Ternäre Fluoride mit vierwertigem Chrom: M″CrF6mit M″ = Ba,Sr, Ca,Mg, Zn,Cd, Hg,Ni

Ternary fluorides with tetravalent chromium: M^IICrF₆ with M^II = Ba, Sr, Ca, Mg, Zn, Cd, Hg, Ni. We obtained hithertoo unknown BaCrF₆ (light yellow) and SrCrF₆ (yellow), both of (hexag.) BaSiF_B-type [a = 7.32₈, c = 7.13₇ Å; and a = 7.10₉ c = 6.86₃ Å, respectively] as well as CaCrF₆ (pink) [a = 5.33₆, c = 14.15₃ Å], MgCrF₆ (pink) [a = 5.09₁ c = 13.14₃ Å], CdCrF₆ (pink) [a = 5.14₆, c = 14.07₅ Å] and HgCrF₆ (orange-yellow) [a = 5.12₈, c = 14.26₅ A], all of (hexag.) LiSbF₆-type. NiCrF₆ (brown) [a = 4.97₅, c = 13.26₂ Å] and ZnCrF₆ (orange-yellow) [a = 5.02₆, c = 13.33₇ Å] crystallize in the hexag. VF₃-type.     

Ternäre Halogenide vom Typ A3MX6. II. Das System Ag3−xNaxYCl6: Synthese,Strukturen, Ionenleitfähigkeit

Ternary Halides of the A₃MX₆ Type. II. The System Ag_3?xNa_xYCl₆: Synthesis, Structures, Ionic Conductivity . The influence of the substitution of Ag⁺ by Na⁺ ions on the crystal structure and the ionic conductivity of Ag₃YCl₆ (stuffed LiSbF₆-type structure) has been investigated. The system Ag_3?xNa_xYCl₆ forms a complete solid solution. The stuffed LiSbF₆-type structure is stable for all compositions. For compounds with Na⁺ contents of x > 1.67, the cryolite-type structure is observed as the high-temperature form. The transition temperature decreases steadily with increasing Na⁺ content. The “end member” phase Na₃YCl₆ transforms at 243 K from the monoclinic cryolite-type structure to the stuffed LiSbF₆-type structure (trigonal, R3 ; a = 697.3(1), c = 1 868.4(14) pm, Z = 3; R = 0.094; R_w = 0.069). The crystal structures of Ag_1.3Na_1.7YCl₆ (trigonal, R3 ; a = 691.5(2), c = 1 853.7(6) pm, Z = 3; R = 0.099, R_w = 0.081) and AgNa₂YCl₆ (trigonal, R3 ; a = 691.7(1), c = 1 853.9(5) pm, Z = 3; R = 0.099, R_w = 0.064) have also been determined. Both chlorides crystallize like Ag₃YCl₆ and Na₃YCl₆-I in the stuffed LiSbF₆-type structure. The monovalent cations, Ag⁺ and Na⁺, are distributed over the five octahedral voids that are occupied by the Ag⁺ ions alone in Ag₃YCl₆. The ionic conductivity for compounds within the solid solution Ag_3?xNa_xYCl₆ decreases with increasing Na⁺ content. The values for Na₃YCl₆ (σ = 1 · 10^?6 Ω^?1 cm^?1 at T = 500 K) are by 2.5 to 3.5 orders of magnitude smaller than those for Ag₃YCl₆ (σ = 6 · 10^?4 Ω^?1 cm^?1 at T = 500 K).     

Der Übergang vom „geordneten”︁ Anti-PbCl2-Gitter zum Anti-PbFCl-Gitter: Ternäre Phasen ABX der Erdalkalimetalle mit Elementen der 4. Hauptgruppe (A = Ca,Sr, Ba; B = Mg; X = Si,Ge, Sn,Pb)

The transition of the “ordered” anti-PbCl₂ lattice in the anti-PbFCl lattice: The ternary phases ABX of the alkaline earths with main group IV elements (A = Ca, Sr, Ba; B = Mg; X = Si, Ge, Sn, Pb) The compounds CaMgX, SrMgX and BaMgX (X = Si, Ge, Sn, Pb) were synthesized and their structures determined. CaMgX and SrMgX crystallize in the “ordered” Anti-PbCl₂-type and are therefore related to the binary compounds Ca₂X(X = Si, Ge, Sn, Pb), which form the Anti-PbCl₂-type too. The phases BaMgX build up the Anti-PbFCl-structure. The relations of these two different structures are discussed in respect to the radii of the components.     

