Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Syntheses,Crystal Structure,and Properties of Hf2Ni2In,Hf2Ni2Sn,Hf2Cu2In,and Hf2Pd2In with Ordered Zr3Al2 Type Structure

Hf₂Ni₂In, Hf₂Ni₂Sn, Hf₂Cu₂In, and Hf₂Pd₂In were synthesized by reacting the elements in an arc-melting furnace under argon and subsequent annealing at 970 K. They crystallize with an ordered Zr₃Al₂ type structure, space group P4₂/mnm which was refined from single crystal X-ray data for Hf₂Ni₂In (a = 713.9(1) pm, c = 660.4(2) pm, wR2 = 0.0665, 513 F² values) and Hf₂Ni₂Sn (a = 703.1(1) pm, c = 676.1(2) pm, wR2 = 0.0423, 507 F² values) with 18 parameters for each refinement. The lattice constants for Hf₂Cu₂In and Hf₂Pd₂In are a = 715.5(1) pm, c = 677.0(1) pm and a = 742.6(1) pm, c = 679.4(2) pm, respectively. The structures may be considered as an intergrowth of distorted CsCl- and AlB₂-like slabs. Magnetic susceptibility measurements indicate Pauli paramagnetism for Hf₂Ni₂In and Hf₂Ni₂Sn, which is consistent with the metallic conductivity observed for Hf₂Ni₂In. ¹¹⁹Sn Mössbauer spectroscopy of Hf₂Ni₂Sn shows one signal with an isomer shift of δ = 1.59(1) mm/s subjected to quadrupole splitting of δE_q = 0.81(1) mm/s.     

Gas-chromatographische Simultanbestimmung von O2, N2, CO,CO2, N2O,SO2, CH4, C2H4 und C2H6 im ppm-Bereich. I. Mitteilung

Zusammenfassung Die vorliegende Arbeit beschreibt ein neues Verfahren zur gas-chromatographischen Simultananalyse von N₂, O₂, CO, CO₂, N₂O, SO₂, CH₄, C₂H₄ und C₂H₆ im Konzentrations-bereich von 10% bis 10 ppm ohne Voranreicherung. Die temperaturprogrammierte Trennung der Einzelkomponenten erfolgt nach Vorsäulensplitting auf zwei parallel geschalteten Säulen. Zur Emittlung der Retentionszeiten und der Peakflächen werden zwei voneinander unabhängige Ultraschalldetektoren verwendet, deren Analogsignale nach Digitalisierung in einem Mikrocomputer verarbeitet werden. Instrumentierung und chromatographische Einzelheiten werden beschrieben und diskutiert.

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Simultaneous gas chromatographic determination of N₂, O₂, CO, CO₂, N₂O, SO₂, CH₄, C₂H₄ and C₂H₆ at the ppm-level. Part I

Summary A new procedure for the simultaneous determination of N₂, O₂, CO, CO₂, N₂O, SO₂, CH₄, C₂H₄ and C₂H₆ by gas chromatography is described. Concentrations from 10% down to 10 ppm can be determined without preconcentration. After a pre-column splitting the individual compounds of the sample are separated by a uniform temperature program on two different columns in parallel. Detection of the effluents is achieved by two individual ultrasonic detectors, the data from which are processed in a micro-computer. Instrumentation and gas chromatographic details are described and discussed.

     

Syntheses,Spectroscopic Studies,and Crystal Structures of Me2Sn(O2PPh2)2, Ph2Pb(O2PMe2)2, and Ph2Pb(O2PPh2)2

Me₂Sn(O₂PPh₂)₂ ( 1 ), Ph₂Pb(O₂PMe₂)₂ ( 2 ), and Ph₂Pb(O₂PPh₂)₂ ( 3 ) have been synthesized by the reactions of Me₂SnCl₂ or Ph₃PbCl with the corresponding diorganophosphinic acid in methanol. X‐ray diffraction studies show that the diorganophosphinate groups behave as double bridges between the metal atoms leading to polymeric ring‐chain structures with M₂O₄P₂ (M = Pb, Sn) eight‐membered rings. The organic groups bonded to the metal atoms are in trans‐position in the resulting octahedral arrangement around the metal atoms. The IR and the mass spectra were reported and discussed.     

