Bromine In Acetonitrile Research Articles

Perbrominated Sulfonium-Substituted closo-Decaborates with exo-Polyhedral Amino Groups [2-B10Br9S((CH2)nNH2)2]– (n = 1–3)

A method for preparing fully brominated sulfonium derivatives of the closo-decaborate anion with functional amino groups (n-Bu4N)[2-B10Br9S((CH2)nNH2)2]– (n = 1–3) has been developed. The method is based on the interaction between sulfonium derivatives of the closo-decaborate anion with phthalimide groups (n-Bu4N)[2-B10Br9S((CH2)npht)2]– (n = 1–3) and elemental bromine in acetonitrile in an inert atmosphere, followed by removal of the phthalimide protection using methylamine.

Csp3–N bond formation in aminothiophenes by 1,1-dibromo isocyanide: the unexpected 1,5-binucleophilicity of substrates

The N-cyclohexylcarbonimidoyl dibromide in situ, generated by cyclohexylisocyanide and bromine in reaction with several deactivated 5-acetyl-4-amino-2-methylsulfanyl-3-carbonitrile, appears as a cyclohexyl transformer to the substrate via Csp3–N bond formation without using any base or catalyst at room temperature. The present transformation suggests three main innovations. First, regarding the selective monoalkylation of aromatic amines, the performed condition is unprecedented. Second, for the first time in the field of isocyanide-based reactions, isocyanide is applied as an alkyl transformer agent. Third, this is the first example of coupling aminothiophenes with a secondary alkyl group. Interestingly, high yield and selectivity, short reaction time, easy purification accompany this protocol. Through this study, we investigated the electronic effects of substituents linked to acetyl on the efficiency of the reaction. Also, the potential of isocyanide dibromide for the synthesis of cyclic guanidine is evaluated. An efficient, useful and general procedure for the synthesis of 5-aroyl-4-cyclohexylamino-2-methylsulfanyl-3-thienyl cyanide via one-pot three-component reaction of 5-acetyl-4-amino-2-methylsulfanyl-3-carbonitrile, cyclohexylisocyanide and bromine in acetonitrile at room temperature has been described. The major advantages of this protocol are high yield and selectivity, short reaction time, easy purification.

Chemical redox reactions and extended PXRD-characterization of triphylite-type compounds AM0.5Fe0.5PO4 (A = Li, Na; M = Mn, Co)

The alkaline content of mixed transition metal phosphates Li(1−y)·zNay·zM0.5Fe0.5PO4 (M = Mn, Co; 0 ≤ y < 1; 0.5 ≤ z ≤ 1) was determined by powder X-ray diffraction data by means of Rietveld analysis and multi-fraction models. The compounds LiM0.5Fe0.5PO4 were synthesized via solid-state reactions. Chemical extraction of Li with bromine in acetonitrile yielded well-crystalline Li0.5M0.5Fe0.5PO4. Subsequent reduction with Na2S in acetonitrile gave a product with a triphylite-type phase of the average composition Li0.5Na0.5M0.5Fe0.5PO4 showing a broad distribution of Li-to-Na-ratios. For Rietveld refinements a set of 11 fractions Li1−yNayM0.5Fe0.5PO4 was used to represent the triphylite-type phase and its composition fluctuation. To obtain samples with compositions close to NazM0.5Fe0.5PO4 (z = 0.5 or z = 1) up to two additional cycles of chemical oxidation and reduction were required. Because of a complex distribution of Li and Na within the triphylite-type phase a model of 121 fractions of Li(1−y)·zNay·zM0.5Fe0.5PO4 was developed to enable proper Rietveld refinements. The scaling factors of the 121 fractions were constrained by a bimodal bivariate normality. The evaluation of the pattern revealed a type of passivation, preventing the compound from complete oxidation or reduction of Fe for higher cycle numbers. Hence, no completely Li-free samples could be obtained.

ChemInform Abstract: Contribution to Halo‐Chalcogenates Chemistry

AbstractReview: 46 refs.

Contribution to Halo‐Chalcogenates Chemistry

AbstractAbstract. 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[SeBr4–xClx]·[NPhMe3]2SeBr1–yCly], [NPhMe3]2[SeBr4–xClx],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[Se0.75Te0.25Br6], catena‐poly[(di‐μ‐bromidobis‐{tetrabromidoselenate/tellurate(IV)})‐ μ‐bromine], [NPhMe3]2n[Se1.5Te0.5Br10·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.

