The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its phenoxyl and aminyl radicals

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine Ph—NH—C₆H₄—OH (D _NH= 353.4, D _OH=339.3 kJ mol^–1) and its semiquinone radicals D _NH(Ph—NH—C₆H₄—O^·) = 273.6, D _OH(Ph—N^·—C₆H₄—OH) = 259.5 kJ mol^–1 were first estimated using the parabolic model and experimental data (rate constants) on two elementary reactions with participation of N-phenyl-1,4-benzoquinonemonoimine (2). One of the reactions, namely, that of 2 with aromatic amines, was studied in this work using a specially developed method.     

Electrochemical Amination in the System Ti(IV)–NH2OH–C6H6: The Efficiency of the Process in a Sulfuric Acid Solution Containing an Organic Solvent

Electrolysis of the system Ti(IV)–NH₂OH–C₆H₆ in an 11 M H₂SO₄ solution shows that using an organic solvent (acetic acid, acetonitrile) during cathodically initiated amination of aromatic substrates permits the production of aromatic amines with the overall yield by hydroxylamine reaching 91%. Due to a chain mechanism of radical substitution, the benzene amination in electrolytes containing 5 M CH₃COOH and 5.5 M CH₃CN terminates largely upon consuming 70–75 and 50–55% of the charge required theoretically for a one-electron process. The maximum efficiency of electrochemical amination is observed at low hydroxylamine conversions and the overall current efficiency for mono- and disubstituted products of the benzene amination may exceed in these conditions 750%.     

Electrochemical Amination: Efficiency of a Radical Substitution

Electrochemical amination of benzene in sulfuric acid electrolytes is studied and experimental conditions for highly efficient synthesis of primary aromatic amino compounds are determined. In the electrolysis of Ti(IV)–NH₂OH–C₆H₆ in 11 M H₂SO₄ solutions containing acetic acid or acetonitrile as organic solvents, aniline and isomeric phenylenediamines are obtained with the total yields by hydroxylamine of 95.6 and 99.6%, respectively. A monoamino compound is the main product of radical substitution in acidic organo-aqueous media. It is found that the use of acetonitrile in electrochemical process is limited to certain sulfuric acid concentrations and temperatures.     

Relationship between reduction potentials and electron affinities of fullerenes and their derivatives

A linear relationship was found between the first reduction potentials (E°_red) and electron affinities (EA) for fullerenes C₆₀ and C₇₀, their hydro- and fluoro-derivatives, and aromatic hydrocarbons: E°_red = –3.04 + 0.81·EA. This equation was used to estimate the unknown values of EA = 2.45 eV for C₆₀H₂, 2.47 eV for C₇₀H₂, –0.15 eV for C₇₀H_36—38, –0.41 eV for C₇₀H_44—46, and E°_red = –1.74—–1.91 V (vs. Fc^0/+) for C₆₀H₁₈.     

Structure and stability of closo-hexaboranes and their heteroanalogs

The molecular and electronic structures of closo-hexaboranes B₆H₆ ^2–, B₆H₇ ^–, and B₆H₈ and closo-heterohexaboranes XYB₄H₄ (X = Y = CH, N; X = BH, Y = CH^–, N^–, NH, O) were studed by the ab initio (MP2(full)/6-311+G**) and density functional (B3LYP/6-311+G**) methods. The bridging H atoms in closo-hexaboranes B₆H₇ ^– and B₆H₈ can undergo facile low-barrier migrations around the boron cage (the barrier heights are about 10—15 kcal mol^–1). All heteroboranes having octahedron-like structures with hypercoordinated N and O atoms are rather stable and can be the subject of synthetic research efforts.     

Diagramme polythermique du systeme ternaire H2O—Al(NO3)3—Mg(NO3)2

The solid—liquid equilibria of the ternary system H₂O—Al(NO₃)₃—Mg(NO₃)₂ were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO₃)₃·9H₂O, Mg(NO₃)₂·9H₂O and Mg(NO₃)₂·6H₂O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis of Schiff bases and benzylamino derivatives containing [1-B<Subscript>10</Subscript>H<Subscript>9</Subscript>NH<Subscript>3</Subscript>]<Superscript>−</Superscript> anion

Reactions of an amino derivative of the closo-decaborate anion [1-B₁₀H₉NH₃]^– with aromatic aldehydes afforded Schiff bases [1-B₁₀H₉NH=CHAr]^– (Ar=Ph, C₆H₄-2-OMe, or C₆H₄-4-NHCOMe). The reduction of the latter with sodium borohydride gave the corresponding benzylamino derivatives [1-B₁₀H₉NH₂CH₂Ar]^–.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2004–2007, September, 2004.     

