Neues über TiF3 und Fluorotitanate(III) : Cs2K[TiF6], Rb2K[TiF6] und TiF3 Mit einer Bemerkung über Rb3[TiF6]

On TiF₃ and Hexafluorotitanates(III): Cs₂K[TiF₆] and Rb₂K[TiF₆], with a remark on Rb₃[TiF₆] By “redox-reaction with the wall” according to A₂B[CuF₆] + Ti = A₂B[TiF₆] + Cu we obtained for the first time single crystals of the Hexafluorotitanates(III). The violett irregular single crystals of Cs₂K[TiF₆] (a = 9.11₅ Å) and Rb₂K[TiF₆] (a = 8.91₀ Å) crystalise in accordance with the single-crystal studies as supposed in spcgrp. O-Fm3m No. 225. Dark blue crystals of TiF₃ crystalises in the VF₃-Typ. Parameters see text. TiF₃ (3.9–251.3 K) and Rb₃[TiF₆] (3.8–251.3 K) have been measured magnetically. The madelung part of lattice energy, MAPLE, and the effective coordination number, ECoN, via the mean fictive ionic radii, MEFIR, are calculated and discussed.     

Structure of molten systems KF?K2TiF6 and KCL-K2TiF6

Congruently melting compounds K₃TiF₇ and K₃TiF₆Cl which are formed in the systems KF? K₂TiF₆ and KCl? K₂TiF₆, respectively, exhibit a strong influence on the structure (ionic composition) of the melts of the corresponding systems. Considering the relatively low symmetry and a high energetic state of the TiF₇^3? and TiF₆Cl^3? complex ions, a high degree of their thermal dissociation might be expected. This assumption was confirmed by two different methods based on a thermodynamic analysis of the phase equilibria and of the volume properties of the investigated systems, respectively. In connection with the former method, the values of the enthalpy of fusion of K₂TiF₆, K₃TiF₇, and K₃TiF₆Cl which were used in the calculations have also been estimated.     

Preparation,crystal structure,and magnetic properties of β-Li3TiF6 = LiLi(TiF6)(TiF6)2 – a double fluoride?

Purple colored single crystals of the β-modification of Li₃TiF₆ have been prepared by heating an appropriate mixture of LiF and TiF₃ at 820°C under an argon atmosphere. β-Li₃TiF₆ crystallizes in C2/c with a = 14.452(2) Å, b = 8.798(1) Å, c = 10.113(1) Å and β = 96.30(1)º. The structure is isotypic to β-Li₃VF₆ and contains isolated compressed TiF₆ octahedra (d_Ti–F = 1.91–2.01 Å). Magnetic properties of β-Li₃TiF₆ were studied and discussed. Band structure calculations and calculations of the Madelung part of the lattice energy, MAPLE, were performed to discuss the chemical bonding.     

Zur Existenz der Verbindung K2TiOF4: Pyrohydrolytischer Abbau von K2TiF6 und thermochemisches Verhalten von K2Ti(O2)F4 · H2O

On the Existence of the Compound K₂TiOF₄: Pyrohydrolytic Degradation of K₂TiF₆ and Thermochemical Behaviour of K₂Ti(O₂)F₄ · H₂O In an attempt to prepare K₂TiOF₄ we used the following three ways; solid-state reaction of K₂TiF₆, TiO₂, and KF, pyrohydrolysis of K₂TiF₆ at 450 and 550°C, and thermal decomposition of K₂Ti(O₂)F₄ · H₂O. In each case the reaction products were mixtures of several compounds, always containing the kryolith-phase K_2+xTiO_xF_6?x and TiO₂. At 130°C K₂Ti(O₂)F₄ · H₂O forms K₂Ti(O₂)F₄ by loss of H₂O, and at 230°C the peroxogroup decomposes, yielding K₂TiOF₄ as main product. K₂TiOF₄ crystallizes tetragonally with the following lattice parameters: a = 769.7(1) and c = 1153.9(2)pm. The i.r. spectrum shows an absorption band at 810 cm^?1, pointing to infinite chains of ? Ti? O? Ti? O? .     

Crystal Structure of Na3Li(TiF6)2

Single crystals of Na₃Li(TiF₆)₂ were synthesized and studied by X-ray diffraction analysis (DAR-UMBk diffractometer, MoK radiation, graphite monochromator); space group P 2₁ c, a = 5.130(1), c = 18.046(4) Å. The structure was solved by the heavy-atom method and refined by the full-matrix least-squares method in anisotropic approximation to R = 0.053 and wR = 0.048 for 468 independent reflections with I > 3(I). The Madelung's constant for the lattice energy was calculated and the structure was compared to structures of other hexafluoro complexes of Group IV elements.     

