Showing papers in "Russian Chemical Bulletin in 2005"

PRIRODA-04: a quantum-chemical program suite. New possibilities in the study of molecular systems with the application of parallel computing

Abstract: Main characteristics are described of the PRIRODA quantum-chemical program suite designed for the study of complex molecular systems by the density functional theory, at the MP2, MP3, and MP4 levels of multiparticle perturbation theory, and by the coupled-cluster single and double excitations method (CCSD) with the application of parallel computing. A number of examples of calculations are presented.

Catalytic oxidation of olefins and alcohols with hydrogen peroxide in a two-phase system giving mono- and dicarboxylic acids

Abstract: The present study considered the influence of various factors on the catalytic activity of systems based on a combination of tetrakis(oxodiperoxotungsto)phosphate(3−) with quaternary ammonium cations, for example, with methyltri-n-octylammonium [Me(n-C8H17)3N]+. The catalysts were tested in oxidation of cycloolefins (cyclohexene and cyclooctene), alcohols (octan-1-ol and phenylmethanol), and unsaturated fatty acids (cis-9-octadecenoic and 12-hydroxy-9Z-octadecenoic acids) with a 30% hydrogen peroxide solution. These reactions proceed under mild conditions (atmospheric pressure, 80–90 °C) to give carboxylic acids. The catalytic systems were characterized by vibrational (IR and Raman) spectroscopy. The state of the systems formed from various precursors, viz., polyoxometallates and phase-transfer catalysts, was studied. It was demonstrated for the first time that the structure formation of peroxo complexes depends on the nature of the halide anion of the quaternary ammonium salt used. The melting points of individual catalytic complexes were determined. The optimal conditions for oxidation were found.

Promising avenues of research in nanoscience: chemistry of semiconductor nanoparticles

Abstract: The state-of-the-art in the field of research on semiconductor nanoparticles is analyzed; cadmium chalcogenide nanoparticles are considered in most detail. Emphasis is placed on the methods of synthesis and on control of the size, composition, and structure of semiconductor nanoparticles — “quantum dots”. The state of the surface plays a significant role in determining the properties of nanoparticles. Organized nanostructures comprised of quantum dots are considered. The properties of semiconductor nanoparticles are described. Prospects for applications of semiconductor nanomaterials are discussed.

Enantioselective hydrogenation of levulinic acid esters in the presence of the RuII-BINAP-HCl catalytic system

Abstract: The rate of hydrogenation of γ-ketoesters MeCOCH2CH2COOR (R = Et, Pri, But) in the presence of the chiral RuII—BINAP catalyst (BINAP is 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5–10 equivalents of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially formed would cyclize by ∼95% to give γ-valerolactone with optical purity of 98–99% ee. When the Ru(COD)(MA)2—BINAP—HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester (R = Et) in EtOH is attained in 5 h at 60 °C under an H2 pressure of 60–70 atm.

Selective synthesis and spectroscopic properties of alkyl-substituted lanthanide( III ) mono-, di-, and triphthalocyanines

Abstract: Methods for the selective synthesis of mono-(RPcLnOAc), di-(RPc2Ln), and triphthalocyanines (RPc3Ln2) of rare-earth metals (Ln = Lu, Er, Eu) from symmetrically substituted 2,3,9,10,16,17,23,24-octaalkylphthalocyanines RPcH2 (R = Et, Bu) were developed. The synthesized complexes were characterized by NMR spectroscopy, mass spectrometry, and electronic absorption spectra. The conditions for 1H NMR spectra recording were optimized. Regularities in changing the spectral properties of the synthesized compounds, depending on the lanthanide nature and the planarity of metal phthalocyanine complexes, were found.

Gas phase kinetic and theoretical studies of reactions of germylenes and dimethylstannylene

Abstract: The results of time resolved gas phase studies of labile germylenes (GeH2 and GeMe2) and dimethylstannylene (SnMe2) reactions reported to date are considered together with data of quantum-chemical investigations of the potential energy surfaces of these systems. Reaction mechanisms are discussed. A comparison of reactivity in the series of carbene analogs, ER2 (E = Si, Ge, Sn, R = H, Me), is made.

