Computational evidence that the inverse kinetic isotope effect for reductive elimination of methane from a tungstenocene methyl-hydride complex is associated with the inverse equilibrium isotope effect for formation of a sigma-complex intermediate.

Calculations on [H2Si(C5H4)2]W(Me)H demonstrate that the interconversion between [H2Si(C5H4)2]W(Me)H and the sigma-complex [H2Si(C5H4)2]W(sigma-HMe) is characterized by normal kinetic isotope effects for both reductive coupling and oxidative cleavage; the equilibrium isotope effect, however, is inverse and is the origin of the inverse kinetic isotope effect for the overall reductive elimination of methane.