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.     

Contribution to Halo‐Chalcogenates Chemistry

Abstract. By direct reactions of selenium with halogen and trimethylphenylammonium halogenide and tetraphenylphosphonium, ethyltriphenylphosphonium, and methyltriphenylphosphonium bromides, the tetrahalogenidoselenates(II) – bis(trimethylphenylammonium)tetrabromidoselenate(II) bromide, [NPhMe₃]₂[SeBr₄] · [NPhMe₃]Br, a mixed bis(trimethylphenylammonium) tetra(bromido/chlorido)selenate(II), [NPhMe₃]₂[SeBr_4–xCl_x] · [NPhMe₃]₂SeBr_1–yCl_y], [NPhMe₃]₂[SeBr_4–xCl_x],the haxahalogenidodiselenates(II) – bis(trimethylphenylammonium) hexabromidodiselenate(II), [NPhMe₃]₂[Se₂Br₆], bis(trimethylphenylammonium) hexachloridodiselenate(II), [NPhMe₃]₂[Se₂Cl₆], a mixed bis(trimethylphenylammonium) bromido/chlorido‐diselenate(II), [NPhMe₃]₂[Se₂Br₅Cl], bis(tetraphenylphosphonium) hexabromidodiselenate(II), [PPh₄]₂[Se₂Br₆], bis(ethyltriphenylphosphonium) hexabromidodiselenate(II), [PEtPh₃]₂[Se₂Br₆], and bis(methyltriphenylphosphonium) hexabromidodiselenate(II), [PMePh₃]₂[Se₂Br₆], were prepared. By the reaction of selenium with bromine in acetonitrile in the presence of trimethylphenylammonium, benzyltrimethylammonium, and tetramethylammonium bromides, the salts of the unique bromidoselenate(I) anions – bis(trimethylphenylammonium) hexabromidotetraselenate(I), [NPhMe₃]₂[Se₄Br₆], bis(benzyltrimethylammonium) hexabromidotetraselenate(I), [NBzMe₃]₂[Se₄Br₆], and bis(tetramethylammonium) octadecabromidohexadecaselenate(I), [NMe₄]₂[Se₁₆Br₁₈], were isolated. First mixed‐valence bromidoselenates(II/I) – bis(tetraethylammonium) octabromidotriselenate(II){dibromidodiselenate(I)}, [NEt₄]₂[Se₃Br₈(Se₂Br₂)], bis(tetraphenylphosphonium) hexabromidodiselenate(II)‐bis{dibromidodiselenate(I)}, [PPh₄]₂[Se₂Br₆(Se₂Br₂)₂], and tetrakis(tetramethylammonium) bis{decabromidotetraselenate(II)}‐bis{dibromidodiselenate(I)}, [(CH₃)₄N]₄[(Se₄Br₁₀)₂(Se₂Br₂)₂] – were synthesized. Mixed bis(trimethylphenylammonium) hexabromidoselenate/tellurate(IV), [NPhMe₃]₂[Se_0.75Te_0.25Br₆], catena‐poly[(di‐μ‐bromidobis‐{tetrabromidoselenate/tellurate(IV)})‐ μ‐bromine], [NPhMe₃]_2n[Se_1.5Te_0.5Br₁₀ · Br₂]_n were isolated. First mixed‐valence bromidoselenate(IV/I)‐bis(trimethylphenylammonium) hexabromidoselenate(IV)‐bis{dibromidodiselenate(I)}, [NPhMe₃]₂[SeBr₆(Se₂Br₂)₂], a number of mixed bromidochalcogenates(IV/I) – bis(trimethylphenylammonium), bis(tetraethylphosphonium), bis(ethyltriphenylphosphonium) hexabromidotellurates(IV)‐bis{dibromidodiselenates(I)}, [NPhMe₃]₂[TeBr₆(Se₂Br₂)₂], [PEt₄]₂[TeBr₆(Se₂Br₂)₂], [PEtPh₃]₂[TeBr₆(Se₂Br₂)₂], bis(triethylmethylammonium) hexabromidotellurate(IV)‐tris{dibromidodiselenate(I)}, [NMeEt₃]_2n[TeBr₆(Se₂Br₂)₃]_n, were synthesized. Mixed‐valence bromidoselenate(IV/II) – bis(methyltriphenylphosphonium) hexabromidoselenate(IV)‐bis{dibromidoselenate(II)},[PMePh₃]₂[SeBr₆(SeBr₂)₂], received by direct synthesis and two mixed‐valence bromidochalcogenates(IV/II) – bis(methyltriphenylphosphonium) and bis(tetrapropylammonium) hexabromidotellurates(IV)‐selenates(II), [PMePh₃]₂[TeBr₆(SeBr₂)₂] and [NⁿPr₄]₂[TeBr₆(SeBr₂)₂], were synthesized from elemental selenium, tellurium dioxide, and corresponding onium bromide. The structures of all compounds were determined by X‐ray diffraction.     

Formation and characterization of conductive thin layers of copper sulfide (CuxS) on the surface of polyethylene and polyamide by the use of higher polythionic acids

Layers of copper sulfide of varying composition and properties are formed on the surface of polyethylene and polyamide by a sorption-diffusion method using solutions of higher polythionic acids, H₂S_nO₆. The concentration of sulfur adsorbed-diffused into PE and PA depends on the degree of the acid sulfurity, n, the temperature of the solution and the period of the polymer treatment. The amount of copper in a sulfide (Cu_xS) layer formed after the sulfured polymer treatment with a solution of Cu(I-II) salt is strongly dependent on the concentration of sulfur in the PE and PA. By the chemical analysis of the obtained sulfide layers was determined that a value of x in the Cu_xS layers varies in the interval 1 < x < 2. The microscopic investigation of transverse sections of PE and PA samples with copper sulfide layers showed that the major part of copper sulfide is in the surface matrix of the polymer. X-ray diffraction studies of the Cu_xS layers obtained seven phases: with x = 2 (chalcocite), 1.9375 (djurleite), 1.8 (digenite), 1.75 (anilite), 1.12 (yarrowite), 1.06 (talnakhite) and 1 (covellite). The measurements of the electrical conductance of Cu_xS layers (0.1-4 S cm⁻²) showed that its value greatly depends on the conditions of PE and PA interaction with H₂S_nO₆ and of further interaction with Cu(I-II) salt solution, on the chemical and phase composition of the layer.