Some features of formation and dissolution of a series of Pu(IV) and Zr alkyl and butyl alkyl phosphates in the system tBP — N-dodecane — Nitric acid — Water

The formation and composition of salts produced on interaction of a series of alkyl- and butylalkylphosphoric acids having alkyl radical chain lengths from C₄ to C₁₀ with Pu(IV) and Zr in organic and aqueous phases of the system TBP — n-dodecane — nitric acid — water have been studied. The composition of compounds was found to depend on the conditions of their formation, being defined first of all by the HNO₃ concentration in aqueous and organic phases.     

Interaction of Thulium,Ytterbium(III) and Lutetium Chlorides with Sodium Chloride

The pseudobinary systems NaCl—LnCl₃ (Ln=Tm, Yb, Lu) were investigated by DTA and X-ray diffraction. Two types of ternary chlorides exist: congruently melting compounds Na₃LnCl₆ with the cryolite-structure, incongruently melting compounds NaLnCl₄ with the NaErCl₄-Ln (Ln=Tm) or the NaLnCl₄-structure (Ln=Yb, Lu). All these structure types contain [LnCl₆]-octahedra.By solution calorimetry and e.m.f. measurements in galvanic cells for solid electrolytes could be proved that all compounds are formed from NaCl and LnCl₃ by gain in lattice enthalpy.This revised version was published online in November 2005 with corrections to the Cover Date.     

Sur de nouveaux composés oxyfluorés des terres rares de structure pyrochlore

The action of NaF on rare earth oxides with the columbite or aeschynite structure leads to pyrochlore-type phases of formula NaTTiNbO₆F (T = Y, Ce, …, Yb). On the other hand, the substitution of cadmium by a rare earth and of oxygen by fluorine in T₂Ti₂O₇ gives isostructural phases of formula CdTTI₂O₆F (T = Y, Nd … Yb). The dielectric properties of the solid solutions between both phases and Cd₂Nb₂O₇ characterize ferroelectric-paraelectric transitions. The substitution of oxygen by fluorine brings about a decrease in the Curie temperature, but a very small substitution rate increases the dielectric constant and the spontaneous polarization.     

Determination of Vapor Pressures Using Extrapolation of Adjusted Retention Times

Vapor pressure is one of the fundamental properties which govern the distribution of organic compounds in the environment. This property is estimated for five series of homologous substituted alkanes of the type H—(CH₂)_n—Y, where Y denotes Cl, Br, CHO, COOCH₃, OCOCH₃ and n varies from 5 to 14 using extrapolation of adjusted retention times to 25 °C. The results are compared with those obtained by using indirect methods for 40 compounds and a significant improvement is obtained. Indeed, the absolute average error percentage for the same series does not exceed 2.6%     

Fullerides: heterometallic superconductors with composition M<Subscript>2</Subscript>M′C<Subscript>60</Subscript> (M = K,Rb; M′ = Yb,Lu, Sc)

One- or two-step reactions of potassium and rubidium fullerides with composition M_k C₆₀ (M = K, Rb; k = 3—6) and K₆C₆₀ + m K mixtures (m = 1, 3) with anhydrous salts MCl₃ (M = La, Pr, Nd, Sm, Gd, Tb, Yb, Lu, Y, Sc) and YbI₂ in a toluene—THF medium afforded heterometallic fullerides M_3–nM_nC₆₀ (n = 1—3). Among these compounds, substituted fullerides with composition M₂MC₆₀ (M = Yb, Lu, Sc) display superconducting properties with critical temperatures of 14—20 K.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1623–1628, August, 2004.     

Chiral Benzamidinate Ligands in Rare‐Earth‐Metal Coordination Chemistry

The treatment of the recently reported potassium salt (S)‐N,N′‐bis‐(1‐phenylethyl)benzamidinate ((S)‐KPEBA) and its racemic isomer (rac‐KPEBA) with anhydrous lanthanide trichlorides (Ln=Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)‐PEBA}₃Sm], bis(amidinate) complexes [{Ln(PEBA)₂(μ‐Cl)}₂] (Ln=Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl)₂(thf)_n] (Ln=Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)–amido complexes [{(S)‐PEBA}₂Ln{N(SiMe₃)₂}] (Ln=Y, Lu) were synthesized by an amine‐elimination reaction and salt metathesis. All of these chiral bis‐ and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac‐PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)‐PEBA}₂Ln{N(SiMe₃)₂}] (Ln=Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound.     

