State of rhodium(III) in sulfuric acid solutions

The formation of rhodium(III) sulfate complexes under moderately rigorous temperature conditions was studied by ¹⁰³Rh and ¹⁷O NMR spectroscopy. The complexes [Rh₂(μ-SO₄)₂(H₂O)₈]²⁺, [Rh₂(^*μ-SO₄)(H₂O)₈]⁴⁺, and [Rh₃(μ-SO₄)₃(μ-OH)(H₂O)₁₀]²⁺ were found to be the most stable species in aged solutions.     

Extraction of rhodium(III) with sulfoxides from hydrochloric acid solutions

Extraction of rhodium(III) from hydrochloric acid solutions with dihexyl sulfoxide (DHSO) and with petroleum sulfoxides (PSOs) was studied, and the optimal conditions for its recovery were found. At a phase contact time of up to 0.5 h, the extraction of rhodium(III) with sulfoxides occurred mainly by an ionassociation scenario. If the phase contact time exceeds 0.5 h, a mixed extraction scenario predominated to form the extracted complexes (L · H⁺) · [RhCl₄L₂]-(DHSO)_o and PSO (LH⁺) · [RhCl₄(H₂O) · L]⁻. The protonation of the extraction agents occurred at the donor oxygen atoms of the sulfoxide group. When rhodium was extracted with PSOs, the coordination of the extractant molecule in the inner coordination sphere of the acido complex to the metal ion occurred through the donor sulfur atom of the sulfoxide group, while with the use of DHSO, through the donor atoms of sulfur and oxygen of the sulfoxide group. Electronic, ¹H NMR, and IR spectroscopy and elemental analysis were used to determine the composition of the extracted compounds and suggest their structure.     

Extraction of rhodium(III) with petroleum sulfoxides from hydrochloric acid solutions

Extraction of rhodium(III) from hydrochloric acid solutions with petroleum sulfoxides was studied. The optimal conditions of its recovery were found. The composition and structure of the compound being extracted was determined by electronic absorption, ¹H NMR, and IR spectroscopies and elemental analysis.     

Cyclometalated rhodium(III) complex with phen-dione ligand

The novel cyclometalated Rh(III) complex, [Rh(phpy-κ²N,C^2′)₂(phen-dione)]PF₆, where phpy-κ²N,C^2′ is pyridine-2-yl-2-phenyl and phen-dione is 1,10-phenanthroline-5,6-dione has been prepared and characterized by elemental analysis, IR, ¹H NMR, and electronic absorption spectroscopies, cyclic voltammetry, and X-ray crystallography. The crystal structure of [Rh(phpy-κ²N,C^2′)₂(phen-dione)]PF₆·CH₃CN shows that the coordination geometry around the Rh(III) is a distorted octahedron, with bite angles of 76.13°-81.09° for all three bidentate ligands.     

Liquid-liquid extraction of rhodium(III) from hydrochloric acid solutions with 1,2,4-triazole derivative

Liquid-liquid extraction of rhodium(III) from hydrochloric acid solutions with a 1,2,4-triazole derivative was studied. Optimal conditions for its recovery were found. Rhodium(III) was shown to be recovered in extraction system by ion-exchange reaction at the time of phase contact not longer than 5 min. When phase contact time increased, rhodium(III) is extracted by a mixed mechanism with simultaneous insertion of two extractant molecules into the inner coordination sphere of rhodium(III) ion. Composition of coordination species of recovered compounds was established by electronic, IR, ¹H and ¹³C NMR spectroscopy and functional analysis, the structure of the coordination species is proposed.     

Separation of rhodium from iridium with sodium borohydride and standardization of rhodium(III) solutions

Of the platinum group metal separations, that of rhodium from iridium is the most difficult. The existing gravimetric methods are too lengthy or make use of organic reagents which ultimately need to be removed before iridium can be determined. The proposed method of separation is rapid, needs no pH control, and easy to carry out. Rh(III) ions are quantitatively reduced to Rh(0) by the action of aqueous sodium borohydride. The separation is best achieved in perchlorate medium in the presence of hydroxylamine. The separation is dependent on the concentration ratio of iridium to rhodium; if this is high, some iridium is co-precipitated; if low, the rhodium obtained is free from even spectrographic traces of iridium. A new method for standardization of Rh(III) solutions with sodium borohydride is proposed.     