Crown compounds for anions. Sandwich complex of cyclic trimeric perfluoro-o-phenylenemercury with [B12H11SCN]2– anion

The reaction of cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) with the polyhedral [B₁₂H₁₁SCN]^2– anion in THF at 20 °C affords the {[(o-C₆F₄Hg)₃](B₁₂H₁₁SCN)}^2– (4) and {[(o-C₆F₄Hg)₃]₂(B₁₂H₁₁SCN)}^2– (5) complexes. Complex 5 was isolated as the tetrabutylammonium salt. X-ray diffraction analysis showed that this complex has a bent-sandwich structure in which the [B₁₂H₁₁SCN]^2– anion is located between the planes of two molecules 1 and is coordinated to both these molecules through B—H—Hg bridges and S—Hg bonds. The stability constants of complexes 4 and 5 in THF (20 °C), which were determined from the IR spectroscopic data, are 16 L mol^–1 and 992 L² mol^–2, respectively.     

Lactones ofFerula gigantea

The following substances have been isolated from an acetone extract ofFerula gigantea B. Fedtsch.: a coumarin — umbelliferone, C₉H₆O₂, mp 230–233°C; and sesquiterpene lactones — talassin A, C₂₅H₃₀O₇, mp 188–191°C; malaphyllinin, C₂₄H₂₄O₇, mp 231–235°C; malaphyll, C₂₉H₃₂O₉, mp 212–213°C; and malaphyllin, C₂₆H₂₈O₉, mp 216–218°C. Structures have been proposed for three new sesquiterpene lactones on the basis of an analysis of their spectral characteristics.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. M. V. Lomonosov Moscow State University, Botanical Garden, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 490–495, July–August, 1979.     

Efficient hydroxylation of aromatic compounds catalyzed by an iron(II) complex with H2O2

A mononuclear iron(II) complex, Et₄N[Fe(C₁₀H₆NO₂)₃], coordinated by three 1‐nitroso‐2‐naphtholate ligands in a fac‐N₃O₃ geometry, was initiated to catalyze the direct hydroxylation of aromatic compounds to phenols in the presence of H₂O₂ under mild conditions. Various reaction parameters, including the catalyst dosage, temperature, mole ratio of H₂O₂ to benzene, reaction time and solvents which could affect the hydroxylation activity of the catalyst, were investigated systematically for benzene hydroxylation to obtain ideal benzene conversion and high phenol distribution. Under the optimum conditions, the benzene conversion was 10.2% and only phenol was detected. The catalyst was also found to be active towards hydroxylation of other aromatic compounds with high substrate conversions. The hydroxyl radical formed due to the reaction of the catalyst and H₂O₂ was determined to be the crucial active intermediate in the hydroxylation. A rational pathway for the formation of the hydroxyl radical was proposed and justified by the density functional theory calculations. Copyright © 2014 John Wiley & Sons, Ltd.     

Reduction of nitrosoarene ligands in binuclear palladium(ii) complexes

Reduction of the binuclear Pd^II complexes Pd₂(OCOR)₂(o-CH₂C₆H₄—NO)₂ (1) and Pd₂(OCOR)₂(o-PhN—C₆H₄—NO)₂ (2) (where R = Me, CF₃, Bu^t, or Ph) by sodium borohydride, an ethanolic solution of KOH, or molecular hydrogen was examined. The first stage of reduction was demonstrated to afford metallic palladium and aromatic amines, viz., o-toluidine o-Me—C₆H₄—NH₂ from complex 1 and aniline Ph—NH₂ from complex 2. The reactions with molecular hydrogen involve deeper stages to yield cyclic ketones (o-methylcyclohexanone and cyclohexanone) and then cycloalkanes (methylcyclohexane and cyclohexane, respectively). The latter reactions are accompanied by elimination of N₂. The mechanism of reduction of complexes 1 and 2 with molecular hydrogen was proposed.     

