title: Heterobi- and -trimetallic Ion Pairs of Zirconocene-Based Isoselective Olefin Polymerization Catalysts with AlMe₃.
abstract: The reactivity towards AlMe3 of discrete cationic ansa-zirconocenes 2 a,b that are ubiquitously used in isoselective propylene polymerization and based on [{Ph(H)C(3,6-tBu2-Flu)(3-tBu-5-Et-Cp)}ZrMe2)] {Cp-Flu} and rac-[{Me2Si-(2-Me-4-Ph-Ind)2}ZrMe2] {SBI} was scrutinized. The first example of a structurally characterized Group 4 metallocene AlMe3 adduct (3 b) is reported. In the presence of excess AlMe3, the {SBI}-based AlMe3 adduct 3 b undergoes a slow decomposition via C-H activation in a bridging methyl unit to yield a new species (4 b) with a trimetallic {Zr(μ-CH2)(μ-Me)AlMe(μ-Me)AlMe2} core. EXSY NMR data for the process 2 b⇄3 b→4 b suggest very rapid and reversible binding of an additional AlMe3 molecule onto AlMe3 adduct 3 b. The resulting heterotrimetallic species intermediates exchange of methyl groups between different metal centers and slowly undergoes the C-H activation reaction towards 4 b.
authors: Organometallics: Materials and Catalysis Laboratories, UMR 6226 CNRS-Université de Rennes 1, Institut des Sciences Chimiques de Rennes, 35042 Rennes Cedex (France).
authors: Gabriel
authors: G
authors: Theurkauff
authors: Ingénierie Chimique et Molécules pour le Vivant, UMR 6226 CNRS-Université de Rennes 1, Institut des Sciences Chimiques de Rennes (France).
authors: Arnaud
authors: A
authors: Bondon
authors: Organometallics: Materials and Catalysis Laboratories, UMR 6226 CNRS-Université de Rennes 1, Institut des Sciences Chimiques de Rennes, 35042 Rennes Cedex (France).|Centre de diffraction X, Institut des Sciences Chimiques de Rennes (France).
authors: Vincent
authors: V
authors: Dorcet
authors: Organometallics: Materials and Catalysis Laboratories, UMR 6226 CNRS-Université de Rennes 1, Institut des Sciences Chimiques de Rennes, 35042 Rennes Cedex (France). jean-francois.carpentier@univ-rennes1.fr.
authors: Jean-François
authors: JF
authors: Carpentier
authors: Organometallics: Materials and Catalysis Laboratories, UMR 6226 CNRS-Université de Rennes 1, Institut des Sciences Chimiques de Rennes, 35042 Rennes Cedex (France). evgueni.kirillov@univ-rennes1.fr.
authors: Evgueni
authors: E
authors: Kirillov
keywords: CH activation; aluminum; ion pairs; structure elucidation; zirconocenes