Osazone anion radical complex of rhodium(III)

One electron paramagnetic parent osazone complex of rhodium of type trans-Rh(L(NHPh)H(2))(PPh(3))(2)Cl(2) (1), defined as an osazone anion radical complex of rhodium(III), trans-Rh(III)(L(NHPh)H(2)(?-))(PPh(3))(2)Cl(2), 1((t-RhL?)), with a minor contribution (～2%) of rhodium(II) electromer, trans-Rh(II)(L(NHPh)H(2))(PPh(3))(2)Cl(2), 1((t-Rh?L)), and their nonradical congener, trans-[Rh(III)(L(NHPh)H(2))(PPh(3))(2)Cl(2)]I(3) ([t-1](+)I(3)(-)), have been isolated and are substantiated by spectra, bond parameters, and DFT calculations on equivalent soft complexes [Rh(L(NHPh)H(2))(PMe(3))(2)Cl(2)] (3) and [Rh(L(NHPh)H(2))(PMe(3))(2)Cl(2)](+) (3(+)). 1 is not stable in solution and decomposes to [t-1](+) and a new rhodium(I) osazone complex, [Rh(I)(L(NHPh)H(2))(PPh(3))Cl] (2). 1 absorbs strongly at 351 nm due to MLCT and LLCT, while [t-1](+) and 2 absorb moderately in the range of 300-450 nm, respectively, due to LMCT and MLCT elucidated by TD-DFT calculations on 3((t-RhL?)), [t-3](+), and Rh(I)(L(NHPh)H(2))(PMe(3))Cl (4). EPR spectra of solids at 295 and 77 K, and dichloromethane-toluene frozen glass at 77 K of 1 are similar with g = 1.991, while g = 2.002 for the solid at 25 K. The EPR signal of 1 in dichloromethane solution is weaker (g = 1.992). In cyclic voltammetry, 1 displays two irreversible one electron transfer waves at +0.13 and -1.22 V, with respect to Fc(+)/Fc coupling, due to oxidation of 1((t-RhL?)) to [t-1](+) at the anode and reduction of rhodium(III) to rhodium(II), i.e., [t-1](+) to electromeric 1((t-Rh?L)) at the cathode.     

Photochemistry of the iron(III) complex with pyruvic acid in aqueous solutions

Photochemistry of the 1: 1 Fe^pIII complex with pyruvic acid (PyrH) in aqueous solutions was studied by stationary photolysis and nanosecond laser flash photolysis with the excitation by the 3rd harmonics of an Nd:YAG laser. The quantum yield of [FeIIIPyr]2+ under the excitation at 355 nm is 1.0±0.1 and 0.46±0.05 in the absence and in the presence of dissolved oxygen, respectively. In experiments on laser flash photolysis, a weak intermediate absorption in the region 580–720 nm was found. The absorption was ascribed to the [FeII…MeC(O)COO•]^p2+ radical complex. Laser flash photolysis of [FePyr]^p2+ in the presence of methyl viologen dications (MV^p2+) resulted in the formation of the MV•+ radical cations. The proposed reaction mechanism includes the inner-sphere electron transfer in the light-excited complex accompanied by the formation of the [Fe^pII…MeC(O)COO•]^p2+ radical complex followed by its transformation into the reaction products.     

Influence ofpH and concentration of complexing agents on fluorescence of europium (III) ethylenediaminetetraacetic acid and europium (III) nitrilotriacetic acid complexes in aqueous solutions

The fluorescence of aqueous solutions of Eu(III) complexes withEDTA andNTA has been investigated. Intensities of the fluorescence bands have been measured as a function of complexone concentrations in the solutions and thepH. The results are interpreted in terms of the different forms of Eu(III) complexes and their relative stabilities.

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Einfluß vonpH und Konzentration der Komplexbildner auf die Fluoreszenz der Komplexe des Europium (III) mit Ethylendiamintetraessigsäure und Nitrilotriessigsäure in wäßrigen Lösungen

Zusammenfassung Die Fluoreszenz von wäßrigen Lösungen der Komplexe des Europium(III) mit Ethylendiamintetraessigsäure und Nitrilotriessigsäure wurde untersucht. Die Intensitäten der Fluoreszenzbanden in Abhängigkeit vonpH und Konzentration der Komplexbildner wurden auf der Basis vorkommender Komplexgeometrien und deren Stabilitäten interpretiert.

