EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh, EH9 3FJ, UK.
Johnson Matthey Technology Centre Sonning Common, Reading, RG4 9NH, UK.
Chemistry. 2021 Jun 16;27(34):8714-8722. doi: 10.1002/chem.202100630. Epub 2021 May 24.
The separation and isolation of many of the platinum group metals (PGMs) is currently achieved commercially using solvent extraction processes. The extraction of rhodium is problematic however, as a variety of complexes of the form [RhCl (H O) ] are found in hydrochloric acid, making it difficult to design a reagent that can extract all the rhodium. In this work, the synergistic combination of a primary amine (2-ethylhexylamine, L ) with a primary amide (3,5,5-trimethylhexanamide, L ) is shown to extract over 85 % of rhodium from 4 M hydrochloric acid. Two rhodium complexes are shown to reside in the organic phase, the ion-pair [HL ] [RhCl ] and the amide complex [HL ] [RhCl (L )]; in the latter complex, the amide is tautomerized to its enol form and coordinated to the rhodium centre through the nitrogen atom. This insight highlights the need for ligands that target specific metal complexes in the aqueous phase and provides an efficient synergistic solution for the solvent extraction of rhodium.
目前，许多铂族金属（PGM）的分离和隔离都是通过溶剂萃取工艺在商业上实现的。然而，铑的萃取是有问题的，因为在盐酸中存在各种形式为[RhCl（H2O）]的络合物，这使得难以设计一种能够萃取所有铑的试剂。在这项工作中，证明了伯胺（2-乙基己胺，L）与伯酰胺（3,5,5-三甲基己酰胺，L）的协同组合可以从 4M 盐酸中萃取超过 85%的铑。结果表明有两种铑络合物存在于有机相中，离子对[HL] [RhCl]和酰胺络合物[HL] [RhCl（L）]；在后一种络合物中，酰胺通过氮原子发生互变异构转化为其烯醇形式并与铑中心配位。这一见解强调了需要针对水相中的特定金属络合物的配体，并为铑的溶剂萃取提供了有效的协同解决方案。
