Phosphoryl-Ligand Adducts of Rare Earth-TriNOx Complexes: Systematic Studies and Implications for Separations Chemistry

Phosphoryl ligands of the general formula O=PR3 (R = Me, OMe, Et, Bu-n, Ph, Pr-i, NMe2) were coordinated to [Nd(TriNOx)] (TriNOx(3-) = ([(2-(BuNO)-Bu-t)C6H4CH2](3)N)(3-)), and the resulting complexes were characterized. Solution equilibrium constants for each complex were determined, demonstrating a large range for phosphoryl ligands' Lewis basicity. Thermogravimetric analyses provided evidence for the qualitative thermodynamic preference of phosphoryl ligands for [Nd(TriNOx)] over the dysprosium analogue. These findings were exploited for the separation of binary mixtures of neodymium/dysprosium and lanthanum/neodymium. Implementation of phosphoryl ligands in the TriNOx separation system expands its scope and demonstrates a fundamentally different mode for separating rare-earth cations based on adducts with neutral donors.