Determination of zirconium,thorium and scandium with 2,5-dihydroxy-1,4-benzoquinone

Zirconium is quantitatively precipitated by 2,5-dihydroxy-1,4-benzoquinone and is separated from scandium in 1 N hydrochloric acid solution. Thorium is separated at pH 0.5 from uranium(VI), cerium(IV), lanthanum, yttrium and scandium. Scandium is quantitatively precipitated by this reagent in the pH range 1.4–2.0 and at pH 1.5 equivalent amounts of lanthanum do not interfere; small amounts of yttrium cause interference.     

Thermogravimetric investigation of scandium,yttrium and the rare earth metal diliturates

Thermolysis curves for scandium, yttrium, lanthanum, cerium(III), neodymium, samarium, gadolinium, dysprosium and erbium diliturates are described, Scandium diliturate forms a 15-hydrate which dehydrates in 3 steps. The other diliturates all form 12-hydrates which dehydrate smoothly. All of the anhydrous diliturates are thermally stable to about 240°.Solubilities in water for scandium, yttrium, lanthanum, cerium(lll), neodymium, samarium. gadolinium, dysprosium and erbium diliturates are given. Scandium diliturate is the most soluble and neodymium diliturate the least soluble. Solubilities of rare earth diliturates not investigated can be predicted approximately.Methods for thermogravimetric determination of yttrium, lanthanum, neodymium, samarium, gadolinium, dyprosium, and erbium as the diliturates have been developed. The precipitates are quite dense, easily handled and filterable. Weighing as the diliturate salts gives these determinations a very favorable gravimetric factor.     

La séparation du scandium,du lanthane et de l'yttrium

The behaviour of scandium on a resin column has been studied and an efficient separation of scandium, lanthanum and yttrium has been effected using citric acid at different pH's. The hysteresis phenomenon which accompanies the adsorption of scandium and its importance for calculations, based on the theory of levels, are discussed.     

Etude par RMN. de polyaminocarboxylates de terres rares,III. Hydroxyéthyliminodiacétates de praséodyme

¹H—NMR. has been used to study the chemistry of the hydroxyethyliminodiacetate complexes of praseodymium in aqueous solution. The ligand exchanges by spontaneous dissociation of the metal-bis-hydroxyethyliminodiacetate (1:2 complex) and of the metal-bis-hydroxyethyliminodiacetate hydroxocomplex, by acid catalysed dissociation of the 1:2 complex, and by a bimolecular process involving the free ligand and the 1:2 complex or the ternary hydroxo-complex. The ligand exchange rate constants are given and the mechanisms discussed.     

Rare-earth metal complexes supported by 1,omega-dithiaalkanediyl-bridged bis(phenolato) ligands: synthesis, structure, and heteroselective ring-opening polymerization of rac-lactide

Monomeric yttrium and lutetium bis(phenolato) complexes [Ln(OSSO){N(SiHMe 2) 2}(THF)] (Ln = Y, Lu) were prepared from the reaction of silylamido complexes [Ln{N(SiHMe 2) 2} 3(THF) 2] with 1 equiv of tetradentate 1,omega-dithiaalkanediyl-bridged bis(phenol) (OSSO)H 2 1- 9 in moderate to high yields. In contrast to the rigid configuration of scandium analogues, the yttrium complexes 2b and 3b and the lutetium complex 3c that contain a C 2 bridge between the two sulfur donors of the ligand are symmetric in solution. The monomeric nature of these complexes was indicated by an X-ray diffraction study of the yttrium complex 6b. The yttrium center in 6b is coordinated to the tetradentate [OSSO]-type ligand, one silylamido group and one THF ligand with the two oxygen donors of the [OSSO]-type ligand located trans. Corresponding bis(phenolato) silylamido complexes of larger rare-earth metals could not be obtained from similar reactions: Reaction of [La{N(SiHMe 2) 2} 3(THF) 2] with 1,2-xylylene-linked bis(phenol) gave a dinuclear lanthanum complex 6d of the formula [La 2(OSSO) 3] with two inequivalent eight-coordinate metal centers. The yttrium and lutetium complexes efficiently initiated the ring-opening polymerization (ROP) of lactides in THF. The heteroselectivity during the ROP of rac-lactide was enhanced when the steric demand of the bis(phenolato) ligand was increased, either by extending the bridge length or by introducing bulky ortho-substituents in the phenoxy units. A C 3 bridge within the ligand backbone is essential to allow configurational interconversion of the active site between Lambda and Delta configuration during polymerization, allowing accommodation of both enantiomers of the monomer in an alternating fashion.     

