PPh4[As3S3Cl4] und PPh4[As3S3Br4]

PPh₄[As₃S₃Cl₄] and PPh₄[As₃S₃Br₄] When As₂S₃ reacts with PPh₄X and HX in 1,2-C₂H₄X₂ (X = Cl, Br), the title compounds are obtained as minor products; the main products are PPh₄[As₂SX₅]. Their crystal structures were determined by X-ray diffraction. PPh₄[As₃S₃Cl₄]: a = 1187.7, b = 1090.9, c = 1191.8 pm, α = 82.91, β = 88,93, γ = 88.52°; twins with twin plane (100); R = 0.109 for 1618 observed reflexions of one twin crystal. PPh₄[As₃S₃Br₄]: a = 1119.7, b = 1177.5, c = 1204.1 pm, α = 81.59, β = 85.88, γ = 88.25°; R = 0.061 for 2331 observed reflexions. Both compounds crystallize in the space group P1 , Z = 2, and can be considered to be isotypic. Nevertheless, PPh₄[As₃S₃Br₄] does not form twins as PPh₄[As₃S₃Cl₄]. The crystals consist of PPh₄⁺ and [As₃S₃X₄]^? ions. In the anions, the three As atoms of an As₃S₃ ring in the chair conformation are commonly joined to an X atom and each As atom is bonded to one further terminal X atom. Cations and anions are packed in alternating layers.     

Neuartige Polyanionen in Zintlphasen. Zur Kenntnis von Ca3Si2As4, Ca3Ge2As4, Sr3Si2As4 und Sr3Ge2As4

New Polyanions in Zintl Phases. On Ca₃Si₂As₄, Ca₃Ge₂As₄, Sr₃Si₂As₄, and Sr₃Ge₂As₄ The new compounds Ca₃Si₂As₄, Ca₃Ge₂As₄, Sr₃Si₂As₄ and Sr₃Ge₂As₄ crystallize in the monoclinic system with lattice constants see “Inhaltsübersicht”. There are two new structure types. Both contain Si₂As₆ or Ge₂As₆ groups connected to chains in different ways. These chains are ordered parallel to each other to sheets with the alkaline-earth atoms between them.     

Polythermal section Sn4P3-Sn4As3

The T-x diagram of the polythermal section Sn₄P₃-Sn₄As₃ of the Sn-P-As system was constructed using the results of X-ray powder diffraction and differential thermal analyses. A continuous series of solid solutions (Sn₄P₃) _x (Sn₄As₃)_{1 ? x} was found to exist. The section is not quasi-binary; in a Sn₄As₃-rich region, this section intersects the peritectic part of the three-phase volume (L + SnAs + α) of the ternary diagram.     

Tetraphenylphosphonium-tetraiodotrithiotriarsenat,PPh4[As3S3I4]

Tetraphenylphosphonium tetraiodotrithiotriarsenate, PPh₄[As₃S₃I₄] PPh₄[As₃S₃I₄] is formed along with PPh₄I₃ and other unidentified compounds by the reaction of As₂S₃, PPh₄I and HI in CH₂I₂ at 80°C. PPh₄[As₃S₃I₄] was characterized by its IR spectrum and an X-ray crystal structure determination (3684 unique observed reflexions, R = 0.083). Crystal data: a = 1390.3, b = 1548.9, c = 1505.4 pm, β = 91.08°, monoclinic, P2₁/c, Z = 4. The crystals are not isotypic with the corresponding chloro and bromo compounds, although the anion constitutions are of the same type. The [As₃S₃I₄]^? ion consists of an As₃S₃ ring in the chair conformation, the three As atoms are commonly linked to a bridging I atom and each As atom is bonded to one terminal I atom. Cations and anions are packed in alternating layers.     

Eight-coordinated arsenic in the Zintl phases RbCd4As3 and RbZn4As3: synthesis and structural characterization

Reported are two new series of Zintl phases, ACd(4)Pn(3) and AZn(4)Pn(3) (A = Na, K, Rb, Cs; Pn = As, P), whose structures feature complex atomic arrangements based on four- and eight-coordinated arsenic and phosphorus. A total of 12 compounds have been synthesized from the corresponding elements via high temperature reactions, and their structures have been established by X-ray diffraction. RbCd(4)As(3), KCd(4)As(3), NaCd(4)As(3), NaZn(4)As(3), KCd(4)P(3), and KZn(4)P(3) crystallize with a new rhombohedral structure (space group R3m, Z = 3, Pearson symbol hR24), while the isoelectronic RbZn(4)As(3), CsCd(4)As(3), CsZn(4)As(3), KZn(4)As(3), CsZn(4)P(3), and RbZn(4)P(3) adopt the tetragonal KCu(4)S(3)-type structure (space group P4/mmm, Z = 1, Pearson symbol tP8). Both structures are very closely related to the ubiquitous CaAl(2)Si(2) and ThCr(2)Si(2) structure types, and the corresponding relationships are discussed. The experimental results have been complemented by linear muffin-tin orbital (LMTO) tight-binding band structure calculations. Preliminary transport properties measurements on polycrystalline samples suggest that the compounds of these families could be promising thermoelectric materials.     

Die Kristallstruktur des Chromarsenids Cr4As3

The crystal structure of Cr₄As₃ has been determined by single crystal photographs: $$\begin{gathered} space group Cm - C_s ^3 \hfill \\ \alpha = 13.16_8 {\AA} \hfill \\ b = 3.54_2 {\AA} \hfill \\ c = 9.30_2 {\AA} \hfill \\ \beta = 102.1_9 \circ \hfill \\ \end{gathered}$$ Cr₄As₃ crystallizes with a novel structure type, which can be derived from the MnP-structure type.     