K2NaGaP2, Cs2NaGaP2, K2NaGaAs2, K2NaInP2 und K2NaInAs2, Verbindungen mit den SiS2-isosteren Polyanionen [MX4/2]3− (MGa,In; XP,As)

K₂NaGaP₂, Cs₂NaGaP₂, K₂NaGaAs₂, K₂NaInP₂ and K₂NaInAs₂, Compounds with the Polyanions [MX_4/2]^3? (M?Ga, In; X?P, As) isosteric with SiS₂ The title compounds are synthesized from stoichiometric mixtures of the elements or from Na, KP(KAs), Cs₄P₆ and MX (M?Ga, In; X?P, As) at 950K. They are isotypic and crystallize in the space group Ibam (No. 72) with Z=4. The anionic partial structure is characterized by infinite chains [MX_4/2]^3? which are isosteric to SiS₂. Vibrational spectra are measured and interpreted based on the symmetry D_4h-P(2/m 2/c)4₂/m of the isolated polymer chain [MX₂]^3?. A good agreement between observed and calculated frequencies is obtained by using a force field of the tetrameric fragment [M₄X₁₀]^18? (three four-membered M₂X₂ rings).     

Structural chemistry of Ba2CdS3, Ba2CdSe3, BaCdS2, BaCu2S2 and BaCu2Se2

The structures of all compounds were determined from three dimensional single crystal X-ray diffraction data and refined by least squares. Ba₂CdS₃ and Ba₂CdSe₃ are isostructural, Pnma, a = 8.9145(6)Å, b = 4.3356(2)Å, c = 17.2439(9)Å for the former compound and a = 9.2247Å, b = 4,4823(6)Å, c = 17.8706(11)Å for the latter, z = 4, R = 0.0751 and R = 0.0462, respectively. The compounds are isostructural with the previously reported Mn analogues and with K₂AgI₃. Cd ions are in tetrahedral environment and the tetrahedra form infinite linear chains by corner sharing. Ba ions are in 7-fold coordination in which 6 anions form a trigonal prism and 1 anion caps one of the rectangular faces. BaCdS₂, Pnma, a = 7.2781(3)Å, b = 4.1670(1)Å, c = 13.9189(6)Å, z = 4, R = 0.0685. Cd ions can be considered to have a triangular planar coordination with CdS distances of 2.47 and 2.53 Å (twice). Two additional S ions are at 2.89 and 3.22 Å to complete a triangular bipyramidal configuration. Ba is in 7-fold coordination with the anions forming a trigonal prism which is capped on one rectangular face. The compound is isostructural with BaCdO₂ and is related to the structure of BaMnS₂. BaCdSe₂ could not be prepared. BaCu₂S₂ and BaCu₂Se₂ are isostructural, Pnma, a = 9.3081(4)Å, b = 4.0612(3)Å, c = 10.4084(5)Å for the sulfide and a = 9.5944(6)Å, b = 4.2142(4)Å, c = 10.7748(8)Å for the selenide, z = 4, R = 0.0634 and 0.0373, respectively. Ba ions are in the usual 7-fold, capped hexagonal prism, coordination. However, 9 Cu ions also can be considered to form a trigonal prism with all rectangular faces capped, around Ba since the BaCu distances range from 3.24 to 3.54 Å for the sulfide and from 3.37 to 3.67 Å for the selenide. One of the Cu ions is in a very distorted tetrahedral environment and the second one is located in a more regular tetrahedral configuration of the anions. Two independent infinite chains of tetrahedra are present. They are formed by sharing of two adjacent edges of each tetrahedron and then these chains in turn are linked by corner sharing into a three-dimensional network of tetrahedra.     

