Selenium dibromide and dichloride in acetonitrile

The nature of 2/1 Cl/Se and Br/Se stoichiometric mixtures in acetonitrile has been studied by UV-visible and Raman spectroscopy. For both mixtures the selenium dihalide has been shown to be the predominant species in solution, although there are other species present in equilibrium with the dihalide, according to 3SeCl₂ = Se₂Cl₂ + SeCl₄ 2SeBr₂ = Se₂Br₂ + Br₂ as demonstrated by both techniques. The Raman spectra of SeCl₂ and SeBr₂ are given. Force constant calculations show that the bonds in the dihalides are the strongest SeCl and SeBr bonds known.     

Gleichgewichtsdruckmessungen im System Se/O/Cl

Equilibrium Measurements in the System Se/O/Cl The evaporation and decomposition behaviour was Studied by total pressure measurements in equilibrium with condensed phases as well as in the unsaturated Vapour. The composition Cl/Se = 4 shows the lowest, the composition Cl/Se = 2 the highest total pressure in the Barogramm of the system Se/Cl. Solid SeCl₄ and liquid Se₂Cl₂ exist as condensed compounds whereas only SeCl₂ exists in the gas. The following data were derived (see ?Inhaltsübersicht”?) from the decomposition sublimation SeCl₄, the decomposition of Se₂Cl₂ and the evaporation and decomposition of SeOCl₂.     

Reaction of Selenium with Bromine in the Presence of Methyltriphenylphosphonium Bromide: Syntheses and Crystal Structures of [PMePh3]2[Se2Br6] and [PMePh3]2[SeBr6(SeBr2)2]

The brown crystals of [PMePh₃]₂[Se₂Br₆] ( 1 ) and red crystals of [PMePh₃]₂[SeBr₆(SeBr₂)₂] ( 2 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of methyltriphenylphosphonium bromide. The crystal structures of 1 and 2 has been determined by the X‐ray methods and refined to R = 0.0373 for 2397 reflections and 0.0397 for 3417 reflections, respectively. The salt 1 crystallizes in the monoclinic space group P2₁/n with the cell dimensions a = 13.202(5) Å, b = 11.954(4) Å, c = 13.418(6) Å, β = 93.08(4)° (193(2)). The crystals of 2 are triclinic, space group with the cell dimensions a = 10.266(3) Å, b = 11.311(3) Å, c = 11.619(2) Å, α = 108.87(2)°, β = 105.72(2)°, γ = 99.40(2)° (193(2) K). In the solid state structure of 1 the dinuclear hexabromo‐diselenate(II) anion is centrosymmetric and consists of two distorted almost square planar SeBr₄ units sharing a common edge through two μ‐bridging Br atoms. The terminal Se^II–Br bonds are 2.3984(11) and 2.4273(11) Å, whereas the bridging μBr–Se^II bonds are 2.7817(11) and 2.9081(12) Å. In the solid state the trinuclear [SeBr₆(SeBr₂)₂]^2? anion of 2 is centrosymmetric too and contains a nearly regular [SeBr₆] octahedron where the four equatorial bromo ligands each have developed bonds to the Se^II atoms of the SeBr₂ molecules. The contacts between the bridging bromo and the Se^II atoms of the SeBr₂ molecules are 3.0603(15) and 3.1043(12) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr₂ molecules as acceptors. The Se^IV–Br distances are in the range 2.5570(9)–2.5773(11) Å and the Se^II–Br bond lengths in coordinated SeBr₂ molecules – 2.3411(12) and 2.3421(10) Å.     

Phasenbeziehungen im System Se?Br und die Kristallstrukturen des dimorphen SeBr4

Phase Relations and Crystal Structures in the System Se? Br The system Se? Br contains two intermediate phases with congruent melting behaviour: α-SeBr (+5°C) and α-SeBr₄ (+123°C). β-SeBr and β-SeBr₄ are metastable with respect to the phase diagram and are irreversibly transformed to the α-modifications by annealing. Phase relations in the Se? Br system are discussed in detail. Single crystals of α- and β-SeBr₄ are obtained by vapour phase transport. β-SeBr₄ is monoclinic, space group C2/c, z = 16, a = 17.02, b = 10.39, c = 15.49 Å, β = 117°, and is an isotype of TeCl₄. α-SeBr₄ is trigonal, space group P31c, z = 16, with a = 10.200(7), c = 30.351(18) Å. In both modifications tetrameric cubane-like molecules [SeBr₄]₄ are present, but with different spatial arrangement. The crystal structure of α-SeBr₄ is discussed in terms of packing aspects.     