Solubility Isotherm and Thermal Analysis of the Selenites of the Three-Component System La2O3—SeO2—H2O at 100°C

The solubility isotherm of the system La₂O₃—SeO₂—H₂O at 100°C was studied. The compounds of the three-component system were identified by the Schreinemakers method as well as by chemical and X-ray phase analyses. Simultaneous TG and DTA analyses of all compounds of the system were made by using a derivatograph. The mechanism of thermal decomposition was described.This revised version was published online in November 2005 with corrections to the Cover Date.     

Investigations into the formation and characterization of microemulsions. I. Phase diagrams of the ternary system water—sodium alkyl benzene sulfonate—hexanol and the quaternary system water—xylene—sodium alkyl benzene sulfonate—hexanol

The phase diagrams of the ternary system water—sodium alkylbenzene sulfonate (NaDBS)-hexanol and the quaternary system water—xylene—NADBS—hexanol have been established at three different temperatures, namely 25, 37, and 50°C. The different phases formed have been qualitatively examined using optical (phase contrast and polarizing) microscopy. The textures of the various liquid crystalline phases in the ternary system have been identified, by comparison with previous studies in the literature. Some of the liquid crystalline phases have been quantitatively assessed using low angle X-ray diffraction. The latter measurements were also used to determine the unit cell dimensions in the various phases studied. With the quaternary system, particular attention was paid to the transparent region which consisted of an L₂ (inverse micellar) phase extending into another transparent region which has a blue “tinge” in some cases, namely the microemulsion (M) region. The amount of water solubilized in the L₂ (reverse micelle) or M + L₂ phase was calculated from the phase diagrams. With the ternary system the results showed a maximum in moles of water solubilized per mole total surfactant (NaDBS + hexanol) at a concentration of 0.3 mole surfactant, at an optimum molar ratio of n-hexanol to NaDBS of 4.5:1. This maximum was about twice with the quaternary system, when compared with that of the ternary system, indicating the importance of the role of xylene in solubilization of water by the surfactants. The present investigation has also shown that the extent of the microemulsion region is significantly reduced by increases of temperature when the NaDBS is lower than 15 wt%.     

Silicide und Germanide mit Gd6Cu8Ge8-Struktur

Zusammenfassung Die Verbindungen {Sc,Y,Tb,Dy,Ho,Er,Tm,Yb,Lu}₆Cu₈Si₈ sowie {Y,Yb}₆Cu₈Ge₈ werden hergestellt. Diese sind isotyp mit der Gd₆Cu₈Ge₈-Struktur. Die Gitterparameter werden ermittelt.

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Silicides and germanides with Gd₆Cu₈Ge₈-structure type

The compounds {Sc,Y,Tb,Dy,Ho,Er,Tm,Yb,Lu}₆Cu₈Si₈ and {Y,Yb}₆Cu₈Ge₈ have been prepared. They were found to be analogous with the Gd₆Cu₈Ge₈-structure type. The lattice parameters have been determined.

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Complexes of Heavy Lanthanides and Yttrium with 3,4-dimethoxybenzoic Acid

