Showing papers in "Russian Chemical Bulletin in 2009"

4,4′-Bis(nitramino)azofurazan and its salts. Study of molecular and crystal structure based on X-ray and quantum chemical data

Abstract: 4,4′-Bis(nitramino)azofurazan 2 was obtained by nitration of 4,4-diaminoazofurazan 1. Molecular and crystal structure of nitramine 2 and its ammonium salt 3 were studied by X-ray method and quantum chemical calculations at M052X/aug-cc-pvdz level of theory. Both compounds adopt ap-ap-ap conformation. It was shown that the structure of furazan cycle significantly depends on the nature of the substituents at carbon atoms. Crystal structures of 2 and 3 are characterized by sufficiently high density (1.996 and 1.832 g cm−3 at 110K and 1.919 and 1.766 g cm−3 at 295 K, respectively), which is provided, in particular, by strong intermolecular hydrogen bonding and π-π stacking interactions. Among substituted azofurazans and primary nitramines examined by X-ray diffraction analysis, 4,4′-bis(nitramino)azofurazan 2 is characterized by the highest density.

New dioxygen-inert triphenylantimony(v) catecholate complexes based on o-quinones with electron-withdrawing groups

Abstract: New triphenylantimony(v) catecholate complexes were synthesized by oxidative addition of sterically hindered o-benzoquinones containing electron-withdrawing substituents in different positions of the carbon ring to triphenylantimony. The complexes were characterized using IR spectroscopy, NMR spectroscopy, and cyclic voltammetry. The oxygen-inertness of the complexes is shown by NMR spectroscopy and electrochemical studies. The introduction of electron-withdrawing substituents to the catecholate ligand shifts the first oxidation potential of the complexes to the electropositive region and thus deactivates the triphenylantimony(v) catecholate complexes in the reaction with molecular oxygen.

Catalytic properties of the macromolecular polyoxomolybdate cluster in selective oxidation of sulfides

Abstract: The catalytic properties of the iron-containing Keplerate [H4Mo72Fe30O254(CH3COO)10-Mo2O7(H2O)H2Mo2O8(H2O)3(H2O)87] • (~80)H2O (1) in the selective liquid-phase oxidation of thio ethers were studied. Compound 1 shows high catalytic activity and selectivity in the oxidation of organic sulfides to sulfoxides when hydrogen peroxide and tert-butyl hydroperoxide are used as oxidants.

Thermochemical properties of dinitramidic acid salts

Abstract: Enthalpies of formation and solution of hydrazinium, guanidinium, aminoguanidinium, and triaminoguanidinium salts of nitric and dinitramidic (HN(NO2)2, DN) acids were determined by combustion and solution calorimetry methods. Enthalpies of formation of respective cations in infinitely dilute aqueous solution were calculated using the enthalpy of formation of the nitrate ion. The enthalpy of formation of the DN acid anion was determined based on the enthalpy of formation and solution of the acid salts. The weight-average enthalpy of formation of the DN acid anion equal to 8.40±0.13 kcal mol−1 was obtained. The enthalpy of solution of ammonium dinitramide (ADN) was measured (8.71±0.01 kcal mol−1). From these data, the enthalpy of formation of ADN was calculated (−32.14±0.14 kcal mol−1). The energy of combustion of ADN was measured by the calorimetry method, and the enthalpy of formation of ADN was calculated for a sample with purity above 99.9% (−32.20±0.19 kcal mol−1). The weight-average enthalpy of formation of ADN equal to −32.16±0.11 kcal mol−1 is recommended for use. Enthalpies of formation of sodium, potassium, and cesium salts of DN acid were determined.

Oxidation of activated aluminum with water as a method for hydrogen generation

Abstract: The activation of aluminum with low-melting gallium-based alloys makes it possible to obtain a material easily oxidizable by water at room temperature to release ~1.2 L of pure hydrogen per 1 g of metal. The kinetics and regularities of the interaction of activated aluminum with water were studied as a function of the amount and composition of metal activators, dispersity of the powder, and temperature. The phase composition of the solid reaction products was shown by X-ray diffraction analysis to depend on temperature and duration of the process.

Nucleophilic addition of alcohols to the C-N multiple bonds of the nitrilium substituent in the anion [2-B10H9(N≡CMe)]−

Abstract: The reactions of salts of the anion [2-B10H9(N≡CMe)]− with aliphatic alcohols ROH (R = CnH2n+1 (n = 1–6) CH2CH2(OEt), Pri, Bui, But, i-C5H11) are studied. These reactions result in hydrolytically stable imidates [2-B10H9{NH=C(OR)Me}]−. Their structures were confirmed by the data from mass spectrometry, IR, 1H, 11B, and 13C NMR spectroscopy. The molecular geometry of [2(Z)-B10H9{NH=C(OBu)Me}]−, which formed in nucleophilic addition reaction of n-butyl alcohol to [2-B10H9(N≡CMe)]−, was established by X-ray diffraction analysis.