Covalency of Sc(III), Y(III), Ln(III) and An(III) as manifested in the enthalpies of solution of anhydrous rare earth halides

The position of scandium and yttrium within lanthanides in respect to the enthalpies of solution of anhydrous rare earth halides has been discussed. It has been indicated that although the respective shift of Sc(III) as a quasi-heavy lanthanide is less pronounced than for Y(III), the overall covalency within the trivalent ions of the scandium group, Ln(III) and An(III) included, is the most pronounced for Sc(III) due to participation of the empty orbitals in bonding: Sc(III)>An(III)>Ln(III)> Y(III). The irregularity of this trend is produced by the superimposed participation of the 5f (An(III)) and, to a lesser extent, of the 4f (Ln(III)) orbitals in bonding. The crucial factor of a maximum difference between the product and substrate coordination number (CN) of the central ion for covalency, separation factor and isotope effect in chemical exchange is emphasized.     

Spectrophotometric study of reactions of scandium,ytrium and lanthanum ions with some triphenylmethane dyes in the presence of cationic surfactants

Optimum conditions for the formation of ternary complexes of scandium, ytrium and lanthanum ions with chrome azurol S, eriochrome cyanine R and pyrocatechol violet in the presence of cetyltrimethylammonium, cetypyridinium and tetradecyldimethylbenzyl-ammonium (zephiramine) ions are described. The spectrophotometric determination of scandium with chrome azurol S and zephiramine exhibits the greatest sensitivity (? = 1.50 × 10⁵ l mol^?1 cm^?1 at 610 nm). In the spectrophotometric determination of scandium with eriochrome cyanine R and cetylpyridinium ion (? = 9.2 × 10⁴ at 600 nm), the interference caused by yttrium is the least. In the best method for yttrium (with pyrocatechol violet and zephiramine), the molar absorptivity is 3.3 × 10⁴ at 660 nm. Lanthanum does not form ternary complexes of analytical interest in these systems. Some aspects of the formation of ternary complexes with cationic surfactants are discussed.     

Spectral interferences in the determination of traces of scandium, yttrium and rare earth elements in “pure” rare earth matrices by inductively coupled plasma atomic emission spectrometry-I. Cerium, neodymium and lanthanum matrices

The present paper deals with spectral interferences from cerium, neodymium and lanthanum on prominent lines of scandium, yttrium and rare earth elements (REE). The “true detection limit” criterion was used for rational wavelength line selection as proposed by boumans and vrakking [Spectrochim. Acta 42B, 819 (1987); 43B, 69 (1988)]. Analysis lines selected for cerium and neodymium matrices suffered both wing and line interferences. In the case of a lanthanum matrix, it is possible to choose mostly analysis lines that are free of line interference and negligible wing interference. The high degree of spectral interferences with a cerium or neodymium matrix significantly worsens the true detection limits. This article is an electronic publication in Spearochimica Acta Electronica (SAE), the electronic section of Spectrochimica Acta Part B (SAB). The hardcopy text is accompanied by a disk with data and text files. The data files comprise in particular the tabular material of this article in electronic form.     

