Heterobi‐ and ‐trimetallic Ion Pairs of Zirconocene‐Based Isoselective Olefin Polymerization Catalysts with AlMe31. (7th April 2015)

• Record Type: Journal Article
• Authors: Theurkauff, Gabriel; Bondon, Arnaud; Dorcet, Vincent; Carpentier, Jean‐François; Kirillov, Evgueni
• Is Part Of: Angewandte Chemie. Volume 127:Number 21(2015)
• Page Start: 6441
• Page End: 6444
• Publication Date: 2015-04-07
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201501967
• Languages: English
• ISSNs: 0044-8249

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The reactivity towards AlMe₃ of discrete cationic ansa‐zirconocenes <bold>2 a, b</bold> that are ubiquitously used in isoselective propylene polymerization and based on [{Ph(H)C(3, 6‐<italic>t</italic>Bu₂‐Flu)(3‐<italic>t</italic>Bu‐5‐Et‐Cp)}ZrMe₂)] {Cp‐Flu} and <italic>rac</italic>‐[{Me₂Si‐(2‐Me‐4‐Ph‐Ind)₂}ZrMe₂] {SBI} was scrutinized. The first example of a structurally characterized Group 4 metallocene AlMe₃ adduct (<bold>3 b</bold>) is reported. In the presence of excess AlMe₃, the {SBI}‐based AlMe₃ adduct <bold>3 b</bold> undergoes a slow decomposition via CH activation in a bridging methyl unit to yield a new species (<bold>4 b</bold>) with a trimetallic {Zr(μ‐CH₂)(μ‐Me)AlMe(μ‐Me)AlMe₂} core. EXSY NMR data for the process <bold>2 b</bold>⇄<bold>3 b</bold>→<bold>4 b</bold> suggest very rapid and reversible binding of an additional AlMe₃ molecule onto AlMe₃ adduct <bold>3 b</bold>. The resulting heterotrimetallic species intermediates exchange of methyl groups between different metal centers and slowly undergoes the CH activation reaction towards <bold>4 b</bold>.</p> </abstract>