Coordination of Trivalent Lanthanides with Bismalonamide Ligands: Implications for Liquid–Liquid Extraction

Tyumentsev, Mikhail S.; Foreman, Mark; Slawin, Alexandra M. Z.; Cordes, David B.; Savolainen, Otto; Ylmén, Rikard; Steenari, Britt‐Marie; Ekberg, Christian

doi:10.1002/ejic.201700801

Cited by 5 publications

(1 citation statement)

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“…A valuable approach for the recovery of REEs is the use of multifunctional ligands, which can selectively separate lanthanide − or actinide cations − or a mixture of both. − These ligands were specifically engineered to express different metal-to-ligand interaction geometries and strengths for a specific metal–ligand entity. In a slightly different approach, Bogart et al showed that dysprosium and neodymium preferentially formed monomeric and dimeric entities, respectively, when using a polydentate N′N3O3 donor ligand.…”

Section: Introductionmentioning

confidence: 99%

Semirigid Ligands Enhance Different Coordination Behavior of Nd and Dy Relevant to Their Separation and Recovery in a Non-aqueous Environment

et al. 2022

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Rare-earth elements are widely used in high-end technologies, the production of permanent magnets (PMs) being one of the sectors with the greatest current demand and likely greater future demand. The combination of Nd and Dy in NdFeB PMs enhances their magnetic properties but makes their recycling more challenging. Due to the similar chemical properties of Nd and Dy, their separation is expensive and currently limited to the small scale. It is therefore crucially important to devise efficient and selective methods that can recover and then reuse those critical metals. To address these issues, a series of heptadentate Trensalbased ligands were used for the complexation of Dy 3+ and Nd 3+ ions, with the goal of indicating the role of coordination and solubility equilibria in the selective precipitation of Ln 3+ −metal complexes from multimetal non-water solutions. Specifically, for a 1:1 Nd/Dy mixture, a selective and fast precipitation of the Dy complex occurred in acetone with the Trensal p-OMe ligand at room temperature, with a concomitant enrichment of Nd in the solution phase. In acetone, complexes of Nd and Dy with Trensal p-OMe were characterized by very similar formation constants of 7.0(2) and 7.3(2), respectively. From the structural analysis of an array of Dy and Nd complexes with Trensal R ligands, we showed that Dy invariably provided complexes with coordination number (cn) of 7, whereas the larger Nd experienced an expansion of the coordination sphere by recruiting additional solvent molecules and giving a cn of >7. The significant structural differences have been identified as the main premises upon which a suitable separation strategy can be devised with these kind of ligands, as well as other preorganized polydentate ligands that can exploit the small differences in Ln 3+ coordination requirements.

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