The complexes of yttrium and heavy lanthanides with 3,4-dimethoxybenzoic acid of the formula: Ln(C₉ H₉ O₄ )₃ ×n H₂ O, where Ln =Y(III), Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III) and Lu(III), and n =4 for Tb(III), Dy(III), n =3 for Ho(III), and n =0 for Er(III), Tm(III), Yb(III), Lu(III) and Y(III) have been prepared and characterized by elemental analysis, IR spectroscopy, thermogravimetric and magnetic studies and X-ray diffraction measurements. The complexes have colours typical of Ln³⁺ ions (Ho - cream, Tb, Dy, Yb, Lu, Y - white, Er - salmon). The carboxylate group in these complexes is a symmetrical, bidentate, chelating ligand. They are crystalline compounds characterized by various symmetry. On heating in air to 1273 K the hydrated 3,4-dimethoxybenzoates decompose in two steps while those of anhydrous only in one stage. The tetrahydrates of Tb and Dy and trihydrate of Ho 3,4-dimethoxybenzoates are firstly dehydrated to form anhydrous salts that next are decomposed to the oxides of the respective metals. The complexes of Er, Tm, Yb, Lu and Y are directly decomposed to the oxides of the appropriate elements. The solubility in water at 293 K for yttrium and heavy lanthanides is in the order of 10^-4 -10^-3 mol dm^-3 . The magnetic moments of the complexes were determined over the range 77–298 K. They obey the Curie-Weiss law. The values of μ_eff calculated for all compounds are close to those obtained for Ln³⁺ by Hund and van Vleck. The results show that there is no influence of the ligand field on 4f electrons of lanthanide ions in these polycrystalline compounds and 4f electrons do not take part in the formation of M-O bonding. This revised version was published online in July 2006 with corrections to the Cover Date.     

Triangulation in the Li2O-Ln2O3-B2O3 (Ln = Nd, Eu, Dy, Yb, and Y) systems and the melting character of ternary compounds

Li₂O-Ln₂O₃-B₂O₃ (Ln = Nd, Eu, Dy, Yb, and Y) ternary systems were studied along their inner sections. Two types of ternary compounds were found: Li₃Ln₂(BO₃)₃ (Ln = Nd, Eu, Dy, and Yb) and Li₆Ln(BO₃)₃ (Ln = Dy and Yb). The systems were triangulated. Melts were chosen for growing single crystals of ternary compounds in multinary systems. Original Russian Text ? Sh.A. Gamidova, 2009, published in Zhurnal Neorganicheskoi Khimii, 2009, Vol. 54, No. 1, pp. 142–145.     

Active nickel-based reduction of organic compounds

The reducing system NiCl₂·2H₂O—Li—arene_cat (cat is catalyst) was proposed for use to reduce a wide range of organic compounds, including alkenes, alkynes, carbonyl compounds, imines, halogenated derivatives, sulfonates, aromatic compounds, hydrazines, azo and azoxy compounds, N-oxides, and nitrones. The degree of reduction can be controlled for some substrates. Deuterium can be incorporated in the reaction products using nickel chloride deuteriohydrate. Nitrones, N-alkoxyamides, and acyl azides are also reduced with the Li—arene_cat system containing no nickel salt.     

Die Abbaustufen von Tetrahydrofuranverbindungen der Seltenerdchloride

Zusammenfassung Die Ermittlung der Abbaustufen von Seltenerdchlorid-Tetrahydrofuran-(THF)-Verbindungen durch isothermen kinetischen Abbau bestätigte die früher auf Grund der Zusammensetzung und Löslichkeit inTHF getroffene Gruppeneinteilung. Die Verbindungen der Zusammensetzung MeCl₃·2THF ergaben eine Zwischenstufe MeCl₃·0,5THF, die der Formel MeCl₃·3,3–3,6THF je eine Phase MeCl₃·THF und MeCl₃·0,5THF. Abweichend verhielten sich die Addukte von La, Ce und Yb. Die Dampfdruckwerte von PrCl₃·2THF und NdCl₃·2THF wurden bei verschiedenen Temperaturen gemessen und daraus die jeweilige Zersetzungsenthalpie bestimmt. Durch direktes Erhitzen im Hochvakuum konnte dasTHF aus allen Verbindungen (außer der des Yb) völlig entfernt werden.

