Free energy calculation of the effects of the fluorinated phosphorus ligands on the C-H and C-C reductive elimination from Pt(IV)

To gain insight into how fluorination of ligands alters the C-H and C-C reductive elimination from Pt(IV) octahedral complexes, metadynamics and static DFT calculations have been performed. We compare the C-H and C-C reductive elimination from Pt(IV) octahedral complexes L2Pt(CH3)3X (X = H or CH3, L2 diphosphine ligand, viz = model of dppe and dppbz ligand and its fluorinated versions). The use of metadynamics simulations is shown to be a powerful tool to describe the reactivity of organometallic compounds, and provide us with the activation free energy of the different processes involved in these reactions: ligand dissociation, C-C and C-H formation. The structural data for the complexes are compared and in the fluorinated complexes, the Pt-P distances are significantly shorter even if the Pt-P dissociation is less energetically demanding compared to the non-fluorinated complexes. The computed free activation energies from metadynamics calculations show that for C-H reductive eliminations direct mechanism and concerted mechanism can occur but the concerted pathway is more favorable. For the C-C reductive elimination, the dissociative pathway has been studied and the use of fluorinated complexes enhances the dissociation capability of the chelating ligand and so should improve the reactivity. We also report computed activation free energy with inclusion of the entropy effect for the dissociation of the diphosphine ligand, necessary step for the C-C reductive elimination.