Über die Verbindung Ca4PtO6

During the recovery of Pt from reaction products of the catalytic NH₃ oxidation by CaO filters a compound is formed, which has been described and structurell investigated as Ca₄PtO₆ by CZAYA¹).     

Darstellung und kristallographische Daten von Tetracalciumplatinoxid Ca4PtO6

On synthesising Ca-silicates from a CaCl₂-flux in the presence of Platinum, Ca₄PtO₆ was found. The compound crystallises orthorhombic (see ?Inhaltsübersicht”?). Relations to Sr₄PtO₆ are described.     

Ein neues Erdalkalimetall-Oxoplatinat-Cuprat Ca3,5Cu0,5PtO6

A new Alkaline-Earth Platinum Copper Oxide: Ca_3.5Cu_0.5PtO₆ Ca_3.5Cu_0.5PtO₆ was prepared and investigated by single crystal X-ray work. (Space group C? C12/m1; a = 9.0743; b = 9.2527; c = 6.4840 Å; β = 91.448°; Z = 4). The crystal structure of the previously unknown compound is closely related to the structure of Sr₃PtCuO₆ and Sr₃IrCuO₆ as well as the rhombohedral phases M₄PtO₆ (M = Ba, Sr, Ca). Typical features of the crystal chemistry are isolated chains of PtO₆ octahedra, alternately allyed by square CuO₄ polygones and trigonal prisms of O^2? around Ca²⁺.     

Pb2PtO4, a new platinum-lead oxide with edge-shared PtO6 octahedral chains

Pb₂PtO₄ was prepared by the solid state reaction between lead monoxide and platinum metal in the appropriate ratio at 690–720°C. It decomposed to PbO and Pt at 735°C. The symmetry is orthorhombic: a = 9.115(4), b = 7.941(4), c = 6.306(4) Å, Z = 2, space group Pbam. The crystal structure was solved by conventional methods to R = 0.049 using 851 independent reflections. The structure consists of chains of edge-shared PtO₆ octahedra extending along the c-axis direction. Lead atoms are stacked in rows in the channels between the chains. The conductivity of Pb₂PtO₄ is low (σ(300 K) ⋍ 10⁻⁵ (Ω · cm)⁻¹), in agreement with the presence of fully oxidized tetravalent platinum.     

Ca4IrO6, Ca3MgIrO6 and Ca3ZnIrO6

Single crystals of tetracalcium iridium hexaoxide, Ca₄IrO₆, tricalcium magnesium iridium hexaoxide, Ca₃MgIrO₆, and tricalcium zinc iridium hexaoxide, Ca₃ZnIrO₆, were prepared via high-temperature flux growth and structurally characterized by single-crystal X-ray diffraction. The three compounds are isostructural and adopt the K₄CdCl₆ structure type, comprised of chains of alternating face-shared [CaO₆], [MgO₆] or [ZnO₆] trigonal prisms and [IrO₆] octahedra, surrounded by columns of Ca²⁺ ions.     

Zur Kenntnis von Ba6Ru2PtO12Cl2

About Ba₆Ru₂PtO₁₂Cl₂ Single crystals of Ba₆Ru₂PtO₁₂Cl₁₂ were prepared by a BaCl₂ flux and investigated by X-ray methods (D? P3 M1; a = 5,805; c = 15.006 Å; Z = 1). The characteristic face shared M₃O₁₂-octahedratriples show an ordered (Ru/Pt/Ru) occupation. Calculation of the Coulomb term of lattice energy support the charge distribution (5⁺/4⁺/5⁺) ions engage three point sites with different coordinations. The connection to other compounds are discussed.     

The Structures and Characterization of Two New Oxides of the Sr4PtO6 Type: NaCa3IrO6 and NaCa3RuO6

NaCa₃IrO₆ ( I ) and NaCa₃RuO₆ ( II ) crystallize with trigonal (rhombohedral) symmetry in the space group R3 c, Z = 6, for I a = 9.272(3) Å, c = 11.214(1) Å; for II a = 9.244(3) Å, c = 11.201(1) Å. NaCa₃IrO₆ ( I ) and NaCa₃RuO₆ ( II ) are isotypic to compounds of the Sr₄PtO₆ structure type. The structures have been solved by means of single crystal X-ray diffraction data analysis with the reliability factors for I of R = 0.032 and R_w = 0.039; and the the reliability factors for II of R = 0.024 and R_w = 0.031. The structure consists of infinite chains of alternating face-sharing MO₆ octahedra, where M?Ir or Ru, and NaO₆ trigonal prisms. The chains are separated by the calcium cations.     

Study of the ionic conductivity of Ca6La4(PO4)2(SiO4)4F2 and Ca4La6(SiO4)6F2

In order to enhance our knowledge about the Ca_10−xLa_x(PO₄)_6−x(SiO₄)_xF₂ (0 ≤ x ≤ 6) series, whose chemical stability decreases as the substitution degree increases, Ca₆La₄(PO₄)₂(SiO₄)₄F₂ and Ca₄La₆(SiO₄)₆F₂ compounds were prepared through a solid-state reaction. Their ionic conductivity was measured by impedance spectroscopy. The results indicate that the conductivity increases with substitution, and fits the Arrhenius equation over the investigated temperature range. At high temperatures, a change in the activation energy has been observed, which has been related to the nature of the Ca/La–F bond, i.e. to the polarizability of lanthanum.     

New calcium germanium nitrides: Ca2GeN2, Ca4GeN4, and Ca5Ge2N6

We report three new calcium germanium nitrides synthesized as crystals from the elements in sealed niobium tubes at 760 degrees C using liquid sodium as a growth medium. Black Ca2GeN2 is isostructural with the previously reported strontium analogue. It is tetragonal P4(2)/mbc (no. 135) with a = 11.2004(8) A, c = 5.0482(6) A, and Z = 8. It contains GeN2(4-) units which have 18 valence electrons, and consequently are bent, like the isoelectronic molecule SO2. In contrast, clear, orange Ca4GeN4 with fully oxidized germanium contains isolated GeN4(8-) tetrahedra and is monoclinic P2(1)/c (no. 14) with a = 9.2823(8) A, b = 6.0429(5) A, c = 11.1612(9) A, beta = 116.498(6) degrees, and Z = 4. Clear, colorless Ca5Ge2N6, also with fully oxidized germanium, contains infinite chains, 1 infinity[GeN2N2/2(5-)], of corner-sharing tetrahedra similar to those found in pyroxenes. However, the precise structure of this latter phase has not yet been determined because of twinning problems.     

Direct determination of the ionization energies of PtC, PtO, and PtO2 with VUV radiation

Photoionization efficiency curves were measured for gas-phase PtC, PtO, and PtO2 using tunable vacuum ultraviolet (VUV) radiation at the Advanced Light Source. The molecules were prepared by laser ablation of a platinum tube, followed by reaction with CH4 or N2O and supersonic expansion. These measurements provide the first directly measured ionization energy for PtC, IE(PtC) = 9.45 +/- 0.05 eV. The direct measurement also gives greatly improved ionization energies for the platinum oxides, IE(PtO) = 10.0 +/- 0.1 eV and IE(PtO2) = 11.35 +/- 0.05 eV. The ionization energy connects the dissociation energies of the neutral and cation, leading to greatly improved 0 K bond dissociation energies for the neutrals: D0(Pt-C) = 5.95 +/- 0.07 eV, D0(Pt-O) = 4.30 +/- 0.12 eV, and D0(OPt-O) = 4.41 +/- 0.13 eV, as well as enthalpies of formation for the gas-phase molecules DeltaH(0)(f,0)(PtC(g)) = 701 +/- 7 kJ/mol, DeltaH(0)(f,0)(PtO(g)) = 396 +/- 12 kJ/mol, and DeltaH(0)(f,0)(PtO2(g)) = 218 +/- 11 kJ/mol. Much of the error in previous Knudsen cell measurements of platinum oxide bond dissociation energies is due to the use of thermodynamic second law extrapolations. Third law values calculated using statistical mechanical thermodynamic functions are in much better agreement with values obtained from ionization energies and ion energetics. These experiments demonstrate that laser ablation production with direct VUV ionization measurements is a versatile tool to measure ionization energies and bond dissociation energies for catalytically interesting species such as metal oxides and carbides.     

Über ein Oxidchlorid des Calciums: Ca4OCl6

An Oxychloride of Calcium: Ca₄OCl₆ Ca₄OCl₆ (hexagonal, P6₃mc, Z = 2), a = 905.8(3), c = 686.3(4) pm, (R = 0.031) crystallizes as colourless needles from reducing melts (CaCl₂, Ca) that contain small amounts of ?oxygen”?. It contains ?isolated”? tetrahedral units [Ca₄O] and is isotypic with e.g., Ba₄OCl₆, Yb₄OCl₆ and K₆HgS₄. Ca₄OCl₆ does not form in the dehydration process of, for example, CaCl₂ · 6 H₂O.     

Heat evolution during hydration of Ca4(Al6O12)(SO4)

The hydration of the sulphatealuminate phase Ca₄(Al₆O₁₂)(SO₄) at room temperature was observed by means of differential calorimetry and quantitative X-ray diffraction phase analysis in situ. The results were used to evaluate the kinetics of the hydration process and to explain the causes of the exothermic effects: an initial surface reaction, the formation of a highly dispersed system, and the crystallization of monosulphate, Ca₄(Al₂O₆)(SO₄) · 12H₂O, and gibbsite, Al(OH)₃. The experiments showed an increase in efficiency of hydration with a higher mass ratio of water to solid phase (from 143.8 kJ/mol) atw/s=1 to 170.0 kJ/mol atw/s=10).

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Zusammenfassung Die Hydration der Sulfat-aluminat-Phase Ca₄(Al₆O₁₂)(SO₄) bei Zimmertemperatur wurde mittels Differentialkalorimetrie und quantitativer in-situ-Röntgenbeugungs-Phasenanalyse verfolgt. Ein vergleich der Ergebnisse erlaubte die Kinetik des Hydratationsprozesses abzuschätzen und die Ursache der exothermen Effekte zu klären: Anfängliche Oberflächenreaktion, Bildung eines hochdispersen Systems, Kristallisation von Monosulfathydrat Ca₄(Al₂O₆)SO₄·12H₂O und Hydrargillit Al(OH)₃. Die Versuche zeigten eine Zunahme der Hydratationseffektivität mit steigendem Verhältnis Wasser: Feststoff (w/s) von 143,8 kJ mol^–1 beiw/s=1 auf 170,0 kJ mol^–1 beiw/s=10.

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in situ ₄(l₆)(S₄). , , ₄(l₂₆)(S₄) · 122 l()₃. : 143,8 ^–1 1 170,0 · ^–1 10.

     

Neue Vertreter der Li8SnO6-Familie: Li8IrO6, Li8PtO6 und Li8CeO6 [1, 2]

New Compounds of the Li₈SnO₆-Type: Li₈IrO₆, Li₈PtO₆, and Li₈CeO₆ For the first time single crystals of Li₈IrO₆ (dark-violet, a = 541.51, c = 1505.84 pm), Li₈PtO₆ (transparent/greenish yellow, a = 541.46, c = 1501.43 pm), and Li₈CeO₆ (transparent/colourless, a = 564.30, c = 1602.71 pm) have been prepared and investigated by x-ray. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Ionic Radii, MEFIR, are calculated and discussed.     

Zur Kenntnis der Oxoplatinate Na2PtO2, Na2PtO3, „K2PtO3”︁ und „Rb2PtO3”︁

The oxoplatinates Na₂PtO₂, Na₂PtO₃, ?K₂PtO₃”? and ?Rb₂PtO₃”?. Hitherto unknown Na₂PtO₂ (greyish black) was prepared. Na₂PtO₂ (orthorhombic, D—Immm; a = 4.58₅, b = 3.11₉, c = 9.58₈ Å) is isotypic with Li₂CuO₂. α-Na₂PtO₃ (darkyellow; red as single-crystals) is monoclinic, C—C2/c (a = 5.41₉, b = 9.38₅, c = 10.75₂ Å, β = 99.67°), Li₂SnO₃-type. According to 3-dimensional single crystal data hitherto unknown β-Na₂PtO₃ (red crystals) is an orthorhombic variant of the Li₂SnO₃-type (a = 18.83₈, b = 6.28₂, c = 9.06₂ Å, Z = 16, D—Fddd; parameters see text); R = 0.080₉, R' = 0.094₈ [256 reflexes (hk0—hk6)]. The Madelung part of the lattice energy (MAPLE) is calculated and discussed for α-, β-Na₂PtO₃, α- and β-PtO₂. For the first time we got K₂PtO₃ and Rb₂PtO₃.     

Strukturen aus AlB2- und CeMg2Si2-analogen Einheiten. Die Verbindungen Eu3Pd4As4, Ca4Pd5P5 und Ca5Pd6P6

Structures with AlB₂- and CeMg₂Si₂-Type Units. The Compounds Eu₃Pd₄As₄, Ca₄Pd₅P₅, and Ca₅Pd₆P₆ The new compounds Eu₃Pd₄As₄, Ca₄Pd₅P₅, and Ca₅Pd₆P₆ (space groups and lattice constants see ?Inhaltsübersicht”?) have been prepared by heating mixtures of the elements. Their structures were determined by means of single-crystal X-ray methods and contain exclusively units, which are characteristic for the AlB₂- and CeMg₂Si₂-type. The non-metal atoms are isolated from each other or connected to pairs; the ratio between these two kinds can be interpreted by ionic splittings of the formulas.