Stabilité des carboxylates de terres,III. Maléates,méthylsuccinates et malates

The stability constants of maleates, methylsuccinates and malates of rare earths have been determined at 25.0 °C and at ionic strength 0,100 (NaClO₄) by a potentiometric method. Each ligand forms 1 : 1 and 1 : 2 complexes in aqueous solution, the malates being the most stable. The first and the second dissociation constants of the ligand acids were also measured. The 1 : 2 maleates of La, Pr, Nd, Sm, and Eu have been isolated.     

The Synthesis and Structure of a Scandium Nitrate Hydroxy-Bridged Dimeric Complex Supported by Bipyridyl Ligands

The current discussion on whether scandium, yttrium and lanthanum should represent Group 3 in the Periodic Table or whether lutetium should replace lanthanum in the group has prompted us to further explore the structural chemistry of the Group 3 elements and compare the coordination numbers and coordination geometries adopted. The steric and electronic properties of the coordinated ligands have a major influence on the structures adopted. We report the synthesis and crystal structure determination of an unusual dinuclear scandium complex [(bipy)(NO₃)₂Sc(µ-OH)₂Sc(NO₃)₂(bipy)] obtained by the reaction of hydrated scandium nitrate with 2,2′-bipyridyl (bipy) in either ethanol or nitromethane. The crystal structure of the complex shows that the scandium centers are eight coordinate, and the structure obtained contrasts with related complexes found in the lanthanide series [Ln(bipy)₂(NO₃)₃] and [Ln(phen)₂(NO₃)₃] (phen = phenanthroline) and in [M(terpy)(NO₃)₃] (M = Sc, Er–Lu), where these complexes are all mononuclear.     

Détermination de constantes de stabilité de chélates par résonance magnétique nucléaire du proton

In a solution containing an excess of two metal ions in regard to a ligand (e.g. NTA) a competitive equilibrium is established. The measure, by proton NMR. spectroscopy, of the individual concentrations of both chelates, and eventually of the free ligand, allows to determine the ratio of the stability constants of the two complexes. As an illustration the ratios of the stability constant of the 1:1 nitrilotriacetate chelates of Pb and Zn, respectively Mo and W, were determined.     

Solvent extraction of some trace metals and iron with <Emphasis Type="Italic">N</Emphasis>-Octyl-<Emphasis Type="Italic">N,N</Emphasis>-bis(dihexylphosphinylmethyl)amine

The processes were studied of the solvent extraction of the ions of triply-charged trace elements including scandium, indium, gallium, and yttrium, as well as iron, with N-octyl-N,N-bis(dihexylphosphinylmethyl) amine solution in toluene, chloroform or methylene chloride from hydrochloric, nitric or perchloric acids aqueous solutions. The metals extraction dependence on the acid concentration showed that the best results were reached using perchloric acid. The calculation of partition coefficients of metals allowed us to reveal a high selectivity of the scandium extraction. The prospects of using the investigated bisphosphinylamine in the technology of extraction, concentration and separation of the trace metals ions was concluded.     

Coordination polymers of indium, scandium, and yttrium

Data on inorganic and metal-organic indium, scandium, and yttrium coordination polymers mainly with halide (pseudohalide) and N,O-donor ligands have been generalized and systematized. The effect of the metal cation nature and coordination number, stereochemistry, and ligand environment on the formation of polymers of different dimensionality is considered. 129 references.     

The determination of fluorine in rare earth fluorides by high temperature hydrolysis

The technique of pyrohydrolysis has been applied to the determination of fluorine in the fluorides of scandium, yttrium, and the lanthanons. These fluorides have been divided into two classes according to their rate of hydrolysis. Lutetium, ytterbium, cerium(III), scandium, gadolinium, terbium, dysprosium, holmium, erbium, and thulium florides can be hydrolyzed in 30 min or less. Yttrium, lanthanum, praseodymium, neodymium, samarium, and europium fluorides require from 45 to 150 min for complete hydrolysis. Accelerators, such as uranium oxide (U₃O₈), chromium(III) oxide, and a mixture of these oxides have been used successfully to reduce the tune required for quantitative hydrolysis of the fluorides in the latter group. The use of the correct accelerator reduces the hydrolysis time to 30 min or less for all these fluorides except lanthanum, praseodymium and neodymium.     

