Das System KCl/ErCl3 und die Modifikationen der Verbindungen K3LnCl6 (Ln = Ce–Lu,Y)

The System KCl/ErCl₃ and the Modifications of Compounds K₃LnCl₆ (Ln = Ce–Lu, Y) The phase diagram of the system KCl/ErCl₃ was investigated by DTA and XRD. Two compounds exist: KEr₂Cl₇ incongruently and K₃ErCl₆ congruently melting. Their thermodynamic functions for the formation from KCl and ErCl₃ were determined by solution calorimetry and emf vs T measurements in a galvanic cell for solid electrolytes. Both compounds are stable down to 0 K. – K₃ErCl₃ exists in three modifications. The structure of T–K₃ErCl₆ was determined by single crystal measurements: S.G. P2₁/c; Z = 4; a = 1309.8(5), b = 767.1(3), c = 1252.6(4) pm, β = 109.94(2)°. – A survey of all known results on compounds K₃LnCl₆ reveals, that from Ln = Ce to Ln = Ho they only are stable at higher temperatures, > 521 °C (Ce) and > –27 °C (Ho), resp.     

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.     

Ternäre Chloride in den Systemen ACl/EuCl3(A = Na?Cs)

Double Chlorides in the Systems ACl/EuCl₃ (A = Na? Cs) The phase diagrams of the pseudobinary systems ACl/EuCl₃ (A = Na? Cs) were investigated by DTA. T? and H? A₃EuCl₆ with A = Cs, Rb and T? and H? NaEuCl₄ were found in addition to other compounds already described in literature. Their powder diffractograms were indexed in analogy to known structure families. By solution calorimetry and measurements of e.m.f. = f(T) in galvanic cells for solid electrolytes the enthalpies ΔH and free enthalpies ΔG for the formation of the ternary chlorides from the compounds adjacent in the systems were determined. With KCl and NaCl only the compounds A₂EuCl₅ and NaEuCl₄ are stable at ambient temperature. Compared to the system with LnCl₃ (Ln = La? Nd) investigated previously, a tendency to structures with lower coordination numbers exists as was already detected in the systems ACl/SmCl₃.     

Ternary Chlorides of the Trivalent Early Lanthanides. Phase diagrams,crystal structures and thermodynamic properties

A comprehensive review on phase diagrams, crystal structures and thermodynamics of ternary chlorides formed in systems ACl/LnCl₃ (A=Cs, Rb, K, Na; Ln=La−Gd) is presented. The review summarizes the author’s own studies, published since 1985, and original papers of other scientists. With the larger alkali metal ions compounds such as A₃LnCl₆, A₂LnCl₅ and ALn₂Cl₇were obtained. With sodium additional compounds NaLnCl₄ and Na₃Ln₅Cl₁₈ were obtained. The crystal structures are discussed with the concept of ionic radii, which determine the coordination numbers of Ln³⁺ and A⁺ cations against Cl⁻ anions. The formation enthalpies of the compounds from ACl and LnCl₃ were determined by solution calorimetry. Gibbs’ free energies and entropies for these reactions were obtained by e.m.f. measurements vs. temperature. The stability of a ternary chloride in a systemACl−LnCl₃ is given by the ‘free enthalpy of synproportionation’, that is, the formation of a compound from its neighbour compounds in the system. This ΔG ⁰ _syn must be negative. A surprising result is, that the highest-melting compounds in the systems, A₃LnCl₆, are formed from ACl+A₂LnCl₅ by a loss in lattice energy. They exist as high-temperature compounds due to sufficiently high gain in entropy at temperatures whereTΔS>ΔH. This revised version was published online in August 2006 with corrections to the Cover Date.     

