl metallocene precatalysts by benzhydrylium ions, tritylium ions, and triarylborane B(C6 F5 )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.
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, München, Germany. guillaume.berionni@cup.uni-muenchen.de.
authors.forename: Guillaume
authors.identifier: http://orcid.org/0000-0002-5422-9113
authors.initials: G
authors.lastname: Berionni
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, München, Germany.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kurouchi
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, München, Germany.
authors.forename: Lucien
authors.initials: L
authors.lastname: Eisenburger
authors.affiliation: Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5-13, 81377, München, Germany.
authors.forename: Herbert
authors.initials: H
authors.lastname: Mayr
keywords: catalyst activation; kinetics; metallocenes; nucleophilicity; polymerization catalysts