Synthesis and Crystal Structure of >Bis(tetrapropylammonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [NnPr4]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

Dark brown crystals of [NⁿPr₄]₂[TeBr₆(SeBr₂)₂] ( 1 ) were obtained when selenium and bromine (1:1) were allowed to react in acetonitrile solution in the presence of tellurium(IV) bromide and tetrapropylammonium bromide. The salt 1 crystallizes in the monoclinic space group P2₁/n with the cell dimensions a = 14.7870(3) Å, b = 9.5523(3) Å, c = 16.7325(3) Å, β = 110.56(10)° (at 123(2) K). In the solid state the [TeBr₆(SeBr₂)₂]^2– anion contains a nearly regular [TeBr₆] octahedron in which the four equatorial bromo ligands have developed bonds to Se^II atoms of the SeBr₂ molecules. The contacts between the bridging bromo and the Se^II atoms of the SeBr₂ molecules are 3.0000(4) and 3.0561(4) Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr₂ molecules as acceptors. The Te^IV–Br distances are in the range 2.6816(3)–2.7131(3) Å and the Se^II–Br bond lengths in the coordinated SeBr₂ molecules are 2.3548(4) and 2.3725(4) Å.     

Die Kristallstrukturen von Pb4SeBr6, Pb5S2J6 und Pb7S2Br10

Crystal Structures of Pb₄SeBr₆, Pb₅S₂I₆, and Pb₇S₂Br₁₀. The crystal structures of Pb₄SeBr₆, Pb₅S₂I₆ and Pb₇S₂Br₁₀ have been determined from single crystal X-ray analyses. Unit cell data see “Inhaltsübersicht”. The compounds have common structural features with the pure halides of lead. In Pb₄SeBr₆ all Pb atoms have trigonal prismatic coordination by Br(Se), additional neighbours above the prism faces completing the coordination number to 7, 8 or 9. In Pb₅S₂I₆ some of the Pb atoms are surrounded by 6 I + 1 S or 5 I + 3 S in the same extended trigonal prismatic arrangement, others are in the centers of PbI₆ octahedra. Pb₇S₂Br₁₀ is isostructural with Th₇S₁₂ with statistical occupancy of part of the metal and nonmetal positions.     

SeBr3[AlBr4] und TeI3[AlI4] – zwei weitere Vertreter des SCl3[AlCl4]-Strukturtyps

SeBr₃[AlBr₄] and TeI₃[AlI₄] – two further Compounds in the SCl₃[AlCl₄] Structure Type The reaction of SeBr₄ and AlBr₃ in a closed glass ampoule at 150°C yields quantitatively SeBr₃[AlBr₄] in form of yellow moisture sensitive crystals. From Te, two equivalents of I₂, and AlI₃ one obtains TeI₃[AlI₄] in form of dark red, moisture sensitive crystals. Both compounds crystallize monoclinic in the space group Pc (SeBr₃[AlBr₄]: a = 670.7(7) pm, b = 663.9(5) pm, c = 1 428.6(2) pm, β = 101.21(9)°, TeI₃[AlI₄]: a = 731.9(1) pm, b = 730.8(1) pm, c = 1 565.5(3) pm, β = 102.01(2)°). They are isotypic and have the SCl₃[AlCl₄] structure type. The structures are built of tetrahedral AlX₄^? ions and of pyramidal EX₃⁺ ions (E = S, Se, Te; X = Cl, Br, I). The chalcogen atoms are additionally coordinated by halogen atoms of surrounding AlX₄^? ions, corresponding to a strongly distorted octahedral coordination EX₃₊₃.     

