Formation of Zirconocene Fluoro Complexes: No Deactivation in the Polymerization of Olefins by the Contact-Ion-Pair Catalysts [Cp′2ZrR]+[RB(C6F5)3]−
✍ Scribed by Perdita Arndt; Ulrike Jäger-Fiedler; Marcus Klahn; Wolfgang Baumann; Anke Spannenberg; Vladimir V. Burlakov; Uwe Rosenthal
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 132 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0044-8249
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✦ Synopsis
In memory of Erhard Kurras
Certain ion pairs [Cp' 2 MMe] + [MeB(C 6 F 5 ) 3 ] À (M = Ti, Zr; Cp' = substituted or unsubstituted h 5 -cyclopentadienyl), formed by the formal abstraction of methyl anions from dimethyl complexes [Cp' 2 MMe 2 ] of the Group 14 transition metals by the strong Lewis acid B(C 6 F 5 ) 3 , are highly active catalysts for the polymerization of a-olefins. [1] Zirconocene complexes of olefins, alkynes, and butadiene were also later activated for catalytic olefin polymerization in a similar way. [2] Recently, we described the reactions of complexes containing two MÀC s bonds, including the zirconacyclopropenes [Cp' 2 Zr(h 2 -RC 2 R)] (R = SiMe 3 ) [3a] and several five-membered zirconacycles, [3b,c] with B(C 6 F 5 ) 3 . A typical example is [rac-(ebthi)Zr(h 2 -Me 3 SiC 2 SiMe 3 )] (A; ebthi = 1,2-ethylene-1,1'bis(h 5 -tetrahydroindenyl)), [4a] which undergoes electrophilic substitution at the five-membered ring of the ebthi ligand upon reaction with B(C 6 F 5 ) 3 , forming the alkenyl complex B [Eq. ( 1)]. [4b] In this complex, the boranate group is substituted at the 3-position of the five-membered ring, and one of its ortho fluorine atoms is coordinated to the zirconium center. The s-bound alkenyl group at the zirconium center participates in an additional agostic interaction. [4b] Upon thermolysis of B [Eq. ( 1)], bis(trimethylsilyl)acetylene is eliminated, and with the cleavage of one BÀC bond, [