Zur Chemie und Kristallchemie von Verbindungen des Typs AcLnX6 (Ac: Th,U; Ln: Seltene Erden; X: Br,I)

On Chemistry and Crystal Chemistry of AcLnX₆ Compounds (Ac = Th, U; Ln = Rare Earths; X = Br, I) . Reactions of AcX₄ (Ac: Th, U; X: Br, I) with Rare Earth Dihalides LnX₂ lead to AcLnX₆ compounds with Ln = Sm, Eu, Dy, Tm, Yb. In the case of the other Rare Earth compounds redox reactions and formation of the trihalides of Ac and Ln occur. Thermodynamic calculations help to understand the reaction paths. Different structure types (β- and γ-ThSnI₆-type) occur depending on the radius ratio of the ions. They are statistical or ordered substitutions variants of AB₃ structures (BiI₃- or PuBr₃-type). The compounds UBI₆ (B: Sr, Eu, Ba) crystallize in their own structure type. All these compounds and those having a β-ThSnI₆ structure can be transformed to a γ-ThSnI₆-type modification under pressure.     

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.     

Die Chloride Na3xM2–xCl6 (M = La?Sm) und NaM2Cl6 (M = Nd,Sm): Derivate des UCl3-Typs. Synthese,Kristallstruktur und Röntgenabsorptionsspektroskopie (XANES)

The Chlorides Na_3xM_2–xCl₆ (M = La? Sm) and NaM₂Cl₆ (M = Nd, Sm): Derivatives of the UCl₃-Type of Structure. Synthesis, Crystal Structure and X-Ray Absorption Spectroscopy (XANES) Single crystals of the derivatives of the UCl₃-type structure Na_3xM_2–xCl₆ (M = La/x = 0.364(4); Ce/0.349(5); Pr/0.318(8); Nd/0.305(5); Sm/0.246(4)) and NaSm₂Cl₆ were grown by different methods generally under reducing conditions. They are addition [Na(Sm₂)Cl₆] and addition/substitution variants [Na_2x(Na_xM_2–x)Cl₆] of the UCl₃ structure type [□(U₂)Cl₆]. X-Ray Absorption Spectroscopy (XANES) at the L_III edge characterizes NaSm₂Cl₆ and NaNd₂Cl₆ as mixed-valence compounds with valences of +2 and +3 in statistical distribution (approximately 1:1) for Sm and Nd, respectively.     

Ternäre Halogenide vom Typ A3MX6. I A3YCl6 (A = K,NH4, Rb,Cs): Synthese,Strukturen, Thermisches Verhalten. Über einige analoge Chloride der Lanthanide

Ternary Halides of the A₃MX₆ Type I. A₃YCI₆ (A = K, NH₄, Rb, Cs): Synthesis, Structures, Thermal Behaviour. Some Analogous Chlorides of the Lanthanides Reaction of the trichlorides MCl₃ (M = Y, Tb? Lu) with alkali chlorides AC1 (A = K, Rb, Cs) in evacuated silica ampoules at 850?900°C yields A₃MCl₆-type chlorides. (NH₄)₃YCl₆ is obtained via the ammonium-chloride route. The crystal structure of Rb₃YCl₆ (monoclinic, C2/c (no. 15), Z = 8, a = 2583(1)pm, b = 788.9(4)pm, c = 1283.9(7)pm, p = 99.63(4)°, R = 0.062, R_w = 0.050) is that of Cs₃BiCl₆. The Rb₃YCl₆/Cs₃BiCl₆ structure and the closely related structures of K₃MoCl₆ and In₂CI₃ are derived from the elpasolite-type of structure (K₂NaAlF₆) making use of the model of closest-packed layer structures. Cell parameters for the chlorides Rb₃MCl₆ (M = Y, Tb? Lu) and Cs₃YCl₆ and Cs₃ErCl₆ as well, which are all isostructural with Rb₃YCl₆, are given. The “system” (K, NH₄, Rb, Cs)YCl₆ has been investigated by DTA and high-temperature X-ray powder diffractometry.     