Structure and Bonding in Bis(1‐naphthyl) Diselenide and Bis{[2‐(N,N‐dimethylamino)methyl]phenyl} Tetraselenide,and Their Brominated Derivatives

The formation and crystal structures of bis(1‐naphthyl) diselenide ( 1 ) and bis{[2‐(N,N‐dimethylamino)methyl]phenyl} tetraselenide ( 2 ) are described. Whereas 1 can be produced in good yields, 2 is formed only as a minor product together with the known main product, bis{[2‐(N,N‐dimethylamino)methyl]phenyl} diselenide. The composition of the reaction mixture is semi‐quantitatively estimated by ⁷⁷Se NMR spectroscopy and DFT calculations. The effect of the n²→σ*(Se–Se) and π→σ*(Se–Se) secondary bonding interactions on the Se–Se bonds is discussed both by DFT calculations and comparison with literature, as available. The bromination of 1 yields monomeric (1‐naphthyl)selenenyl bromide ( 3 ) in good yields. That of the reaction mixture of (C₆H₄CH₂NMe₂)Se_x (x = 2–4) and Se₈ afforded (C₆H₄CH₂NMe₂H)₂[SeBr₄] ( 4 ) and (C₆H₄CH₂NMe₂H)₂[SeBr₆] ( 5 ) in addition to (C₆H₄CH₂NMe₂)SeBr, which has been previously reported.     

Thermochemische Untersuchungen zum System Bi/Se/O. I. Das Phasendreieck Bi2Se3/Bi2O2Se/Se

Thermochemical Investigation on the System Bi/Se/O. I The Phase Triangle Bi₂Se₃/Bi₂O₂Se/Se By total pressure measurements of compositions in the subsystem Bi₂Se₃/Bi₂O₂Se/Se was shown, that in thermodynamic equilibrium the three phases Bi₂Se₃/Bi₂O₂Se/Se coexist. The barogram of the triangle reduces to the barogram of the line Bi₂Se₃? Se, the compound Bi₂O₂Se is not from influence of the total pressure in the investigated temperature range.     

Synthesis and Crystal Structure of Tetrakis(tetramethylammonium) Bis[decabromotetraselenate(II)]‐bis[dibromodiselenate(I)], [(CH3)4N]4[(Se4Br10)2(Se2Br2)2], the Salt of a Mixed‐Valence Bromoselenate(II/I) Anion

Brown crystals of [NMe₄]₄[(Se₄Br₁₀)₂(Se₂Br₂)₂] ( 1 ) were obtained from the reaction of selenium and bromine in acetonitrile in the presence of tetramethylammonium bromide. The crystal structure of 1 was determined by X‐ray diffraction and refined to R = 0.0297 for 8401 reflections. The crystals are monoclinic, space group P2₁/c with Z = 4 and a = 12.646(3) Å, b = 16.499(3) Å, c = 16.844(3) Å, β = 101.70(3)° (123 K). In the solid‐state structure, the anion of 1 is built up of two [Se₄Br₁₀]^2– ions. Each shows a triangular arrangement of three planar SeBr₄ units sharing a common edge through two μ₃‐bridging bromine atoms, and one SeBr₂ molecule, which is linked to the Se^II atoms of two SeBr₄ units; between the Se₄Br₁₀^2– ions a dimerized Se₂Br₂ molecule (Se₄Br₄) is situated and one Se^I atom of each Se₂Br₂ molecule has two weak contacts [3.3514(14) Å and 3.3952(11) Å] to two bromine atoms of one SeBr₄ unit. Four Se^I atoms of a dimerized Se₂Br₂ molecule are in a almost regular planar tetraangular arrangement. Contacts between the Se^II atom of the SeBr₂ molecule and the Se^II atoms of two SeBr₄ units are 3.035(1) Å and 3.115(1) Å, and can be interpreted as donor‐acceptor type bonds with the Se^II atoms of SeBr₄ units as donors and the SeBr₂ molecule as acceptor. The terminal Se^II–Br and μ₃‐Br–Se^II bond lengths are in the ranges 2.3376(10) to 2.4384(8) Å and 2.8036(9) to 3.3183(13) Å, respectively. The bond lengths in the dimerized Se₂Br₂ molecule are: Se^I–Se^I = 2.2945(8) Å and 3.1398(12), Se^I–Br = 2.3659(11) and 2.3689(10) Å.     