Syntheses and Crystal Structures of Lanthanide Chloride Complexes with Diglyme

Reactions of [LnCl₃(DME)₂] (Ln = Nd, Sm, Ho, Lu; DME = dimethoxyethane) and diglyme (diglyme = diethylen glycol dimethyl ether) in THF resulted in polymeric [LnCl₃(diglyme)]_n (Ln = Nd ( 1 ), Sm ( 2 )) or mononuclear complexes [LnCl₃(diglyme)(THF)] (Ln = Ho ( 3 ), Lu ( 4 )). Neodymium and samarium atoms in 1 and 2 are eight‐coordinated by three oxygen atoms from diglyme, one terminal and four bridging chloride ions. Holmium and lutetium atoms in 3 and 4 are seven‐coordinated by three oxygen atoms from diglyme, three chloride ions and one oxygen atom from THF. [ErCl₃(diglyme)(H₂O)] ( 5 ) resulted from the reaction of ErCl₃·6H₂O, (CH₃)₃SiCl and diglyme in THF. The molecular structures of 3 , 4 and 5 are similar, with either a molecule of THF coordinated to the lanthanide atom in 3 and 4 or with a molecule of water coordinated in 5 .     

Ternary chlorides of the trivalent late lanthanides

A comprehensive review on phase diagrams, crystal structures and thermodynamic properties of ternary chlorides formed in the systems ACl/LnCl₃ (A=Na, K, Rb, Cs) is presented. It continues an earlier review with the same contents on the lanthanides from La to Gd [1]. In both papers the author's own studies, published since 1985, together with original papers from other scientists are treated. With the three larger cations compounds of the composition A₃LnCl₆, A₂LnCl₅, ALn₂Cl₇ and beginning with holmium Cs₃Ln₂Cl₉ are formed. With sodium the compounds Na₃Ln₅Cl₁₈ (Ln=La to Sm) and NaLnCl₄ (Ln=Eu to Lu) also exist. The stability of a ternary chloride in a system ACl/LnCl₃ is given by the 'free enthalpy of synreaction', the formation of a compound from its neighbour compounds in its system. This must be negative. A surprising result is that the highest – melting compounds in the systems, A₃LnCl₆, are formed from ACl and A₂LnCl₅ with a loss of lattice energy, U. They exist as high-temperature compounds due to a sufficiently high gain in entropy at temperatures where the entropy term TΔS compensates the endothermic ΔH.     

Synthese und Aufbau von (4-Picolinium)[LnCl4(H2O)3] (Ln = La,Ce, Pr,Nd)

Preparation and Crystal Structure of (4-Picolinium)[LnCl₄(H₂O)₃] (Ln = La, Ce, Pr, Nd) The complex water containing chlorides (4-Picolinium)[LnCl₄(H₂O)₃] (Ln = La, Ce, Pr, Nd) were prepared for the first time, and the crystal structures of (4-Picolinium)[LnCl₄(H₂O)₃] (Ln = La, Pr) were determined on single crystals by X-ray methods. The isotypic compounds crystallize with triclinic symmetry, space group P1 , Z = 2. Surprisingly there exist the dimeric complex anions [Ln₂Cl₈(H₂O)₆]^2? (Ln = La, Pr).     

Zur Kenntnis der Zustandsdiagramme SECl3/MCl2 (SE = La,Sm, Gd,Yb; M = Sr,Ba)

On Phase Diagrams of Rare Earth Trichlorides/MCl₂ (Rare Earth = La, Sm, Gd, yb; M = Sr, Ba) The systems LaCl₃(SmCl₃, GdCl₃, YbCl₃)? SrCl₂(BaCl₂) were determined by difference thermal analysis. The phase diagrams contain compounds of the formula BaLnCl₅, M₂LnCl₇, Ba₃LnCl₉ and probably Sr₄LnCl₁₁, which decompose peritectoidally resp. peritectically. Sr₂SmCl₇ and Sr₂GdCl₇ are isotypic, and as indicated by the very similar reflection patterns of the Guinier photographs related to the structure of the compound Sm₃Cl₇. The phase diagrams are comparable to the systems LnCl₃? LnCl₂ with similar radii quotients of the cations. The enthalpies of mixing of the systems LaCl₃(GdCl₃, YbCl₃)? SrCl₂ were measured calorimetrically. The values are exothermic, the minima were found at approximately 65 mol-% SrCl₂.     