Direktsynthese und Kristallstruktur von [BeBr2(CH3CN)2

AbstractThe berylliumbromide‐acetonitrile complex [BeBr2(CH3CN)2] (1) was prepared in a one‐step synthesis from beryllium powder and bromine in acetonitrile at room temperature to give colourless single crystals, which were characterized by X‐ray diffraction and IR spectroscopy. Compound 1 crystallizes orthorhombically in the space group Pnma with four formula units per unit cell. Lattice dimensions at 100(2) K: a = 1253.1(1), b = 1003.7(1), c = 650.8(1) pm, R1 = 0.0217. The structure of 1 consists of monomeric molecules with site symmetry m and distances Be–Br of 214.7(5) pm and Be–N of 171.3(4) pm.

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

AbstractBrown 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 SeII atoms of two SeBr4 units; between the Se4Br102– ions a dimerized Se2Br2 molecule (Se4Br4) is situated and one SeI 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 SeI atoms of a dimerized Se2Br2 molecule are in a almost regular planar tetraangular arrangement. Contacts between the SeII atom of the SeBr2 molecule and the SeII 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 SeII atoms of SeBr4 units as donors and the SeBr2 molecule as acceptor. The terminal SeII–Br and μ3‐Br–SeII 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: SeI–SeI = 2.2945(8) Å and 3.1398(12), SeI–Br = 2.3659(11) and 2.3689(10) Å.

Topochemical Synthesis, Anion Exchange, and Exfoliation of Co−Ni Layered Double Hydroxides: A Route to Positively Charged Co−Ni Hydroxide Nanosheets with Tunable Composition

This paper describes the topochemical synthesis of Co−Ni layered double hydroxides (LDHs) from brucite-like Co−Ni hydroxides through a novel oxidative intercalation process employing bromine as an oxidizing agent, and their exfoliation into positively charged unilamellar nanosheets in formamide after anion-exchange treatment. In this protocol, hexagonal microplatelets of brucite-like Co−Ni hydroxides in variable composition were prepared by homogeneous precipitation of a mixed solution of divalent cobalt and nickel ions via hexamethylenetetramine hydrolysis. Subsequent treatment of the brucite-like Co−Ni hydroxides with excessive bromine in acetonitrile promoted partial oxidation of Co2+ into Co3+, producing Br−-intercalated Co−Ni LDHs inheriting the hexagonal morphology. This rational topochemical approach was applicable for realizing a pure phase of Co−Ni LDHs with nickel content up to 50% (metal content). Chemical analyses indicated that as-prepared Co−Ni−Br LDHs were unexceptionally characterized by a...

Topochemical Synthesis of Monometallic (Co2+–Co3+) Layered Double Hydroxide and Its Exfoliation into Positively Charged Co(OH)2 Nanosheets

From platelets to sheets: A topochemical phase conversion employing bromine in acetonitrile transforms β-Co(OH)2 into monometallic Co2+–Co3+ layered double hydroxide (LDH) with a Co2+/Co3+ ratio of 2:1 (see the elemental maps of Co, Br, and O in a Br−-intercalated Co2+–Co3+ LDH platelet). Further treatment allows exfoliation of Co2+–Co3+ LDH into positively charged Co(OH)2 nanosheets. Scale bars: 2 μm.

A Convenient Method for Oxidation of Organophosphorus Pesticides in Organic Solvents

Since organophosphorus pesticides can be oxidized to oxons in vivo and in the environment and their determination based on inhibition of cholinesterases can be more sensitive after their oxidation to oxons, development of an efficient method for their in vitro oxidation is important for their toxicological and analytical studies. This study demonstrated that treatment of organophosphorus pesticides with 10 molar excess bromine in acetonitrile is a rapid and efficient method for their oxidation. For the nine organophosphorus pesticides tested, the reaction was complete within a few seconds. All reactions gave the respective oxons as single major product, except that of fenthion, which gave two major products, the respective oxon and another product from further oxidation of the oxon. The yields of the oxons were 82–100%. The inhibitory power of the pesticides on acetylcholinesterase before and after oxidation was measured and, for all pesticides tested, the power after oxidation was much higher than that before oxidation. Inhibition calibration curves for both unoxidized and oxidized forms of fenitrothion and parathion were obtained. The sensitivity of the detection of these pesticides was much higher after oxidation.

