Influence of geometry on reductive elimination of hydrocarbyl-palladium-carbene complexes

The influence of spectator ligand bite angle and the twist angle of the carbene on the reductive elimination of N-heterocyclic carbenes (NHCs) from palladium bis-phosphine complexes has been investigated using density functional theory. The spectator bite angle was found to have a significant influence on both the activation energy (E-act) and the enthalpy of reaction. Widening of the bite angle was found to lower E-act and increase the enthalpy of reaction. In contrast, rotation of the carbene with respect to the PdL2 plane was found to have little influence on E-act. At carbene twist angles approaching 0degrees however, relief of the increased steric strain provides a considerable driving force for the decomposition reaction.