Synthesis and Crystal Structure of Bis(methyltriphenylphosphonium) Hexabromotellurate(IV)‐bis{dibromoselenate(II)}, [PMePh3]2[TeBr6(SeBr2)2], the Salt of a Mixed‐valence Bromotellurate(IV)‐Selenate(II) Anion

Brown crystals of [PMePh₃]₂[TeBr₆(SeBr₂)₂] ( 1 ) were obtained when selenium and bromine (1:1) react in acetonitrile solution in the presence of tellurium(IV) bromide and methyltriphenylphosphonium bromide. The salt 1 crystallizes in the triclinic space group P1¯ with the cell dimensions a = 10.3630(14)Å, b = 11.5140(12)Å, c = 11.7605(17)Å, α = 108.643(9)°, β = 106.171(10)° and γ = 99.077(9)° (296 K). In the solid state the [TeBr₆(SeBr₂)₂]^2— anion contains a nearly regular [TeBr₆] octahedron where the four equatorial bromo ligands each have developed a bond to the Se^II atom of a SeBr₂ molecule. The contacts between the bridging bromo and the Se^II atoms of the SeBr₂ molecules are observed in the range 3.11—3.21Å, and can be interpreted as bonds of the donor‐acceptor type with the bridging bromo ligands as donors and the SeBr₂ molecules as acceptors. The Te^IV—Br distances are in the range 2.67—2.72Å, and the Se^II—Br bond lengths in coordinated SeBr₂ molecules in the range 2.33—2.34Å.     

Electrophilic addition of selenium and telluriom halides to methyldiethynylsilane

Regio- and stereoselective electrophilic addition reactions of SeCl₂, SeBr₂, SeCl₄, SeBr₄ to methyldiethynylsilane lead to predominant formation of the Z-isomers of 3,6-dihalo-4-methyl-1,4-selenasilafulvenes, disiloxanes on their bases, as well as disiloxanes formed upon the reaction with methyldiethynylsilane. TeCl₄ reacts with methyldiethynylsilane with predominant formation of the E-isomer of 1,1,3,6-tetrachloro-1-methyl-1-(methyldiethynylsiloxy)-1,4-tellura(IV)silafulvene as a result of the reaction of the intermediate E-isomer of 4-methyl-1,1,3,6-tetrachloro-1,4-tellura(IV)silafulvene with methyldiethynylsilane. The structure of the products was proved by the methods of ¹H, ⁷⁷Se NMR, IR spectroscopy and chromatomass spectrometry.     

On the structure of arylselenium tribromides

The IR and Raman spectra of arylselenium tribromides X = C₆H₄SeBr₃ where X = H, Br, Cl, CH₃ are reported. It is suggested that the solids are possibly tetramers in the solid state formed by donor-acceptor interaction between units RSeBr₂⁺ and Br^?. Each selenium atom is in a highly symmetrical or pseudo-symmetrical environment.     

Determination of selenium at ng/g- and pg/g-levels by hydride generation-atomic absorption spectrometry in biotic materials

Summary For the determination of Se in environmentally relevant materials in the ng/g- and pg/g-range by hydride generation-AAS, H₂Se was preconcentrated on Chromosorb W at –150° C prior to its atomization in a silica tube. The individual steps of the procedure — decomposition, reduction of Se(VI) to Se(IV), generation, preconcentration and atomization of H₂Se — were optimized, partly using the radioisotope Se-75. Se was determined directly in some water samples, in human hair, finger nails and human serum after decomposition in HNO₃/ HClO₄ and combustion in oxygen, and in proteins of human serum after isotachophoretic separation and decomposition in HNO₃/HClO₄. The detection limit of the overall procedure was found to be 6 pg absolute and the linear dynamic range extends to 6 ng.