Functionalization of saturated hydrocarbons

Alkanes and cycloalkanes (isobutane, butane, isopentane, isohexane, and methylcyclopentane) react with benzene or bromobenzene at 0–20 °C in the presence of RCO⁺Al₂X₇ ^– complexes (R=Me, Pr, or Ph; X=Cl or Br) to give products of the alkylacylation of arenes. The yields of alkylated aromatic ketones reach 60–87 % in 5–30 min, whereas the yields of unalkylated aromatic ketones (the competitive reaction) reach 0–40 %. The reactions of isobutane or isopentane with benzene result exclusively inpara isomers oft-BuC₆H₄COR or a mixture of Me₂(Et)CC₆H₄COR and Me(i-Pr)CHC₆H₄COR isomers (11), respectively. The reaction of isobutane with benzene also proceeds regioselectively and gives only one isomer, 2-Br-t-BuC₆H₄COR.For Part 2 seeIzv. Akad. Nauk, Ser. Khim., 1991, No 1, 105 [Bull. Acad. Sci. USSR. Div. Chem. Sci., 1991, No 1, 90 (Engl. Transl)].Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1253–1257, July, 1993.The authors express their gratitude to B. I. Bakhmutov for his assistance in interpreting the spectra.     

Synthesen von Heterocyclen, 119. Mitt.: Über Reaktionen des Salicylsäurechlorids mit aromatischen Thioamiden

Zusammenfassung Salicylsäurechlorid (1) reagiert mit aromatischen Thioamiden unter HCl- und H₂S-Abspaltung zu 4H-1,3-Benzoxazinonen (2–5), welche mit verd. HCl zu N-Acylsalicylsäureamiden (6–9) gespalten werden.

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Salicyloyl chloride (1) reacts with aromatic thioamides to 4H-1.3-benzoxazinones (2–5), which can be hydrolized with dil. HCl yielding N-acyl-salicyloyl-amides (6–9).

     

Die Umsetzung von Diphenylphosphinigsäurechlorid mit Natriumsalzen von aromatischen Sulfinsäuren zu Diphenylphosphinsäure-S-arylestern

Zusammenfassung Die Umsetzung von Diphenylphosphinigsäurechlorid mit Alkalisalzen aromatischer Sulfinsäuren führt unter Reduktion am Schwefel, Oxydation am Phosphor und Ausbildung einer Bindung zwischen Phosphor und Schwefel, zu Diphenylthiophosphinsäure-S-arylestern: (C₆H₅)₂P(O)–S–Ar (Ar=C₆H₅, 4-CH₃C₆H₄, 4-ClC₆H₄, 2-Cl-5-CH₃-C₆H₃, 2-C₁₀H₇). Die besten Ausbeuten (40–85%) wurden mitDMF als Lösungsmittel erhalten. Aliphatische Phosphinigsäurechloride geben keine Bindung zwischen P und S. Ebenso tritt keine Umsetzung ein, wenn im Säurechlorid eine P–O-Struktur vorliegt. Auch die Umsetzung von (C₆H₅)₂PCl und (C₆H₅)₂P(O)Cl mit Sulfonsäuren anstelle der Sulfinsäuren führt zu keiner P–S-Verknüpfung. Diese Phosphor-Schwefel-Bindung in den Thiophosphinsäure-S-estern stellt die schwächste Stelle im Molekül dar, da ein hydrolytischer, oxydativer oder reduktiver Angriff diese Bindung wieder löst.

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Reaction of diphenylchlorophosphine with alkali salts of aromatic sulfinic acids leads to diphenylthiophosphinates; reduction occurs at the sulfur atom, oxidation at the phosphorus atom and a bond between phosphorus and sulfur is formed: (C₆H₅)₂P(O)–S–Ar, Ar=C₆H₅, 4-CH₃C₆H₄, 2-ClC₆H₄, 2-Cl-5-CH₃-C₆H₃, 2-C₁₀H₇. The best yields were obtained in dimethyl formamide as solvent. With aliphatic chlorophosphines no bond formation beetween sulfur and phosphorus occurred. Similarly no reaction was observed, when a phosphorus atom in a higher state of oxidation was present, as for example in diphenylphosphonylchloride. Also, no reaction took place when sulfonic instead of sulfinic acids were used. The weakest bond found to exist in the diphenylthiophosphinates was the P–S-linkage, which readily undergoes hydrolytic, oxidative or reductive cleavage.

