Switchable Phase Behavior of [HBet][Tf2N]–H2O upon Neodymium Loading: Implications for Lanthanide Separations

Task-specific ionic liquids (TSILs) present an opportunity to replace traditional organic solvents for metal dissolution or separation. To date, a thorough investigation of the physical properties of biphasic TSIL–H2O systems and the effects of metal loading is lacking. In this work, the change in the liquid–liquid equilibrium of [HBet]­[Tf2N]–H2O upon the addition of Nd­(III) is investigated by cloud-point measurements. The addition of Nd(III), drops the upper critical solution temperature by over 20 °C. Further investigation of the [HBet]­[Tf2N]–Nd(III) system led to the formation of single crystals of [Nd2(H2O)8(μ2-Bet)2(μ3-Bet)2]­[(Cl)2(Tf2N)4] from the TSIL phase.