Massenspektroskopische Analyse der Verdampfung von AlF3

Mass Spectrometric Investigation of Vaporization of AlF₃ The vaporization of AlF₃ was investigated by two different equipments for mass spectrometric analysis. The formation of the gas complex HAlF₄ was detected during the vaporization process of AlF₃ affected by small water content. Besides, a probable formation of other complex species has been confirmed.     

Development of a new analytical method for online simultaneous qualitative determination of aluminium (free aluminium ion, aluminium-fluoride complexes) by HPLC-FAAS

The paper presents a novel method for simultaneous online examination of inorganic forms of aluminium: AlF₂⁺, AlF^2+, and Al³⁺ by means of the high performance liquid chromatography hyphenated with a detection by the atomic absorption spectrometry with flame atomization (HPLC-FAAS) without post-column reaction. The application of optimization procedure conditions of chromatographic separation of inorganic forms of aluminium was achieved by the analytical column IonPac CS5A (Dionex) with guard column IonPac CG5A (Dionex) and an aqueous ammonium chloride mobile phase, at pH about 3 with gradient elution. The separation of Al forms with nominal charge of 1+, 2+, 3+ required a run time of less than 8 min during a single analysis. The proposed method has been successfully used for the examination of aluminium forms formation AlF_n⁽³⁻ⁿ⁾⁺ in environmental samples.     

Calorimetric Investigations of Some Phases in the System Sodium Fluoride - Aluminium Fluoride

Beside the two well-known minerals cryolite, Na₃AlF₆, and chiolite, Na₅Al₃F₁₄, the binary system NaF-AlF₃ also contains a third compound, NaAlF₄, sodium tetrafluoroaluminate. Solid NaAlF₄ has been prepared from its vapour under controlled conditions. The stability of NaAlF₄ has been investigated by differential scanning calorimetry. It is shown that the disproportionation of the compound: 5NaAlF_4(s)=Na₅Al₃F_14(s)+2AlF_3(s) takes place at considerable rate between 700 and 900 K. The enthalpy of this reaction is calculated and found to be -66.9 kJ. Enthalpies of the two solid state transitions α-Na₃AlF₆ → β-Na₃AlF₆ and α-AlF₃ → β-AlF₃ have also been measured and new values are reported. The enthalpy of formation of chiolite, Na₅Al₃F₁₄, at 900 K has been recalculated from enthalpy increment data obtained by drop calorimetry. A value of ΔH₉₀₀ ^o = -7513.6±12.0 kJ mol^-1 has been obtained. This value is in disagreement with the recommended value given in JANAF Thermochemical Tables given at 900 K ΔH_f ^o = -7559.2 kJ mol^-1. This revised version was published online in July 2006 with corrections to the Cover Date.     

(H3O)2NaAl3F12, isostructural with A2NaAl3F12 (A = K+, Rb+, Cs+) fluorides having HTB‐type sheets

The title compound, (H₃O)₂NaAl₃F₁₂ [dihydronium sodium trialuminum(III) dodecafluoride], was obtained by solvothermal synthesis from the reaction of aluminium hydroxide, sodium hydroxide, 1,2,4‐triazole and aqueous HF in ethanol at 463 K for 48 h. The structure consists of AlF₆ octahedra organized in [AlF₄⁻]_n HTB‐type sheets (HTB is hexagonal tungsten bronze) separated by H₃O⁺ and Na⁺ cations.     

On the synthesis of ammonium xenon(VI) hexafluoromanganate(IV)

The reaction between NH₄MnF₃ and xenon hexafluoride yields ammonium xenon(VI) hexafluoromanganate(IV). The persistance of the NH⁺₄ in the environment of the XeF₆, during the synthesis of the salt, can be attributed to the positive charge because XeF₆ is electrophylic and will oxidize neutral or negatively charged species but not cations. Ammonium xenon(VI) hexafluoromanganate(IV) was characterized by chemical analysis, magnetic susceptibility measurements, thermogravimetric studies and vibrational spectroscopy. The spectroscopic evidence supports the formulation NH⁺₄XeF⁺₅MnF²₆^?.     