Schwingungsspektren von As4S4 und As4Se4

Vibrational Spectra of As₄S₄ and As₄Se₄ The vibrational spectra of solid α- and β-As₄S₄ and the Raman spectrum of molten As₄S₄ have been recorded. The assignments of the frequencies are proposed mainly based on polarization data. The Raman melt spectra suggest that As₄S₄ molecules (symmetry D_2d) are retained in the molten state. A partial decomposition of the melt by prolonged laser irradiation was observed. The Raman spectrum of solid As₄Se₄ is presented and the frequencies are tentatively assigned to an As₄Se₄ molecule of the cradle type, possessing D_2d symmetry.     

Energetics of formation of TiGa3As4 and TiGa3P4 intermediate band materials

Using density functional theory quantum methods, total energy values and vibrational properties have been computed, and thermodynamic properties evaluated, for Ti-substituted GaAs and GaP, proposed as candidates for intermediate band photovoltaic cells. The calculations predict that the formation of these materials from the binary compounds implies an increase in total energy (that is ascribed largely to the change in coordination undergone by Ti, from six-fold to four-fold), and thus phase separation rather than mixed compound formation would be favored. However, the mentioned increase is not larger (for the arsenide case it is actually smaller) than that predicted for Mn-substituted GaAs, a material which has been experimentally made, and therefore the obtention of these Ti-substituted materials is expected to be feasible as well. Vibrational and disorder entropy contributions to the formation free energy of the ternary compounds have been also computed; they compensate partially for the total energy increase, and indicate that the thermodynamic feasibility of the materials synthesis improves for low Ti concentrations and high temperature conditions.     

Neue Moleküle A4B3 im System P4Se3–As4Se3

Novel A₄B₃ Molecules in the System P₄Se₃–As₄Se₃ By means of ³¹P-NMR and masspectroscopic measurements in the system P₄Se₃–As₄Se₃ was shown that in the melt and vapour phase at all compositions molecules of the type P_{4 ? n}As_nSe₃ are formed. A separation was possible by liquid chromatography (RP 18-column). The concentration distribution of the different species is nearly statistical. In the solid state at ambient temperature regions of solid solubility with α-P₄Se₃, α⁺-phase, α-P₄S₃ and α-As₄Se₃ structure were observed. P₃AsSe₃ could be transformed into a plastically-crystalline phase with β-P₄S₃ structure. At higher temperatures the phase decomposes slowly. The thermal behaviour of PAs₃Se₃ is strongly influenced by the heating rate. Using low heating rates it decomposes into an amorphous phase, by fast heating a transformation into a metastable plastically-crystalline modification was achieved. During long extraction with CS₂ molecules P_{4 ? n}As_nS_{3 ? m}Se_m are formed by an exchange reaction. They can also be prepared by melting the proper amounts of the elements.     

(HgBr2)3(As4S4)2: An Adduct of HgBr2 Molecules and Undistorted As4S4 Cages

(HgBr₂)₃(As₄S₄)₂ is obtained by high temperature reaction of stoichiometric amounts of HgBr₂ and As₄S₄. It crystallizes in the monoclinic space group P2₁/c with the lattice constants a = 9.593(5) Å, b = 11.395(5) Å, c = 13.402(5) Å, β = 107.27(3)°, V = 1399(1) ų, and Z = 2. The crystal structure consists of molecular units built from two undistorted As₄S₄ cages which are coordinated weakly by three almost linear HgBr₂ units. Raman spectra clearly indicate minor bonding interactions between HgBr₂ and As₄S₄.     

Das Käfigmolekäl P2As2S3

The Cage Molecule P₂As₂S₃ The reaction between P₄S₃ and Ss₂S₃ a t 500°C in a sealed tube is reported. From the reaction products the new compound P₂As₂S₃ was isolated. According to its properties and vibrational spectrum it has the structure of a cage molecule analogous to P₄S₃ in which 2P-atoms of the P₃-ring are substituted by 2 As-atoms.     

Kristallstruktur und Phasenumwandlungen von As(CH3)4I

Crystal Structure and Phase Transitions of As(CH₃)₄I The crystal structure of α-As(CH₃)₄I at room temperature was determined using single crystal data: cubic, space group Pa3 , a = 1 198.0(2) pm. Therefore α-As(CH₃)₄I displays a novel crystal structure, which is not comparable to known AB-Typ structures with respect to the arrangement of anions and the baricenters of the complex cations. Differential thermal analysis showed three phase transitions at 103, 175 and 215°C. The lattice parameters of the high temperature phases (temperature dependent Guinier measurements) are: β-As(CH₃)₄I (tetragonal): a = 845.2(2) pm, c = 615.0(2) pm; γ-As(CH₃)₄I (hexagonal): a = 737.7(2) pm, c = 1 082.2(3) pm; and to δ-As(CH₃)₄I (hexagonal): a = 705.8(2) pm, c = 1 147(1) pm. β-and γ-As[(CH₃)]₄I are isotypic to N(CH₃)₄Cl and As(CH₃)₄Br, respectively.     

KNi3(AsO4)(As2O7)

The structure of the title compound, potassium trinickel arsenate diarsenate, is built up from corner‐ and edge‐sharing NiO₆ octahedra, AsO₄ tetrahedra and As₂O₇ groups, giving rise to a polyhedral connectivity which produces large tunnels running along the crystallographic [010] direction. The K⁺ cations are located within these tunnels.