Oxidative Addition of Haloheteroarenes to Palladium(0): Concerted versus SN Ar-Type Mechanism

Bert U W Maes; Stefan Verbeeck; Tom Verhelst; Audrey Ekomié; Niklas von Wolff; Guillaume Lefèvre; Emily A Mitchell; Anny Jutand

doi:10.1002/chem.201406210

Oxidative Addition of Haloheteroarenes to Palladium(0): Concerted versus SN Ar-Type Mechanism

Chemistry. 2015 May 18;21(21):7858-65. doi: 10.1002/chem.201406210. Epub 2015 Apr 8.

Authors

Bert U W Maes¹, Stefan Verbeeck, Tom Verhelst, Audrey Ekomié, Niklas von Wolff, Guillaume Lefèvre, Emily A Mitchell, Anny Jutand

Affiliation

¹ Organic Synthesis, Department of Chemistry, University of Antwerp, 2020 Antwerpen (Belgium). bert.maes@uantwerpen.be.

PMID: 25858175
DOI: 10.1002/chem.201406210

Abstract

The kinetics of the oxidative additions of haloheteroarenes HetX (X=I, Br, Cl) to [Pd(0) (PPh3 )2 ] (generated from [Pd(0) (PPh3 )4 ]) have been investigated in THF and DMF and the rate constants have been determined. In contrast to the generally accepted concerted mechanism, Hammett plots obtained for substituted 2-halopyridines and solvent effects reveal a reaction mechanism dependent on the halide X of HetX: an unprecedented SN Ar-type mechanism for X=Br or Cl and a classical concerted mechanism for X=I. These results are supported by DFT studies.

Keywords: arenes; homogeneous catalysis; kinetics; oxidative addition; reaction mechanisms.