Effects of Mn2+ on the chrome‐free colored Ti/Zr‐based conversion coating on 6063 aluminum alloy

The conversion coating with golden color and improved corrosion resistance had been prepared by adding Mn²⁺ in the Ti/Zr conversion coating solution. Comparing with that of conversion coating without Mn²⁺, the optimal treatment time of this conversion coating was much shorter and the corrosion resistance was obviously improved. The effect of Mn²⁺ on the formation of golden Ti/Zr conversion coating was thoroughly investigated by means of energy dispersive X‐ray spectroscopy, SEM, XPS, and Raman and electrochemical workstation. The results showed that the conversion coating had a double‐layer structure: the outer layer consisted of the metal‐organic complex and the inner layer was mainly made up of Na₃AlF₆. Mn²⁺ was oxidized into MnOOH in solution and precipitated on the substrate surface which provided the nucleus to Na₃AlF₆ crystal and accelerated Na₃AlF₆ crystal formation and also made the microstructure of conversion coating change to the cubic. The mechanism of the formation of the conversion coating can be deemed as nucleation, growth of Na₃AlF₆ crystal, and formation of metal‐organic complex. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and structure of hydroxylammonium fluoroaluminate

Abstract  

Hydroxylammonium fluoroaluminate with the formula (NH₃OH)₂AlF₅ was synthesized by the reaction of solid NH₃OHF and an aqueous solution of aluminum in HF, and its structure was determined by single-crystal X-ray diffraction. The structure consists of NH₃OH⁺ cations and centrosymmetrical AlF₆ octahedra, which are formed by sharing two opposite corners connected in polymeric (AlF₅)_n²⁻ anions. Oxygen and nitrogen atoms of hydroxylammonium cations are donors of hydrogen bonds to terminal fluorine atoms of fluoroaluminate chains. The compound crystallizes monoclinic P2/c, with cell parameters a = 10.8675(3) ?, b = 7.3098(2) ?, c = 7.2071(2) ?, and β = 91.080(2)°. The thermal decomposition of the compound was studied by TG, DSC, and X-ray powder diffraction. By controlled heating of (NH₃OH)₂AlF₅, a new compound with the formula (NH₃OH)AlF₄ was obtained, and the final product of the decomposition is γ-AlF₃.     

Ein Fluoridphosphat von Mangan(III) mit ungewöhnlicher Schichtstruktur: Na7[Mn5F13(PO4)3(H2O)3]

A Fluoride Phosphate of Manganese(III) with Unusual Layer Structure: Na₇[Mn₅F₁₃(PO₄)₃(H₂O)₃] The title compound was crystallized from a solution of MnF₃ · 3 H₂O in aqueous HF by addition of NaH₂PO₄ · H₂O in 2 M phosphoric acid. The crystal structure has been determined at 295 and 150 K on a trigonal crystal twinned by merohedry: Space group P3c1, Z = 4, a = 1055,0(1), c = 2314,0(1) pm (a = 1052,5(1), c = 2304,2(1) pm at 150 K), wR₂ = 0.0651 (0.0651). The structure contains anionic layers formed by triangular moieties of three [MnF₃O₂(H₂O)] octahedra sharing one common μ₃-F atom and bridged by three phosphate groups. Three of those groups, respectively, are interconnected by two [MnF₃O₃] octahedra over six phosphate O-atoms to form a trigonal layer in the a,b plane. Stacking of these layers gives channels along the c axis in which most of the Na⁺ ions are located. The [MnF₃O₂(H₂O)] octahedra show strong elongation along the μ₃-F–Mn–OH₂ axis mainly due to the Jahn-Teller effect whereas in the [MnF₃O₃] octahedra with C₃ symmetry weak signs only of a dynamical Jahn-Teller-effect can be observed. The magnetic properties (μ_eff = 4.61 μ_B, 3-D ordering point T_N = 3.3 K) were determined on powders and possible magnetic exchange pathways are discussed.     

