Selenium Tetrabromide Research Articles

ChemInform Abstract: The Synthesis and Cytotoxic Properties of Selenopheno[3,2‐c]‐ and Selenopheno[2,3‐c]quinolones.

AbstractNovel selenophenoquinolones (IV) and (VII) are synthesized by reaction of appropriate alkynylquinolone derivatives (III) or (VI), resp., with in situ generated selenium tetrabromide.

Selenium‐Rich Octanuclear Iridium Clusters with Mixed‐Valent Selenium Ligands in the Densest Known Packing of Ellipsoids

AbstractDark‐red air‐stable crystals of Ir8Se28Br14·2H2O were obtained by reacting iridium in an excess of selenium and selenium tetrabromide at 300 °C for one week. The crystal structure is monoclinic (space group P21/n) with a = 1274.66(3) pm, b = 1211.48(3) pm, c = 1743.82(4) pm, and β = 91.227(1)° at 296(1) K. The structure consists of uncharged clusters Ir8Se28Br14 = (Ir3+)8(Se22–)(Se42–)6(SeBr2)2(Br–)10 with two water molecules attached to each of them. Selenium adopts three different oxidation states, –I in the diselenide dumbbell, –I and ±0 in the tetraselenide chains, and +II in the SeBr2 units. The iridium(III) cations are coordinated octahedrally by selenium atoms and bromide ions. The octahedra share common vertices, while the oligoselenide anions provide high intra‐cluster connectivity: μ6‐η2 in the case of Se22– and μ4‐η3 for Se42–. In parts the cluster resembles a cut‐out of the rhombohedral Ir3Se8 framework structure. The ellipsoidal clusters form an excellent approximation of the mathematically predicted densest known packing of ellipsoids, featuring the coordination number of 14.

Reaction of selenium tetrabromide with acetylene

The reaction of selenium dioxide with concn. HBr is known to give selenium tetrabromide, which adds to acetylene in the absence of solvent leading to bis(2bromovinyl)selenium dibromide (I) (the yield and isomeric composition were not given) [1]. According to the data of [2], the reaction of acetylene with selenium tetrabromide generated in the system SeO2/ conc. HBr/ether, results in compound I as a mixture of the Е,Еand Z,Z-isomers in the 1 : 1.15 ratio in the yield of 54% and 1,1-dibromoselenophene in 40% yield [2]. The mixture of the Е,Еand Z,Z-isomers failed to be separated by column chromatography (only one value of Rf for the presumed mixture of the Е,Еand Z,Z-isomers of compound I was given [2]). The structure of compound I was proved by H NMR spectra and elemental analysis, no С NMR spectra were given in [2] for compound I.

Synthesis and Reactivity of Divinylselenium Dichlorides and Dibromides

Regio- and stereospecific electrophilic addition reactions of selenium tetrachloride and selenium tetrabromide to propargyl alcohols are reported. (Z,Z)-Bis(β-chlorovinyl)selenium dichlorides were isolated in high yields, and their reactivity was dependent on their substitution pattern. Products derived from unsubstituted, α-methyl-, or α,α-dimethylpropargyl alcohols readily underwent transfer of chlorine atoms to one of the two double bonds. (Z,Z)-Bis(β-chlorovinyl)selenium dichlorides derived from γ-phenyl- or γ-isopropenylpropargyl alcohols underwent cyclization to form benzoselenophene derivatives; this was accompanied by the formation of the corresponding dichloro-substituted allylic alcohols. In contrast, selenium tetrachloride reacts with γ-phenylpropargyl alcohol exclusively as a chlorinating agent, giving (3-chloroprop-1-yn-1-yl)benzene quantitatively. Products of regio- and stereospecific electrophilic addition of selenium tetrabromide are also described. Reaction mechanisms are proposed.