Evidences for the Formation of Chromium in the Unusual Oxidation State Cr(IV): III. Experimental Electronic Structure of the Channel Compounds TlxCr5Se8 (x=1 and 0.2)

The X-ray photoemission core level spectra of TlCr5Se8 and Tl0.2Cr5Se8 definitely exclude the oxidation of Tl(I) to Tl(III) when Tl is removed using a topotactic redox reaction between TlCr5Se8 and bromine in acetonitrile. Alterations are only observed for the multiplett structure of the Cr 3s core level giving evidences for a partial oxidation of Cr(III) to Cr(IV). Significant differences are observed in the valence band regions that were investigated with He I and He II radiation. For the Tl-poor sample an increased electron density at the Fermi level is observed in accordance with the higher electrical conductivity of this sample. The variations of the emissions in the region down to about 3 eV below EF can nicely be explained on the basis of the reduced Tl content and a partial oxidation of Cr(III) to Cr(IV).

Evidences for the Formation of Chromium in the Unusual Oxidation State Cr(IV): I. Chemical Reactivity, Microhomogeneity, and Crystal Structures of the Nonstoichiometric Channel Compounds TlxCr5Se8(0 ≤x≤ 1)

The topotactic redox reaction between TlCr5Se8and bromine in acetonitrile leads to the formation of metastable samples with 0 ≤x< 1 of TlxCr5Se8. Preparation at elevated temperatures yields for the first time a ternary transition metal chalcogenide crystallizing in the TlV5S8type structure with a Tl contentx< 0.33. As expected the topotactic redox reaction does not follow simple kinetics but is rather explained on the basis of the superposition of at least three different fundamental steps. EDAX investigations conducted on selected single crystals reveal that dependent on the deintercalation temperature, Tl is laterally inhomogeneous distributed along the needle axis which coincides with the crystallographicbaxis. A pronounced maximum is observed at the middle of the crystals. In stoichiometric TlCr5Se8the detailed analysis of the anisotropic displacement parameters of the Tl atoms reveal that the Tl atoms are displaced from the central position by about 0.26 Å. As a consequence the Tl atoms are coordinated by seven Se atoms in an irregular coordination polyhedron. Since the positionsx0zare related by a center of symmetry they cannot be occupied simultaneously. Hence it must be assumed that TlCr5Se8has a domain structure with local symmetryCm. In the Tl poorer phases the refinement of the Tl atoms at the central position leads to unusual highU22components. The observed microinhomogenity as well as an enhanced mobility and/or static disorder of the Tl atom within the channel may be responsible for this. The value forU11decreases with decreasing Tl content whereasU33is not affected. This observation is indicative for a different displacement of the Tl atoms from the central position. With respect to the possible reaction mechanisms, according to our structural investigations, the oxidation of monovalent Tl to trivalent Tl can be excluded. With decreasing Tl content the lattice parameters exhibit very anisotropic behavior, which is a direct consequence of the large changes of the interatomic Cr–Cr distances. The average 〈Cr–Se〉 as well as the nonbonding Se–Se distances are only slightly affected. These results suggest an oxidation of the formally trivalent Cr to the unusual tetravalent state Cr(IV), rather than the formation of valence band holes.

Room temperature synthesis and structural characterization of monoclinic LiCuO 2 by X-ray and neutron diffraction

LiCuO 2 was synthesized at room temperature by delithiation of Li 2CuO 2 using bromine in acetonitrile. The product shows broad diffraction profiles which were analysed by the Rietveld refinement technique on X-ray and neutron powder data. The phase conforms to the NaCuO 2 structure type ( C2/ m, Z=2) with the cell a=5.733(1) A ̊ , b=2.7176(3) A ̊ , c=5.622(1) A ̊ , β=120.68(2)°.

Peptides containing dipropylglycine

Using 4-heptanone in the Ugi reaction, it is possible to prepare a peptide containing a single residue of dipropylglycine (Dpg) in modest yield, but attempts to form peptides containing contiguous Dpg residues were unsuccessful. Methods of extending Dpg-Dpg to higher homo-oligomers have been examined. Carboxyl extension of N-trifluoroacetyl (Tfa)-Dpg2 is possible through its oxazolin-5(4H)-one, but only as far as the tripeptide. However, amino extension of Dpg2-OBut by successive steps of addition of 2-trifluoromethyl-4,4-dipropyloxazolin-5 (4H)-one and N-deprotection allowed preparation of Tfa-Dpg6-OBut in good yield. Removal of the Tfa group from Dpg residues is only possible using sodium borohydride reduction under conditions which lead to partial reduction of the t-butyl esters of protein amino acids. The use of the N',N'-dibenzylhydrazide (DBH) group for C-protection, however, circumvents this problem. Direct regeneration of carboxyl from DBH is possible with bromine in acetonitrile, and catalytic reduction gives the free hydrazide. Tfa-Dpg--NHNH2 can be oxidatively coupled to Gly-OBut but not to Dpg-OBut. Tfa-Dpg3-N3 undergoes Curtius rearrangement in preference to peptide bond formation, and Dpg3-N3 eliminates isocyanic acid on heating to form N-(Dpg)2-heptylideneimine.

