Does the Preferred Mechanism of a Catalytic Transformation Depend on the Density Functional? Ethylene Hydrosilylation by a Metal Complex as a Case Study

Abstract

For an extended set of density functionals (BP86, BLYP, B3LYP, B3PW91, PBE, PBE0, mPWPW, MPW1K, M06-L, M06, MPW3LYP, TPSS) we explored the key steps of four mechanisms of ethylene hydrosilylation (Glaser–Tilley, Chalk–Harrod, modified Chalk–Harrod, and σ-bond metathesis) by a Rh­(I) catalyst, previously studied at the B3LYP level. The Chalk–Harrod and the σ-bond metathesis mechanisms were determined to be preferred for all these functionals. The preference among these two mechanisms and the corresponding highest relative barriers (6.6–11.8 kcal·mol^–1) depend on the functional. To a certain extent, the differences in the description of the reaction can be traced back to the correlation part of the functionals. For the most notable functional-dependent barrier, similar values were calculated when the LYP correlation functional and the functionals M06-L and M06 were employed, but distinctively different values resulted from the functionals PBE, PW91, and TPSS