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The isothermally determined degradation steps of the compounds of the chlorides of the rare earths with tetrahydrofurane (THF) correspond with the grouping which had already been found following their composition and solubilities inTHF. The compounds of the composition MeCl₃·2THF gave an intermediate MeCl₃·0,5THF, the compounds MeCl₃·3.3–3.6THF formed the intermediate phases MeCl₃·THF and MeCl₃·0.5THF. The adducts of La, Ce and Yb did not correspond to this generalisation. The vapor pressures above PrCl₃·2THF and NdCl₃·2THF were determined at different temperatures, and the corresponding enthalpies of decomposition were calculated. Heating in a high vacuum completely removes allTHF except from the Yb compounds.

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Frau Prof. Dr.E. Cremer zum Geburtstag gewidmet.     

Synthese und Kristallstrukturen der Ternären Selten-Erd-Chloride NaMCl4 (M = Eu—Yb,Y)

Synthesis and Crystal Structures of the Ternary Rare Earth Chlorides NaMCl₄ (M = Eu—Yb, Y) Single crystals of NaErCl₄ were obtained from the melt of NaCl and ErCl₃ (1:1 molar ratio) by slow cooling. It crystallizes in the monoclinic crystal system (space group P2/c) with the structure of α-NiWO₄ with a = 632.24(9) pm, b = 759.78(9) pm, c = 674.2(1) pm, b? = 92.310(3)°, Z = 2. Two preparative routes to pure powder samples of the chlorides NaMCl₄ are described. At room temperature, these are found to be isotypic with NaErCl₄ (M = Tm—Yb; II) while the triclinic structure of NaGdCl₄ is adopted with M = Gd—Ho, Y (I). Phase transitions from one structure to the other are observed for all compounds. The transition temperatures decrease with decreasing size of the ion M³⁺.     

Dilatometric examinations of lead(II) oxychlorides

The thermal properties of the lead(II) oxychlorides Pb₅Cl₂O₄, Pb₃Cl₂O₂ and Pb₂Cl₂O, formed in the binary system PbO-PbCl₂, were examined. During thermal and dilatometric analyses of these compounds, several thermal and dilatational effects not previously described in the literature were found to occur.     

Synthesis, chemical bonding and physical properties of RERhB4 (RE=Y, Dy-Lu)

The compounds of rare-earth metals with rhodium and boron RERhB₄ (RE=Y, Dy-Lu) crystallize with the orthorhombic structure type YCrB₄ (space group Pbam, Pearson symbol oP24). The crystal structures of the compounds with RE=Y, Er, Tm and Yb were refined by using single-crystal diffraction data. Analysis of chemical bonding for YRhB₄ and YbRhB₄ was performed by electron localizability indicator and by calculation of quantum chemical charges (quantum theory of atoms in molecules). Boron and rhodium form the 3-D polyanion containing planar nets of three-bonded boron atoms interconnected by rhodium along [001]. The interaction of the RE species with the rhodium-boron polyanion is predominantly ionic. Magnetic susceptibility data of TmRhB₄ and YbRhB₄ showed that the RE species are in 4f¹² (Tm) and 4f¹³ (Yb) electronic states, respectively. In the low-temperature region, the specific heat revealed a Schottky anomaly for TmRhB₄ while an antiferromagnetic transition is observed at 3.5 K for YbRhB₄. X-ray absorption measurement at the Yb L_III edge for YbRhB₄ reveals the 4f¹³ state of ytterbium.     

Solution and Solid-State Photophysical Properties of Positional Isomeric Acrylonitrile Derivatives with Core Pyridine and Phenyl Moieties: Experimental and DFT Studies

