Car-Parrinello molecular dynamics study of CuF, AgF, CuPF 6 and AgPF 6 in acetonitrile solvent and Cluster-Continuum calculation of the solvation free energy of Cu(I), Ag(I) and Li(I)

The CuF species in acetonitrile solution is a potential intermediate in copper catalyzed fluorination. In the process, different species such as Cu +, Ag +, CuF and AgF could be involved. The objective of this work is to provide relevant data on the structure of these species in solution phase, as well as the corresponding solvation thermodynamics to better understand the equilibrium for formation of CuF. To attain this goal, ab initio Car-Parrinello molecular dynamics method and cluster-continuum quasichemical approach were used. It was found that Cu + and Ag + ions are tetracoordinated by acetonitrile molecules, being possible to observe the release of one coordinated acetonitrile to the solution to form a tricoordinate structure, suggesting a dissociative mechanism for ligand exchange. The CuF species was found to form a predominant tricoordinate complex, with copper coordinated to two acetonitrile molecules. The AgF species have presented more labile ligand feature, with silver ion interconverting between bi- and tricoordinate structure, involving coordination to one and two acetonitrile molecules, respectively. The solvation free energy calculated for Cu + and Ag + are in good agreement with available experimental data. The present results indicate that CuF can be easily formed from dissolved AgF and Cu + species in acetonitrile solution. Consequently, CuF could play an important role in copper catalyzed fluorination.