Neues über Hexafluoromanganate(IV). MIIMnF6 mit M=Mg,Ca, Zn,Cd, Hg,Ni, Cu,Ag

Newly obtained are NiMnF₆ (ochre-yellow) and ZnMnF₆ (orangeyellow), both VF₃-type [a = 4.91₀, c = 13.16₉ Å (Ni); a = 4.96₆, c = 13.29₃ Å (Zn)], as well as CdMnF₆ (yellow) and HgMnF₆ (orange), both of LiSbF₆ type [a = 5.08₇, c = 14.00₇ Å (Cd); a = 5.08₄, c = 14.12₅ Å (Hg)]. CuMnF₆ (copper-red) and AgMnF₆ (blackbrown) show complicated powder diagrams. MgMnF₆ and CaMnF₆ belong to the LiAbF₆ type, too [Guinier-photographs].     

Ternäre Halogenide vom Typ A3MX6. III [1, 2]. Synthese,Strukturen und Ionenleitfähigkeit der Halogenide Na3MX6 (X = Cl,Br)

Ternary Halides of the A₃MX₆ Type. III [1, 2]. Synthesis, Structures, and Ionic Conductivity of the Halides Na₃MX₆ (X = Cl, Br) The bromides Na₃MBr₆ crystallize with the stuffed LiSbF₆-type structure (type I; M = Sm? Gd) or with the structure of the mineral cryolite (type II; M = Gd? Lu). The structure types were refined from single crystal X-ray data (Na₃SmBr₆: trigonal, space group R3 , a = 740.8(2) pm, c = 1 998.9(8) pm, Z = 3; Na₃YBr₆: monoclinic, space group P2₁/n, a = 721.3(4) pm, b = 769.9(2) pm, c = 1 074.8(4) pm, β = 90.60(4)°, Z = 2). Reversible phase transitions from one structure to the other occur. The phase transition temperatures were determined for the bromides as well as for the chlorides Na₃MCl₆ (M = Eu? Lu). The refinement of both structures for one compound was possible for Na₃GdBr₆ (I: trigonal, space group R3 , a = 737.1(5) pm, c = 1 887(2) pm, Z = 3; II: monoclinic, space group P2₁/n, a = 725.2(1) pm, b = 774.1(3) pm, c = 1 080.1(3) pm, β = 90.76(3)°, Z = 2). All compounds exhibit ionic conductivity of the sodium ions which decreases with the change from type I to type II. The conductivity of the bromides is always higher when compared with the respective chlorides.     

Study on A4BX6 compounds. I. Structure Refinement of Ternary Cd Halides A4CdX6 (A = NH4, K,Rb, In,Tl; X = Cl,I)

The refinement of the structures of rhombohedral (NH₄)₄CdCl₆, K₄CdCl₆, and Rb₄CdCl₆ (K₄CdCl₆-type) and of tetragonal In₄CdI₆ and Tl₄CdI₆ (Tl₄HgBr₆-type) using single crystal data is reported. The discussion of the crystal chemistry of these compounds furnishes new structural relations and a first hint of the role, which ns² cations play in these structures. All compounds of the A₄BX₆ family can clearly be separated with respect to their structure in a structure field diagram in the basis of the size relations A/X and B/X.     