Mode Selective Stereomutation and Parity Violation in Disulfane Isotopomers H2S2, D2S2, T2S2

We report quantitative calculations of stereomutation tunneling in the disulfane isotopomers H₂S₂, D₂S₂, and T₂S₂, which are chiral in their equilibrium geometry. The quasi‐adiabatic channel, quasi‐harmonic reaction path Hamiltonian approach used here treats stereomutation including all internal degrees of freedom. The torsional motion is handled as an anharmonic reaction coordinate in detail, whereas all the remaining degrees of freedom are taken into account approximately. We predict how stereomutation is catalyzed or inhibited by excitation of the various vibrational modes. The agreement of our theoretical results with spectroscopic data from the literature on H₂S₂ and D₂S₂ is excellent. We furthermore predict the influence of parity violation on stereomutation as characterized approximately by the ratio (ΔE_pv/ΔE_±) of the (local or vibrationally averaged) parity violating potential ΔE_pv and the tunneling splittings ΔE_± in the symmetrical case. This ratio is exceedingly small for the reference molecules H₂O₂ and D₂O₂, and still very small (2⋅10⁻⁶ cm⁻¹) for H₂S₂, which, thus, all exhibit essentially parity conservation in the dynamics. However, for D₂S₂ it is ca. 0.002, and for T₂S₂ it is ca. 1, which seems to be the first case where such intermediate mixing through parity violation is quantitatively predicted for spectroscopically accessible molecules. The consequences for the spectroscopic detection of molecular parity violation are discussed briefly also in relation to other molecules.     

Preparation,Crystal Structure,Vibrational Spectra,and Thermal Behavior of Rb2H2P2O6·2H2O

Single crystals of Rb₂H₂P₂O₆ · 2H₂O could be obtained from aqueous solutions of hypodiphosphoric acid and rubidium carbonate. Its crystal structure was determined by X‐ray diffraction and it crystallizes in the monoclinic space group P2₁/c with Z = 4. The salt‐like title compound consists of [H₂P₂O₆]^2– units in staggered P₂O₆‐skeleton conformation, Rb⁺ cations, and H₂O molecules, held together by intermolecular hydrogen bonds of the type O ··· O. The vibrational spectra (IR/FIR and Raman) of the rubidium salt were recorded and an assignment of the vibrational modes is proposed based on the point group C_2h for the P₂O₆‐skeleton of the anion. The thermal behavior of Rb₂H₂P₂O₆ · 2H₂O is dominated by a complex TG decay indicating a simultaneous H₂O delivery coupled with a disproportionation of [H₂P₂O₆]^2–, what is also supported by Raman spectra of heated samples.     

Magnesium and cadmium containing Heusler phases REPd2Mg,REPd2Cd,REAg2Mg,REAu2Mg and REAu2Cd

Twenty-eight new Heusler phases REPd₂Mg, REPd₂Cd, REAg₂Mg, REAu₂Mg and REAu₂Cd with different rare earth elements were synthesized from the elements in sealed niobium ampoules in a water-cooled sample chamber of an induction furnace. The samples were characterized by powder X-ray diffraction. The cell volumes show the expected lanthanide contraction. The structures of YPd₂Cd, GdPd₂Cd, GdAu₂Cd, Y_1.12Ag₂Mg_0.88 and GdAg₂Mg were refined based on single crystal diffractometer data. The magnetic properties were determined for fifteen phase pure samples. LuAu₂Mg is a weak Pauli paramagnet with a susceptibility of 1.0(2) × 10⁻⁵ emu mol⁻¹ at room temperature. The remaining samples show stable trivalent rare earth ions and most of them order magnetically at low temperatures. The ferromagnet GdAg₂Mg shows the highest ordering temperature of T_C = 98.3 K. ¹¹³Cd and ⁸⁹Y MAS NMR spectra of YAu₂Cd and YPd₂Cd confirm the presence of unique crystallographic sites. The resonances are characterized by large Knight shifts, whose magnitude can be correlated with electronegativity trends.     

