Abstract

AbstractThe 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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