Mg3Ni20P6 und Mn3Ni20P6 — Zwei neue Phosphide mit Cr23C6-Struktur

Mg₃Ni₂₀P₆ and Mn₃Ni₂₀P₆ - Two new Phosphides with Cr₂₃C₆-type Structure The crystal structures of Mg₃Ni₂₀P₆ (a = 11.113(3)A) and Mg₃Ni₂₀P₆ (a = 11.085(1)Å) were determined by single crystal X-ray investigations. Both compounds, prepared by heating appropriate mixtures of the elements, crystallize in a ternary variant of the Cr₂₃C₆-type structure (Fm3m), which is well-known due to a large number of ternary borides.     

Studies on ABX6 Compounds. II. The BaThBr6 structure type

The compounds AThBr₆ (A: Ca, Sr, Ba) crystallize in an ordered substitution variant of the PuBr₃ type. Their syntheses and special features of the crystal structures are described.     

Study on A4BX6 Compounds. II [1]. Refinement of the Structure of Rb4PbBr6 and a Note on the Existence of “Rb4Hgl6” and “K4CdI6”

Rb₄PbBr₆ was prepared by solid state reaction of the binary compounds and the structure refined with single crystal data (a = 1332.9(4), c = 1647.8(5) pm; space group R3 c; K₄CdCl₆-type arrangement). Attempts to synthesize Rb₄HgI₆ and K₄CdI₆ were unsuccessful. The results are discussed on the basis of a structure field diagram for A₄BX₆ compounds.     

Neue schnelle Ionenleiter vom Typ MMIIICl6 (MI = Li,Na, Ag; MIII = In,Y)

Novel Fast Ion Conductors of the Type M M^IIICl₆ (M^I = Li, Na, Ag; M^III = In, Y) The ternary chlorides Li₃InCl₆, Na₃InCl₆, Ag₃InCl₆, and Li₃YCl₆ have been studied by difference scanning calorimetry, high-temperature X-ray, infrared, and high-temperature Raman methods. Impedance spectroscopic measurements exhibit fast ionic conductivity increasing in the sequence Na₃InCl₆ < Li₃YCl₆ < Ag₃InCl₆ < Li₃InCl₆. In the range of 300°C, Li₃InCl₆ is the best lithium ion conductor known so far (σ = 0,2 Ω^?1 cm^?1 at 300°C). With the exception of Na₃InCl₆, the chlorides exhibit complicated order-disorder phase transitions.     

Studies on ABX6 Compounds. III. The SnZrCl6 structure type

The compound SnZrCl₆ crystallizes in an ordered substitution variant of the MnF₃ type. The synthesis of this compound and special features of its crystal structure are described.     

ZnTa2O6, ein neuer Vertreter des tri-α-PbO2-Typs (mit ergänzenden Daten über ZnNb2O6)

ZnTa₂O₆, a New Member of tri-α-PbO₂-Type (with Supplement Data about ZnNb₂O₆) For the first time single crystals of ZnTa₂O₆ were prepared and investigated by single crystal X-ray work. a = 4.702, b = 17.094, c = 5.070 Å, space group D?Pbcn. ZnTa₂O₆ shows [MO₆]-octahedra-chains with a typical metal distribution. 2/3 of these chains contain alternating Zn²⁺- and Ta⁵⁺-ions. For that reason ZnTa₂O₆ does not belong to the Columbitstructure but to the tri-α-PbO₂-type.     

Etude cristallochimique et spectroscopique des fluoroniobates MNbF6 avec M = Mg,Ca, Mn,Fe, Co,Ni, Zn,et Cd

The compounds MNbF₆ were synthesized for M = Mg, Ca, Mn, Fe, Co, Ni, Zn, and Cd. They have a ReO₃-type structure, or one derived from it, and are isostructural with MNbF₇ compounds. The insertion of fluoride anions in the ReO₃-type structure is discussed. Studies of the spectroscopic uv and visible behavior were carried out, and assignments of absorption bands of solid samples were made in terms of crystal field theory, assuming an octahedral surrounding of the niobium ion and of the bivalent cation.     

