Solvation of Metal Cations in Non-aqueous Liquids

The role that alkali cations in non-aqueous solvents play in organic reactions continues to be a topic of interest. In particular it has been observed that these cations can alter the stereoselectivity of organic reactions. Our interest is to first understand the nature of cation–ether complexes, then to investigate the role that the cation plays in the reaction. We have used the electronic structure techniques Hartree-Fock (HF), Second-order Møller-Plesset perturbation theory (MP2), and the Becke three-parameter exchange functional coupled with the nonlocal correlation functional of Lee, Yang, and Parr (B3LYP) to study the structure and properties of tetrahydrofuran (THF) and dimethyl ether (DME) solvation complexes with Li⁺, Na⁺, K⁺, Cu⁺, and MgCl⁺. The values calculated for DME complexes were compared with existing experimentally determined data. The B3LYP/6-31⁺G^? model chemistry was found to be the most accurate and efficient method of modeling the cation–DME molecular system. The energetic trends observed in the DME results were also observed in the THF data. Based on the accuracy of the calculations and the computational cost of the calculations, B3LYP was found to be the most desirable method of modeling these types of systems.