Mechanism of nitration of nitrogen-containing heterocyclic N-acetonyl derivatives. General approach to the synthesis of N-dinitromethylazoles

Abstract: A general synthetic procedure for the synthesis of N-dinitromethyl derivatives of nitrogen-containing heterocycles has been developed. The procedure includes the destructive nitration of heterocyclic N-acetonyl derivatives of tetrazoles, 1,2,4- and 1,2,3-triazoles, pyrazoles, imidazoles and their bicyclic analogs, as well as imides of carboxylic and sulfonic acids and substituted hydrazines with mixtures of sulfuric and nitric acids. The kinetic study of the reaction mechanism was performed using UV and NMR spectroscopy. It was found that the NO2 groups were sequentially introduced into the methylene fragment by the addition of the nitronium ion to multiple bonds of intermediate enols followed by hydrolysis of the acetyl moiety. The rate and direction of the enolization (due to the CH2 and CH3 groups) of the N-acetonyl compounds in sulfuric acid solutions were determined by the study of the deuterium exchange kinetics. The synthesis of the N-dinitromethyl compounds is complicated by side reactions, such as the decomposition of intermediate α-nitroketone, the nitration of the methyl group in the acetonyl moiety, and the nitration of the dinitromethyl products to trinitromethyl derivatives.

Catalytic [2+1] cycloaddition of diazo compounds to [60]fullerene

Abstract: A catalytic method for the efficient synthesis of 5,6-open and 6,6-closed (2π+1π) fullerene adducts by [2+1] cycloaddition of ethyl 2-alkyl(hetaryl)-2-diazoacetates to [60]fullerene in the presence of a three-component catalyst Pd(acac)2—PPh3—Et3Al have been developed.

Sorbents based on N-(2-carboxyethyl)chitosan cross-linked by nanosecond electron beams

Abstract: Methods for the synthesis of new chelating chitosan derivatives containing 2-carboxyethyl groups were developed. Their macromolecules were cross-linked by the irradiation with a nanosecond electron beam, which gave for the first time sorbents with a high sorption capacity for CuII ions. The maximum sorption capacity, which is achieved in the pH range 6.5–7.2. and the Langmuir adsorption constant of Cu2+ ions on the sorbent with the degree of substitution 0.91 are 1.37 mmol g−1 and 152.51 L mol−1, respectively. The structures of the formed complexes in the sorbent phase were characterized by ESR spectroscopy.

Photochemistry of the iron(III) complex with pyruvic acid in aqueous solutions

Abstract: Photochemistry of the 1: 1 FepIII complex with pyruvic acid (PyrH) in aqueous solutions was studied by stationary photolysis and nanosecond laser flash photolysis with the excitation by the 3rd harmonics of an Nd:YAG laser. The quantum yield of [FeIIIPyr]2+ under the excitation at 355 nm is 1.0±0.1 and 0.46±0.05 in the absence and in the presence of dissolved oxygen, respectively. In experiments on laser flash photolysis, a weak intermediate absorption in the region 580–720 nm was found. The absorption was ascribed to the [FeII…MeC(O)COO•]p2+ radical complex. Laser flash photolysis of [FePyr]p2+ in the presence of methyl viologen dications (MVp2+) resulted in the formation of the MV•+ radical cations. The proposed reaction mechanism includes the inner-sphere electron transfer in the light-excited complex accompanied by the formation of the [FepII…MeC(O)COO•]p2+ radical complex followed by its transformation into the reaction products.

Microscopic mechanisms of magnetic transitions in chain polymeric copper(II) complexes with nitronyl nitroxide radicals

Abstract: Parameters of exchange interactions in heterospin chain polymeric complexes of Cu(hfac)2 (hfac is hexafluoroacetylacetonate anion) with pyrazolyl-substituted nitronyl nitroxides LR (R = Me, Et, Pr, Bu) were estimated using quantum chemical computational methods. The magnetic properties of the considered chain polymeric complexes can be described within the framework of the model of isolated exchange clusters. Experimental data on the structural dynamics of chains polymeric with “head-to-tail” (R = Me) and “head-to-head” (R = Et, Pr, Bu) motifs are discussed in the context of the concept of gradual phase transitions. Based on the analysis performed, a hypothesis of microscopic mechanisms of magnetic transitions in crystals of this type of compounds was proposed.