Potentiometric Study of Aluminium-Fluoride Complexation Equilibria and Definition of the Thermodynamic Model

Complexation constants of the Al³⁺/F⁻ system were determined at different ionic strengths in a NaClO₄ (1.0, 2.0 and 3.0 mol⋅dm⁻³) ionic medium by means of a potentiometry using two electrode systems: an ion fluoride selective electrode as well as a glass electrode. All the experimentation was performed at 25 °C. The main species in the complexation equilibria were determined as AlF²⁺, AlF₂⁺, AlF₃⁰, AlF₄⁻, AlF₅²⁻ and AlF₆³⁻. The differences found in the complexation constants for the ionic strength considered were explained by the different behavior of the interaction parameters for the AlF _n ³⁻ⁿ species. These parameters were calculated using the Modified Bromley’s Methodology (MBM). The corresponding thermodynamic quantities were also determined. From all the results obtained, it can be concluded that pH, fluoride concentration and ionic strength influenced the distribution of the fluoride-aluminium complexes.     

Structural Study of Alkaline 1-Phenyl-1H-1, 2, 3, 4-tetrazole-5-thiolate Salts: An Example of Periodicity in Alkaline Cations

The alkaline 1-phenyl-1H-1, 2, 3, 4-tetrazole-5-thiolate salts, M[C₆H₅N₄CS] (M = Li ( 1 ), Na ( 2 ), K ( 3 ), Rb ( 4 ) and Cs ( 5 )) were obtained and characterized by means of mass spectrometry (FAB⁺) and NMR (¹H; ¹³C) spectroscopy. The structures of Na ( 2 ), K ( 3 ), Rb ( 4 ) and Cs ( 5 ) compounds were determined by X-ray diffraction methods. The ligand shows a rich variety of coordination patterns with the alkaline cations. The formation of a four-membered ring MSCN in the compounds with heavier alkali cations (K, Rb and Cs) is shown. In all the cations the coordination number around it increases with the ionic radius. Compounds with Cs⁺ and Rb⁺ exhibited the formation of Cs-C and Rb-C interactions with the phenyl group.     

Synthese,Kristallstruktur und thermischer Abbau von Fluoroaluminaten der Zusammensetzung (NH4)[M(H2O)6][AlF6] (M = Zn,Ni), [Zn(H2O)6][AlF5(H2O)] und (PyH)4[Al2F10] · 4 H2O

Synthesis, Crystal Structure and Thermal Behaviour of Fluoroaluminates of the Composition (NH₄)[M(H₂O)₆](AlF₆) (M = Zn, Ni), [Zn(H₂O)₆][AlF₅(H₂O)], and (PyH)₄[Al₂F₁₀] · 4 H₂O Four new fluoroaluminates were obtained from fluoroacidic solutions of respective metal salts. The compounds of zinc ( I a : P2₁/c, a = 12.688(3), b = 6.554(1), c = 12.697(3) Å, β = 95.21(3)°, V = 1051.5(4) ų, Z = 4) and nickel ( I b : P2₁/c, a = 12.685(3), b = 6.517(1), c = 12.664(2)Å, β = 94.55(2)°, V = 1043.6(4) ų, Z = 4) are isotypic and represent a new structure type consisting of two different cations, NH₄⁺ and [M(H₂O)₆]²⁺ and [AlF₆]^3–‐anions. [Zn(H₂O)₆][AlF₅(H₂O)] ( II : C2/m, a = 10.769(2), b = 13.747(3), c = 6.487(1)Å, β = 100.02(3)°, V = 945.7(3) ų, Z = 4) is characterized by a H₂O/F‐disorder in the [AlF₅(H₂O)]‐octahedra in two trans positions. In (PyH)₄[Al₂F₁₀] · 4 H₂O ( III : Cmc2₁, a = 15.035(3), b = 20.098(4), c = 12.750(4) Å, V = 5364(2) ų, Z = 8), bioctahedral [Al₂F₁₀]^4– anions have been found for the first time. The structures are described and discussed in comparison. The new compounds were used as precursors in order to obtain new AlF₃‐phases. However, the thermal decomposition did not result in the formation of any new metastable AlF₃‐phase. Instead, phase mixtures of either α‐AlF₃ and β‐AlF₃ or AlF₃ and MF₂ were obtained.     