Ternäre Chloride in den Systemen ACl/DyCl3 (A = Cs,Rb, K)

Ternary Chlorides in the Systems ACl/DyCl₃ (A = Cs, Rb, K) The phase diagrams of the pseudobinary systems ACl/DyCl₃ (A = Cs, Rb, K) were investigated by DTA. With all alkali metals compounds A₃DyCl₆ (elpasolite family) and Ady₂Cl₇ are formed. Compounds A₂DyCl₅ exist only with Cs (Cs₂DyCl₅-type) and K (K₂PrCl₅-type). By solution calorimetry the formation enthalpies of the ternary chlorides from (nACl + DyCl₃) were measured and ‘synproportionation enthalpies’ for the formation from the compounds, adjacent in the phase diagrams, calculated. K₃DyCl₆ is the only compound, which is formed with a loss in lattice enthalpy. E.m.f. measurements in dependence on the temperature have revealed that, as for the other compounds A₃DyCl₆, a remarkable gain in entropy exists, which stabilizes K₃DyCl₆ at T ≧ 312 K. This entropy gain correlates with the existence of isolated DyCl₆^3? octahedra.     

Theoretical study of the structures of [M(18C6)](HFA)2 complexes (M = Ba,Sr, Pb,Cd, Mn; 18C6 = 18-crown-6; HFA = hexafluoroacetylacetonate anion)

The structures of the [M(18C6)]²⁺ cations (M = Ba, Sr, Pb, Cd, Mn) and their salts [M(18C6)](HFA)₂ and [M(18C6)](NO₃)₂ have been calculated by the density functional theory method (in the B3LYP/6-311++G** + LanL2Dz approximation). Upon geometry optimization, the gas-phase structures of compounds of different composition have been calculated; for them, the strength of binding of the central cation to the crown ether (18C6) and the degree of structural similarity have been evaluated. The structure of the [NH₄(18C6)]⁺ cation identified in a practical synthesis has also been considered. For metal cations acting as a central atom, NH ₄ ⁺ and [M(18C6)]²⁺ complex cations, as well as for intermediate and ultimate products [M(18C6)](NO₃)₂ and [M(18C6)](HFA)₂ (M = Ba, Sr, Pb, Cd, Mn), the electronic chemical potential and Pearson hardness, which enables the consideration of the propensity of various reagents to interact with each other in terms of the empirical HSAB principle (hard with hard and soft with soft), have been evaluated. Comparison of the estimates with the properties of the synthesized compounds with M = Ba, Sr, and Pb makes it possible to preliminarily verify the applicability of this principle to the systems under consideration and predict some properties of isostructural analogues important in the search for methods of synthesis of [M(18C6)](HFA)₂, where M = Cd and Mn. The possibility of establishing a correlation between the electron density of the system, stability, and hydrolytic activity of complexes has been shown.     

Ternäre Halogenide vom Typ A3MX6. IV. [1]. Ternäre Halogenide des Scandiums mit Natrium,Na3ScX6 (X = F,Cl, Br): Synthese,Strukturen, Ionenleitfähigkeit

Ternary Halides of the A₃MX₆ Type. IV. Ternary Halides of Scandium with Sodium, Na₃ScX₆ (X = F, Cl, Br): Synthesis, Structures, Ionic Conductivity X-ray studies on single crystals of Na₃ScF₆ and Na₃ScBr₆ show, that Na₃ScF₆ crystallizes with the cryolite type (monoclinic, P2₁/n, Z = 2, a = 560.16(9), b = 580.31(8), c = 812.1(2)pm, β = 90.720(14)°) and Na₃ScBr₆, as the only ternary bromide of the rare earth elements with sodium, in the Na₃CrCl₆ type (trigonal, P3 1c, Z = 2, a = 728.95(7), c = 1309.29(17)pm). The ionic conductivity of powder samples of Na₃ScF₆, Na₃ScBr₆ and of Na₃ScCl₆ was studied by impedance spectroscopy. Activation energies were determined as 1.22 eV, 0.80 eV and 0.71 eV for the fluoride, chloride and bromide, respectively. The differences are explained from the crystal structures and the sizes and polarizabilities of the anions.