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Article

The “Indenyl Effect” in Zirconocene Dihydride Chemistry

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Christopher A. Bradley, Ivan Keresztes, Emil Lobkovsky, and Paul J. Chirik*

Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853

Organometallics, 2006, 25 (8), pp 2080–2089

DOI: 10.1021/om060035t

Publication Date (Web): March 9, 2006

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

Abstract

The second-order rate constants for the insertion of cyclohexene into substituted bis(indenyl)zirconocene dihydrides, (η⁵-C₉H₅-1,3-R₂)₂ZrH₂ (R = SiMe₃, CHMe₂), to yield the cyclohexyl hydride complexes have been measured. Comparison of these values to the corresponding tetrahydroindenyl derivatives (η⁵-C₉H₉-1,3-R₂)₂ZrH₂ reveals significantly faster insertion reactions for the bis(indenyl) compounds. Accordingly, primarily σ-donating ligands such as PMe₃, PEt₃, and tetrahydrothiophene coordinate to (η⁵-C₉H₅-1,3-(CHMe₂)₂)₂ZrH₂ to form (η⁵-C₉H₅-1,3-(CHMe₂)₂)₂ZrH₂(L) compounds, one of which (L = PMe₃) has been structurally characterized. In contrast, the more electron-rich zirconocene tetrahydroindenyl dihydrides exhibit weaker binding in solution. Taken together, these results establish an “indenyl effect” in zirconocene hydride chemistry likely arising from increased electrophilicity of the metal center, rather than a change in hapticity along the reaction coordinate.

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Published In Issue April 10, 2006
Received January 11, 2006

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Article

The “Indenyl Effect” in Zirconocene Dihydride Chemistry