     

Square-planar copper(II) complexes with a novel tetradentate amido-carboxylate ligand. Crystal structure of [Co(H2O)6][Cu(mda)] · 2H2O

A novel O—N—N—O-type tetradentate ligand H₄mda (H₄mda = malamido-N,N-diacetic acid) and the corresponding square-planar copper(II) complexes have been prepared and characterized. The mda^4– ligand coordinates to the copper(II) ion via two pairs of deprotonated ligating atoms (two carboxylate oxygens and two deprotonated amide nitrogens) with in-plane square chelation. A four-coordinate, square-planar geometry has been established crystallographically for the [Co(H₂O)₆][Cu(mda)] · 2H₂O complex. Structural data correlating the square-planar geometry of the [Cu(mda)]^2– unit are discussed in relation to information obtained for similar complexes. The i.r., electronic, absorption and reflectance spectra of the complexes are analysed in comparison with related complexes of known geometries.     

Stereoselective formation of ansa-metallocenes in reactions of radical-anionic salts of acenaphthylene with lanthanide and calcium halides

ansa-Metallocenes (⁵:⁵-C₂₄H₁₆)M(THF)₂ (M = Sm (1), Yb (2), Ca (3)) and (⁵:⁵-C₂₄H₁₆)MI(THF) (M = Dy (8), Er (9), Tm (10), Lu (11)) were prepared in 50—90% yields by the in situ reactions of two equivalents of potassium acenaphthylenide K⁺C₁₂H₈ ^– with MI₂ or MI₃, respectively. Complexes 2 and 3 were also obtained by direct reduction of acenaphthylene with ytterbium and calcium naphthalenides, respectively. An ESR signal of the acenaphthylene radical anion, which was observed upon dissolution of compound 2 in THF, indicates that the [C₂₄H₁₆]^2– ansa-ligand dissociated into two [C₁₂H₈]^·– radical anions. Hydrolysis of complex 2 in benzene afforded 1,1",3,3"-tetrahydro-3,3"-biacenaphthylene (4) and 3,3",4,4"-tetrahydro-3,3"-biacenaphthylene (5). The reaction of complex 2 with ZrCl₄ and the reaction of compound 3 with Me₃SiCl proceeded with the cleavage of the C—C bond between two acenaphthylene fragments of the [C₂₄H₁₆]^2– ansa-ligand to produce (²-C₁₂H₈)ZrCl₂(THF)₃ (6) and bis(trimethylsilyl)acenaphthene (Me₃Si)₂C₁₂H₈ (7), respectively. Compounds 1—3, 6, 7, and 11 were characterized by ¹H and ¹³C NMR spectroscopy. The temperature dependence of the ¹H NMR spectrum of compound 11 in tetrahydrofuran is indicative of the dynamic exchange of the solvent molecules in the coordination sphere of the Lu atom. After cooling of the solution to 210 K, the dynamic process was terminated as evidenced by the nonequivalence of the ¹H signals of two acenaphthylene fragments. According to the X-ray diffraction data for complex 11, dimerization of two acenaphthylene radical anions at the Lu atom gave rise to the rac-ansa-metallocene structure. In compound 11, the Lu atom is ⁵-coordinated by two five-membered rings of the acenaphthylene ligands and also by the I atom and the THF molecule. The coordination environment about the Lu atom is a distorted tetrahedron. The average distance between the lutetium atom and the carbon atoms of the five-membered rings is 2.623 .     