Synthesis,Spectral Studies,and Crystal Structure of [Me2ClSnO2AsMe2] and [Et2ClSnO2AsMe2]

The treatment of Me₂SnCl₂ and Et₂SnCl₂ with HO₂AsMe₂ in methanol leads to [Me₂ClSnO₂AsMe₂] ( 1 ) and [Et₂ClSnO₂AsMe₂] ( 2 ), respectively. X‐ray diffraction studies show that the O₂AsMe₂ groups function as bidentate bridge ligands between R₂ClSn units forming polymeric chain structures. 1 consists of double chains, in which the oxygen atoms of each O₂AsMe₂ group of one chain interact in a chelate mode with the tin atom of the other affording seven‐coordinated tin atoms, whereas the structure of 2 is built of single chains in which the tin atoms exhibt a distorted trigonal‐bipyramidal geometry with an axial O‐Sn‐Cl angle of 160°. The vibrational and mass spectra are given and discussed.     

Reactivity of positively charged cobalt cluster ions with CH4, N2, H2, C2H4, and C2H2

Reactivity of positively charged cobalt cluster ions (Co _n ⁺ ,n=2?22), produce by laser vaporization, with various gas samples (CH₄, N₂, H₂, C₂H₄, and C₂H₂) were systematically investigated by using a fast-flow reactor. The reactivity of Co _n ⁺ with the various gas samples is qualitatively consistent with the adsorption rate of the gas to cobalt metal surfaces. Co _n ⁺ highly reacts with C₂H₂ as characterized by the adsorption rate to metal surfaces, and it indicates no size dependence. In contrast, the reactions of Co _n ⁺ with the other gas samples indicate a similar cluster size dependence; atn=4, 5, and 10?15, Co _n ⁺ highly reacts. The difference can be explained by the amount of the activation energy for chemisorption reaction. Compared with neutral cobalt clusters, the size dependence is almost similar except for Co ₄ ⁺ and Co ₅ ⁺ . The reactivity enhancement of Co ₄ ⁺ and Co ₅ ⁺ indicates that the cobalt cluster ions are presumed to have an active site for chemisorption atn=4 and 5, induced by the influence of positive charge.     

Structural,electronic and elastic properties of the Laves phases WFe2, MoFe2, WCr2 and MoCr2 from first-principles

A theoretical analysis of the phase stability, electronic and mechanical properties, and Debye temperatures of the C14-type Laves phases (WFe₂, MoFe₂, WCr₂ and MoCr₂) has been presented from density functional theory. The phase stability follows the order: WFe₂>MoFe₂>WCr₂>MoCr₂. An exchange of electrons takes place between Fe and W/Mo atoms, and there is also electron transfer between Cr and W/Mo. The W–W and Mo–Mo bonds are of the valence character, while the Fe–W/Mo and Cr–W/Mo bonds are of ionic character. The bonding force of A–A is greater than that of A–B in C-14 AB₂ type Laves phases (WFe₂, MoFe₂, WCr₂ and MoCr₂). The ductility of MoCr₂ is higher than others. The hardness of WFe₂ (14.1 GPa) is the highest, and the hardness of MoCr₂ is the lowest. The incompressibility for these laves phases along c-axis is larger than that along a-axis. The Debye temperature (θ_D) of MoFe₂ is 619 K, which is the highest in those phases. These laves phases also have high melting points, which follows the order: WFe₂>MoFe₂>WCr₂>MoCr₂.     