Reactions of stereoselective addition of selenium dibromide and monobromide to acetylene

The reaction of selenium tetrabromide with acetylene afforded bis(2-bromovinyl)selenium dibromide as a mixture of isomers [1]. No information existed on the reaction of selenium dibromide and monobromude with acetylene. We perform systematic research on the reactions of selenium halides with unsaturated compounds [2–12]. It was shown for the first time in [2, 3] that selenium dichloride and dibromide were suitable for the preparation of organoselenium compounds. By the addition of selenium dichloride and dibromide to divinyl sulfide, diorganyldiethynylsilanes and –germanes new heterocyclic compounds were synthesized [2–12]. We performed for the first time the reactions of selenium dibromide and monobromide with acetylene. They proceed as a stereoselective anti-addition with the formation of a previously unknown E,E-bis(2bromovinyl)-selenide (I) in 90–98% yield. of selenium monobromide with acetylene in chloroform at 30–40°C resulted in selenide I in 98% yield (calculated on the taken selenium monobromide) and was accompanied by the elemination of elemental selenium. The reactions were characterized by high stereoselectivity: exclusively compound of the E,E-configuration was obtained. This stereoslectivity might originate from the involvement into the reaction cyclic intermediates A, B. The formation of analogous intermediates in the reactions of electrophilic addition of compounds with a selenium–halogen bond to alkynes was previously established [13].

Neue Kronenether‐stabilisierte Oxoniumhalogenochalkogenate: [H3O(Dibromo‐benzo‐18‐Krone‐6)]2[Se3Br10] und [H5O2(Bis‐dibromo‐dibenzo‐24‐Krone‐8]2[Se3Br8

AbstractNovel Oxonium Halogenochalcogenates Stabilized by Crown Ethers: [H3O(Dibromo‐benzo‐18‐crown‐6)]2[Se3Br10] and [H5O2(Bis‐dibromo‐dibenzo‐24‐crown‐8]2[Se3Br8]Two novel complex oxonium bromoselenates(II,IV) and –(II) are reported containing [H3O]+ and [H5O2]+ cations coordinated by crown ether ligands. [H3O(dibromo‐benzo‐18‐crown‐6)]2[Se3Br10] (1) and [H5O2(bis‐dibromo‐dibenzo‐24‐crown‐8]2[Se3Br8] (2) were prepared as dark red crystals from dichloromethane or acetonitrile solutions of selenium tetrabromide, the corresponding unsubstituted crown ethers, and aqueous hydrogen bromide. The products were characterized by their crystal structures and by vibrational spectra. 1 is triclinic, space group $\rm P{\bar 1}$ (Nr. 2) with a = 8.609(2) Å, b = 13.391(3) Å, c = 13.928(3) Å, α = 64.60(2)°, β = 76.18(2)°, γ = 87.78(2)°, V = 1404.7(5) Å3, Z = 1. 2 is also triclinic, space group $\rm P{\bar 1}$ with a = 10.499(2) Å, b = 13.033(3) Å, c = 14.756(3) Å, α = 113.77(3)°, β = 98.17(3)°, γ = 93.55(3)°. V = 1813.2(7) Å3, Z = 1. In the reaction mixture complex redox reactions take place, resulting in (partial) reduction of selenium and bromination of the crown ether molecules. In 1 the centrosymmetric trinuclear [Se3Br10]2− consists of a central SeIVBr6 octahedron sharing trans edges with two square planar SeIIBr4 groups. The novel [Se3Br8]2− in 2 is composed of three planar trans‐edge sharing SeIIBr4 squares in a linear arrangement. The internal structure of the oxonium‐crown ether complexes is largely determined by the steric restrictions imposed by the aromatic rings in the crown ether molecules, as compared to complexes with more flexible unsubstituted crown ether ligands.

Mechanism of the cyclization of dimethyl diethynyl silane with selenium tetrabromide: Computational and structural studies, and monitoring

The structure of 2,4-dibromo-2-dibromomethyl-3,3-dimethyl-1-selena-3-silacyclopentene-4, formed by regioselective electrophilic addition of SeBr 4 to dimethyl diethynyl silane, has been determined using X-ray analysis technique. Quantum chemistry methods were used to study elementary stages of the reaction. It was found that the first stage consisted of SeBr 4 conversion into bimolecular complex Br 2⋯SeBr 2, initiated by dimethyl diethynyl silane. Possible formation of five-membered and six-membered heterocycles involves different cyclization mechanisms. The formation of only five-membered heterocycle is explained by kinetically preferable ring closure through four-center transition state. The conclusions obtained by calculations were confirmed by monitoring of the reaction using 1H NMR method.

