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Article

Zirconium Sandwich Complexes with η⁹ Indenyl Ligands: Well-Defined Precursors for Zirconocene-Mediated Coupling Reactions

Supporting Info

Christopher A. Bradley,^† Ivan Keresztes,^† Emil Lobkovsky,^† Victor G. Young,^‡ and Paul J. Chirik*^†

Contribution from the Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455

J. Am. Chem. Soc., 2004, 126 (51), pp 16937–16950

DOI: 10.1021/ja045072v

Publication Date (Web): December 3, 2004

†

Cornell University.

‡

University of Minnesota.

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

, pc92@cornell.edu

Abstract

A family of isolable, well-defined bis-indenyl zirconium sandwich complexes, (η⁵-C₉H₅-1,3-R₂)(η⁹-C₉H₅-1,3-R₂)Zr (R = silyl, alkyl), have been prepared by either alkane reductive elimination or alkali metal reduction of a suitable zirconium(IV) dihalide precursor. Crystallographic characterization of two of these derivatives, R = SiMe₂CMe₃ and CHMe₂, reveals unprecedented η⁹ coordination of one of the indenyl ligands. Variable-temperature and EXSY NMR studies establish that the η⁵ and η⁹ rings are rapidly interconverting in solution. The sandwich complexes serve as effective sources of low-valent zirconium reacting rapidly with both olefins and alkynes at ambient temperature. In contrast to bis-cyclopentadienyl chemistry, the olefin adducts of the bis-indenyl zirconium sandwiches undergo preferential C−H activation to yield the corresponding allyl hydride compounds, although reaction with excess olefin proceeds through the η²-olefin adduct, forming the corresponding zirconacyclopentane.