Benchmarking of DFT methods using experimental free energies and volumes of activation for the cycloaddition of alkynes to cuboidal Mo3S4 clusters

Here, the kinetics of the concerted [3 + 2] cycloaddition reaction between the [Mo₃(μ₃-S)(μ-S)₃Cl₃(dmen)₃]⁺ (dmen = N,N′-dimethyl-ethylenediamine) ([ 1 ]⁺) cluster and various alkynes to form dithiolene derivatives is thoroughly studied, with measurements at different temperatures and pressures allowing the determination of the free energies and volumes of activation. These parameters, together with the available single-crystal X-ray diffraction structures, are used to test a number of commonly used density functional theory (DFT) methods from Jacob's ladder, as well as the effects associated with the size of the basis sets, the way in which solvent effects are taken into account, or the inclusion of dispersion effects. Overall, a protocol that leads to average deviations between experimental and computed ΔV^‡ and ΔG^‡ values similar to the uncertainty of the experimental measurements is obtained.