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Mechanisms of dihydrogen activation by zirconocene alkyl and hydride derivatives : A molecular orbital analysis of a 'direct hydrogen transfer' reaction mode

Mechanisms of dihydrogen activation by zirconocene alkyl and hydride derivatives : A molecular orbital analysis of a 'direct hydrogen transfer' reaction mode

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BRINTZINGER, Hans-Herbert, 1979. Mechanisms of dihydrogen activation by zirconocene alkyl and hydride derivatives : A molecular orbital analysis of a 'direct hydrogen transfer' reaction mode. In: Journal of Organometallic Chemistry. 171(3), pp. 337-344. ISSN 0022-328X

@article{Brintzinger1979Mecha-23914, title={Mechanisms of dihydrogen activation by zirconocene alkyl and hydride derivatives : A molecular orbital analysis of a 'direct hydrogen transfer' reaction mode}, year={1979}, doi={10.1016/S0022-328X(00)82657-1}, number={3}, volume={171}, issn={0022-328X}, journal={Journal of Organometallic Chemistry}, pages={337--344}, author={Brintzinger, Hans-Herbert} }

Mechanisms of dihydrogen activation by zirconocene alkyl and hydride derivatives : A molecular orbital analysis of a 'direct hydrogen transfer' reaction mode eng Journal of Organometallic Chemistry ; 171 (1979), 3. - S. 337-344 Brintzinger, Hans-Herbert 2013-07-26T07:28:49Z deposit-license The formation of an adduct between a dihydrogen and a d<sup>0</sup> species of the general type (C<sub>5</sub>R<sub>5</sub>)<sub>2</sub>Zr(R′)<sub>2</sub> (R,R′ = H or CH<sub>3</sub>) is suggested to involve a process analogous to that in CO adduct formation, and is studied by an extended Hückel molecular orbital analysis. Back donation into σ* H<sub>2</sub> orbitals arises from high-lying M-R′ bonding orbitals and determines the stability of alternative adduct geometries. Two isomeric H<sub>2</sub> adducts can interconvert by an intramolecular hydrogen shift. With D<sub>2</sub>, this reaction sequence leads to hydrogen isotope exchange. The transition state of this reaction mode contains a three-centre (H⋯H⋯H)<sup>−</sup> ligand configuration with bonding properties similar to those of an allyl ligand; it does not involve an oxidative change in the charge on the metal nor generation of a positively charged, protonic hydrogen species by heterolytic H<sub>2</sub> cleavage. The term ‘direct hydrogen transfer’ is proposed for this type of elementary reaction. For H<sub>2</sub>-induced alkane elimination from group IV metallocene alkyl derivatives, an analogous reaction mechanism, involving formation of a H<sub>2</sub> adduct and a subsequent intramolecular hydrogen shift toward the alkyl ligand, is predicted to proceed with moderate activation energies. 2013-07-26T07:28:49Z Brintzinger, Hans-Herbert 1979

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