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

Area of Science:

• Computational Chemistry
• Catalysis
• Physical Chemistry

Background:

• Accurate Gibbs energy estimation is crucial for understanding and designing catalytic reactions.
• Metathesis catalysts involving ruthenium complexes are important in organic synthesis.
• Method selection for computational chemistry requires rigorous validation.

Purpose of the Study:

• To develop a protocol for selecting computational methods for Gibbs energy estimation.
• To benchmark computational methods against experimental data for catalytic reactions.
• To assess the accuracy of various computational approaches for organometallic complexes.

Main Methods:

• Layered meta-benchmarking analysis combining computational and experimental data.
• Gas-phase energy calculations using DLPNO-CCSD(T)/CBS as a reference.
• Benchmarking of enthalpy and Gibbs energy including solvation and entropy effects.
• Evaluation of different density functionals (e.g., ωB97XD, M06) and solvation models (IEF-PCM, SMD).

Main Results:

• DLPNO-CCSD(T)/CBS is a reliable reference for large systems.
• ωB97XD and M06 functionals demonstrated high accuracy.
• Solvation model choice is system-dependent; IEF-PCM and SMD performance varied.
• Low-frequency vibrations significantly impact entropy calculations, requiring adjusted cut-off parameters.
• Solvation is critical for enthalpy but insufficient for entropy accuracy.

Conclusions:

• Accurate Gibbs energy calculations for organometallic reactions necessitate the precise evaluation of all components: electronic energy, enthalpy, entropy, and solvation.
• A comprehensive, layered benchmarking approach is essential for method selection.
• Matching computational Gibbs energy terms with benchmarked experimental and computational values ensures reliable predictions.