The compounds I (Z)-2-(phenyl)-3-(2,4,5-trimethoxyphenyl)acrylonitrile with one side (2,4,5-MeO-), one symmetrical (2Z,2′Z)-2,2′-(1,4-phenylene)bis(3-(2,4,5-trimethoxyphenyl)acrylonitrile), II (both sides with (2,4,5-MeO-), and three positional isomers with pyridine (Z)-2-(pyridin-2- 3, or 4-yl)-3-(2,4,5-trimethoxyphenyl)acrylonitrile, III–V were synthetized and characterized by UV-Vis, fluorescence, IR, H¹-NMR, and EI mass spectrometry as well as single crystal X-ray diffraction (SCXRD). The optical properties were strongly influenced by the solvent (hyperchromic and hypochromic shift), which were compared with the solid state. According to the solvatochromism theory, the excited-state (μ_e) and ground-state (μ_g) dipole moments were calculated based on the variation of Stokes shift with the solvent’s relative permittivity, refractive index, and polarity parameters. SCXRD analyses revealed that the compounds I and II crystallized in the monoclinic system with the space group, P2₁/n and P2₁/c, respectively, and with Z = 4 and 2. III, IV, and V crystallized in space groups: orthorhombic, Pbca; triclinic, P-1; and monoclinic, P2₁ with Z = 1, 2, and 2, respectively. The intermolecular interactions for compounds I–V were investigated using the CCDC Mercury software and their energies were quantified using PIXEL. The density of states (DOS), molecular electrostatic potential surfaces (MEPS), and natural bond orbitals (NBO) of the compounds were determined to evaluate the photophysical properties.     

Crystal structure and thermal stability of Ni151.5Pb24S92. Search for selenium- and tellurium-containing analogs

The crystal structure of the subvalent nickel—lead sulfide, which has been described previously as Ni₆₀Pb₉S₃₁, was established and the composition of this sulfide was refined based on powder X-ray diffraction data. The true Ni_151.5Pb₂₄S₉₂ composition of this compound was confirmed by the EDX techniques. The temperature range of stability of this compound (490—578 °C) was refined by differential thermal analysis. In the search for analogs, the triangulation of the Ni—Pb—Se and Ni—Pb—Te systems at 540 °C was carried out for the first time. No new ternary phases were detected.     

Solid state reactions in Al based composites made by mechanofusion

Mixtures of aluminium and other metal powders were milled in a Hosokawa AM-15F mechanofusion system in order to produce composite materials with coated or layered microstructure. These composites were then annealed or used in plasma spraying experiments. The intermetallic phases produced in the consecutive steps of the treatment were investigated by different methods.In the case of the Al-Ni powder system the presence of intermetallic phases confirmed that phase forming solid state reactions start during the first, mechanofusion step. After milling the powder mixture in the Hosokawa equipment, crystalline Al₃Ni could be detected by TEM. A second intermetallic phase, Al₃Ni₂ was also observed after a heat treatment at 750 K. In Al-Cu-Fe and Al-Cu-Co powder composites, produced by milling, binary and ternary phases could be found only after plasma spraying. That means that in these cases the thermodynamic and kinetic requirements of the reactions could not be fulfilled by this mild milling. Nevertheless, the considerably large specific surface of the metal-metal interfaces, formed during the milling process in the ternary composites, makes it possible to produce multi-phase coatings from these composites. It means that only two technological steps are required (milling — plasma spraying). All of the other known technologies consist of three steps: alloy preparation — milling — plasma spraying or alloy preparation —atomisation — plasma spraying.Similarities and differences between the reactions taking place in thin films and thin and/or small milled particles are discussed.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday     

Negative thermal expansion in rare earth molybdates

Negative thermal expansion in rare earth molybdates of A₂Mo₃O₁₂ family (A=Y, Er, Yb and Lu) is measured by high temperature X-ray diffraction and dilatometry. Rare earth molybdates which are isostructural with the corresponding rare earth tungstates, also exhibit this phenomena attributed to transverse acoustic vibrations. The rare earth molybdates of A₂M₃O₁₂ family with an orthorhombic structure (A=Y, Er, Yb and Lu) are highly hygroscopic and exhibit negative thermal expansion after the complete removal of water molecules. Axial thermal expansion co-efficient calculated from high temperature X-ray diffraction (RT-1073K) shows rare earth size effect. As the ‘A’ cation decreases in size, the thermal expansion co-efficient along ‘b’ axis and the linear thermal expansion co-efficient become less negative. The thermal expansion behaviour of the tetragonal La₂Mo₃O₁₂ is also reported to demonstrate the effect of crystal structure.