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Bestimmung von Selen im ng/g- und pg/g-Bereich durch Hydrid-Atomabsorptionsspektrometrie in biotischen Matrices

Zusammenfassung Zur Bestimmung von Selen in umweltrelevanten Matrices im ng/g- und pg/g-Bereich durch Hydrid-AAS wurde H₂Se auf Chromosorb W bei –150° C vor der Atomisierung in der Quarzküvette angereichert. Die einzelnen Verfahrensschritte — Aufschluß, Reduktion von Se(VI) zu Se(IV), H₂Se-Entwicklung, H₂Se-Anreicherung und Atomisierung — wurden, teilweise mit dem Radioisotop Se-75, optimiert. Se wurde in einigen Wässern direkt, in Humanhaar, Fingernägeln und Humanserum nach Aufschluß in HNO₃/HClO₄ und nach Verbrennung im Sauerstoffstrom und in Proteinen von Humanserum nach isotachophoretischer Trennung und Aufschluß in HNO₃/ HClO₄ bestimmt. Die Nachweisgrenze des gesamten Verfahrens liegt bei 6 pg absolut und der lineare Bereich erstreckt sich bis 6 ng.

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Dedicated to Prof. Dr. R. Bock on the occasion of his 70th birthday     

Die Kristallstrukturen von SeCl3 +SbCl6−, SeBr3+GaBr4−, PCl4+SeCl5− und (PPh4+)2SeCl42− · 2 CH3CN

Crystal Structures of SeCl₃⁺SbCl₆^?, SeBr₃⁺GaBr₄^?, PCl₄⁺SeCl₅^?, and (PPh₄⁺)₂SeCl₄^2? · 2 CH₃CN The crystal structures of the title compounds were determined by X-ray diffraction. SeCl₃⁺SbCl₆^?: Space group P2₁/m, Z = 4, structure determination with 1795 observed unique reflections, R = 0.022. Lattice dimensions at ?80°C: a = 940.9, b = 1066.3, c = 1234.9 pm, β = 102.79°. The compound forms ion pairs with the structure of a double octahedron with linked surfaces. SeBr₃⁺GaBr₄^?: Space group Pc, Z = 2, structure determination with 1461 observed unique reflections, R = 0.058. Lattice dimensions at ?60°C: a = 660.1, b = 655.3, c = 1431.3 pm, β = 101.177°. The compound crystallizes in the SCl₃[AlCl₄] lattice type. Between the ions there are two relatively short Se … Br? Ga contacts. PCl₄⁺SeCl₅^?: Space group Ima2, Z = 8, structure determination with 1757 observed unique reflections, R = 0.029. Lattice dimensions at ?50°C: a = 1651.6, b = 1201.2, c = 1166.4 pm. The SeCl₅^? ions are associated to chains via interionic Se? Cl … Se contacts along the crystallographic c-axis. (PPh₄⁺)₂SeCl₄^2? · 2CH₃CN: Space group P2₁/n, Z = 2, structure determination with 2578 observed unique reflections, R = 0.050. Lattice dimensions at ?80°C: a = 1288.5, b = 726.0, c = 2585.8 pm, β = 101.65°. The compound includes planar-tetragonal SeCl₄^2? ions, which almost meet D_4h symmetry.     

Untersuchungen zum System Ge/I

Investigations on the System Ge/I The enthalpy and entropy of evaporation of GeI₄ was determined by measurements of the pressure over liquid GeI₄. The values for the decomposition reaction 2GeI₂, s = Ge, s + GeI₄, g and the sublimation of GeI₂ were derived from measurements of the total pressure over solid GeI₂. The measurements of the total pressure above the saturation ranges of GeI₄, and GeI₂, s in dependence of the mass employed and the temperature gives a sat of data, from which the values of the enthalpies of formation and the standard entropies of GeI₄, g and GeI₂g, respectively, result.     

