Factors Controlling β-Elimination Reactions in Group 10 Metal Complexes

Abstract

Trends in reactivity of β-chloride and β-hydride elimination reactions involving Group 10 transition-metal complexes have been computationally explored and analyzed in detail by DFT. These reactions do not require the initial formation of a vacant coordination site; they proceed concertedly without a prior ligand-dissociation step. Whereas β-chloride elimination is associated with relatively moderate activation barriers, the high barriers calculated for analogous β-hydride eliminations suggest that the latter process is unfeasible for this type of compounds. This differential behavior is analyzed within the activation strain model, which provides quantitative insight into the physical factors controlling these β-elimination reactions. The effects of the nature of the Group 10 transition metal (Ni, Pd, Pt), as well as the substituents attached to the β-eliminating fragment (R2C CR2X; R, X=H, Cl) on the transformation have also been considered and are rationalized herein. Dramatic differences: β-Chloride elimination reactions involving Group 10 metal polymerization catalysts (see scheme) do not require initial formation of a vacant coordination site and proceed with relatively moderate activation barriers. In sharp contrast, the computed barriers for the analogous β-hydride eliminations are prohibitively high.