Nitropyrazoles 14. Synthesis of 1,3,4-trinitropyrazole and its behavior in the nucleophilic substitution reactions. General method of synthesis of 5-substituted 3,4-dinitropyrazoles

Abstract: For the first time pyrazole containing three nitro groups in the pyrazole cycle, viz., 1,3,4-tri-nitropyrazole, was obtained by N-nitration of 3,4-dinitropyrazole. 1,3,4-Trinitropyrazole enters the cine-substitution reaction of N-nitro group under the action of 0-, N-, and C-nucleophyls under mild conditions. Thus, general method of synthesis of 5-substituted 3,4-dinitropyrazoles containing free NH fragment was worked out.

Acyclic and cyclic forms of the radicals HO4⋅ CH3O4⋅ and C2H5O4·: ab initio quantum chemical calculations

Abstract: Acyclic and cyclic structures and total energies of radicals HO4⋅ CH3O4⋅ and C2H5O4· were calculated by ab initio quantum chemical methods. Depending on the computational method and basis sets used, the cyclic conformer of the HO4· radical is 4.8 to 7.3 kJ mol-1 more stable than the acyclic one. For the first two representatives of the homologous series of alkyl tetraoxyl radicals, CH3O4· and C2H5O4, MP2/6-311++G** calculations predict insignificant energy differences (1.2 kJ mol-1) between six-membered cyclic and acyclic conformers. Apparently, these radicals can exist in both forms.

“One-step” synthesis of nonsolvated aluminum hydride

Abstract: The direct reaction of lithium tetrahydroaluminate with aluminum chloride in an ether— toluene mixture at temperatures ≥90 °? was studied. Under these conditions, nonsolvated aluminum hydride is formed in a yield ≥80%. The product formed represents agglomerates with the highly developed surface and has satisfactory hydrolytic and thermal stability but an increased lithium chloride content (0.25–2.2 wt.%). The decrease in the percentage of this impurity to 0.2 wt.% is achieved by using chloroalanes AlHb3-n Clbn •xOEtb2 (n ≤ 1) instead of aluminum chloride along with vigorous stirring and an increase in the synthesis—crystallization temperature to >100 ° ?. The use of compounds based on magnesium tetrahydroaluminate, LiAlHb4• Mg(AlHb4)b2 or LiCl• Mg(AlHb4)b2, as modifying agents increases the thermal stability of the hydride and decreases the agglomeration of the crystals.

Cation binding by 21,31-diphenyl-l 2,42-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxalina-2 (2,3),3(3,2)-diindolizinacyclopentadecaphane and its acyclic analog

Abstract: The binding of cations Li+, Na+, K+, Cs+, Ag+, Zn2+, Ni2+, Co2+, NH4 + (group I), H+, Mg2+, Al3+, Ga3+ (group II), and Ca2+, Pb2+ (group III) by 21,31-diphenyl-l 2,42-dioxo- 7,10,13-trioxa-l,4(3,1)-diquinoxalina-2(2,3),3(3,2)-diindolizinacyclopentadecaphane (1), which contains two indolizine and two quinoxaline fragments and 3,6,9-trioxaundecanes spacer, and by its acyclic analog (2) was studied using cyclic voltammetry in MeCN/0.1 M Bu4NBF4. It was concluded that the ions of group I are not bound by these compounds, the ions of group II exhibit the reversible redox-switched binding by the carbamoyl groups of the quinoxaline fragments, whereas the ions of group III are bound not only by the initial compounds and radical cations 1 and 2, but also by dication 1. This binding of the Ca2+ and Pb2+ ions stabilizes dication 1.

Tetradentate nitrogen-containing ligands bis-5-(2-pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-ones and their coordination compounds with CuI and CuII

Abstract: Tetradentate N4-type organic ligands containing two 5-(2-pyridylmethylidene)-2-thio-3,5-dihydro-4H-imidazol-4-one fragments linked by two-, four-, or six-carbon polymethylene bridges between the sulfur atoms were synthesized. Mono- and dinuclear complexes of these ligands with copper(II) chloride, as well as with copper(I) and copper(II) perchlorates, were prepared. The structure of the coordination compound (5Z,5′Z)-2,2′-(butane-1,2-diyl-disulfanyldiyl)bis-5-(2-pyridylmethylidene)-3-phenyl-3,5-dihydro-4H-imidazol-4-one with copper(I) perchlorate was established by X-ray diffraction. The copper atom in this complex is in a distorted tetrahedral coordination formed by four nitrogen atoms of two imidazole and two pyridine rings. The perchlorate anion is located in the outer sphere of the complex and is not involved in the coordination with the copper ion. The electrochemical study of the ligands and the complexes was carried out by cyclic voltammetry and rotating disk electrode voltammetry. The initial reduction of the complexes under study occurs at the metal atom. The length of the polymethylene bridge in the ligand has only a slight effect on the redox properties of the ligands and the complexes.