Synthese und Bau von (4-Picolinium)2[LnCl4(H2O)3]Cl (Ln = Eu,Ho)

Preparation and Structure of (4-Picolinium)₂[LnCl₄(H₂O)₃]Cl (Ln = Eu, Ho) The complex water containing chlorides (4-Picolinium)₂[LnCl₄(H₂O)₃]Cl (Ln = Eu, Ho) were prepared for the first time. The crystal structures were determined on single crystals by X-ray methods. The isotypic compounds crystallize with triclinic symmetry, space group P–1, Z = 2. Surprisingly the structures contain the complex anions [LnCl₄(H₂O)₃]^? (Ln = Eu, Ho) where the ligands form a distorted pentagonal bipyramid, which to our knowledge has not been observed in lanthanide compounds till now.     

Rb3LnCl6 · 2 H2O (Ln = La?Nd): Darstellung,Kristallstruktur und thermisches Verhalten

Rb₃LnCl₆ · 2 H₂O (Ln = La? Nd): Preparation, Crystal Structure, and Thermal Behaviour The compounds Rb₃LnCl₆ · 2 H₂O (Ln = La? Nd) were prepared from acetic acid as powders. The preparation from aqueous solutions does not yield the pure products because RbCl precipitates as first compound. The structure of Rb₃LaCl₆ · 2 H₂O was determined by X-ray analysis of a single crystal obtained from aqueous solution. The compounds with Ln = La? Nd are isotypic. They crystallize hexagonally in the space group P6₃/m (Rb₃LaCl₆ · 2 H₂O: a = 1 220.4(2) pm, c = 1 688.6(3) (pm) with Z = 6. Anionic trimeric units [Ln₃Cl₁₂(H₂O)₆]^3? are stacked along the c-axis over the corners of the unit cell. In the stacking frequency the units are rotated by 60° with respect to each other around the c-axis. The coordination number (C. N.) of Ln³⁺ is 8, which is satisfied by four bridging and two terminal chloride ions and two water molecules. The coordination spheres of the three rubidium ions in the different atomic positions are composed differently, their C.N. are 9, 8(+1) and 6(+6). The thermal dehydration of the compounds occurs in one step. The hydrates decompose at ca. 100°C to form the anhydrous compounds Rb₂LnCl₅ und RbCl since the anhydrous chlorides Rb₃LnCl₆ are thermodynamically stable above ca. 400°C only.     

Thermochemische Untersuchungen an Mischungen einiger Lanthanoidchloride mit CuCl,AgCl und TlCl

Thermochemical Investigations on Mixtures of Some Lanthanoide Halides with CuCl, AgCl, and TlCl The phase diagrams CuCl/LaCl₃ (GdCl₃, YbCl₃), AgCl/LaCl₃ (GdCl₃, YbCl₃) and TlCl/LaCl₃ (GdCl₃, YbCl₃) were determined by difference thermal analysis. The systems with CuCl resp. AgCl as component are eutectic, however in mixtures with YbCl₃ the compounds Cu₃YbCl₆ and Ag₃YbCl₆, resp., which decompose peritectically, were observed. The systems with thallous chloride contain several compounds, namely TlLn₂Cl₇ (TlCl/GdCl₃ resp. YbCl₃), Tl₂LnCl₅ (TlCl/LaCl₃ resp. GdCl₃) and Tl₃LnCl₆ (TlCl/GdCl₃ resp. YbCl₃). The enthalpies of mixing of liquid mixtures of AgCl/LaCl₃ and AgCl/YbCl₃ were measured calorimetrically at 1173 K. On comparing the alkali chloride–lanthanoide chloride systems with the MCl systems presented in this paper some differences were observed. The M⁺ ions with d¹⁰ configuration decrease the tendency to form ternary halides in the MCl? LnCl₃ systems, the enthalpies of mixing are also much less exothermic than those of the comparable NaCl + LnCl₃ mixtures. The Tl⁺ ion with d¹⁰ s² configuration on the other hand behaves like an alkali cation of comparable size.     