Neutron activation analysis study of distribution of certain elements between plant and soil

Some elements are recognized as essential for the optimal growth of plants but their number and their role is not clearly asserted up to now. Instrumental neutron activation analysis has been employed to determine the elements arsenic, barium, bromide, cerium, europium, gold, hafnium, lanthanum, lutecium, samarium, scandium, tantalum, thorium and ytterbium in different parts of Helleborus cyclophyllus BOISS. and in the soil in which the plant had grown. It has been found that bromine is selectively accumulated in plant from soil, where the value in petioles is four times higher than the value in soil while the value in leaves is about twice as high. The other elements determined show a certain distribution in plant organs but no selective accumulation.     

Complexes of Some Pyrido[1,2-a]pyrimidinium Perchlorates with Scandium,Yttrium, and Lanthanum. Crystal and Molecular Structure of 3-Chloro-9-Hydroxy-2,4-Dimethylpyrido[1,2-a]pyrimidinium Perchlorate

Complexes of scandium, yttrium, and lanthanum nitrates with 3-chloro-9-hydroxy-2,4-dimethylpyrido[1,2-a]pyrimidinium perchlorate (HL¹ClO₄) and 9-hydroxy-2,4-dimethylpyrido[1,2-a]pyrimidinium perchlorate (HL²ClO₄) were obtained. Their composition was formulated as Sc(LClO₄)₂(NO₃) and M(LClO₄)₂(NO₃)₂ (L = L¹ or L²; M = Y or La); structures for the complexes obtained were proposed. The crystal and molecular structure of HL¹ClO₄ was determined. Dissociation and complexation of HL¹ClO₄ and HL²ClO₄ in aqueous ethanol were studied using the spectroscopic method. Ligand dissociation and complexation constants were calculated. It was shown that a chlorine-containing organic ligand only slightly changes the composition and stability of the metal complexes.     

Structural parameters of the close environment of group III metal ions in aqueous solutions of their salts

Published data obtained by various research methods and our own experimental results on the structural characteristics of the nearest environment of aluminum, gallium, indium, thallium, as well as scandium, yttrium and lanthanum ions in aqueous solutions of their salts under ambient conditions are summarized. The structural parameters, like coordination number, interparticle distance, parameters of the second coordination sphere and the types of ion association are discussed. The hydrate complexes of the ions of aluminum and gallium subgroups are compared.     

Sur la séparation des terres rares XIII. Systèmes de solubilité comprenant des chlorures de terres cériques [1]

In aqueous solution, the chlorides of lanthanum, cerium and praseodymium cristallize as heptahydrates, those of the other rare earth elements as hexahydrates. Therefore, a miscibility gap exists in the solid phases in all systems comprising the two types of chlorides. Five ternary systems and a quaternary one with this behaviour have been studied.     

Determination of rare earths in selected rare earth matrices by spark source mass spectrometry

Three methods of preparing rare earth samples for mass spectrographic analysis are presented. Techniques for adding appropriate internal standards are described and relative sensitivity factors for rare earth impurities in rare earths, lanthanum, yttrium and scandium matrices are presented. Although indium has some value as an internal standard in rare earth samples, best analytical results are obtained when selected rare earths are used as internal standards.     

Stabilité des carboxylates de terres rares,IV N-acétylglycinates

The stability constants of N-acetylgycinates of some rare earths in aqueous solution have been determined by a potentiometric method, and by a solvent extraction technique. The ligand forms 1:1 complexes which are stabilized by relatively large positive entropies of formation, the corresponding enthalpies being endothermic. This backs up the assumption that a conjugate base of an amino acid forms innersphere complexes and acts as a unidentate ligand towards a rare earth cation, like a simple carboxylate.