Metal chelate exchange in the organic phase-II Extraction and exchange constants of dithizonates and diethyldithiocarbamates

Dithizonates and diethyldithiocarbamates of Ag, Tl(I), Cu(II), Zn, Cd, Hg(II), Pb, Fe(II), Co(II), Ni, Pd(II), In(III), As(III), Sb(III), Bi, Se(IV) and Te(IV) have been prepared and their reactions in carbon tetrachloride have been studied spectrophotometrically. From the exchange constants determined, the extraction constants of metal diethyldithiocarbamates have been calculated. Where formation of mixed chelates has been observed, corresponding exchange constants have been determined. Finally, the influence of organic solvents (CCl(4), CHCl(3), C(6)H(6) and C(6)H(5)Cl) on the exchange reaction of zinc diethyldithiocarbamate with dithizone has been investigated.     

Metal chelate exchange in the organic phase-I Theory: application in spectrophotometry and complex chemistry

Metal chelates, extracted from an aqueous phase by organic solvents, can react with other chelating agents (or their metal chelates) dissolved in the same solvent. This exchange of metal chelates in the organic phase can be used for (1) investigation of the exchange equilibrium and composition of the metal chelates formed, (2) determination of the extraction constants, (3) preparation of new inner-complexes soluble in organic solvents, and (4) spectrophotometric determination of small amounts of metals. The theory and experimental verification of this phenomenon are given. The extraction constants of silver and zinc diethyldithiocarbamates in carbon tetrachloride have been determined by means of the extraction constants of the corresponding dithizonates. A mixed complex of arsenic(III) with dithizone and diethyldithiocarbamic acid has been prepared and its properties studied. A simple method for spectrophotometric determination of microgram quantities of arsenic is proposed.     

Stability constants of some metal dithizonates

The overall stability constants of electroneutral dithizonates of bismuth, cadmium, cobalt(II), copper(II), iron(II), lead(II), manganese(II), mercury(II), nickel, palladium(II), silver, tin(II) and zinc were determined by means of stoichiometric dilution in aqueous solution stabilized by hydroxylamine hydrochloride, at pH 5.50-10.02. Stability constants of complexes ML of bivalent metals were determined under similar conditions but with an excess of metal.     

Metal-metal chelate exchange reactions in the ion source of a mass spectrometer

In the mass spectra of several transition metal chelates with diethyldithiocarbamate as a ligand, intense peaks are present which could be assigned to extraneous metal (particularly nickel) containing ions. Using an Au-Rh coated ion source, evidence was obtained for the occurrence of exchange reactions in the region of the filament assembly.     

The oxinates of thorium and some cerite earths

The pH of precipitation of oxinates of thorium, cerium and lanthanum has been studied. By controlling the pH of precipitation, thorium has been separated as the oxinate.From a spectrochemical study of the 4 and 5 oxinates of thorium in dilute hydrochloric acid, acetone, carbontetrachloride, chloroform, and toluene, it has been suggested that the 5 complex is a definite compound, but not an addition body of the 4 compound.A colorimetric estimation of thorium has been suggested by measuring absorption at 320 mμ in hydrochloric acid and 330 mμ in acetone. 2 p.p.m. of the oxide has thus been estimated.     

Determination of organic and inorganic mercury compounds by reverse-phase high-performance liquid chromatography after extraction of the compounds as their dithizonates

A sensitive and selective method is described for the simultaneous determination of inorganic and organic mercury compounds. The mercury compounds are extracted into toluene or chloroform with dithizone, and the dithizonates are separated by liquid chromatography on an ODS column. Complete resolution was obtained between methylethyl-, phenyl- and inorganic mercury with a mobile phase of THF/methanol (2:1) with 0.05 M acetate buffer pH 4 (62 + 38), containing 50 μM EDTA. The mercury chelates were detected spectrophotometrically at 475 nm. The detection limits were at the subnanogram level. The method is applicable to human urine, tap water and tomatoes.     

Ionization constants for very weak organic acids in aqueous solution and apparent ionization constants for water in aqueous organic mixtures

A potentiometric method using a glass electrode has been applied to determination of apparent ionization constants for water in binary mixtures of water with tetrahydrofuran, methanol, 1,3-propanediol, glycerol, sucrose, and glucose at 25°C. Further calculations with these apparent ionization constants, which are now based explicitly on the previously implicit assumption that ionization of the organic component is negligible compared to ionization of water, permit evaluation of ionization constants for several very weak acids in purely aqueous solvent. Resulting pK values derived from this work and from our earlier work are as follows: glucose (12.38), sucrose (12.75 and 12.80), glycerol (14.05 and 14.07), ethylene glycol (14.44 and 14.52), methanol (15.2), 1,3-propanediol (14.8 and 15.0), 1-propanol (15.1), 2-propanol (15.7), and 2-methyl-2-propanol (15.0).     