Mechanism and Parameters Controlling the Decomposition Kinetics of Na2SiF6 Powder to SiF4

Sodium hexafluorosilicate (Na₂SiF₆) powder has been used as a silicon source for formation of Si₃N₄ coatings by the hybrid precursor system‐chemical vapor deposition (HYSY‐CVD) route. The quantitative effect of processing time, temperature, gas flow rate, and process atmosphere (N₂ and N₂:5% NH₃) upon the fractional weight loss during the decomposition of Na₂SiF₆ was studied using a standard L₉ Taguchi experimental design and analysis of variance. The decomposition kinetics of Na₂SiF₆(s) was studied theoretically and experimentally in the temperature range of 550–650ºC by applying the shrinking core model. It was found that regardless of atmosphere type, the reaction order is n ≈ 0.12 and that a two‐stage mixed mechanism consisting of chemical reaction and boundary layer gas transfer controls the decomposition rate. The determined fractional weight loss during Na₂SiF₆ decomposition in nitrogen atmosphere is about 1.05–1.5 orders of magnitude greater than that in N₂:NH₃. The gas flow rate affects the dissociation activation energy, being of 121, 109, and 94 kJ/mol in N₂ and of 140, 120, and 115 kJ/mol in N₂:NH₃, for the flow rates of 20, 60, and 100 cm³/min, respectively, in both atmosphere types. A good agreement is observed by comparing experimental weight loss data with model predictions.     

Thermochemical properties of the Fe-analogue of cryolite, Na3FeF6

Relative enthalpies for low-and high-temperature modifications of Na₃FeF₆ and for the Na₃FeF₆ melt have been measured by drop calorimetry in the temperature range 723–1318 K. Enthalpy of modification transition at 920 K, δ_trans H(Na₃FeF₆, 920 K) = (19 ± 3) kJ mol⁻¹ and enthalpy of fusion at the temperature of fusion 1255 K, δ_fusH(Na₃FeF₆, 1255 K) = (89 ± 3) kJ mol⁻¹ have been determined from the experimental data. Following heat capacities were obtained for the crystalline phases and for the melt, respectively: C _p(Na₃FeF₆, cr, α) = (294 ± 14) J (mol K)⁻¹, for 723 = T/K ≤ 920, C _p(Na₃FeF₆, cr, β) = (300 ± 11) J (mol K)⁻¹ for 920 ≤ T/K = 1233 and C _p(Na₃FeF₆, melt) = (275 ± 22) J (mol K)⁻¹ for 1258 ≤ T/K ≤ 1318. The obtained enthalpies indicate that melting of Na3FeF6 proceeds through a continuous series of temperature dependent equilibrium states, likely associated with the production of a solid solution.      

Thermal Behaviour of Ammonium Oxofluorotitanates(IV)

The thermal behaviour of ammonium oxofluorotitanates (NH₄)₃TiOF₅, (NH₄)₂TiOF₄ and NH₄TiOF₃ was investigated by thermoanalytical, X-ray and IR spectroscopic methods. The first decomposition stages under quasi-isobaric conditions are characterized by the formation of (NH₄)₂TiF₆ and ammonium oxofluorotitanate with the less content of ammonium and fluorine than in the initial compound. The decomposition process is accompanied by the Ti(IV) reducing due to ammonia evolved. The new ammonium oxofluorotitanate of high volatility was isolated and characterized. Ammonium-containing non-stoichiometric titanium oxyfluorides are the final products of thermal decomposition of ammonium oxofluorotitanates.This revised version was published online in November 2005 with corrections to the Cover Date.     

Crystal Structures of LiCsTiF6 and Cs2TiF6 and Internal Mobility of Complex Anions

Single crystals of LiCsTiF₆(I) and Cs₂TiF₆(II) are characterized by X-ray diffraction analysis (DAR-UMBk and SMART 1000 CCD diffractometers, MoK radiation, graphite monochromator; anisotropic least squares refinement to R = 0.038 and R _w = 0.046 (I) and R ₁ = 0.017 and wR ₂ = 0.046 (II)). Packing modes of structural units in the crystals are considered. Types of internal motions of complex TiF₆ ^2– ions are established, and their activation energies in the crystals of LiCsTiF₆ and Cs₂TiF₆ are estimated in the temperature range 200–500 K.     

