Speciation of Chlorido Complexes of Rhodium(III) in Ethylene Glycol

The speciation of rhodium(III) chlorido complexes was investigated in ethylene glycol, in the presence and absence of lithium chloride, by rhodium-103 NMR and EXAFS spectroscopy. All major rhodium(III) complexes were identified based on their species-specific isotopologue and isotopomer patterns. EXAFS analysis confirmed the results deduced from the rhodium-103 NMR spectra. The strikingly different shifting behavior observed with increasing lithium chloride concentration was linked to the established behavior of rhodium(III) in NMR spectroscopy. Density functional theory (DFT) calculations were performed to elucidate the underlying factors of the observed trends, highlighting their potential as an additional tool for the speciation of rhodium(III) complexes, even for NMR spectra with a low signal-to-noise ratio. These results give a deeper insight into the speciation of rhodium(III) in a nonaqueous environment and contribute to the fundamental basis needed to understand the extraction behavior of rhodium(III) in nonaqueous solvent extraction.