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, nBu, Ph, iPr,
NMe2) were coordinated to [Nd­(TriNOx)]
(TriNOx3– = ([(2-tBuNO)­C6H4CH2]3N)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.