Uber Hexafluorotitanate (III). Cs2MTiF6 und Rb2MTiF6 (M  K bzw. Na); mit einer Bemerkung über Tl3TiF6

On Hexafluorotitantes (III). Cs₂MTIF₄ and Rb₂MTIF₄(M?K, Na); with a Remark on TI₃TIF₆ By heating the binary fluorides in a closed system we obtained Cs₂KTiF₆ (a = 9.12₄ Å), Rb₂KTiF₆ (a = 8.93₂ Å) and Rb₂NaTiF₆ (a = 8.53₃ Å), all cubic Elpasolithes of light blue colour as well as Cs₂NaTiF₆ (hexagonal a = 6.27₂, c = 30.91 Å, isotypic with Cs₂NaCrF₆) and Tl₃TiF₆ TiF₃ (3.1–295.5°K) and Cs₂KTiF₆ (74.9–297.7°K) have been measured magnetically. The spectra of reflection in the range of 10 000 to 30 000 cm^?1 of TiF₃ and the new quaternary fluorides are similar. The Madelung Part of Lattice Energy (MAPLE) is calculated and discussed.     

Synthesis,crystal structure and thermal properties of Na2Ti(CF3COO)6(CF3COOH)2

The compound Na₂Ti(CF₃COO)₆(CF₃COOH)₂ was synthesized as colorless crystals, extremely unstable in air, by the reaction of TiCl₄ with trifluoroacetic acid and sodium trifluoroacetate. Crystallographic studies have shown that this sodium trifluoroacetatotitanate is the first example of a tetravalent titanium carboxylate [Ti(RCOO)₆]²– containing titanium in an octahedral environment of oxygen atoms of carboxylate groups. Thermal decomposition of Na₂Ti(CF₃COO)₆(CF₃COOH)₂ in an argon atmosphere results in the complex fluoride Na₂TiF₆.     

Rerefinement of K2[TiF6]

Crystals of dipotassium hexa­fluoro­titanate(IV), K₂[TiF₆], were grown from aqueous solution. The crystal structure was refined with anisotropic displacement parameters. Ti⁴⁺ is octahedrally coordinated by F^? (point group m), and K⁺ is 12‐coordinate (point group 3m). The dispersion of birefringence is presented.     

Phasenbeziehungen und Natriumionenleitung im quasi-binären System Na2SiF6/Na3AlF6

Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na₂SiF₆/Na₂AIF₆ . The phase diagram of the Na₂SiF₆/Na₃AlF₆ system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na₃AlF₆ accomodates up to 73 mol.-% Na₂SiF₆ maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na₃AlF₆ with Na₂SiF₆.     

One‐Step Solvothermal Synthesis of Single‐Crystalline TiOF2 Nanotubes with High Lithium‐Ion Battery Performance

Single‐crystalline TiOF₂ nanotubes were prepared by a one‐step solvothermal method. The nanotubes are rectangular in shape with a length of 2–3 μm, width of 200–300 nm, and wall thickness of 40–60 nm. The formation of TiOF₂ nanotubes is directly driven by the interaction between TiF₄ and oleic acid in octadecane to form the 1D nanorods, and this is followed by a mass diffusion process to form the hollow structures. The synthesis approach can be extended to grow TiOF₂ nanoparticles and nanorods. Compared with TiO₂, which is the more commonly considered anode material in lithium‐ion batteries, TiOF₂ has the advantages of a lower Li‐intercalation voltage (e.g., to help increase the total voltage of the battery cell) and higher specific capacities. The TiOF₂ nanotubes showed good Li‐storage properties with high specific capacities, stable cyclabilities, and good rate capabilities.     

Synthesis of NH<Subscript>4</Subscript>TiOF<Subscript>3</Subscript> Crystals in the Presence of Polyoxyethylene Ethers

The effect of polyoxyethylene ethers as surfactants on the morphology of NH₄TiOF₃ crystals obtained by hydrolysis of (NH₄)₂TiF₆ in the presence of boric acid is analyzed. Depending on the molecular weight of the polyoxyethylene ether, the geometric dimensions (thickness and lateral size) of the crystals change. The obtained samples were characterized by X-ray and electron diffraction, Raman spectroscopy, and scanning electron microscopy. The heat treatment of NH₄TiOF₃ powders gives anatase mesocrystals retaining the initial particle morphology.     

