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Alkylaluminum-complexed zirconocene hydrides : identification of hydride-bridged species by NMR spectroscopy

Alkylaluminum-complexed zirconocene hydrides : identification of hydride-bridged species by NMR spectroscopy

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BALDWIN, Steven M., John E. BERCAW, Hans-Herbert BRINTZINGER, 2008. Alkylaluminum-complexed zirconocene hydrides : identification of hydride-bridged species by NMR spectroscopy. In: Journal of the American Chemical Society. 130(51), pp. 17423-17433. ISSN 0002-7863. eISSN 1520-5126. Available under: doi: 10.1021/ja8054723

@article{Baldwin2008-12-24Alkyl-23662, title={Alkylaluminum-complexed zirconocene hydrides : identification of hydride-bridged species by NMR spectroscopy}, year={2008}, doi={10.1021/ja8054723}, number={51}, volume={130}, issn={0002-7863}, journal={Journal of the American Chemical Society}, pages={17423--17433}, author={Baldwin, Steven M. and Bercaw, John E. and Brintzinger, Hans-Herbert} }

Brintzinger, Hans-Herbert Baldwin, Steven M. Reactions of unbridged zirconocene dichlorides, (R<sub>n</sub>C<sub>5</sub>H<sub>5−n</sub>)<sub>2</sub>ZrCl<sub>2</sub> (n = 0, 1, or 2), with diisobutylaluminum hydride (HAl<sup>i</sup>Bu<sub>2</sub>) result in the formation of tetranuclear trihydride clusters of the type (R<sub>n</sub>C<sub>5</sub>H<sub>5−n</sub>)<sub>2</sub>Zr(μ-H)<sub>3</sub>(Al<sup>i</sup>Bu<sub>2</sub>)<sub>3</sub>(μ-Cl)<sub>2</sub>, which contain three [Al<sup>i</sup>Bu<sub>2</sub>] units. Ring-bridged ansa-zirconocene dichlorides, Me<sub>2</sub>E(R<sub>n</sub>C<sub>5</sub>H<sub>4−n</sub>)<sub>2</sub>ZrCl<sub>2</sub> with E = C or Si, on the other hand, are found to form binuclear dihydride complexes of the type Me<sub>2</sub>E(R<sub>n</sub>C<sub>5</sub>H<sub>4−n</sub>)<sub>2</sub>Zr(Cl)(μ-H)<sub>2</sub>Al<sup>i</sup>Bu<sub>2</sub> with only one [Al<sup>i</sup>Bu<sub>2</sub>] unit. The dichotomy between unbridged and bridged zirconocene derivatives with regard to tetranuclear versus binuclear product formation is proposed to be connected to different degrees of rotational freedom of their C<sub>5</sub>-ring ligands. Alkylaluminum-complexed zirconocene dihydrides, previously observed in zirconocene-based precatalyst systems activated by methylalumoxane (MAO) upon addition of HAl<sup>i</sup>Bu<sub>2</sub> or Al<sup>i</sup>Bu<sub>3</sub>, are proposed to be species of the type Me<sub>2</sub>Si(ind)<sub>2</sub>Zr(Me)(μ-H)<sub>2</sub>Al<sup>i</sup>Bu<sub>2</sub>, stabilized by interaction of their terminal Me group with a Lewis acidic site of MAO. Bercaw, John E. 2008-12-24 Alkylaluminum-complexed zirconocene hydrides : identification of hydride-bridged species by NMR spectroscopy Bercaw, John E. eng Journal of American Chemical Society ; 130 (2008), 51. - S. 17423-17433 deposit-license 2013-06-19T14:22:29Z Baldwin, Steven M. Brintzinger, Hans-Herbert 2013-06-19T14:22:29Z

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