Speciation analysis of aluminium and aluminium fluoride complexes by HPIC-UVVIS

The study presents a new analytical method for speciation analysis in fractionation of aluminium fluoride complexes and free Al³⁺ in soil samples. Aluminium speciation was studied in model solutions and soil extract samples by means of high performance ion chromatography (HPIC) with UV-VIS detection using post-column reaction with tiron for the separation and detection of aluminium fluoride complex and Al³⁺ forms during one analysis. The paper presents particular stages of the chromatographic process optimization involving selecting the appropriate eluent strength, type of elution or concentration and quantity of derivatization reagent. HPIC was performed on a bifunctional analytical column Dionex IonPac CS5A. The use of gradient elution and the eluents A: 1 M NH₄Cl and B: water acidified to pH of eluent phase, enabled full separation of fluoride aluminium forms as AlF₂⁺, AlF₃⁰, AlF₄⁻ (first signal), AlF²⁺ (second signal) and form Al³⁺ in a single analytical procedure. The proposed new method HPIC-UVVIS was applied successfully in the quantitative and qualitative analysis of soil samples.     

Phase relations and thermodynamic properties in the ternary reciprocal system LiFNaFNa3AlF6Li3AlF6

The ternary reciprocal sytem LiFNaFNa₃AlF₆Li₃AlF₆ has been investigated by thermal analysis, differential thermal analysis, quenching, X-ray diffraction, microscopy, and calorimetry. The phase diagrams of the following systems are given: LiFNaF (revised), LiFAlF₃, Na₃AlF₆LiF, and LiFNaFNa₃AlF₆Li₃AlF₆. Some values of heat of mixing and heat content in the system have been measured.It is shown that molten mixtures in this system can be treated as consisting of the following species: Li⁺, Na⁺, AlF^3-₆, AlF₃ and F^-. At high contents of alkali fluoride the dissociation of the AlF^3-₆ ion to AlF₃ and F^- will, however, be negligible.On the basis of the calorimetric data, heats of mixing and dissociation, together with the degree of dissociation of AlF^3-₆, in the systems LiFAlF₃ and LiFNa₃AlF₆ have been calculated. The partial Gibbs free energy, enthalpy and entropy of Na₃AlF₆ in the system LiFNa₃AlF₆ have also been calculated. Finally the activity of Na₃AlF₆ in the latter system has been calculated by treating it as a part of the ternary reciprocal system 3LiF+Na₃AlF₆→Li₃AlF₆+3NaFA satisfactory agreement between the Flood, Førland and Grjotheim theory and the experimental values is obtained at small Na₃AlF₆ concentrations.     

Ab initio molecular orbital studies of the structure and potential energy surface of the LiAlF4 complex

Ab initio molecular orbital calculations have carried out on various structures of LiAlF₄ complex using minimal and extended basis sets. A C_2v structure with two fluorines in the bridge was found to be more stable than structures with one and three fluorines in the bridge. Migration of the Li⁺ in the complex is found to be relatively easy and the AlF^?₄ anion is found to be distorted from tetrahedral symmetry.     

Struktur und magnetische Eigenschaften von Bis{3‐amino‐1,2,4‐triazolium(1+)}pentafluoromanganat(III): (3‐atriazH)2[MnF5]

Structure and Magnetic Properties of Bis{3‐amino‐1,2,4‐triazolium(1+)}pentafluoromanganate(III): (3‐atriazH)₂[MnF₅] The crystal structure of (3‐atriazH)₂[MnF₅], space group P1, Z = 4, a = 8.007(1) Å, b = 11.390(1) Å, c = 12.788(1) Å, α = 85.19(1)°, β = 71.81(1)°, γ = 73.87(1)°, R = 0.034, is built by octahedral trans‐chain anions [MnF₅]^2–_∞ separated by the mono‐protonated organic amine cations. The [MnF₆] octahedra are strongly elongated along the chain axis (<Mn–F_ax> 2.135 Å, <Mn–F_eq> 1.842 Å), mainly due to the Jahn‐Teller effect, the chains are kinked with an average bridge angle Mn–F–Mn = 139.3°. Below 66 K the compound shows 1D‐antiferromagnetism with an exchange energy of J/k = –10.8 K. 3D ordering is observed at T_N = 9.0 K. In spite of the large inter‐chain separation of 8.2 Å a remarkable inter‐chain interaction with |J′/J| = 1.3 · 10^–5 is observed, mediated probably by H‐bonds. That as well as the less favourable D/J ratio of 0.25 excludes the existence of a Haldene phase possible for Mn³⁺ (S = 2).     