Reaction of Selenium Tetrabromide with Dimethyldiethynylsilane.

Reaction of Selenium Tetrabromide with Dimethyldiethynylsilane.

Reaction of selenium tetrabromide with dimethyldiethynylsilane

Reaction of selenium tetrabromide with dimethyldiethynylsilane

ChemInform Abstract: Electrophilic Reactions of Group 6 Element Halides. Part 13. Addition of Selenium Tetrabromide and Selenium Tetrachloride to Acetylene and Its Derivatives.

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ChemInform Abstract: Reaction of N‐Substituted Allylacetic Amides with Selenium and Tellurium Tetrahalides.

AbstractThe allylacetamides (I) react with selenium tetrabromide, obtained in situ from selenium dioxide (II) and hydrobromid acid, to give the bis‐(tetrahydrofuranylmethyl)selenium dibromides (III).

Reactions of N-substituted allylacetic acid amides with selenium and tellurium tetrahalides

The addition of selenium tetrabromide to the olefinic bond of N-substituted allylacetic acid amides (reagent molar ratio 2∶1) proceeds counter to Markownikoff's rule with the formation of tetrahydrofuran derivatives. The addition of tellurium tetrahalides under the same conditions (reagent molar ratio 1∶1) proceeds in accordance with Markownikoff's rule with the formation of tetrahydropyran derivatives.

Electrophilic reactions of halides of group vi elements. 7. Reactions of allylbenzene and allyl phenyl ether with selenium tetrahalides

The reaction of selenium tetrachloride with allylbenzene and allyl phenyl ether proceeds in accordance with the Markownikoff rule to give 1:2 adducts. The use of selenium tetrabromide changes the course of the reaction and leads to the production of a mixture of adducts in accordance with and counter to the Markownikoff rule, as well as products of cyclization of the intermediate monoadducts to 2-bromomethyl-2,3-dihydrobenzo[b]selenophene or 2-bromomethyl-benzo-1,4-selenoxane derivatives.

SYNTHESE VON BIS-BROMMETHYLSELENID

Abstract The reaction of bromine with oligomeric or polymeric selenoformaldehydes leads to the formation of bis-bromomethyl selenide. Addition of more bromine to this compound leads to a crystalline adduct and furthermore to the formation of selenium, dibromethane and selenium tetrabromide.

Oeganic compounds of selenium and tellurium

2,3-Disubstituted 2,3-dihydrobenzo[b]selenophenes were obtained in the form of trans isomers by the action of selenium tetrabromide on dibenzal- and benzalacetone in benzene.

ChemInform Abstract: NEUTRON‐ACTIVATION ANALYSIS OF SELENIUM, OSMIUM AND RUTHENIUM IN ROCKS, SEDIMENTS AND BIOLOGICAL MATERIALS BY SUCCESSIVE DISTILLATIONS WITH THREE KINDS OF STRONG PHOSPHORIC ACID REAGENTS

Chemischer InformationsdienstVolume 6, Issue 48 Preparative Inorganic Chemistry ChemInform Abstract: NEUTRON-ACTIVATION ANALYSIS OF SELENIUM, OSMIUM AND RUTHENIUM IN ROCKS, SEDIMENTS AND BIOLOGICAL MATERIALS BY SUCCESSIVE DISTILLATIONS WITH THREE KINDS OF STRONG PHOSPHORIC ACID REAGENTS KIKUO TERADA, KIKUO TERADASearch for more papers by this authorKEN MATSUMOTO, KEN MATSUMOTOSearch for more papers by this authorTOSHIYASU KIBA, TOSHIYASU KIBASearch for more papers by this author KIKUO TERADA, KIKUO TERADASearch for more papers by this authorKEN MATSUMOTO, KEN MATSUMOTOSearch for more papers by this authorTOSHIYASU KIBA, TOSHIYASU KIBASearch for more papers by this author First published: December 2, 1975 https://doi.org/10.1002/chin.197548447AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume6, Issue48December 2, 1975 RelatedInformation