An approach to the structure and spectra of copper barbiturate trihydrate

In the neutral title complex [Cu(C₄N₂H₃)₂(H₂O)₃] or [Cu(BBR)₂(H₂O)₃] (BBR^– = Barbiturate), the Cu^II ion, in the slightly distorted square-pyramidal geometry, is coordinated by two O atoms of the two monodentate barbiturates and three O atoms of three water ligands. The average bond length of Cu—O (BBR^–) is 1.981(5) Å and the average bond length of Cu—O (H₂O) at the basal sites is 1.94(5) Å, i.e. much shorter than that of Cu—O (H₂O) [2.175(11) Å]. The crystal structure is characterized by an extensive network of hydrogen bonds in which each [Cu(BBR)₂(H₂O)₃] entity links to six adjacent [Cu(BBR)₂(H₂O)₃] by O(C=O) ··· H—O(H₂O) bonds. Tautomerism in the coordination process for BBR^– was found from the crystal structure and i.r. spectral analysis. The interaction of Cu^II and BBR^– in aqueous solution was also investigated by electronic spectra and electrochemical method. It was observed that the copper ion could not only form the [Cu(BBR)₂(H₂O)₃] complex in aqueous but also catalyze the decomposition of BBR^– at pH 1.1.     

Polynuclear Nickel(II) and Cobalt(II) Complexonates with Nitrilotrimethylenephosphonic Acid

Complexation in the Co(II)–H₆X–H₂O, Ni(II)–H₆X–H₂O, and Co(II)–Ni(II)–H₆X–H₂O systems (H₆X is nitrilotrimethylenephosphonic acid) was studied by spectrophotometry. The formation of binuclear complexonates Ni₂H₂X · 7H₂O, Co₂H₂X · 5H₂O, and NiCoH₂X · 6H₂O was demonstrated. These compounds were isolated from the solution, their composition was determined, the thermal stability was studied, and the kinetic parameters of dehydration were calculated.     

Solubility Properties of the Systems Chromium Salts–Amino Acids–Water

Solubility properties of the ternary systems of Cr(NO₃)₃–His–H₂O, Cr(NO₃)₃–Met–H₂O, and CrCl₃–His–H₂O (His—histidine, Met—methionine) have been investigated in the whole concentration range by the phase equilibrium semimicromethod, and the corresponding phase diagrams have been constructed. It was shown that the new complexes Cr(His)(NO₃)₃ · 3H₂O, Cr(His)₂(NO₃)₃ · 3H₂O, Cr(His)₃(NO₃)₃ · 3H₂O, Cr(His)Cl₃ · H₂O, Cr(His)₂Cl₃ · H₂O, and Cr(His)₃Cl₃ · H₂O are formed in the Cr(NO₃)₃/CrCl₃–His–H₂O system, while Cr(Met)(NO₃)₃ · H₂O and Cr(Met)₂(NO₃)₃ · H₂O complexes are formed in the system Cr(NO₃)₃–Met–H₂O. Under the guidance of the phase diagrams, the complexes were prepared and characterized by chemical and elemental analysis, IR spectroscopy, and thermogravimetry data. The influences of metal cations, anions and the structures of amino acids on the formation of complexes were discussed.     

Synthesis,crystal structure and magnetic properties of a two-dimensional mixed-valence assembly [Fe(salen)]2[Fe(CN)5NO]

A cyanide-bridged Fe^III–Fe^II mixed-valence assembly, [Fe^III(salen)]₂[Fe^II(CN)₅NO] [salen = N,N-ethylenebis(salicylideneiminato)dianion], prepared by slow diffusion of an aqueous solution of Na₂[Fe(CN)₅NO] · 2H₂O and a MeOH solution of [Fe(salen)NO₃] in an H tube, has been characterized by X-ray structure analysis, i.r. spectra and magnetic measurements. The product assumes a two-dimensional network structure consisting of pillow-like octanuclear [—Fe^II—CN—Fe^III—NC—]₄ units with dimensions: Fe^II—C = 1.942(7) Å, C—N = 1.139(9) Å, Fe^III—N = 2.173(6) Å, Fe^II—C—N = 178.0(6)°, Fe^III—N—C = 163.4(6)°. The Fe^II—N—O bond angle is linear (180.0°). The variable temperature magnetic susceptibility, measured in the 4.8–300 K range, indicates the presence of a weak intralayer antiferromagnetic interaction and gives an Fe^III–Fe^III exchange integral of –0.033 cm^–1.