Comparative XPS Study of Al2O3 and CeO2Sulfation in Reactions with SO2, SO2 + O2, SO2 + H2O,and SO2 + O2 + H2O

The interactions of Al₂O₃, CeO₂, Pt/Al₂O₃, and Pt/CeO₂ films with SO₂, SO₂ + H₂O, SO₂ + O₂, and SO₂ + O₂ + H₂O in the temperature range 300–673 K at the partial pressures of SO₂, O₂, and H₂O equal to 1.5 × 10², 1.5 × 10², and 3 × 10² Pa, respectively, were studied using X-ray photoelectron spectroscopy. The formation of surface sulfite at T 473 K (the S 2p _3/2 binding energy (E _b) is 167.5 eV) and surface sulfate at T 573 K (E _b = 169.2 eV) was observed in the reactions of Al₂O₃ and CeO₂ with SO₂. The formation of sulfates on the surface of CeO₂ occurred much more effectively than in the case of Al₂O₃, and it was accompanied by the reduction of Ce(IV) to Ce(III). The formation of aluminum and cerium sulfates and sulfites on model Pt/Al₂O₃ and Pt/CeO₂ catalysts occurred simultaneously with the formation of surface platinum sulfides (E _b of S 2p _3/2 is 162.2 eV). The effects of oxygen and water vapor on the nature and yield of sulfur-containing products were studied.     

Interaction of antimony(III) chloride with thiourea, 2-mercapto-5-methyl-benzimidazole, 3-methyl-2-mercaptobenzothiazole, 2-mercaptopyrimidine,and 2-mercaptopyridine

New antimony(III) chloride complexes with heterocyclic thioamides, thiourea (TU), 2-mercapto-5-methyl-benzimidazole (MMBZIM), 3-methyl-2-mercaptobenzothiazole (MMBZT), 2-mercaptopyrimidine (PMT), 2-mercaptopyridine (PYT) of formulae [SbCl₃(TU)₂] (1), [SbCl₃(MMBZIM)₂] (2), [SbCl₃(MMBZT)₂] (3), [SbCl₃(PMT)₂] (4), [SbCl₃(μ ₂-S)(PYT)₂] (5) were synthesized and characterized by elemental analysis, FT-IR and FT-Raman spectroscopies, and TG-DTA analysis. The crystal structure of 5 was also determined by X-ray diffraction. [C₁₀H₁₀Cl₃N₂S₂Sb] (5) crystallizes in space group C2/c, with a?=?25.0169(10)?Å, b?=?9.7952(3)?Å, c?=?12.9329(5)?Å, β?=?109.702(4)°, and Z?=?8. Crystals of 5 grown from acetonitrile solutions adopt a square-pyramidal geometry. The equatorial plane is formed by three chlorides and one sulfur atom from the thione ligand while the second sulfur is axial. The complexes were evaluated for their biological activities and compared with [SbCl₃(MMI)₂] (6) (MMI?=?2-mercapto-1-methylimidazole) and other isostructural ones. The complexes showed moderate cytostatic activity against murine leukemia cells (L1210), murine mammary carcinoma cells (FM3A), human T-lymphocyte (Molt4/C8, CEM), and human cervix carcinoma (HeLa) cells. The chloro and iodo derivatives show better cytostatic activity than the bromo ones.     

Shock-tube studies of the reactions of NO2 with NO2, SO2, and CO

The thermal decomposition of NO₂ and its atom-transfer reactions with SO₂ and CO have been studied behind incident shock waves using photometric detection methods. From the decomposition study it is possible to obtain information on the rate of the reaction 2NO₂ → antisymmetric-NO₃ + NO. The results on the reaction, NO₂ + SO₂ → NO + SO₃ extend the earlier work of Armitage and Cullis to about 2000°K. The reaction with CO [NO₂ +] [CO NO + CO₂] at shock temperatures is somewhat faster than predicted from available low-temperature data and provides a modification of the rate-constant expression that is applicable over a wide temperature range.     

