Separation of rhodium and iridium by anion-exchange thin-layer chromatography

Ohne Zusammenfassung

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Spectro photometric determination of thallium(I) and dimethylthallium compounds in small concentrations

     

The separation of rhodium and iridium by ion flotation

Mixtures of iridium(IV) and rhodium(III) as IrCl^2-₆ and RhCl^3-₆ are separated by ion flotation. The iridium(IV) is selectively floated from aqueous solutions of pH 2 and 0.05% Ce(IV) with either hexadecyltripropylammonium bromide (HTPAB) or hexadecyltributylammonium bromide (HTBAB). The rhodium(III) does not float under the same conditions. The floated iridium sublate is collected in n-butyl acetate without contamination by the unfloated rhodium. Data are presented also for the separation and recovery of the Ir(IV) and Rh(III) with the above surfactants, hexadecyltrimethyl-ammonium bromide (HTMAB) and hexadecyltriethylammonium bromide (HTEAB) from solutions of various sodium chloride and hydrochloric acid concentrations. The use of solvent sublation for recovering the floated iridium is examined. The separation is fast, practical, simple and does not require expensive reagents or apparatus. For these reasons, the separation of iridium and rhodium by ion flotation offers advantages over previous methods.     

Anion-exchange separation of rhodium and iridium by ECTEOLA-cellulose column

Summary The separation of Rh(III) and Ir(IV) in amounts of 20–5300 and 20–7700 g, respectively, and in ratios of RhIr=1100 to 1001 was achieved without cross-contamination by use of a 3 g ECTEOLA-cellulose column. Rh was first eluted with 40 ml of a 3 mol/l HCl-1% (w/v) NaClO₃ solution. Ir(IV) was desorbed with 60 ml of a 6 mol/l HCl-0.1% (w/v) NaClO₃ solution. Quantitative recoveries were obtained for each metal. The present method provides much better resolution than the other existing anion-exchange methods and can effectively be applied to the separations and recoveries of Rh and Ir(III or IV) present in a more extensive range of amounts and ratios.

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Anionenaustausch-Trennung von Rhodium und Iridium mit Hilfe einer ECTEOLA-Cellulose-Säule

     

The separation of rhodium and iridium on a microscale

Summary In response to the great need for methods of separation of rhodium and iridium, a procedure has been developed in which rhodium is displaced from a boiling, dilute sulphuric acid solution by antimony dust. A method is described for the separation of antimony from iridium by distilling the former as the trichloride after which the iridium is determined withp-nitrosodimethylaniline. The rhodium in the antimony residue may be determined with either stannous chloride or 2-mercapto-4,5-dimethylthiazole.

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Zusammenfassung Da ein gutes Verfahren für die Trennung von Rhodium und Iridium benötigt wird, wurde eine Methode untersucht, bei der das Rhodium aus kochender, schwach schwefelsaurer Lösung durch Antimonstaub gefällt wird. Das Rhodium im Niederschlag kann entweder mit Zinn(II)-chlorid oder mit 2-Merkapto-4,5-dimethylthiazol photometrisch bestimmt werden.Das in Lösung gehende Antimon stört bei Bestimmung des Iridiums und wird deshalb als Trichlorid aus der Lösung ausgetrieben, wonach das Iridium mittels der Farbreaktion mit p-Nitrosodimethylanilin photometrisch bestimmt wird.

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Résumé Répondant à la grande nécessité de disposer de méthodes de séparation du rhodium et de l'iridium, les auteurs ont mis au point une technique dans laquelle le rhodium est déplacé, par la poudre d'antimoine dans une solution d'acide sulfurique diluée et bouillante. Ils décrivent ensuite une méthode de séparation de l'antimoine de l'iridium par distillation du trichlorure d'antimoine; l'iridium est ensuite dosé par la p-nitrosodiméthylaniline. Quant au rhodium il peut être dosé dans le résidu d'antimoine soit par le chlorure stanneux, soit par le 2-mercapto-4,5-diméthylthiazole.

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The authors are grateful for financial assistance from the National Research Council of Canada.     

Partial separation of rhodium and iridium using polyurethane foam

Rhodium/III/ solutions react with tin/II/ chloride to form a short-lived yellow complex which is extracted by polyurethane foam. Iridium/IV/ solutions are decolourised by tin/II/ chloride but the metal is poorly extracted by foam. The rhodium/III/ complex is readily desorbed from foam using hydrochloric acid and acetone.     