Chemical characterization of short-lived selenium and their daughter isotopes from thermal neutron induced fission of 235U at a gas-jet facility

Selenium nuclides are available from thermal neutron induced nuclear fission of ²³⁵U at the gas-jet facility at the Swiss spallation neutron source (SINQ) at Paul Scherrer Institute, Switzerland. The formation of stable selenium compounds, their transport yields using the gas-jet system and their relative thermal decomposition temperature were investigated under oxidizing and reducing conditions in the target chamber. Using O₂, H₂, CO, and propene as additional gases, the selenium isotopes are suggested to form H₂SeO₃, H₂Se, COSe, and C₃H₆Se, respectively, with overall ⁸⁴Se yields of 1.5%, 4.7%, 6.3%, and 21.9%, respectively. Adsorption enthalpy, vapour pressure, solubility and acidity data for these species were collected from the literature or estimated from other known thermochemical properties. Carrier free bromine isotopes (⁸⁴Br, ⁸⁶Br) in the form of HOBr were obtained by thermally decomposing H₂SeO₃ and retaining elemental Se under oxygen rich conditions on quartz at 400 K.     

Synthesis and Crystal Structure of Bis(tetraethylammonium) Octabromo‐triselenate(II)‐{dibromodiselenate(I)}, [NEt4]2[Se3Br8(Se2Br2)], the Salt of a Mixed‐valence Bromoselenate(II,I) Anion

The brown crystals of [NEt₄]₂[Se₃Br₈(Se₂Br₂)] ( 1 ) were obtained when selenium and bromine reacted in the solution of acetonitrile in the presence of tetraethylammonium bromide. The crystal structure of 1 has been determined by the X‐ray methods and refined to R = 0.0308 for 10433 reflections. The crystals are monoclinic, space group P2₁ with Z = 2 and a = 12.0393(3) Å, b = 11.8746(3) Å, c = 13.1946(3) Å, β = 96.561(1)° (123 K). In the solid state structure the anion of 1 is built up of Se₃Br₈ unit which consists of a triangular arrangement of three planar SeBr₄ units sharing a common edge through two μ₃‐bridging Br atoms, and one Se₂Br₂ molecule which is linked to one of μ₃‐bridging Br atoms. The three Se^II atoms form a triangle which is almost perpendicular to the planes given by three SeBr₄ moieties. The contact between the μ₃Br and the Se^I atom of the Se₂Br₂ molecule is 3.1711(8) Å and can be interpreted as a bond of the donor‐acceptor type with the μ₃Br as donor and the Se₂Br₂ molecule as acceptor. The terminal Se^II‐Br and μ₃Br‐Se^II bond lengths are in the ranges 2.3537(7)–2.4737(7) Å and 2.7628(7)–3.1701(7) Å, respectively. The bond lengths in coordinated Se₂Br₂ molecule are: Se^I‐Se^I = 2.2636(9) Å, Se^I‐Br = 2.3387(11) and 2.3936(8) Å.     

The crystal structure of NaAs4O6Br

The crystal structure of NaAs₄O₆Br [a = 5.237(1), B = 8.043(1), C = 18.978(2) Å; space group Pmcn-D¹⁶_2h; Z = 4] was solved by a direct method strategy and was refined to an R value of 0.038 for 1515 intensities and 68 variables. The structure is characterized by neutrally charged and slightly waved As₂O₃ sheets arranged parallel to (001). These sheets are combined by the Na and Br atoms. The Na atom is coordinated to nine oxygen atoms and one bromine atom and the Br atom is coordinated to six arsenic atoms and one sodium atom. The compound NaAs₄O₆Br was synthesized by thermal treatment of NaBr and As₂O₃ in methanol solution [400(5) K, saturation vapor pressure].     

79,81Br NQR Spectra of bromochalcogenide complexes of Au(III), Pt(IV), and Pd(II)

Conclusions The structure of bromochalcogenide complexes of gold, platinum, and palladium, viz., AuBr₄· SeBr₃, PtBr₆(SeBr₃)₂, PtBr₆(TeBr₃)₂, and PdBr₂(SeBr₂)₂, has been established with the aid of the NQR spectra of the bromine atoms. In the compounds of gold and platinum investi gated SeBr₃ groupings are coordinated as ligands, and in the palladium complex SeBr₂ groupings serve as ligands.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1545–1548, July, 1986.