Mechanism of the η3-η1-η3 Isomerization in Allylpalladium Complexes: Solvent Coordination, Ligand, and Substituent Effects
2001 (English)In: Organometallics, ISSN 0276-7333, E-ISSN 1520-6041, Vol. 20, 5464-5471 p.Article in journal (Refereed) Published
The mechanism of the η3 → η1 → η3 isomerization of (η3-allyl)palladium complexes occurring as catalytic intermediates in important synthetic transformations has been studied by applying density functional theory at the B3PW91(DZ+P) level. It was found that under catalytic conditions, in the condensed phase, the isomerization process involves tetracoordinated (η1-allyl)palladium intermediates. In these intermediates a solvent molecule or another ancillary ligand coordinates to palladium. The stability of the (η1-allyl)palladium intermediates critically depends on the electronic effects and on the coordination ability of the solvent molecules and the ancillary ligands. The theoretical calculations indicate a dσ → π* type hyperconjugative interaction occurring in the η1-allyl moiety of the intermediary complexes. These hyperconjugative interactions influence the structure of the complexes and the activation barrier to rotation through the C1−C2 bond. Alkyl substitution of the metalated carbon leads to destabilization of the (η1-allyl)palladium complexes, which increases the activation energy of the syn/anti isomerization process. This substituent effect arises from a dual steric and electronic destabilizing interaction between the methyl substituent and the metal atom.
Place, publisher, year, edition, pages
2001. Vol. 20, 5464-5471 p.
IdentifiersURN: urn:nbn:se:su:diva-22713DOI: 10.1021/om010793dOAI: oai:DiVA.org:su-22713DiVA: diva2:189306
Part of urn:nbn:se:su:diva-1052004-04-222004-04-222010-08-02Bibliographically approved