Electronic Asymmetry of an Annelated Pyridyl-Mesoionic Carbene Scaffold: Application in Pd(II)-Catalyzed Wacker-Type Oxidation of Olefins

Sayantani Saha, Suman Yadav, Noor U.Din Reshi, Indranil Dutta, Sooraj Kunnikuruvan, Jitendra K. Bera

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

The two donor modules of an annelated pyridyl-mesoionic carbene ligand (aPmic) have different σ- and π-bonding characteristics leading to its electronic asymmetry. A Pd(II) complex 1 featuring aPmic catalyzes the oxidation of a wide range of terminal olefins to the corresponding methyl ketones in good to excellent yields in acetonitrile. The catalytic reaction is proposed to proceed via syn-peroxypalladation and a subsequent rate-limiting 1,2-hydride shift, which is supported by kinetic studies. The electronic asymmetry of aPmic renders a well-defined coordination sphere at Pd. The favored arrangement of reactants on the metal center features an olefin trans to the pyridyl module and a tbutylperoxide trans to the carbene. This arrangement gains added stability by the π-delocalization paved by the compatible orbitals on Pd, the pyridyl module, and the olefin that is perpendicular to the Pd(aPmic) plane. The π-interactions are absent in an alternate arrangement wherein the olefin is trans to the carbene. Density functional theory studies reveal the matching orbital overlaps responsible for the preferred arrangement over the other. This work provides an orbital description for the electronic asymmetry of aPmic.

Original languageEnglish
Pages (from-to)11385-11393
Number of pages9
JournalACS Catalysis
Volume10
Issue number19
DOIs
StatePublished - 2 Oct 2020
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2020 American Chemical Society.

Keywords

  • Wacker-type oxidation
  • annelated carbenes
  • catalysis
  • electronically asymmetric ligands
  • mesoionic carbenes

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