Synthesis and reactions of 3-acetyl-6-methyl-2-(methylthio)pyridine

Abstract: A reaction of methyllithium with 3-cyano-6-methylpyridine-2(1 H)-thione followed by alkylation of the resulting 3-acetylpyridinethione, or a direct reaction of methyllithium with 3-cyano-6-methyl-2-(methylthio)pyridine, afforded 3-acetyl-6-methyl-2-(methylthio)pyridine. The ketone obtained was examined in bromination reactions under various conditions. Bromi-nation in methanol or chloroform, proceeding through the formation of sulfonium bromides, gave substituted 3-(bromoacetyl)pyridine. A reaction of 3-acetyl-6-methyl-2-(methyl-thio)pyridine with N-bromosuccinimide in CCl4 afforded N-(pyridinesulfenyl)succinimide. The bromo ketone was used for the synthesis of various heterocyclic compounds.

Concentration profile of vapor—liquid interface for spherical drops

Abstract: The modified lattice-gas model is used to construct the model and the concentration profiles of the liquid—vapor for spherical drops of different size. A monotonic character of the temperature dependence of the width of the transition layer between the liquid and the vapor is demonstrated. The dependence of the surface tension on the drop size was studied. The calculation was carried out in the quasichemical approximation, which takes into account the correlation effects of the neighboring interacting molecules. The results are in qualitative agreement with earlier density functional theory calculations and calculations by the van der Waals theory of capillarity. The numerical analysis of the molecular model of the spherical drop gives two types of solution, which correspond to equilibrium and metastasble states of the drop.

Synthesis of 3,4,5-trinitropyrazole

Abstract: A first representative of exhaustively C-nitrated pyrazoles was obtained by oxidation of 5-amino-3,4-dinitropyrazole.

A new convenient four-component synthesis of 6-amino-2H, 4H-pyrano[2,3-c]pyrazole-5-carbonitriles and one-pot synthesis of 6 ′-amino-5-cyano-1,2-dihydrospiro-[(3H)-indole-3,4 ′-(4 ′H)-pyrano[2,3-c]pyrazol]-2-ones

Abstract: A new convenient method for the synthesis of 6-amino-2H,4H-pyrano[2,3-c]pyrazole-5-carbonitriles, namely, four-component condensation of carbonyl compounds (aromatic aldehydes, heterocyclic ketones), malononitrile, β-keto esters, and hydrazine hydrate in ethanol in the presence of triethylamine as a catalyst, which occurs selectively, is developed. One-pot two-step modification of this method is proposed for the synthesis of spiro[(3 H)-indole-3,4 ′-(4′H)-pyrano[2,3-c]pyrazol]-2-ones.

Insertion of carbon disulfide and the nitrile group into the diaziridine ring of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in ionic liquids catalyzed by BF3 · Et2O

Abstract: The present study revealed two new reactions resulting in the diaziridine ring expansion, viz., the insertion of the CS2 molecule and the CN group of activated nitriles into the C—N bond of the diaziridine fragment of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes. These reactions can be performed only in ionic liquids in the presence of BF3 · Et2O as the catalyst. Based on these reactions, we developed simple one-pot methods for the synthesis of 3-aryldihydro-5 H-pyrazolo[1,2- c][1,3,4]thiadiazole-1-thiones and 1-aryl-6,7-dihydro-1 H,5H-pyrazolo-[1,2-a][1,2,4]triazoles in high yields. Dipolar intermediates of new reactions, which are direct precursors of the final products, were detected by NMR methods. One of the intermediates was isolated and characterized. The reaction of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with benzoyl cyanide affords (2-benzoyrpyrazolidin-1-yl)(aryl)acetonitriles.

Metal phthalocyanine-catalyzed addition of polychlorine-containing organic compounds to C=C bonds

Abstract: Organopolychlorine compounds (CCl4, CCl3CO2Et, CCl3CHO) add at the double bond of various olefins under the catalysis of the metal phthalocyanine complexes. A possibility of quantitative catalyst recovery was shown.