Neutron-activation Analysis of Selenium, Osmium and Ruthenium in Rocks, Sediments and Biological Materials by Successive Distillations with Three Kinds of Strong Phosphoric Acid Reagents

Abstract A new separation scheme is presented for the neutron-activation analysis of selenium, osmium and ruthenium in solid samples such as rocks, sediments and biological materials. A neutron-irradiated sample accompanying the carriers of the three elements was heated with the bromide-SPA reagent to 250°C, whereupon selenium came out as gaseous selenium tetrabromide. The second distillation was performed by heating the residual sample with Ce(IV)-SPA reagent till 285°C to separate osmium as osmium tetroxide gas. The last distillation of ruthenium as ruthenium tetroxide followed under heating the residue with the Cr(VI)-SPA reagent till 245°C. Each distillate was absorbed in an appropriate absorbing solution from which selenium metal, osmium thiourea chromithiocyanato complex, and ruthenium metal were respectively recovered and they were submitted to γ-counting by means of a Ge(Li) detector coupled with a multi-channel pulse height analyzer. The chemical recoveries of the added carriers were found to be about 80% for selenium and above 90% for osmium and ruthenium.

Separation and determination of selenium in rocks, marine sediments and plankton by direct evolution with the bromide-condensed phosphoric acid reagent

A new method is presented for the quantitative separation and determination of selenium by direct evolution with the bromide-condensed phosphoric acid reagent (Br −-CPA) from rocks, marine sediments and plankton. In the reaction with the Br −1-CPA, selenium(IV) and (VI) in the solid samples are evolved as selenium tetrabromide, and can be collected in an absorbing solution of 0.3 M hydrochloric acid and 06 M perchloric add (1:1), and then determined spectrophotometrically with 4-substituted o-phenylenediamines followed by the extraction of the resulting 5-substituted piazselenol into toluene. Elemental selenium and selenide do not react with the Br −-CPA, but can be determined after oxidation to selenite with potassium iodate. Therefore, successive distillations, the first with Br −-CPA and the second with IO 3 −-Br −-CPA, give a satisfactory means of diflerential determination of selenium(IV) and (VI), and elemental selenium and selenide. This method can be successfully applied for the separation of selenium in the neutron-activation analysis of standard rock samples, marine sediments and plankton, giving good and reliable results.

Reactions of 1,1-diarylethylenes with selenium compounds

The synthesis of substituted benzoselenopheno[2,3-b]benzoselenophens from 1,1-diarylethylenes was achieved in much higher yields with diselenium dichloride than with seleninyl chloride. 1,1-Bis-(2,4-dimethylphenyl)-ethylene with either selenium tetrachloride or diselenium dichloride yielded the corresponding 2,2-diarylvinyl selenide; reactions of other diarylethylenes with selenium tetrachloride or tetrabromide gave selenium-free products. The reaction with seleninyl chloride was extended to yield a di-1-benzoselenopheno[2,3-b:2′,3′-b′]benzodiselenophen.

The Raman and far-infrared spectra of some solid selenium and tellurium tetrahalides

The Raman and far-infrared spectra of solid selenium and tellurium tetrachlorides and tellurium tetrabromide are reported. The infrared spectra of selenium tetrabromide and the mixed halides SeClBr3 and SeCl3Br were also studied. Three possible structures for these compounds were considered: a simple ionic formulation MX3+X– of C3v symmetry, a covalent MX4 molecule of C2v symmetry, and a distorted ionic structure of Cs symmetry resulting from interionic charge-transfer. The vibrational spectra suggest a C2v covalent structure.