Theoretical study of isomerism in the molecules N2O,PNO, P2O,N2S,PNS, and P2S

We have carried out nonempirical calculations of the potential surface for isomeric rearrangements of the molecules N₂O, N₂S, PNO, PNS, P₂O, and P₂S. It was found that for the molecules N₂O and N₂S a linear structure is considerably more favorable than a cyclic one, which lies 60 kcal·mole^–1 higher and has low stability. For P₂O and P₂S the linear and cyclic isomers have similar energies. For PNO and PNS there are two linear isomers and one cyclic isomer. The isomers are separated by appreciable barriers and can exist independently. It is predicted for the ABC molecules with 16 valence electrons that if two or all three of the atoms belong to the third or a later period, then the cyclic isomers should be favored to at least the same extent as the linear isomers.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 794–802, April, 1990.     

TiO2/Mo-TiO2 的制备、表征和光催化活性

 采用溶胶-凝胶法制备了掺 Mo 的 TiO2 粉末, 再由其制得 TiO2/Mo-TiO2 复合物光催化剂. 使用 X 射线光电子能谱、X 射线衍射、透射电镜、N2 吸附-脱附、紫外-可见漫反射光谱和荧光光谱等手段对催化剂进行了表征. 在紫外光照射下, 以甲基橙溶液降解为探针反应, 研究了 Mo 掺杂量对样品光催化活性的影响. 结果表明, Mo-TiO2 催化剂的活性不如纯 TiO2, 这是因为 Mo 离子促进了光生载流子的复合; 而带有 n-n 异质结半导体结构的 TiO2/Mo-TiO2 复合催化剂具有比纯 TiO2 和 Mo-TiO2 催化剂更高的光催化活性. 当 Mo 掺杂摩尔分数为 2%, TiO2:Mo-TiO2 质量比为 10:1 时, 活性是纯 TiO2 的 1.57 倍.     

Relative rate constants for reactions of HFC 152a, 143, 143a, 134a,and HCFC 124 with F or Cl atoms and for CF2CH3, CF2HCH2, and CF3CFH radicals with F2, Cl2, and O2

Relative rate experiments using UV photolysis of F₂ or Cl₂ have been used to determine rate constant ratios for several hydrofluorocarbon (HFC) reactions with Cl or F atoms and for HFC alkyl radicals with molecular halogens. For mixtures with F₂ present, dark reactions are, also, observed which are attributed to thermal dissociation of the F₂ to form F atoms. At 296 K, the rate of reaction (1a) [CF₂HCH₃ + F → CF₂CH₃ + HF] relative to (1b) [CF₂HCH₃ + F → CF₂HCH₂ + HF] is k_1a/k_1b = 0.73 (±0.13) and is independent of T (= 262–348 K). At 296 K, the ratio of reaction (2a) [CF₂HCH₂F + F → products] to that of (k_1a + k_1b) is (k_1a + k_1b)/k_2a = 2.7 (±0.4), and for reaction (2b) [CF₃CH₃ + F → products] (k_1a + k_1b)/k_2b = 22 ± 12. The temperature dependence (263–365 K) of the rate constant of reaction (3) [CF₃CFH₂ + Cl → products] relative to reaction (4) [CF₃CFClH + Cl → products] is k₃/k₄(±10%) = 1.55 exp(?300 K/T). For the alkyl radicals formed from HFC 152a (CF₂HCH₂ and CF₂CH₃) and from HFC 134a (CF₃CFH), rate constants for the reactions with F₂ and Cl₂ were measured relative to their reactions with O₂. The rate constant of reaction (5cl) [CF₂CH₃ + Cl₂ → CF₂ClCH₃ + Cl] relative to (5o) [CF₂CH₃ + O₂ → CF₂(O₂)CH₃] is k_5cl/k_5o(±15%) = 0.3 exp(200 K/T). For reaction (5f) [CF₂CH₃ + F₂ → CF₃CH₃ + F], k_5f/k_5o(±35%) = 0.23. The ratio for reaction (6f) [CF₂HCH₂ + F₂ → CF₂HCH₂F + F] relative to (6o) [CF₂HCH₂ + O₂ → CF₂HCH₂O₂] is k_6f/k_6o(±40%) = 1.23 exp(?730 K/T). The rate constant ratio for reaction (8cl) [CF₃CFH + Cl₂ → CF₃CFClH + Cl] relative to reaction (8o) [CF₃CFH + O₂ → CF₃CFHO₂] is k_8cl/k_8o(±18%) = 0.16 exp(?940 K/T). For reaction (8f) [CF₃CFH + F₂ → CF₃CF₂H + F], k_8f/k_8o(±35%) = 0.6 exp(?860 K/T). © 1993 John Wiley & Sons, Inc.     