Thermodynamic and kinetic analysis of metal ion complexation by photochromic spiropyrans

Abstract: This review focuses on the results of the studies of metal ion complexation by spiropyrans published mostly in recent years. Introduction of ionophore substituents in the molecules of photochromic spiropyrans induces a reasonably strong bonding in the complexes of these compounds with metal ions. The degree of complexation depends on the state (open or closed) of the photochromic spiropyran fragment. Directed synthesis of structures able to form complexes with metal ion requires knowledge of structure-property relationships based, among other, on the studies of the compounds synthesized earlier. This requires accurate determination of thermodynamic and kinetic parameters of complex formation. Difficulties of such quantitative analysis due to the presence of several interrelated equilibria in the system are discussed.

Synthesis and transformations of metallacycles

Abstract: An efficient method for the synthesis of spiro[3.3]heptanes and spiro[3.4]octanes of various structures has been developed using cycloalumination of substituted methylidenecyclobutanes with Et3Al in the presence of Cp2ZrCl2. A possibility of transformation of the in situ formed spiroaluminacyclopentanes to the corresponding thiophanes, selenophanes, and cyclopentanols in high yields and selectivity has been demonstrated.

Activation of small molecules by a rhodium bis(phosphinite) pincer complex

Abstract: Rhodium hydrido chloride pincer complex RhH(Cl)[2,6-(Buptb2PO)b2Cb6Hb3] was synthesized and used for the preparation of new complexes with labile two-electron ligands Rh(L)[2,6-(Buptb2PO)b2Cb6Hb3] (L = MeCN or S(CHb2)b4) and complexes with small molecules, such as CO, Ob2, Hb2, and Nb2.

Stereoselective [2+2] photocycloaddition in bispseudosandwich complexes of bis(18-crown-6) stilbene with alkanediammonium ions

Abstract: Due to hydrogen bonding, bis(18-crown-6) stilbene forms 1 : 1, 1 : 2, and 2 : 2 complexes with H3N+(CH2)nNH3+ 2ClO4− salts (n = 2—10, 12). The length of the polymethylene chain in the diammonium ions affects the phototransformation direction of stilbene and the composition of the products. In the 2: 2 bispseudosandwich complexes with relatively short alkanediammonium ions (n = 2—4), the stereoselective reaction of [2+2] photocycloaddition proceeds to form mainly the rctt-isomer of the cyclobutane derivative. The structure of rctt-cyclobutane derivative as a complex with H3N+(CH2)4NH3+2ClO4- was confirmed by X-ray diffraction analysis.

Synthesis of substituted dibenz[ b,f ]oxepines from 2,4,6-trinitrotoluene

Abstract: 1,3-Dinitro[b,f]dibenzoxepine undergoes nucleophilic substitution with O-and S-nucleophiles, the nitro group at position 1 (peri-nitro group) being selectively replaced. The factors responsible for the selectivity of the reaction are discussed.

Chemical bonding in the crystal structure of 1-hydrosilatrane

Abstract: A study has been made of the crystal and molecular structure of 1-hydrosilatrane HSi(OCH2CH2)3N. The quantum chemical calculations of its crystal structure have been carried out. According to an estimate of the energy, the coordination bond N→Si is by 5 kcal mol−1 stronger than that in the crystal of 1-methylsilatrane. The charge values calculated within the framework of the topological analysis of the electron density demonstrate that the electron density of the coordination bond N→Si is primarily transferred to the region of the equatorial bonds Si—O and, to a lesser extent, to the bond Si—H. On going from the isolated molecule of 1-hydrosilatrane to its crystal, the interatomic distance N—Si decreases, mainly owing to the weak intermolecular interaction C—H...O.

Reaction of tellurium tetrachloride with acetylene

Abstract: Addition of TeCl4 to acetylene affords hitherto unknown (E,E)-bis(chlorovinyl)tellurium dichloride (II), which represents a promising intermediate for the synthesis of organotellurium products.

Synthesis and spectral properties of 4-amino- and 4-acetylamino-N-arylnaphthalimides containing electron-donating groups in the N-aryl substituent

Abstract: A method for the synthesis of N-aryl-substituted 4-amino- and 4-acetylaminonaphthalimide derivatives with mono- and dialkoxy groups or a 15-crown-5 moiety in the N-aryl substituent is described. The introduction of electron-donating alkoxy groups into the benzene ring of the N-aryl fragment results in fluorescence quenching of the naphthalimide chromophore, which is most pronounced in the spectra of N-acetyl derivatives. The photophysical properties of the synthesized 4-amino- and 4-acetylaminonaphthalimides depend on the solvent polarity and its specific solvating ability due to H-bonding. The crown-containing compounds are promising fluorescent chemosensors for metal cations.