Polyurethane foam for the extraction of rhodium and its separation from iridium

The rate of reaction of rhodium with thiocyanate at 90 degrees in the presence of lithium chloride or sufficient hydrochloric acid and the subsequent extraction of the metal from hydrochloric acid medium by polyether-type polyurethane foam was investigated. The effect of the chloride salts of different cations decreased in the order Li(+) > Na(+) > K(+) indicating that Rh(SCN)(6)(3-) is extracted through a simple solvent-extraction mechanism rather than the "cation-chelation" mechanism. The separation of rhodium and iridium was also examined and the results indicated that in the presence of 5-fold excess of iridium, an average of 95 +/- 2% iridium remained in the aqueous phase while an average of 93 +/- 2% rhodium was retained by the foam.     

Separation of rhodium and iridium by multiple fractional extraction

Mixtures of the chloro complexes of rhodium(III) and iridium(IV) were resolved by a nine stage multiple extraction technique. The solutes are partitioned in a hydrochloric acid-tributyl phosphate system. Rhodium is concentrated in the raffinate while iridium is concentrated in the extractant. 99% of the rhodium and 94% of the iridium are recovered free of the other metal. Experimental results agree reasonably well with the results predicted by a theoretical treatment of the distribution data.     

Dihydrogen complexes of iridium and rhodium

A series of iridium and rhodium pincer complexes have been synthesized and characterized: [(POCOP)Ir(H)(H(2))] [BAr(f)(4)] (1-H(3)), (POCOP)Rh(H(2)) (2-H(2)), [(PONOP)Ir(C(2)H(4))] [BAr(f)(4)] (3-C(2)H(4)), [(PONOP)Ir(H)(2))] [BAr(f)(4)] (3-H(2)), [(PONOP)Rh(C(2)H(4))] [BAr(f)(4)] (4-C(2)H(4)) and [(PONOP)Rh(H(2))] [BAr(f)(4)] (4-H(2)) (POCOP = κ(3)-C(6)H(3)-2,6-[OP(tBu)(2)](2); PONOP = 2,6-(tBu(2)PO)(2)C(5)H(3)N; BAr(f)(4) = tetrakis(3,5-trifluoromethylphenyl)borate). The nature of the dihydrogen-metal interaction was probed using NMR spectroscopic studies. Complexes 1-H(3), 2-H(2), and 4-H(2) retain the H-H bond and are classified as η(2)-dihydrogen adducts. In contrast, complex 3-H(2) is best described as a classical dihydride system. The presence of bound dihydrogen was determined using both T(1) and (1)J(HD) coupling values: T(1) = 14 ms, (1)J(HD) = 33 Hz for the dihydrogen ligand in 1-H(3), T(1)(min) = 23 ms, (1)J(HD) = 32 Hz for 2-H(2), T(1)(min) = 873 ms for 3-H(2), T(1)(min) = 33 ms, (1)J(HD) = 30.1 Hz for 4-H(2).     

The separation of platinum and iridium by ion flotation

The anionic chlorocomplexes of platinum(IV) and iridium(III) are separated by ion flotation from acidic, aqueous solutions with cationic surfactants of the type C₁₆H₃₃NR'₃Br, where R' is methyl, ethyl, n-propyl, or n-butyl. The PtCl₆^2-, which forms readily floatable salts with each of the surfactants, is selectively floated from the IrCl₆^3- and recovered after flotation in n-butyl acetate. The efficiency of the separation increases as the R' chain length increases and a quantitative separation is obtained with hexadecyltributyl-ammonium bromide (HTBAB) in 0.1 M HCl solutions. Since the flotation properties of Ir(IV) are similar to those of Pt(IV), hydroxylamine hydrochloride is used to reduce Ir(IV) to Ir(in) selectively in the presence of Pt(IV).     

The separation of iridium and ruthenium by ion flotation

Mixtures of iridium(IV) and ruthenium(III) as IrCl^2?₆ and RuCl^t—₆ are separated by ion flotation. Iridium (IV) is selectively floated from mixtures of the metal complexes in aqueous 1.0 M hydrochloric acid with hexadecylpyridinium bromide (HPB) and nitrogen. Ruthenium(III) does not float under the same conditions. In order to assess the usefulness of this procedure, the separation was also investigated with hexadecyltrimethylammonium bromide and hexadecyltripropylammonium bromide, from solutions of varying concentrations of sodium chloride, sodium nitrite and hydrochloric acid. Under optimal conditions at the 5 × 10^?5 M level, 78% of the iridium is recovered free of ruthenium, provided that excess of HPB and > 1 M chloride are present.     

