Does the
Preferred Mechanism of a Catalytic Transformation
Depend on the Density Functional? Ethylene Hydrosilylation by a Metal
Complex as a Case Study
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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<sup>–1</sup>) 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