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Article

Carbon−Oxygen Bond Cleavage with η⁹,η⁵-Bis(indenyl)zirconium Sandwich Complexes

Supporting Info

Christopher A. Bradley,^† Luis F. Veiros,^‡ Doris Pun,^† Emil Lobkovsky,^† Ivan Keresztes,^† and Paul J. Chirik*^†

Contribution from the Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, and Centro de Quimica Estrutural, Complexo I, Instituto Superior Tcnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal

J. Am. Chem. Soc., 2006, 128 (51), pp 16600–16612

DOI: 10.1021/ja065456g

Publication Date (Web): December 8, 2006

†

Cornell University.

‡

Instituto Superior Técnico.

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

Treatment of the η⁹,η⁵-bis(indenyl)zirconium sandwich complex, (η⁹-C₉H₅-1,3-(SiMe₃)₂)(η⁵-C₉H₅-1,3-(SiMe₃)₂)Zr, with dialkyl ethers such as diethyl ether, CH₃OR (R Et, ⁿBu, ^tBu), ⁿBu₂O, or ⁱPr₂O resulted in facile CO bond scission furnishing an η⁵,η⁵-bis(indenyl)zirconium alkoxy hydride complex and free olefin. In cases where ethylene is formed, trapping by the zirconocene sandwich yields a rare example of a crystallographically characterized, base-free η⁵,η⁵-bis(indenyl)zirconium ethylene complex. Observation of normal, primary kinetic isotope effects in combination with rate studies and the stability of various model compounds support a mechanism involving rate-determining CH activation to yield an η⁵,η⁵-bis(indenyl)zirconium alkyl hydride intermediate followed by rapid β-alkoxide elimination. For isolable η⁶,η⁵-bis(indenyl)zirconium THF compounds, thermolysis at 85 °C also resulted in CO bond cleavage to yield the corresponding zirconacycle. Both mechanistic and computational studies again support a pathway involving haptotropic rearrangement to η⁵,η⁵-bis(indenyl)zirconium intermediates that promote rate-determining CH activation and ultimately CO bond scission.