Zur Kenntnis der Hexafluoromanganate(III)

The preparation of the up to now unknown compounds [Co(NH₃)₆]MnF₆, [Cr(NH₃)₆]MnF₆ and [Rh(NH₃)₆]MnF₆ is reported. The compounds crystallize in the space group T_h⁶–Pa3, with four formula units in a cell. The magnetic moment of [Co(NH₃)₆]MnF₆ has been measured (4,94 B.M.). The spectra of the above compounds and of K₃MnF₆ and K₂NaMnF₆ in the ultraviolet, visible and infrared region have been measured and discussed. The static distortion of MnF^3?₆ in K₃MnF₆ and K₂NaMnF₆ and a dynamic effect of the compounds with a complex cation due to the JAHN -TELLER theorem show two different types of infrared spectra.     

Fine structure of 6A1g → 4A1g, 4Eg (4G) absorption band in MnF2

Systematic spectroscopic measurements of the spectral lines in MnF₂ have been carried out in the temperature range 10–300 K. Observations of exciton and exciton–magnon sidebands in the fine structures of the ⁶A_1g → ⁴A_1g, ⁴E_g (⁴G) state of Mn⁺² ions are reported at low temperatures for MnF₂. The fine structure of the C-band is mainly attributed to spin multiplicity in the ordered state. In addition, the pure exciton bands have been identified and the ratios for the separation energies between these lines are fitted with the ratios expected form Lande interval rule.     

Room temperature syntheses of MnF3, MnF4 and hexafluoromanganete(IV) salts of alkali cations

Elemental fluorine oxidises MnF₂ in anhydrous hydrogen fluoride (aHF) as a solvent at room temperature yielding pure MnF₃. In the presence of a UV source, MnF₂ is completely oxidised by photodissociated F₂ in aHF to MnF₄. Photochemical reactions with elemental fluorine on 2AF (A=Li, Na, K, Rb, Cs)/MnF₂ mixtures in aHF as a solvent at room temperature yield pure A₂MnF₆ compounds. An attempt to prepare CsMn^VF₆ by oxidation of MnF₂ with UV-irradiated F₂ in the presence of an equimolar amount of CsF in aHF failed. The final products of these reactions were mixtures of MnF₄ and Cs₂MnF₆. Described syntheses represent milder approaches for the preparation of larger amounts of MnF₃, MnF₄, and A₂MnF₆ on a gram scale.     

DVM-Xα calculations on the ionization potentials of MXk+1− complex anions and the electron affinities of MXk+1 “superhalogens”

The ionization potential (IPs) of the MX_k+1^? complex anions BO₂^?, AlO₂^?, NO₃^?, PO₃^?, ClO₄^?, BeF₃^?, MgF₃^?, BF₄^?, AlF₄^?, SiF₅^?, and PF₆^? are calculated by a self-consistent discrete variational Xα method (SCF DVM-Xα). The calculations are carried out both within a numerical Hartree-Fock (HF) basis and within analytical double zeta ones. Valence IPs obtained in both bases coincide with each other within limits of 0.5–1.0 eV. A comparison of the electronic structures of oxygen and flourine containing anions is made. Assuming the first IP of the MX_k+1 ion to be approximately equal to the electron affinity (EA) of MX_k+1, estimates of the EAs for the radicals BO₂, AlO₂, NO₃, PO₃, ClO₄, BeF₃, MgF₃, BF₄, AlF₄, SiF₅, and PF₆ are obtained. It is shown that EA of the MX_k+1 should be low if the highest occupied MO of the corresponding MX_k+1^? anion contains AOs of the central atom (or in terms of localized MOs the central atom possesses a lone pair). In contrast, if the highest occupied MO of an anion is formed from ligand AOs only (or in terms of localized orbitals the central atom does not possess any lone pairs) the EA of a radical should be large. The estimated EAs of the MX_k+1 radicals are used for a comparison between possibilities of heterolytical and homolytical channels of the L-MX_K+1 bond destruction in complex salts of alkali metals.