Über Perrhenate. 2. Zur Kenntnis von Li5ReO6 und Na5ReO6 – mit einer Bemerkung über Na5IO6

On Perrhenates. 2. On Li₅ReO₆ and Na₅ReO₆ — with a Note on Na₅IO₆ The crystal structures of Li₅ReO₆ and Na₅ReO₆ were determined for the first time in full detail from four-circle diffractometer data (AgKα radiation). They and Na₅IO₆, also (according to powder data) crystallize with the monoclinic system (C2/m, Z = 2). The structure may be described as a distorted derivative of the NaCl type; data see ?Inhaltsübersicht”?. Effective Coordination Numbers, ECoN, and the Madelung Parts of the Lattice Energy, MAPLE, have been calculated and are discussed.     

Synthesen und einige thermische und strukturelle Eigenschaften von Hydraziniumfluorotitanaten(IV)

Zusammenfassung Die Synthesen von [N₂H₅]₂TiF₆, [N₂H₅]₂TiF₆ · 2 HF und N₂H₆TiF₆ sind beschrieben, die thermischen Eigenschaften, die Infrarotspektren werden diskutiert. Eine Disproportionierung von Hydrazin in Stickstoff und Ammoniak wurde festgestellt. Die Zuordnung der Infrarotbanden (4000–250 cm^–1) deutet bei den ersten zwei Verbindungen auf die Hydrazinium¹⁺-Verbindungen hin.

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The synthesis and some thermal and structural properties of hydrazinium fluorotitanates(IV)

The synthesis of [N₂H₅]₂TiF₆, [N₂H₅]₂TiF₆ · 2 HF and N₂H₆TiF₆ is described. The thermal properties and infrared spectra of the obtained compounds are discussed. Disproportionation of hydrazinium into nitrogen and ammonia is observed. The assignation of the bands in infrared spectra [4000 to 250 cm^–1] of the first two compounds is consistent with the presence of hydrazinium¹⁺ ion.

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Mit 2 Abbildungen     

Les Phases Na5NbO5 et Na5TaO5 Structure Cristalline de Na5NbO5

Na₅Nb0₅ and Na₅Ta0₅ Phases. Crystal Structure of Na₅NbO₅ New ternary oxides of formulas Na₅NbO₅ and Na₅TaO₅ have been prepared. They crystallize in the monoclinic system (space group C2/c). The crystal structure of Na₅NbO₅ has been determined. It derives from a NaCl-type structure by ordering of the cations and of the oxygen vacancies in the anionic sublattice, the corresponding formula being Na_5/6Nb_1/6O_5/6□_1/6. Sodium and niobium have a distorted square-pyramidal surrounding.     

Über Oxoosmate(VII) Na5[OsO6] und Li5[OsO6]

On Oxoosmates(VII). Na₅[OsO₆] and Li₅[OsO₆] For the first time bluish black single crystals of Na₅[OsO₆] have been prepared. The structure was determined according to four-circle-diffractometer data. According to powder samples Li₅[OsO₆] is isotypic to Na₅[OsO₆]. Both are of the NaCl-type like Na₅[ReO₆] (space-group C2/m (No. 12, I.T.), Z = 2): Na₅[OsO₆]: a = 568.10(4), b = 975.00(6), c = 559.65(5) pm, β = 111.00° (1), 436 hkl, 4° ? Θ ? 30°, MoK, R = 2.7%, R_W = 2.6%. Li₅[OsO₆]: a = 568.10(4), b =975.00(6), c = 559,65(5) pm, β = 111.00° (1). Effective Coordination Numbers, ECoN, and the Madelung Part of Lattice Energy, MAPLE, are calculated and discussed.     

Über das thermische Verhalten einiger Lithium-und Natriumhexafluorometallate(IV)

Thermal Behaviour of Some Lithium and Sodium Hexafluorometallates(IV) Rutile is formed by thermolysis from Li₂TiF₆ and on the other hand at first brookite originates from Na₂TiF₆. The nucleation of the final products is favoured not only by the similarity of the lattice geometries between initial product and final product but also by the chemical influences of small concentrations of defined impurities. The thermal behaviour of the lithium-and sodium haxafluorometalates A₂MF₆ (with M-element of the IV. main group) is compared among one another. The expansion of the lattices and the transformation of the phases are determined with the aid of the high-temperature-Guinier-method and some differences are shown to the same reactions in a great quantity of the substances. It is described γ-Na₂SnF₆ with a Na₂SiF₆ structure type.