Conductometric titration studies of the reactions of tris(dimethylamino)phosphine and tris(dimethylamino)arsine with halogens and interhalogens

Conductometric titrations of some tris(dimethylamino)phosphine-halogen and -interhalogen systems in acetonitrile have shown in each case that 1:1 and 2:1 adducts are formed. All of the 2:1 adducts in the series (Me 2N) 3PCl n I 4− n and (Me 2N) 3PBr n I 4− n have been obtained as crystalline solids. The electrolytic conductance of the adducts in acetonitrile is reported. The conductometric titration of tris(dimethylamino)arsine with bromine in acetonitrile indicates the formation of a 1:1 and a 2:1 adduct. The reaction of tris(dimethylamino)arsine with interhalogens gives tetrakis(dimethylamino)arsonium trihalides.

Halomethyl—metal compounds L. Preparation of monohalomethyl derivatives of germanium, tin, lead and mercury via halomethylzinc halides

The reaction of iodomethylzinc iodide or bromomethylzinc bromide in THF with the appropriate metal or organometallic halide was used in the present ation of Me 3SnCH 2I, Me 3SnCH 2Br, Me 2Sn(CH 2I) 2, Me 2Sn(CH 2Br) 2, Me 2PhSnCH 2I, Ph 3SnCH 2I, Sn(CH 2I) 4, Ph 3PbCH 2I, Hg(CH 2I) 2 and Hg(CH 2Br) 2. In most cases the product yields were very good. The reaction of iodomethylzinc iodide with trimethylchlorogermane gave in low yield both Me 3GeCH 2I and Me 3GeCH 2GeMe 3. These compounds were obtained in much better yield when ICH 2ZnI was allowed to react with germanium tetrachloride and the reaction product was methylated with MeMgBr. The reaction of iodomethyl-tin compounds with silver chloride and bromine in acetonitrile served well in the preparation of Me 3SnCH 2Cl, Me 3SnCH 2Br, Me 2Sn(CH 2Cl) 2, Me 2Sn(CH 2Br) 2 and Me 2PhSnCH 2Cl. Experiments in which mixtures of Et 3SiD and n-Bu 3SiH were allowed to react with ICH 2ZnI in refluxing ether or with Hg(CH 2I) 2/Ph 2Hg in refluxing benzene gave only Et 3SiCH 2D and n-Bu 3SiCH 3. This eliminates from consideration the possibility that these reactions proceed by a two-step alkylation-reduction or reduction-alkylation sequence.

Kinetics of the bromine-tribromide-bromide redox processes on platinum electrodes in acetonitrile solutions

The electrochemistry of solutions of lithium bromide and bromine in acetonitrile has been investigated in the temperature range from 0 to 30°C, using a platinum rotating disk working electrode from 200 to 2000 rpm. Both the anodic and cathodic current/voltage curves are characterized by two well-defined waves From the diffusion-controlled processes, the diffusion coefficients of the defusing species have been evaluated. The current/voltage curves in a region before the limiting current have an appreciable degree of irreversibility. The kinetic parameters were obtained by the Frumkin-Tedoradse method for intermediate kinetics and it is shown that the processes formally fit the type of reaction mechanisms already postulated for the iodine-tri-iodide-iodide system in dimethylsulphoxide and acetonitrile.

Reaction of transition metals with bromine in acetonitrile

The reactions of titanium, vanadium, and chromium with bromine in acetonitrile have been re-examined. The major products of the reaction were TiBr4(MeCN)2, VBr2(Br3)(MeCN)3, and [CrBr2(Br3)(MeCN)2]n. The latter polymeric complex breaks down in two steps in the parent solvent to form CrBr2(Br3)(MeCN)3 followed by CrBr3(MeCN)3. The simple halide complex was found to be identical with the complex formed from CrBr3 and MeCN. Spectral and conductivity studies indicate that the tribromide ion is bonded directly to the metal in these cases. In solution the vanadium complex appears to undergo co-ordination disproportionation. The mechanism of the reaction and the bonding in the complexes are discussed.