Heterobi‐ and ‐trimetallic Ion Pairs of Zirconocene‐Based Isoselective Olefin Polymerization Catalysts with AlMe3 |
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| Authors: | Dr Gabriel Theurkauff Dr Arnaud Bondon Dr Vincent Dorcet Prof?Dr Jean‐François Carpentier Dr Evgueni Kirillov |
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| Institution: | 1. Organometallics: Materials and Catalysis Laboratories, UMR 6226 CNRS‐Université de Rennes 1, Institut des Sciences Chimiques de Rennes, 35042 Rennes Cedex (France);2. Ingénierie Chimique et Molécules pour le Vivant, UMR 6226 CNRS‐Université de Rennes 1, Institut des Sciences Chimiques de Rennes (France);3. Centre de diffraction X, Institut des Sciences Chimiques de Rennes (France) |
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| 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 . |
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| Keywords: | aluminum C H activation ion pairs structure elucidation zirconocenes |
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