The "indenyl effect" in zirconocene dihydride chemistry

Christopher A. Bradley; Ivan Keresztes; Emil Lobkovsky; Paul J. Chirik

doi:10.1021/om060035t

The "indenyl effect" in zirconocene dihydride chemistry

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

Research output: Contribution to journal › Article › peer-review

28 Scopus citations

Abstract

The second-order rate constants for the insertion of cyclohexene into substituted bis(indenyl)zirconocene dihydrides, (η ⁵-C ₉H ₅-1,3-R ₂) ₂ZrH ₂ (R = SiMe ₃, CHMe ₂), to yield the cyclohexyl hydride complexes have been measured. Comparison of these values to the corresponding tetrahydroindenyl derivatives (η ⁵-C ₉H ₉-1,3-R ₂) ₂ZrH ₂ reveals significantly faster insertion reactions for the bis(indenyl) compounds. Accordingly, primarily σ-donating ligands such as PMe ₃, PEt ₃, and tetrahydrothiophene coordinate to (η ⁵-C ₉H ₅-1,3-(CHMe ₂) ₂) ₂ZrH ₂ to form (η ⁵-C ₉H ₅-1,3-(CHMe ₂) ₂) ₂ZrH ₂(L) compounds, one of which (L = PMe ₃) 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.

Original language	English (US)
Pages (from-to)	2080-2089
Number of pages	10
Journal	Organometallics
Volume	25
Issue number	8
DOIs	https://doi.org/10.1021/om060035t
State	Published - Apr 10 2006
Externally published	Yes

All Science Journal Classification (ASJC) codes

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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title = "The {"}indenyl effect{"} in zirconocene dihydride chemistry",

abstract = "The second-order rate constants for the insertion of cyclohexene into substituted bis(indenyl)zirconocene dihydrides, (η 5-C 9H 5-1,3-R 2) 2ZrH 2 (R = SiMe 3, CHMe 2), to yield the cyclohexyl hydride complexes have been measured. Comparison of these values to the corresponding tetrahydroindenyl derivatives (η 5-C 9H 9-1,3-R 2) 2ZrH 2 reveals significantly faster insertion reactions for the bis(indenyl) compounds. Accordingly, primarily σ-donating ligands such as PMe 3, PEt 3, and tetrahydrothiophene coordinate to (η 5-C 9H 5-1,3-(CHMe 2) 2) 2ZrH 2 to form (η 5-C 9H 5-1,3-(CHMe 2) 2) 2ZrH 2(L) compounds, one of which (L = PMe 3) 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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AU - Bradley, Christopher A.

AU - Keresztes, Ivan

AU - Lobkovsky, Emil

AU - Chirik, Paul J.

PY - 2006/4/10

Y1 - 2006/4/10

N2 - The second-order rate constants for the insertion of cyclohexene into substituted bis(indenyl)zirconocene dihydrides, (η 5-C 9H 5-1,3-R 2) 2ZrH 2 (R = SiMe 3, CHMe 2), to yield the cyclohexyl hydride complexes have been measured. Comparison of these values to the corresponding tetrahydroindenyl derivatives (η 5-C 9H 9-1,3-R 2) 2ZrH 2 reveals significantly faster insertion reactions for the bis(indenyl) compounds. Accordingly, primarily σ-donating ligands such as PMe 3, PEt 3, and tetrahydrothiophene coordinate to (η 5-C 9H 5-1,3-(CHMe 2) 2) 2ZrH 2 to form (η 5-C 9H 5-1,3-(CHMe 2) 2) 2ZrH 2(L) compounds, one of which (L = PMe 3) 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.

AB - The second-order rate constants for the insertion of cyclohexene into substituted bis(indenyl)zirconocene dihydrides, (η 5-C 9H 5-1,3-R 2) 2ZrH 2 (R = SiMe 3, CHMe 2), to yield the cyclohexyl hydride complexes have been measured. Comparison of these values to the corresponding tetrahydroindenyl derivatives (η 5-C 9H 9-1,3-R 2) 2ZrH 2 reveals significantly faster insertion reactions for the bis(indenyl) compounds. Accordingly, primarily σ-donating ligands such as PMe 3, PEt 3, and tetrahydrothiophene coordinate to (η 5-C 9H 5-1,3-(CHMe 2) 2) 2ZrH 2 to form (η 5-C 9H 5-1,3-(CHMe 2) 2) 2ZrH 2(L) compounds, one of which (L = PMe 3) 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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The "indenyl effect" in zirconocene dihydride chemistry

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