Syntheses,Structures, and Properties of New Quaternary Gold-Chalcogenides: K2Au2Ge2S6, K2Au2Sn2Se6, and Cs2Au2SnS4

The new compounds K₂Au₂Ge₂S₆ ( 1 ), K₂Au₂Sn₂Se₆ ( 2 ), and Cs₂Au₂SnS₄ ( 3 ) have been synthesized through direct reaction of the elements with a molten polyalkalithiogermanate(stannate) flux at 650, 550, and 400 °C, respectively. Their crystal structures have been determined by single crystal X-ray diffraction techniques. 1 crystallizes in the monoclinic space group P2₁/n with a = 10.633(2) Å, b = 11.127(2) Å, c = 11.303(2) Å, β = 115,37(3)°, V = 1208,2(3) ų and Z = 4, final R(Rw) = 0.045(0.106). 2 crystallizes in the tetragonal space group P4/mcc with a = 8.251(1) Å, c = 19.961(4) Å, V = 1358,9(4) ų and Z = 4, final R(Rw) = 0.040(0.076). 3 crystallizes in the orthorhombic space group Fddd with a = 6.143(1) Å, b = 14.296(3) Å, c = 24.578(5) Å, V = 2158.4(7) ų and Z = 4, final R(Rw) = 0.039(0.095). The structures of 1 , 2 , and 3 consist of infinite, one-dimensional anionic chains containing X₂Q₆^4– units linked by Au⁺ ions and charge balancing K⁺/Cs⁺ ions situated between the chains. All compounds were investigated with differential thermal analysis, FT-IR, and solid state UV/VIS diffuse reflectance spectroscopy.     

Bond dissociation energies and radical heats of formation in CH3Cl,CH2Cl2, CH3Br,CH2Br2, CH2FCl,and CHFCl2

An analysis of thermochemical and kinetic data on the bromination of the halomethanes CH_4–nX_n (X = F, Cl, Br; n = 1–3), the two chlorofluoromethanes, CH₂FCl and CHFCl₂, and CH₄, shows that the recently reported heats of formation of the radicals CH₂Cl, CHCl₂, CHBr₂, and CFCl₂, and the C? H bond dissociation energies in the matching halomethanes are not compatible with the activation energies for the corresponding reverse reactions. From the observed trends in CH₄ and the other halomethanes, the following revised ΔH°_f,298 (R) values have been derived: ΔH°_f(CH₂Cl) = 29.1 ± 1.0, ΔH°_f(CHCl₂) = 23.5 ± 1.2, ΔH_f(CH₂Br) = 40.4 ± 1.0, ΔH°_f(CHBr₂) = 45.0 ± 2.2, and ΔH°_f(CFCl₂) = ?21.3 ± 2.4 kcal mol^?1. The previously unavailable radical heat of formation, ΔH°_f(CHFCl) = ?14.5 ± 2.4 kcal mol^?1 has also been deduced. These values are used with the heats of formation of the parent compounds from the literature to evaluate C? H and C? X bond dissociation energies in CH₃Cl, CH₂Cl₂, CH₃Br, CH₂Br₂, CH₂FCl, and CHFCl₂.