Eugene W. Berg

Fractional sublimation of the β-diketone chelates of the lanthanide and related elements

Abstract Various β-diketone chelates of Sc(III), Y(III), Th(IV), U(IV). U(VI), Zr(IV) and the lanthanides have been prepared, characterized and investigated to determine if they were volatile and stable. The ligands employed were acetylacetone(AA), trifluoroacetylacetone(TFAA), hexafluoroacetylacetone(HFAA), and dipivaloyl-methane(DPM). The chelates were sublimed in a fractional vacuum sublimator and the recrystallization temperature zones recorded for individual chelates. None of the lanthanide acetylacetonates arc volatile but the Sc(III), Th(IV), U(IV) and dioxouranium(VI) acetylacetonates are thermally stable and quite volatile below 150° at 1 mm mercury pressure. The lanthanide, Sc(III), Y(III), and dioxouranium(VI) trifluoroacetylacetonates are volatile and can be vacuum-sublimed below 150°, but are thermally unstable; only the Th(IV) chelate is sufficiently stable to be quantitatively recovered by sublimation. The Sc(III), Y(III), Th(IV), and lanthanide hexafluoroacetylacetonates are thermally stable and easily sublimed below 125° in vacua or at atmospheric pressure. All the dipivaloylmethanates studied were thermally stable and volatile and could be quantitatively recovered by vacuum sublimation below 140°. The volatility of the HFAA and DPM lanthanide chelates increased with an increase in atomic weight (a decrease in ionic radii) of the lanthanides. The lack of volatility observed for the lanthanide AA and TFAA chelates is attributed to the fact that only hydrates of the chelates were formed, which decomposed at elevated temperatures in vacuo to form basic polymeric compounds. Separations are proposed for numerous binary mixtures of the β-diketone chelates of the lanthanide and related elements. Recrystallization temperature zones are given for the following binary mixtures which were quantitatively resolved by the fractional sublimation technique; 118-88° for Nd(DPM) 3 and 84-48° for Tm(DPM) 3 ; 72-49° for Sc(DPM) and 120-88° for Pr(DPM); 128-79° for La(DPM) 3 and 79-47° for Yb(DPM) 3 ; 70-47° for Th(TFAA) 4 and 116-96° for Gd(TFAA) 3 ; 52-42° for Th(HFAA) 4 and 120-80° for La(HFAA) 3 .

Vapor pressure-temperature data for various metal β-diketone chelates

Abstract Vapor pressure-temperature data, molar heats of sublimation, and sublimation temperatures are given for 29 metal β-diketone chelates. The chelatcs studied were these of Be(II), Al(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) with acetyl-acetone, acetyltrifluoroacctone, benzoylacetone, benzoyltrifluoroacetone, 2-furoyl-trifluoroacetone, and 2-thenoyltrifluoroacetone. The observed difference in volatilities of the various metal chelatcs of a given ligand is the basis for a suggestion that various mixtures of metal ions can be resolved by a fractional sublimation scheme.

Fractional sublimation of various metal chelates of dipivaloylmethane

Abstract Twenty different metal chelates of dipivaloylmethane were prepared and characterized by melting points, carbon-hydrogen analyses, and infrared and n.m.r. absorption data. The pure chelates were sublimed in the Berg fractional vacuum sublimator and the temperature condensation (sublimation) zones were recorded for each chelate under standardized conditions. The beryllium(II) chelate was the most volatile and the lanthanide and actinide chelates among the least volatile dipivaloylmethanates. The only volatile alkaline earth metal chelates were those of Be(II) and Mg(II); the Ca(II), Sr(II) and Ba(II) chelates were not volatile under the conditions used. Overall it was found that the chelates of dipivaloylmethane exhibited volatilities similar to those of the corresponding metal acetylacetonates but less than those of the trifluoroacetylacetonates and the hexafluoroacetylacetonates. The chelates of benzoylacetone, benzoyltrifluoroacetone and thenoyltrifluoroacetone are less volatile than the corresponding chelates of dipivaloylmethane. The data suggest that some 64 different binary and ternary mixtures of metal dipivaloylmethane chelates can be quantitatively resolved. Seven binary and three ternary mixtures of the metal chelates were resolved satisfactorily.

Thiothenoyltrifluoroacetone: a new chelon

Abstract The thioderivative of 2-thenoyltrifluoroacetone, 1,1,1-trifluoro-4-(2-thienyl) 4-mercaptobut-3-en-2-one (STTA) was prepared. NMR and infrared spectra confirmed the previously suggested structure2. The sulfur is attached to the carbon adjacent to the thienyl group and exists almost entirely in the thio-enolic form. The chelates of STTA with Ni(II), Cu(II), Pb(II), Zn(II). Co(II), Cd(II). Pd(II) and Hg(II) were prepared in a neutral to slightly basic medium, and characterized by analysis. NMR, infrared, visible and ultraviolet spectra, DTA, TGA and fractional sublimation. The chelates are relatively stable, insoluble in water, soluble in non-polar and some polar organic solvents, sublimable, and intensely colored compared to their normal diketone analogs. The selectivity of the reagent has not been completely established but divalent ions chelate more readily than trivalent ions; Fe(III), Al(III), Cr(III) apparently do not chelate. The new chelon may be useful as a color-developing reagent for the colorimetric analysis of such ions as Zn(II), Cd(II), Hg(II) and Pb(II). The molar extinction coefficients are given for the chelon and the chelates investigated

Countercurrent extraction separation of some platinum group metals

Abstract Distribution coefficients were determined for the partitioning of the chloro-complexes of platinum, palladium, rhodium, and iridium between tributyl phosphate and various concentrations of hydrochloriic acid. Theoretical calculations based on the experimentally determined distribution coefficients indicated that a seventeen stage countercurrent extraction apparatus would resolve mixtures of platinum and palladium, platinum and rhodium, and rhodium and iridium. Mixtures of platinum and palladium, and platinum and rhodium were resolved in a fashion predicted by theory. Mixtures of rhodium and iridium were not completely resolved.