Studies of the solvent extraction of cadmium and silver dithizonates

An extensive study was made of the solvent extraction of cadmium and silver dithizonates into chloroform A few extractions of silver dithizonate were made into carbon tetrachloride. In most cases extraction curves of PH versus % metal extracted were obtained and reported in terms of the PH of 50% extraction. The shift of the extraction curves to higher PH values due to the effect of ions in the aqueous phase which complex with the cadmium or silver ions was investigated An equation was developed which would predict the PH of 50% extraction for the extraction from the solutions containing these complexing ions The effects of chloride, bromide and iodide ions on the extraction of cadmium and the effects of chloride, bromide, iodide, thiocyanate and thiosulfate ions on the extraction of silver. Extraction constants for the various extractions were determined.     

Substitution kinetics of chelate complexes as studied by isotopic exchange

The fact that isotopic exchange reactions take place at chemical equilibirum makes this type of reaction useful for kinetic studies. In the case of chelate complexes [M(chel)_n] isotopic exchange reactions can be classified as metal exchange reactions. [M(chel)_n]+^*M⇆[^*M(chel)_n]+M and ligand exchange reactions [M(chel)_n]+^*chel⇆[M(chel)_n−1 ^*chel]+chel The literature on type (a) and type (b) reactions of mainly transition metal complexes is reviewed with respect to the kinetic information obtained. The value and the limitations of isotopic exchange studies as a kinetic technique are discussed.     

Hypercoordination in triphenyl oxinates of the group 14 elements

The triphenyl oxinates of the group 14 elements (M = Si, Ge, Sn, and Pb) contain the 8-hydroxyquinoline ligand (HOx), which can function in either a bidentate or monodentate fashion. The compounds Ph₃MO_x were prepared by reaction of the triphenylmetal chloride with HOx in the presence of an HCl scavenger triethylamine or, sodium acetate, and in the case of lead, with the sodium salt of 8-hydroxyquinoline. The interaction of the nitrogen with the central atom was studied through the use of the NMR chemical shifts of the central metal atom and the ¹⁵N atom of the ligand. The chemical shifts of the central metal provided evidence that the triphenylgermanium and silicon oxinates are uncoordinated while the triphenyltin and lead oxinates are five-coordinate. These conclusions are confirmed by molecular modeling, ¹⁵N chemical shifts and the metal-¹³C one bond coupling constants at the ipso carbon. The NMR data provides evidence that the strength of the interaction of the nitrogen with the metal increases from silicon and germanium to lead. Two peaks in the 5-coordinate region of the ²⁰⁷Pb NMR spectra can be rationalized with the postulate that strong interaction with lead produces two geometrical isomers. Two peaks were also present in the 5-coordinate region of the ¹¹⁹Sn NMR spectra at low temperatures indicating a rapid exchange between the two geometrical isomers at room temperature.     

Dissociation constants of some organic acids

Dissociation constants of di(nonylphenyl)dithiophosphoric acid, di(nonylphenyl)phosphoric acid and 9-phenyltetracosansulphuric acid, determined by two methods, are reported.     

Systematic study of the solvent extraction of metal oxinates

The extraction of 32 metals (Be, Mg, Ca, Sr, Ba, Sc, La, Ti, Zr, Th, V, Nb, Cr, Mo, W, U, Mn, Fe, Co, Ni, Pd, Cu, Ag, Zn, Cd, Hg, Al, Ga, In, Tl, Pb and Bi) with oxine solution has been studied. The effects of pH, oxine concentration and water-soluble complexing agents (oxalic acid, tartaric acid, hydrocyanic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid and 1,2-diaminocyclohexanetetraacetic acid) have been investigated. From these results the extraction constants and stability constants ot the metal complexes with the various complexing agents investigated have been calculated.     

Ion exchange in organic solvents

Studies on the partitioning of plutonium from 30% TBP by ion-exchange absorption on macroporous cation exchanger Amberlyst-15 have been described. Detailed loading experiments indicate that the resin absorbs plutonium in preference to uranium from loaded organic phase at low organic phase acidities (around 0.2M). Absorption behaviour of some fission products on the resin in 30% TBP is also reported. Possibility of using this procedure as an alternate method for plutonium partitioning from IAP stream of Purex process has been discussed.     

