Neodymium(III) Complexes of Dialkylphosphoric and Dialkylphosphonic Acids Relevant to Liquid–Liquid Extraction Systems

Abstract

The complexes formed during the extraction of neodymium(III) into hydrophobic solvents containing acidic organophosphorus extractants were probed by single-crystal X-ray diffractometry, visible spectrophotometry, and Fourier-transform infrared spectroscopy. The crystal structure of the compound Nd(DMP)3 (1, DMP = dimethyl phosphate) revealed a polymeric arrangement in which each Nd(III) center is surrounded by six DMP oxygen atoms in a pseudo-octahedral environment. Adjacent Nd(III) ions are bridged by (MeO)2POO(-) anions, forming the polymeric network. The diffuse reflectance visible spectrum of 1 is nearly identical to that of the solid that is formed when an n-dodecane solution of di(2-ethylhexyl)phosphoric acid (HA) is saturated with Nd(III), indicating a similar coordination environment around the Nd center in the NdA3 solid. The visible spectrum of the HA solution fully loaded with Nd(III) is very similar to that of the NdA3 material, both displaying hypersensitive bands characteristic of an pseudo-octahedral coordination environment around Nd. These spectral characteristics persisted across a wide range of organic Nd concentrations, suggesting that the pseudo-octahedral coordination environment is maintained from dilute to saturated conditions.

Isomorphous rare-earth tris[bis(2,6-diisopropylphenyl) phosphate] complexes and their catalytic properties in 1,3-diene polymerization and in the inhibited oxidation of polydimethylsiloxane

“…Established structures of bi-and mononuclear complexes are particularly rare. The crystal structures of tris(dialkyl/diaryl phosphate) complexes of rare earths are mainly coordination polymers bearing dimethyl/ diethyl phosphate ligands [see the Cambridge Structural Database (CSD), Version 5.38 with updates, May 2017; Groom et al, 2016]: [Ln{(MeO) 2 PO 2 } 3 ] 1 [Ln = La (CSD refcode HEBDEX; Guang-Fu et al, 1994), Nd (LAHREU; Lumetta et al, 2016), Sm (JEVVOV; Li et al, 1989) and Eu (KIXGON;Li et al, 1991)], [La{(MeO) 2 PO 2 } 3 (H 2 O)] 1 (JIGVEA; Liu et al, 1990) and [Ln{(EtO) 2 PO 2 } 3 ] 1 {Ln = Nd [BOVREJ (Lebedev et al, 1982) and BOVREJ01 (Rafizadeh et al, 2009)], Ce [JOGJEU (Han et al, 1990) and KETWUC (Amani et al, 2006)] and Pr (JOGJIY; Han et al, 1990)}. The coordination polymer structures of the tris(dialkyl phosphate) complexes usually lead to poorer catalytic activity.…”

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

“…As a rule, such ligands are not suitable for collecting crystallography data, because long alkyl groups decrease the crystallinity of metal complexes. Homologous ligands with shorter alkyl groups are used instead for crystallography research, since it is argued that they form complexes with an equal coordination environment of a metal. For instance, different‐length alkyl groups in N ‐tetrasubstituted methylmalonamide, ethylmalonamide, and butylmalonamide do not change the coordination environment of a lanthanum(III) central ion in the respective nitrato crystal complexes.…”

Literature Review: Crud Formation at the Liquid/Liquid Interface of TBP-Based Solvent-Extraction Processes

“…Signs of incipient white interfacial crud appear at the meniscus with 30 millimolar (mM) NdCl 3 ; the crud quantities increase with further increase in NdCl 3 concentration. Energy dispersive spectrometric analyses showed the crud contained neodymium, carbon, oxygen, and phosphorus, thus giving good evidence that the crud was, or derived from, the neodymium solvate (Lumetta et al 2016). An image of bentonite, a water-swelling clay, added as a crud surrogate to an equal volume (1liter, total) test of 2 M HNO 3 and 30 vol% TBP in n-dodecane, is given in Figure 2 of Zimmer and Borchardt (1986).…”