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.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry