Die Kristallstrukturen der hexagonalen Elpasolithe Ba3NiSb2O9 und Ba3CuSb2O9 – röntgenographische und spektroskopische Ergebnisse

The Structures of the Hexagonal Elpasolite-Type Compounds Ba₃NiSb₂O₉ and Ba₃CuSb₂O₉ The results of an X-ray single crystal study of the hexagonal elpasolite Ba(NiSb₂)⁽⁶⁾O₉ are given. (Space group: C; a = b = 5.837 Å, c = 14.392 Å; Z = 2). The structure can be described by close-packed BaO₃ layers alternating in the sequence c c h c c h … (hex. BaTiO₃ type). Groups of two octahedra with common faces are connected by SbO₆ octahedra via common corners. They are occupied alternately by Ni and Sb. The final reliability index was R = 3.0%. The Cu²⁺-compound is of the same structural type. The ligand field and EPR spectra are discussed in comparison with related Ni²⁺ and Cu²⁺ compounds.     

Darstellung und spektroskopische Charakterisierung der Monofluorohydro-closo-Borate [B6H5F]2− und [B12H11F]2−

Preparation and Spectroscopic Characterization of the Monofluorohydro-closo-borates [B₆H₅F]^2? and [B₁₂H₁₁F]^2? By treatment of [B₆H₆]^2? with 1-(chloromethyl)-4-fluoro-1,4-diazabicyclo[2.2.2]octane-bis(tetrafluoroborate)in acetonitrile monofluorohydro-closo-hexaborate [B₆H₅F]^2? ( 1 ) is formed in good yields. [B₁₂H₁₂]^2? reacts with unhydrous HF yielding the monofluorododecaborate [B₁₂H₁₁F]^2? ( 2 ). These compounds are separated by ion exchange chromatography on diethylaminoethyl(DEAE) cellulose from by-products. The ¹¹B nmr spectra exhibit the characteristic patterns (1 : 4 : 1) of a monosubstituted B₆ octahedron and (1 : 5 : 5 : 1) of a monosubstituted B₁₂ icosahedron with strong downfield shifts of the ipso-B nuclei at +9.3 ppm ( 1 ) and at +9.0 ppm ( 2 ). The ¹⁹F nmr spectra reveal quartets at ?212 ppm ( 1 ) and ?209 ppm ( 2 ) proving a B? F bonding. In the i.r. spectra, for ( 1 ) in the Raman spectrum too, cage vibrations depending on the F substituent at 1195 ( 1 ) and at 1182/1154 cm^?1 ( 2 ) are observed. The Raman spectra show the B₆F stretching mode at 535 cm^?1 and the B₁₂F stretching vibration at 445 cm^?1.     

Zur Kenntnis der Strontiumpolysulfide Präparative,röntgenographische und schwingungsspektroskopische Untersuchungen

X-ray, I.R., and Raman Data of Strontium Polysulfides The strontium polysulfides SrS₂, SrS₃A, and SrS₃B were studied in terms of preparation, thermal decomposition, and phase transition. The i.r. and Raman spectra of the strontium polysulfides as well as the normal coordinates of the phonon modes are presented and discussed in comparison with the respective barium compounds. From the spectra it is shown that S₃^2? entities are present in SrS₃A as in SrS₃B.     

Die Feinstruktur in den Schwingungs- und elektronischen Absorptionsspektren von [CrO4]2− und [MnO4]−

Finestructure in the Vibrational and Electronic Absorption Spectra of [CrO₄]^2? and [MnO₄]^? The ir and ra spectra of Tl₂[CrO₄] and (C₂H₅)₄N[MnO₄] are measured and assigned. Details of the preresonance- and resonance-Raman effect are discussed. The exact knowledge of the vibrational spectrum enables the understanding of the complicated vibrational finestructure in the electronic absorption spectrum of (C₂H₅)₄N[MnO₄]. For the states of the charge-transfer t₁ → e* bands are found at 15 000, 15 170 cm^?1 for ¹T₁(I), at 17 646, 17 708, 17 809 cm^?1 for ¹T₂(II) and at 17 920, 17 992 and 18 080 cm^?1 for ³T₂(III). The electronic origin for the states of the t₂ → e* chargetransfer is at 24 661 for ¹T₁(IV) and 30 230 cm^?1 for ¹T₂(V). The vibrational coupling is only with the totally symmetric Mn? O-stretching-vibration. Bands at 29 500 cm^?1 and 44 450 cm^?1 are assigned to the ¹T₂-states of the t₁, t₂ → t₂* charge-transfer.     

Röntgenographische und schwingungsspektroskopische Untersuchungen an Spinell-Mischkristallen des Systems (Zn,Ga) Cr2Se4

X-ray and I. R. Spectroscopic Studies on Spinel Solid Solutions of the Zn_1–xGa_0.67xCr₂Se₄ System With the aim to get new compounds with spinel defect structure of the ß-In₂S₃ type, we studied the phase diagram of the Zn_1–xGa_0.67xCr₂Se₄ system. The spinel type solid solutions formed within x = 0—0.6 show a relatively large phase width with respect to the metal selenium ratio, i. e. the parameter z in the formula Zn_1–xGa_0.67(x+0.5z)Cr_2–z^IIICr_z^IISe₄. Ternary Ga_0.67Cr₂Se₄ does not exist, it decomposes to Cr₂Se₃ and Ga₂Se₃. Instead of the ß-In₂S₃ type, superstructure reflections of LiFeCr₄O₈ type are observed.     

Darstellung,Eigenschaften, röntgenographische und spektroskopische Untersuchung von Tl4Nb2S11 und Tl4Ta2S11

On Polychalcogenides of Thallium with M₂Q₁₁ Groups as a Structural Building Block. I Preparation, Properties, X‐ray Diffractometry, and Spectroscopic Investigations of Tl₄Nb₂S₁₁ and Tl₄Ta₂S₁₁ The new ternary compounds Tl₄Nb₂S₁₁ and Tl₄Ta₂S₁₁ were prepared using Thallium polysulfide melts. Tl₄M₂S₁₁ crystallises isotypically to K₄Nb₂S_8.9Se_2.1 in the triclinic space group P 1 with a = 7.806(2) Å, b = 8.866(2) Å, c = 13.121(3) Å, α = 72.72(2)°, β = 88.80(3)°, and γ = 85.86(2)° for M = Nb and a = 7.837(1) Å, b = 8.902(1) Å, c = 13.176(1) Å, α = 72.69(1)°, β = 88.74(1)°, and γ = 85.67(1)° for M = Ta. The interatomic distances as well as angles within the [M₂S₁₁]^4– anions are similar to those of the previously reported data for analogous alkali metal polysulfides. Significant differences between Tl₄M₂S₁₁ and A₄M₂S₁₁ (A = K, Rb, Cs) are obvious for the shape of the polyhedra around the electropositive elements. The two title compounds melt congruently at 732 K (M = Nb) and 729 K (M = Ta). The optical band gaps were estimated as 1.26 eV for Tl₄Nb₂S₁₁ and as 1.80 eV for the Tantalum compound.     

Züchtung und röntgenographische Untersuchung von Einkristallen des Alumothiosilicats Mn1,84Al0,16Si0,84Al0,16S4

Crystal Growth and Structure of the Alumothiosilicate Mn_1.84Al_0.16Si_0.84Al_0.16S₄ Single Crystals of the alumothiosilicate Mn_1.84Al_0.16Si_0.84Al_0.16S₄ were grown by chemical transport reaction. The compound represents the first example of this type of silicate. The crystals were characterized by electron microprobe analyses and X-ray methods. The compound crystallizes in the olivine type structure, space group Pnma, a = 1 266.9(2), b = 739.6(3), c = 592.8(1) pm. The mean bond lengths are very similar to those in Mn₂SiS₄. That part of aluminum which is situated at the octahedral sites is not equally distributed amongst both types of octahedral positions but is enriched on the smaller and more symmetric M(1) position.     

Ca6GaN5 und Ca6FeN5. Verbindungen mit [CO3]2−-isosteren Anionen [GaN3]c− und [FeN3]6−

Ca₆GaN₅ and Ca₆FeN₅: Compounds Containing [CO₃]^2?-isosteric Anions [GaN₃]^6? and [FeN₃]^6? The isotypic phases Ca₆GaN₅ and Ca₆FeN₅ (hexagonal, P6₃/mem; a = 627.7(3)/ 623,7(1) pm, c = 1219.8(3)/1233.2(6) pm; Z = 2) are prepared by reaction of Ca/Ga mixtures (molar ratio 6:1) and Fe/Ca₃N₂/Ca mixtures (molar ratios from 3:1:13 to 5:2:15) with nitrogen at temperatures of 850°C and 950°C to 1100°C, respectively. The structures contain trigonal-planar anions [MN₃]^6? which are isosteric to carbonate ions (Ga? N: 195,1(28) pm; Fe? N: 177,0(15) pm). The structures are closely related to those compounds of the hydrotalcite group.     

Festkörperreaktionen in Chalkogenidsysfemen,IV [1]: Röntgenographische und elektrische Untersuchungen am System HgCr2(SexS1–x)4

Inhaltsübersicht. Im Spinellsystem HgCr₂Se_xS_1–x)₄ besteht im Gegensatz zu den entsprechenden Zink- und Cadmiumverbindungen, die lückenlose Mischkristallreihen bilden, zwischen 0,20 < x < 0.75 einp Mischungslücke. Im Bereich der Mischungslücke werden HgSe und Cr₂S_3–ySe_y-Mischkristalle gebildet. Die Gitterkonstanten der Spinellmischkristalle erfüllen nur auf der selenreichen Seite des Phasendiagramms die Végardsche Regel. Der Reaktionsverlauf wurde mit Hilfe von Leitfähigkeitsmessungen sowie thermoanalytischer Untersuchungen verfolgt. Über die Möglichkeit der Spinellbildung des Systems wird diskutiert. X-ray and Electric Measurements on the HgCr₂(Se_xS_1–x)₄ System Abstract. In the HgCr₂(Se_xS_1–x)₄ system there is no spinel structure in the 0.20 < x < 0.75 concentration range. In the miscibility gap the formation of HgSe and Cr₂8_3–ySe_y mixed crystals has been noticed. The lattice constants of the spinel solid solutions obey Végard's law only on the selenium-rich side of the phase diagram. Both the temperature dependence of electric conductivity and the thermal analysis of the starting mixtures were studied. The possibility of formation of spinels in the system is discussed.     

Die isotypen Verbindungen BaRh2Si2, BaIr2Si2 und BaPt2Ga2 – eine monokline Verzerrungsvariante der CaRh2B2-Struktur

The Isotypic Compounds BaRh₂Si₂, BaIr₂Si₂, and BaPt₂Ga₂ – a Monoclinic Distortion Variant of the CaRh₂B₂ Structure The new compounds BaRh₂Si₂ (monoclinic, P2₁/c, a = 792.6(1) pm, b = 664.5(7) pm, c = 767.9(4) pm, β = 91.2(1)°, Z = 4, 2867 reflexions, 47 parameters, R = 0.024), BaIr₂Si₂ (monoclinic, P2₁/c, a = 792.47(6) pm, b = 664.28(6) pm, c = 772.22(6) pm, β = 92.181(7)°, Z = 4, 1939 reflexions, 47 parameters, R = 0.037) and BaPt₂Ga₂ (monoclinic, P2₁/c, a = 850.4(1) pm, b = 647.3(1) pm, c = 819.8(1) pm, β = 95.97(1)°, Z = 4, 1506 reflexions, 47 parameters, R = 0.038) were prepared by reaction of the elements. Their structures were determined from single crystal data. The compounds crystallize isotypically with a distortion variant of the CaRh₂B₂ type of structure.     

Tribochemische und thermische Umwandlungen von LnTa3O9 (Ln = Pr,Nd) – röntgenographische und elektronenmikroskopische Untersuchungen

Tribochemical and Thermal Transitions of LnTa₃O₉ (Ln = Pr, Nd) — X-ray and Electron Microscopic Investigations Upon grinding crystals of M1? LnTa₃O₉ (Ln = Pr, Nd) [3] undergo a tribochemical phase transition. This leads to a new modifikation M2? LnTa₃O₉ with a significant higher density. We tried to find out more about the structure with high resolution electron microscopic investigations. According to electron diffraction and powder patterns the lattice parameters are (CuKα₁, λ = 1,54051 Å): M2? PrTa₃O₉: a = 6.2545(7) Å, b = 7.6736(7) Å, c = 6.5316(8) Å, β = 93.93(9)°; M2? NdTa₃O₉: a = 6.2552(5) Å, b = 7.6598(7) Å, c = 6.5103(4) Å, β = 94.096(7)°; (Z = 2). Using the intensities of powder patterns two structure models were calculated (space group P2₁/m, P2/m; R < 20%, heavy metal positions only). A through focus series of high resolution images was in better agreement with the first model (space group P2₁/m). Both models show a remarkable similarity to the structure of M? CeTa₃O₉ [4]. A thermal phase transition leads to M? PrTa₃O₉ and M? NdTa₃O₉ which are both isostructural to M? CeTa₃O₉.     

Thiohalogeno-Verbindungen von Niob und Tantal: NbSCl3, TaSCl3, [NbSCl5]2−, [TaSCl5]2−, [NbSBr4]− Die Kristallstrukturen von (PPh4)2[NbSCl5] · 2 CH2Cl2 und NEt4[NbCl6]

Thiohalo Compounds of Niobium and Tantalum: NbSCl₃, TaSCl₃, [NbSCl₅]^2?, [TaSCl₅]^2?, [NbSBr₄]^?. Crystal Structures of (PPh₄)₂[NbSCl₅] · 2 CH₂Cl₂ and NEt₄[NbCl₆] NbSCl₃ can be obtained from NbCl₅ by reaction with H₂S or bistrimethylsilyl sulfide in a suspension of CCl₄ or CH₂Cl₂, respectively; in the latter case the product contains a rest of trimethylsilyl groups. This also applies for TaSCl₃, NbSBr₃ and TaSBr₃, which are formed from the metal pentahalides and S(SiMe₃)₂. NEt₄[NbSCl₄] is formed together with NEt₄[NbCl₆] in the reaction of NbCl₅ with NEt₄SH in CH₂Cl₂. PPh₄[NbCl₆] reacts with S(SiMe₃)₂ in dichloromethane yielding (PPh₄)₂[NbSCl₅] · 2 CH₂Cl₂, whereas PPh₄[NbSBr₄] is obtained from PPh₄[NbBr₆] and S(SiMe₃) under the same conditions. (PPh₄)₂[TaSCl₅] · 2 CH₂Cl₂ was obtained from TaSCl₃ and PPh₄Cl in CH₂Cl₂. According to an X-ray crystal structure determination (PPh₄)₂[NbSCl₅] · 2 CH₂Cl₂ crystallizes in the β-(AsPh₄)₂[UCl₆] · 2 CH₂Cl₂ type with positionally disordered, octahedral anions. Crystal data: a = 1 021.7, b = 1120.4, c = 1 243.3 pm, α = 70.77, β = 80.24, γ = 80.54°, space group P1 , Z = 2; 2462 unique observed reflexions, R = 0.036. NEt₄[NbCl₆] crystallizes isotypic to NEt₄[WCl₆], a = 723.5, b = 1 018.0, c = 1 174.6 pm, β = 100.07°, space group P2₁/n, Z = 2; 1 875 reflexions, R = 0.075.     

Präparative und röntgenographische Untersuchungen über das System Al2S3?ZnS (Temperaturbereich 800–1080°C)

Einkristalle von α-ZnAl₂S₄ mit Spinellstruktur (a = 10,009₃ Å) lassen sich durch chemische Transportreaktion bei 740°C erhalten. Beim Erhitzen der Verbindung auf 800–900°C tritt Zerfall in eine ZnS-arme defekte Spinellphase und in eine ZnS-reiche Phase mit defekter Wurtzitstruktur ein. Bei 830–860°C liegen die Grenzen des zweiphasigen Bereichs etwa bei Zn_0,98Al_2,01S₄ (kubische α-Phase, a = 10,007₂ Å (25°C)) und Zn_1,80Al_1,47S₄ (hexagonale Wurtzitphase, a = 3,76₀, c = 6,1₅ Å (25°C)). Mischungen von ZnS, Al und S entsprechend der Zusammensetzung Zn_xAl_8/3?2x/3S₄ mit 0,33 ≤ x ≤ 0,98, die auf 830–860°C (70–140 h) erhitzt worden sind, liefern nach Abkühlung auf Raumtemperatur homogene Produkte mit defekter Spinellstruktur. Die bei der Zusammensetzung Al₂S₃ · ZnS beobachtete Mischungslücke setzt sich bei höherer Temperatur unter Verschiebung der Phasengrenzen und Ausbildung von Hochtemperatur-Phasen fort. Eine Hochtemperaturmodifikation des ZnAl₂S₄ existiert bis 1080°C nicht. Mischungen von ZnS, Al und S mit 0,44 ≤ x ≤ 0,85, die auf 1060–1080°C (72–96 h) erhitzt worden sind, zeigen nach Abkühlung auf Raumtemperatur eine bisher nicht beschriebene rhomboedrische Hochtemperaturphase (γ-Phase), deren Struktur als eine Defektstruktur des ZnIn₂S₄-Typs aufgefaßt werden kann. Bei x = 1,00 erhält man nach thermischer Behandlung bei 1060–1080°C ein zweiphasiges Produkt, das neben der γ-Phase eine orthorhombische Phase (β-Phase, Überstruktur des Wurtzit-Typs) enthält. Die β-Phase tritt als einzige Phase auf, wenn für die Ausgangsmischung gilt: 1,40 ≤ x ≤ 1,70. Die Löslichkeit von Al₂S₃ in ZnS (Wurtzit) unter Bildung einer statistischen Defektstruktur des Wurtzit-Typs reicht bei 1060–1080°C bis Zn_1,70?1,80Al_1,53?1,47S₄(Al₂S₃ · (2,2-2,5) ZnS). Preparative and X-Ray Investigations on the System Al₂S₃? ZnS (Temperature Region 800–1080°C) Single crystals of α-ZnAl₂S₄ with spinel structure (a = 10.009₃ Å) have been obtained by chemical transport reaction at 740°C. Heating of the compound to 800–900°C leads to decomposition and formation of a ZnSαpoor defect spinel phase and a ZnS-rich phase with a defect wurtzite structure. The boundaries of the two-phase region at 830–860°C are approximately Zn_0,98Al_2.01S₄ (cubic α-phase, a α 10.007₂ Å (25°C)) and Zn_1.80Al_1.47S₄ (hexagonal wurtzite-phase, a = 3.76₀, c = 6.1₅ Å (25°C)). Mixtures of ZnS, Al and S with the composition Zn_xAl_8/3?2x/3S₄ and 0.33 ≤ x ≤ 0.98, which are heat treated at 830–860°C (70–140 h), yield after cooling to room temperature homogeneous products with a defect spinel structure. The miscibility gap at the composition Al₂S₃ · ZnS continues at higher temperatures with a shift of the phase boundaries and formation of high-temperature phases. A high-temperature modification of ZnAl₂S₄ does not exist up to 1080°C. When mixtures of ZnS, Al and S with 0.44 ≤ x ≤ 0.85 are heat treated at 1060–1080°C(72-96 h), a rhombohedra1 high-temperature phase (γ-phase) is obtained after cooling to room temperature, which has not previously been observed. I t s structure can be described as a defect structure of the ZnIn, S, type. With x = 1.00, after thermal treatment a t 1060-1080°C, a two-phase product is obtained, containing γ-phase in addition to an orthorhombic phase (β-phase, super-lattice of the wnrtzite type). The β-phase is the only phase occuring in products with 1.40 ≤ x ≤ 1.70. The solubility of Al, S, in ZnS (wurtzite) at 1060-1080°C with formation of a defect wurtzite structure, in which the cations are disordered, reaches as far as Zn_l.70?1.80Al_l.53?1.47S₄[Al₂S₃·(2.2-2.5)ZnS].     

Elektronenstruktur von strukturell offenen Derivaten des [Mo6X14]2−-Clusters: [Mo5Cl13]2− und [Mo4I11]2−

Electronic Structure of Structural Open Derivatives of the [Mo₆X₁₄]^2?-Cluster: [Mo₅Cl₁₃]^2? and [Mo₄I₁₁]^2? The electronic structure of structural open derivatives of the [Mo₆X₁₄]^2?-cluster [Mo₅Cl₁₃]^2? and [Mo₄I₁₁]^2? has been studied by the EHMO method. In [Mo₅Cl₁₃]^2? 9 occupied MO's with dominant Mo4d character are responsible for the formation of the 8 metal-metal bonds. In [Mo₄I₁₁]^2? the stronger covalent character of the Mo? I bonds affects the localization and the energy of molecular orbitals and also the charge distribution. The metal-metal bonds are formed by 8 MO's containing considerable participation of halogen AO's contrary to the chloride cluster. There is no bonding between the Mo atoms at the wing tips of the Mo₄ butterfly and the reason for decreasing the dihedral angle between the Mo₃ planes in [Mo₄I₁₁]^2? compared with the octahedral angle is apparently the stabilization of the whole system (Mo? Mo and Mo? I bonds). The unpaired electron occupies in both clusters a slightly antibonding (with regard to the Mo? Mo bonds) orbital.     

Über die Darstellung der Dichlormethylen-halogensulfenium-Salze Cl2CSCl+ AsF6− und Cl2CSBr+ AsF6− [1]

The Synthesis of the Dichloromethylene-halogenosulfenium Salts Cl₂CSCl⁺ AsF₆^? and Cl₂CSBr⁺ AsF₆^? The sulfenium salts Cl₂CSCl⁺ AsF₆^? and Cl₂CSBr⁺ AsF₆^? are synthesized by oxidative halogenation of thiophosgene, Cl₂CS with X₂/AsF₅ (X = Cl, Br) at 195 K and are characterized by vibrational as well as NMR spectroscopy.     

Röntgenographische und spektroskopische Untersuchungen an Ba2Ni(N3)6· 3H2O

Preparation and X-Ray Examination of Ba₂Ni(N₃)₆ · 3 H₂O Ba₂Ni(N₃)₆ · 3 H₂O has been prepared by the reaction of an aqueous solution of Ba(N₃)₂ with basic nickel azide. The crystals are green, the lattice constants are: a = 7.09 Å, b = 7.09 Å, c = 16.30 Å, α = 74.58°, β = 105.42°, γ = 97.10°, N = 2. Optical spectra point to an octahedral microsymmetry of the azide ions around nickel.     

Untersuchungen an oxidischen Katalysatoren. XXXVI. Struktur und thermisches Verhalten röntgenamorpher Al2O3–SiO2-Festkörper

Studies on Oxide Catalysts. XXXVI. Structure and Thermal Behaviour of Silica–Alumina The effect of thermal treatment up to 500°C on silica-alumina was studied by i.r. investigation in the lattice vibration region and the condensation degree of the silicate fragments in the silica-alumina was characterized using the molybdato method. The results of both methods demonstrate the proton form of the amorphous alumosilicates to be thermal instable and to undergo extraction of the aluminium from the alumosilicate lattice. The consequences resulting from this process on the catalytic efficiency of silica-alumina in the cracking reaction of cumene are discussed.