Interaction of organic dyes and proteins-determination of the binding constants spectrophotometrically

Summary The spectral change of a small molecule (S) induced by addition of a large molecule (P) was examined theoretically and experimentally, assuming that the interaction betweenS andP follows theLangmuir adsorption isotherm. It was found that intermolecular binding constants could be determined accurately and conveniently by extrapolation to zero of two simple graphic relations, namely, the observed molar extinction coefficient ofS in the presence ofP versus the ratio of (the concentration ofS/the concentration ofP), and of the former versus the reciprocal value of the latter. This spectrophotometric method was applied to the binding of bovine serum albumin and Ponceau3 R and of bovine serum albumin and HABA at p_H 7.0. The results obtained by this method were comparable with those obtained by equilibrium dialysis or by conventional spectrophotometric method.

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Zusammenfassung Unter der Annahme, daß dieLangmuirsche Absorptionsisotherme auch bei der Assoziation hoch-(HMV) und niedermolekularer Verbindungen (NMV) gilt, wurden die Bindungskonstanten bestimmt. Es wurden die spektralen Änderungen in der UV-Absorption der NMV bei Zusatz verschiedener HMV-Mengen gemessen. Die Bindungskonstanten lassen sich durch Kombination zweier graphischer Darstellungen exakt und einfach bestimmen: erstens aus der Beziehung zwischen dem molaren Extinktionskoeffizienten der NMV in Anwesenheit verschiedener HMV-Konzentrationen und dem Konzentrationsverhältnis von NMV zu HMV und zweitens aus dem Zusammenhang der molaren Extinktionskoeffizienten mit den reziproken Werten des oben genannten Konzentrationsverhältnisses. Mit dieser neuen Methode wurden die Bindungskonstanten bei p_h 7.0 von Rinderserumalbumin und Ponceau 3 R bzw. HABA berechnet und mit den durch andere Methoden bestimmten Konstanten verglichen. Die Werte stimmen mit denen aus der Dialysemethode und aus der üblichen spektralphotometrischen Methode überein.

     

About the calculation of exchange coupling constants in polynuclear transition metal complexes

The application of theoretical methods based on the density functional theory with hybrid functionals provides good estimates of the exchange coupling constants for polynuclear transition metal complexes. The accuracy is similar to that previously obtained for dinuclear compounds. We present test calculations on simple model systems based on H. He and CH(2). He units to compare with Hartree-Fock and multiconfigurational results. Calculations for complete, nonmodeled polynuclear transition metal complexes yield coupling constants in very good agreement with available experimental data.     

Ionization constants for water and for very weak organic acids in aqueous organic mixtures

A potentiometric method using a glass electrode has been applied to the determination of apparent ionization constants for water in binary mixtures of water with 11 organic solvents at 25°C. Further calculations with these apparent ionization constants permit evaluation of the acid ionization constant for some of the organic solvents as solutes in purely aqueous solvent by two different methods. Resulting values of pK _a derived from this work are: 1,2-propanediol (14.8 and 14.8), 2,3-butanediol (15.0 and 14.7), 1,3-butanediol (15.5 and 14.8), 1,4-butanediol (14.5 and 14.4), 2-butene-1,4-diol (14.0 and 13.9), 2-butyne-1,4-diol (12.1 and 12.4), 2-methoxyethanol (15.2 and 14.8), 2-ethoxyethanol (15.0 and 14.5), and triethylene glycol (14.6 and 14.3). None of the 11 solvents shows appreciable basicity.     

Comparison between thermal analysis and mass spectroscopic studies of uranyl oxinates

The 5,7-dichloro, 5,7-dibromo, 5,7-diiodo and 5,6-dinitro derivatives of oxine (ligandsL ₁,–L ₄) were used to prepare uranyl chelates (A ₁–A ₄). Thermal analysis (DTA) and mass spectroscopic studies were performed. The stoichiometries of the chelates were determined by elemental analysis, molecular weight determination applying an -spectroscopic liquid scintillation counter and mass spectral measurements. The uranylligand ratios were found to be 11 for A₁, 13 for A₂, 12 (monohydrate) for A₃, and 12 forA ₄. The correlation between the thermal analysis and mass spectra was examined. The activation energy required for each step of thermal degradation of the ligands and chelates was calculated. The natures of most of the molecular ions obtained in the mass spectra were also explained.