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Keywords:

  • computer chemistry;
  • ligand effects;
  • palladium;
  • phosphane ligands;
  • reductive elimination

Abstract

The reductive eliminations of ArCF3 from PdII complexes bearing small- and large-bite-angle phosphane ligands have been investigated using computational methods. QM/QM′ and QM/MM studies were applied and complemented with CP2 K molecular dynamics investigations. The ligand substituents were varied and a decomposition analysis was performed to allow us to gain insights into the steric and electronic properties of the ligands. The greater reactivity of Xantphos-derived (Xantphos=4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) complexes in the reductive elimination of ArCF3 is primarily due to the lower repulsive effect of the phoshine substituents in the transition state than in the reactant complex, combined with the increased electronic interaction in the transition state. For DPPE (1,2-bis(diphenylphosphino)ethane), the steric effect of the ligand substituents is greater in the transition state, leading to a higher reaction barrier overall for reductive elimination. There is no direct correlation of the reactivity with the bite angle of the reactant complexes. Only for complexes with large ligand substituents may the bite angle of the Pd complexes be used as a guide for reactivity.