Palladium-catalyzed activation of HnA–AHnbonds (AHn= CH3, NH2, OH, F)

Abstract

AbstractWe have quantum chemically studied activation of HnA–AHnbonds (AHn= CH3, NH2, OH, F) by PdLncatalysts with Ln= no ligand, PH3, (PH3)2, using relativistic density functional theory at ZORA-BLYP/TZ2P. The activation energy associated with the oxidative addition step decreases from H3C–CH3to H2N–NH2to HO–OH to F–F, where the activation of the F–F bond is barrierless. Activation strain and Kohn–Sham molecular orbital analyses reveal that the enhanced reactivity along this series of substrates originates from a combination of (i) reduced activation strain due to a weaker HnA–AHnbond; (ii) decreased Pauli repulsion as a result of a difference in steric shielding of the HnA–AHnbond; and (iii) enhanced backbonding interaction between the occupied 4datomic orbitals of the palladium catalyst and σ* acceptor orbital of the substrate.