Fractional sublimation of various metal acetylacetonates

Abstract A simple fractional sublimator is described which possesses a continuous temperature gradient along its length. Samples are placed in the high temperature end of the tube and volatilized at 1-mm pressure. The gases are moved through the tube with air as a carrier. The metal chelates recrystallize on the walls of the tube in discrete and reproducible temperature zones. Characteristic recrystallization zones are reported for 21 metal acetylacetonates. The chelates can be grouped according to zone temperatures into 6 fairly distinct groups over the range 15 to 200°, which makes many separations possible. Separations of mixtures of Mg, Al and Be ; Ni, Fe and Be ; and, Cu and Fe were studied quantitatively. The separations achieved compared favorably with those reported by gas chromatography. The method offers real promise for the purification of a number of metals but appears especially good as a method for beryllium and certain platinum group metals.

Separation of rhodium and iridium by multiple fractional extraction

Abstract 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.

Fractional sublimation of various metal b-diketone chelates

Abstract The vacuum fractional sublimation of various metal β-diketone chelates was compared with the fractional sublimation of the metal acetylacetonates reported earlier. Characteristic recrystallization temperature zones are reported for a number of metal acetylacetonates, acetyltrifluoroacetonates, hexafluoroacetylacetonates, benzoylacetonates, and benzoyltrifluoroacetonates. The substitution of a trifluoromethyl for a methyl group in the ligand molecule increased the volatility of the corresponding metal chelates, but this increased volatility did not lead to improved separations by fractional sublimation. In particular, the hexafluoroacetylacetonates tended to recrystallize as microcrystals in diffuse zones which extended over much of the sublimation tube and the benzoyltrifluoroacetonates tended to distill rather than sublime, with the liquids flowing down the wall of the tube. The best separations were achieved among the metal acetylacetonates. The chelates studied are generally stable and can be recovered from the sublimation apparatus in near quantitative yields. Separations of mixtures of Be, Mg, and Cr ; Fe, Mg and Al ; and Fe and Al were studied critically. Although the separations were not complete, they compared favorably with some reported gas-chromatographic separations.

Fractional sublimation of some metal chelates of thenoyltrifluoroacetone

Abstract Studies on the fractional sublimation of various metal β-diketone chelates have been extended to include the chelates of thenoyltrifluoroacetone (TTA). Many of the common metal chelates were found to be stable, to sublime readily, and to form well-defined zones in the vacuum fractional sublimator. Of the 17 chelates reported only those of manganese (II) and iron(II) were not volatile. The chelates of UO 2 (II), Zr(IV), Pb(II), and Cr(III) partially decomposed during sublimation and their recovery was incomplete. The recovery of the sublimed chelates of Ni(II), Mg(II), Al(III), Pd(II), Co(II), Cu(II). Fe(III), Tl(III), Zn(II) and Be(II) ranged from 87 to 100%, with most recoveries being quantitative. The sublimation recrystallization zone temperatures of the various chelates are compared to those of the metal acetylacetonates and the benzoyltrifluoroacetonates; in general, the metal chelates of TTA sublime more readily than those of benzoyltrifluoroacetone but are potentially less useful for fractional sublimation separations than the corresponding metal acetylacetonates. Even so, a quantitative separation of iron(III) from Ni(II), Al(III), Mn(II), and Fe(II) is proposed that depends upon the fractional sublimation of the TTA chelates.

Countercurrent extraction separation of some platinum group metals: part III

Abstract The bromo complexes of platinum(IV), palladium(II), rhodium(III), and iridium(IV) were prepared and studies were made on their distribution between hydrobromic acid solutions and various common solvents. The solvents employed were n-tributyl phosphate (TBP), methyl isobutyl ketone, amyl acetate, and various TBP-benzene mixtures. Distribution coefficients as a function of HBr concentration are given for each metal for each solvent system. A careful study of the measured distribution coefficients clearly showed that a number of binary and ternary mixtures of the metals can be resolved with a Craig countercurrent distribution apparatus. Rh-Pt and Rh-Pd mixtures in 4.38M HBr solutions were quantitatively separated on a Io-stage Craig apparatus using a 90% TBP-10% benzene solvent. Rh-Ir mixtures in 4.38 M HBr were resolved by 3 consecutive batch extractions with 90% TBP-10% benzene. Mixtures of Pd, Rh, and Ir in 4.38 M HBr were resolved in 90 stages using methyl isobutyl ketone as the solvent. Pd, Rh and Ir were recovered in 97.0, 87.6 and 94.5% yields, respectively. Mixtures of Pd, Rh and Pt in 4.38 M HBr were resolved in 90 stages using amyl acetate and methyl isobutyl ketone as solvents. Pd, Rh and Pt were recovered in 90.0, 96.0 and 94.0% yields, respectively. Two computer programs for the IBM 1620 Computer are given ; these facilitate the comparison of theoretical and actual solute distributions.