     

Extraction of rhodium(III) by a bisacylated diethylenetriamine derivative from hydrochloric acid solutions

The extraction of rhodium(III) with a bisacylated diethylenetriamine derivative from hydrochloric acid solutions was studied. Optimum conditions for rhodium(III) extraction were determined. It was found that, at a contact time to 10 min, the extraction occurred by an ion-association mechanism. At a contact time longer than 10 min, rhodium(III) was extracted by a mixed mechanism with the insertion of an extractant molecule into the inner coordination sphere of the rhodium(III) ion. The composition of the extracted compound was determined using electronic, ¹H and ¹³C NMR, and IR spectroscopy and elemental analysis, and the structure of this compound was proposed.     

Extraction of rhodium(III) by 1,3-diamyl-2-imidazolidinethione from hydrochloric acid solutions

The extraction of rhodium(III) with 1,3-diamyl-2-imidazolidinethione from hydrochloric acid solutions was studied. Optimum conditions for rhodium(III) extraction were determined. It was found that rhodium(III) was extracted from a 0.5 M solution of HCl at a phase contact time of 3 h by a coordination mechanism. The composition of the extracted compound was determined using electronic, ¹H and ¹³C NMR, and IR spectroscopy and elemental analysis. It was demonstrated that the extracting agent coordinated to the rhodium(III) ion through the sulfur atom.     

Photochemical behaviour of the Nd(III) and Ho(III) complexes of ethylenediaminetetraacetic acid

The photochemical decomposition of Nd³⁺/EDTA and Ho³⁺/EDTA has been carried out at 300 nm, and followed by changes within the hypersensitive absorption transitions of these ions. It was found that a single decarboxylation of the EDTA ligand occurred, and CO₂ gas was evolved. The reaction terminates after approx. 1 mol of CO₂ per mole of EDTA is produced, since the photoproduct absorbs strongly at 300 nm. Initial quantum yields were found to vary with pH, but averaged between 0.1 and 0.5 mol/Einstein.     

Analysis of nitrilotriacetic acid (NTA), ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) in water, particularly waste water

Summary Two chromatographic techniques can be considered for the detection of the complexing agents NTA, EDTA and DTPA in water: gas chromatography (GC) and liquid chromatography (HPLC). GC is capable of detecting all three compounds in concentrations of as little as 0.001 mg/l. However, this requires a complex and time-consuming sample preparation (enrichment, derivatization). HPLC represents a possible alternative for detecting EDTA and DTPA. Without enrichment it is possible to reach a detection limit of 0.1 mg/l, i.e., while this method is rather less sensitive, it provides results in a much shorter time. If the sample concentrations are high enough, this method is more suitable for conducting routine monitoring of emissions of EDTA and DTPA in waste water. Simple matrices such as surface water or drinking water can be enriched on a pre-column to reduce the detection limit.Dedicated to Professor Dr. Wilhelm Fresenius on the occasion of his 80th birthday     

Synthesis and properties of superconductors prepared from ethylenediaminetetraacetic acid (EDTA)-ethylenediamine (ED) polyamide YBC chelate

Single-phase Y₁Ba₂Cu₃O_7-x has been synthesized by a polymer-metal chelate precursor technique. Ethylenediaminetetraacetic acid (EDTA)-ethylenediamine (ED) polyamide was used as chelating polymer for Y, Ba, and Cu. The titration curves of the polymer in the absence and presence of each metal ion showed the chelate formations. The polymer was dissolved in water and the metal nitrates of Y, Ba, and Cu (1:2:3 in mole ratio) were stoichiometrically added to form a homogeneous molecular complex. The clear polymermetal chealate film was obtained by removal of the solvent without phase separation. This precursor was dried, calcined, and sintered to develop the superconducting (1,2,3) phase. The 1,2,3 phase produced was found to be pure according to x-ray diffraction pattern and it possessed good superconducting properties, i.e., the onset of superconductivity was seen at 90.0 K and the resistance rapidly decreased with decreasing temperature, reaching substantially zero at 88.6 K. Scanning electron microscope (SEM) and face and point analyses by electron probe microanalysis (EPMA) showed that Y, Ba, and Cu elements were uniformly dispersed at least micron order. © 1994 John Wiley & Sons, Inc.