Structure of SmCl3, DyCl3, and HoCl3 molecules based on the data of synchronous electron diffraction and mass-spectrometric experiment

Saturated vapors of SmCl₃, DyCl₃, and HoCl₃ have been studied in the framework of a synchronous electron diffraction and mass-spectrometric experiment at temperatures 1205 K, 1160 K, and 1148 K, respectively. In vapors of all compounds, along with monomer molecular forms, an insignificant (up to 2 mol.%) amount of dimers was detected. Parameters of the effective configuration of monomer molecules were determined. For molecules SmCl₃, DyCl₃, and HoCl₃ values of internuclear distances r _g(Ln-Cl) were 2.511(5) Å, 2.453(5) Å, and 2.444(5) Å, values of valence angles ∠_g(Cl-Ln-Cl) were 115.6(11)°, 116.8(10)°, and 116.6(10)°, respectively. It is shown that parameters of the r _g-structure are not incompatible with the notion of a planar equilibrium geometrical configuration of molecules SmCl₃, DyCl₃, and HoCl₃. Main tendencies in the change of structural and vibration characteristics in the series of lanthanide trichlorides are considered.     

Synthesis and structural study of a lithium complex of 6-methyl-2-(trimethylsilylamino)pyridine and its use in the formation of some lanthanoid complexes

Lithiation of 6-methyl-2-(trimethylsilylamino)pyridine (APyTMSH) occurs smoothly in tetrahydrofuran (thf) affording [Li(APyTMS)(thf)]₂ (1). Treatment of anhydrous lanthanoid chlorides (LnCl₃, Ln=Gd, Er) with 1.5 equivalents of (1) yields the solvent-free homoleptic tris–amido complexes [Ln(APyTMS)₃], (Ln=Gd (2); Ln=Er (3)). Similar treatment of LnCl₃ (Ln=Gd, Er) with one equivalents of 1 putatively generates the heteroleptic species [Ln(APyTMS)₂Cl], (Ln=Gd (4); Ln=Er (5)) in situ, however, these compounds undergo redistribution in hexane to yield homoleptic 2 and 3 and the anhydrous lanthanoid halides (Ln=Gd, (6), Ln=Er (7)) and were therefore not fully characterised. These lanthanoid reagents are extremely moisture sensitive as examplified by the low yield isolation of [APyH₂·H]₂[ErCl₅(thf)] during one prepartion of 3. The structures of compounds 1, 2, 3 and 8 were characterised by X-ray crystallographic methods. The X-ray structure of 1 is a centrosymmetric dimer similar to its diethyl ether analogue. Compounds 2 and 3 are six-coordinate homoleptic mononuclear species and compound 8 comprises the unprecedented [ErCl₅(thf)]⁻ anion within an intricate hydrogen-bonded ionic system.     

Separating Behaviors of Heavier Rare Earth Metal Ions in Centrifugal Partition Chromatography with Di(2-Ethylhexyl) Phosphoric Acid

Abstract

The separating behaviors of SmCl₃, EuCl₃, GdCl₃, TbCl₃, DyCl₃, HoCl₃, ErCl₃, TmCl₃, YbCl₃, and LuCl₃ in Centrifugal Partition Chromatography with the stationary phase containing a separator, Di(2-ethylhexyl) phosphoric acid (D2EHPA), are examined. The separation trends of these heavier rare earth metal ions were found to be almost as expected from the observations reported for the lighter rare earth metal ions. And the separator is also useful for mutual separation of these heavier rare earth metal ions.     

The ternary system CsCl−NaCl−LaCl3

The ternary system CsCl?NaCl?LaCl₃ was investigated by means of differential thermal analysis and X-ray powder diffraction analysis. There exists one congruently melting compound, Cs₂NaLaCl₆, crystallizing with the cubic elpasolite structure. No quasi-binary section exists for the whole system, however three binaries range from the ternary compound Cs₂NaLaCl₆ to NaCl, CsLa₂Cl₇ and Cs₃LaCl₆ resp., dividing the system in three areas of composition: one triangle, Cs₃LaCl₆?Cs₂NaLaCl₆?CsLa₂Cl₇, containing additionally a compound Cs₂LaCl₅ below 510°C, and the two areas CsCl?NaCl?Cs₂NaLaCl₆?Cs₃LaCl₆ and Cs₂NaLaCl₆?NaCl?LaCl₃?CsLa₂Cl₇, containing a mixed crystal range between LaCl₃ and Na₃La₅Cl₁₈. These areas could be further divided in five triangles, so that the whole system contains six Alkemade triangles.     