Purine-based carbenes at rhodium and iridium

Purine-based carbenes can be attached to catalysis-related metals like rhodium and iridium through the standard method of in situ deprotonation of the respective azolium salts. Thus, 1,3,7,9-tetramethylxanthinium tetrafluoroborate is obtained by the reaction of trimethyloxonium tetrafluoroborate and caffeine. The salt and 7,9-dimethylhypoxanthinium iodide were used as a consecutive precursor to form rhodium (I) and iridium (I) carbene complexes of the type [M(L)(L_Carbene)₂]I and M(L)(L_Carbene)(I) (M = Rh, Ir, L_Carbene = 1,3,7,9-tetramethylxanthine-8-ylidene, 7,9-dimethylhypoxanthine-8-ylidene, L = η⁴-1,5-COD, CO) (COD = 1,5-cyclooctadiene). All compounds were characterized by ¹H NMR, ¹³C NMR, mass spectrometry and/or elemental analysis.     

Thin-layer chromatographic separation of rhodium(III) and iridium(III, IV) by anion exchange

Summary The TLC behaviour of Rh(III), Ir(III) and Ir(IV) has been investigated in the two systems consisting of DEAE-cellulose or ECTEOLA-cellulose and 5 M HCl media containing H₂O₂. These systems, especially in combination with a simple chemical pretreatment of samples (with LiCl, HCl and H₂O₂), can effectively be applied to the complete separation of mixtures of Rh(III) and Ir(III) or Ir(IV) in a wide range of ratios and amounts (Rh: Ir=1100 to 1001).

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Dünnschicht-chromatographische Trennung von Rhodium(III) und Iridium(III, IV) durch Anionenaustausch

Zusammenfassung Das dünnschicht-chromatographische Verhalten von Rh(III), Ir(III) und Ir(IV) wurde in H₂O₂-haltiger 5 M salzsaurer Lösung auf DEAE-sowie ECTEOLA-Cellulose untersucht. In Kombination mit einer einfachen chemischen Vorbehandlung der Probe (mit LiCl, HCl, H₂O₂) kann eine wirkungsvolle Trennung von Rh(III) und Ir(III) oder Ir(IV) über einen weiten Konzentrationsbereich erzielt werden (Rh: Ir=1100 bis 1001).

     

The determination of traces of iridium in rhodium by neutron activation analysis

Iridium traces were determined in rhodium by thermal neutron activation for 2 days at a flux of 4.10¹¹ n·cm^-2·sec^-1. After cooling for at least 1 week, the samples were analysed by γ-spectrometry. No radiochemical separations were required. Special attention was paid to self-absorption phenomena in the rhodium samples.     

A new solvent extraction scheme for the separation of platinum,palladium, rhodium and iridium

A new scheme is proposed for the separation of platinum, palladium, rhodium and iridium in hydrochloric acid solutions, by solvent extraction. Platinum and palladium are complexed with 2-mercaptobenzothiazole and potassium iodide and simultaneously extracted into chloroform, thus separating them from rhodium and iridium. Palladium is separated from platinum by extracting its dimethylglyoxime complex into chloroform, while rhodium is separated from iridium by extracting its 2-mercaptobenzothiazole complex into chloroform after reduction with tin(II) chloride.     

d8 rhodium and iridium complexes of corannulene

[(COE)2M]+ fragments (M = Rh, Ir; COE = cyclooctene) react with corannulene to give eta6-bound complexes [(COE)2Rh(eta6-C20H10)]PF6 and [(COE)2Ir(eta6-C20H10)]PF6. Both compounds were characterized by X-ray diffraction studies, and binding in the solid state is compared with that of their aromatic analogues [(COE)2M(eta6-arene)]PF6 (aryl = benzene and phenanthrene). Solution NMR studies show that the [(COE)2Rh]+ fragment walks over the curved aromatic surface of corannulene, whereas the Ir analogue is not fluxional. Experimental as well as computational studies suggest that inter-ring movement of the Rh complex follows a hub migration mechanism. Initial reactivity studies indicate that the [(COE)2M]+ fragments can undergo chemical transformations, such as transfer dehydrogenation and substitution reactions, while still bound to corannulene.     

Synthesis of macroporous poly(vinyldiethylenetriamine) chelating resin and the enrichment—separation of rhodium and iridium

Poly(vinyldiethylenetriamine) chelating resin was synthesized from macroporous poly(vinyl chloride) and used for the enrichment-separation of rhodium and iridium. The efficiency, rate and equilibrium constant adsorption of rhodium and iridium on the resin were determined and real samples were analysed. The mechanism of rhodium and iridium enrichment is discussed.     

Extractive spectrophotometric determination of platinum, rhodium and iridium

Platinum, iridium and rhodium in mixtures are determined sequentially, with rubeanic acid, tin(II) chloride and tin(II) iodide respectively. The working ranges (in microg) are: Pt 7-100, Rh 7-70, Ir 7-30.