Right Answer for the Right Reason? Benchmarking Protocols and Pitfalls on a Ru-Metathesis Example

A layered meta-benchmarking analysis was devised withthe aim ofillustrating how to produce an experimental/computational protocolfor the method selection and estimation of Gibbs energies of catalyticallyprominent reactions. Our test subject involved the active-latentequilibrium through the cis-trans isomerism of two metathesiscatalysts: mesitylene-Ru-SCF3-Cl and diisopropylphenyl-Ru-SCF3-Cl. The strategy was two-fold: first to perform a computationalbenchmark for the energies in the gas phase, followed by benchmarkingthe enthalpy and the Gibbs energy, including solvation and entropy,from experimental references. This wedding cake build-upof subsequent methods applied to our particular small test reactionindicates that: (1) DLPNO-CCSD(T)/CBS works well as a reference methodfor large systems. (2) Among several functionals & omega;B97XD andM06 were the most accurate. (3) Choosing between IEF-PCM and SMD solvationmodels turned out to be case dependent. (4) For the vibrational entropiccomponent, low-frequency vibrations often produce humungous errors,which can be improved by Cramer and Truhlar's or Grimme'smethods; however, their cut-off parameters had to be lowered fromtheir standard values. (5) Solvation methods are important for enthalpies,but they are inadequate for entropies. (6) All of these componentsare equally important for the accuracy of organometallic complexes'reactions. The only way to find the right method for the right reasonsis to be sure to match all of the Gibbs energy terms to benchmarkedexperimental and computational values.

Automated summary

A layered meta-benchmarking analysis was conducted to demonstrate a protocol for method selection and estimation of Gibbs energies of catalytically prominent reactions. The study focused on the active-latent equilibrium of two metathesis catalysts and utilized a computational benchmark for gas phase energies, followed by benchmarking enthalpy and Gibbs energy from experimental references. The results indicated the effectiveness of certain reference methods, the accuracy of specific functionals, and the importance of solvation models and entropy in the estimation of Gibbs energy.