The chlorides Na3MCl6 (M  Eu?Lu,Y, Sc): Synthesis,crystal structures,and thermal behaviour

Single crystals of Na₃ErCl₆ were obtained via the metallothermic reduction of ErCl₃ with Na. The crystal structure is that of the mineral cryolite with a = 684.54(4), b = 725.18(4), c = 1012.39(6) pm, β = 90.768(5)°, Z = 2, space group P2₁/n. Two applicable synthetic routes to pure powder samples of the chlorides Na₃MCl₆ (M ? Eu? Lu, Y, Sc) are described. With M ? Dy? Lu, Y, Sc, these are isotypic with Na₃ErCl₆ while those with M ? Eu, Gd, Tb adopt a ?stuffed”? LiSbF₆-type structure. The dimorphism of Na₃GdCl₆ and dependence of the lattice constants and the molar volume upon temperature has been investigated: At 205°C, a first-order phase transition from the stuffed LiSbF₆-type Na₃GdCl₆-I to the cryolite-type Na₃GdCl₆-II occurs exhibiting a 3.71% negative molar volume discontinuity.     

Ternäre Chloride in den Systemen ACl/GdCl3 (A = Na?Cs)

Ternary Chlorides in the Systems ACl/GdCl₃ (A = Na? Cs) The phase diagrams of the pseudobinary systems ACl/GdCl₃ (A = Na? Cs) were investigated by DTA. Their powder diffractograms were indexed in analogy to known structure families. By solution calorimetry and measurements of e.m.f. = f(T) in galvanic cells for solid electrolytes the enthalpies ΔH⁰ and free enthalpies ΔG⁰ for the formation of the ternary chlorides from the compounds adjacent in the systems were determined. The systems with A = K, Rb, Cs are analogous to those with Sm³⁺ and Eu³⁺. There exist compounds A₃GdCl₆, A₂GdCl₅ and AGd₂Cl₇. Cs₂GdCl₅ is crystallysing in the Cs₂DyCl₅ type; the Rb- and K-compounds and also Na₂GdCl₅ have the K₂PrCl₅?structure. In the system NaCl/GdCl₃ additionally the compounds NaGdCl₄ and Na₃GdCl₆ were found. L? Na₃GdCl₆ is metastable compared with (NaCl + Na₂GdCl₅); above 265°C stable H? Na₃GdCl₆ is existing (cryolite-structure).     

Die Systeme des Typs MCl/AlCl3/SO2 (M = Li,Na, K,NH4)

The MCl/AlCl₃/SO₂ Systems (M = Li, Na, K, NH₄) Phase diagrams of the ternary systems of the type MCl/AlCl₃/SO₂ were determined by measurement of SO₂ pressure, solubilities, and by thermal analysis. The complete phase diagram in the range from ?30 to +50°C is given for the case M = Na, partial diagrams for M = Li, K, NH₄. There exist solid compounds of the type MAlCl₄ · nSO₂ (M = Li, Na; n = 1.5 and 3) (M = K; n = 1.5 and 5) (M = NH₄; n = 5). Liquid phases can be obtained at room temperature and atmospheric pressure in the NaCl or LiCl containing systems.     

Ternäre Chloride in den Systemen ACl/YCl3 (A = Cs,Rb, K,Na)

Ternary Chlorides in the Systems ACl/YCl₃ (A = Cs, Rb, K, Na) Phase diagrams of the pseudobinary systems ACl/YCl₃ (A = Cs, Rb, K, Na) were investigated by DTA and XRD. In all systems compounds of the type A₃YCl₆ and AY₂Cl₇ are formed. Furthermore the chlorides A₂YCl₅ exist with A = Cs, Rb and K, and Cs₃Y₂Cl₉ and NaYCl₄ were found. The unit cells of compounds with still unknown structure, were determined by X-ray diffraction on crystal powders. By a combination of solution calorimetry and e.m.f. measurements in galvanic cells for solid electrolytes thermodynamic functions for the formation of A_nYCl_n+3 from (nACl + YCl₃) were measured. The compounds Cs₃Y₂Cl₉, Rb₂YCl₅ and K₃YCl₆ are stable in competition with the adjacent compounds in their systems only at temperatures > 0 K. The systems ACl/YCl₃ are only gradually different from the systems ACl/HoCl₃.     

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⁺.