Acceptor-type graphite intercalation compounds and new carbon materials based on them

Abstract: The problems of synthesis and study of the physicochemical properties of graphite intercalation compounds (GIC) formed upon insertion of various molecules into the interplanar space of graphite are considered. Binary and ternary intercalation compounds with protonic acids (HNO3, CH3COOH, H3PO4, H2SO4, etc.) are described. The results of systematic research into graphite intercalation by potentiometry, calorimetry, powder X-ray diffraction, conductivity measurements, DTA, chemical analysis, and other methods are given. These results underlie elucidation of the characteristic and peculiar features of acid insertion into graphite. The physicochemical properties and practical applications of GIC and low-density carbon materials are analyzed.

Nature of weak inter- and intramolecular contacts in crystals 2. Character of electron delocalization and the nature of X—H...H—X (X = C, B) contacts in the crystal of 1-phenyl-o-carborane

Abstract: High-resolution single crystal X-ray study of 1-phenyl-o-carborane was carried out and the experimental and theoretical (B3LYP/6-311G** calculated) electron density distributions in the title compound were investigated. Character of electron delocalization in 1-phenyl-o-carborane was examined by analyzing the deformation electron density maps, maps of the Laplacian of the electron density, and maps of the electron localization function. Crystal-structure-forming X—H...H—X (X = C, B) intermolecular contacts were revealed and analyzed. The energies and geometric parameters of these contacts were compared with the results of quantum chemical calculations of the crystal structure and with characteristics of the same type of intramolecular contacts.

Palladium-catalyzed activation of E-E and C-E bonds in diaryl dichalcogenides (E = S, Se) under microwave irradiation conditions

Abstract: The first example of palladium-catalyzed stereoselective addition of diphenyl disulfide and diphenyl diselenide to the triple bond of terminal alkynes under microwave irradiation conditions is described. It was found that both the element—element (E-E) and carbon—element bonds can be activated in the catalytic system studied. The products of both reactions were isolated in quantitative yields. According to quantum-chemical calculations, the reaction mechanism involves the oxidative addition of the E-E bond to Pd0. Depending on the microwave power and reaction conditions, the next stage is either the reaction with alkyne or the carbon—element bond activation. The product of the oxidative addition of Ph2Se2 to Pd0, namely, dinuclear complex [Pd2(SePh)4(PPh3 2], was detected by 31P{1H}NMR spectroscopy directly in the Ph2Se2/PPh3 melt formed under microwave irradiation conditions.

Synthesis and spectral properties of malononitrile-based merocyanine dyes

Abstract: Di-, tetra-, and hexamethine merocyanines derived from malononitrile and heterocycles with moderate (dyes 1–6), strong (7–9), and weak (10 and 11) electron-releasing ability were synthesized. The electronic structures of merocyanines 10 and 11 are similar to the neutral polyene state, whereas those of 7–9 are similar to the ideal polymethine state. These tendencies become more pronounced with increasing length of the polymethine chain. The merocyanines derived from heterocyclic residues with weak or moderate electron-releasing ability exhibit a positive solvatochromism, whereas those with strong electron-releasing ability show a negative solvatochromism. An increase in the polarity of the solvent makes the former compounds more similar to polymethines, whereas the latter become more similar to polyenes bearing opposite charges on the end groups. The nature of the factors (nonspecific solvation, specific nucleophilic and electrophilic solvation, and vibronic interactions) responsible for the observed characteristic features was analyzed.

Polysaccharides of Algae 58. The polysaccharide composition of the Pacific brown alga Alaria fistulosa P. et R. (Alariaceae, Laminariales)

Abstract: Quantitative determination of mannitol, fucoidan and alginate in different parts of the thallus (the blade, the midrip, the sporophylls, and the stipe with rhizoids) of the brown alga Alaria fistulosa, collected from the coastal waters of Paramushir Island, was carried out. Sporophylls were shown to differ considerably in carbohydrate composition from all other parts of the plant. In particular, the fucoidan content in sporophylls is several times as high as that in the blade. Alginate preparations isolated from sporophylls and from blade have different proportions of monomers (mannuronic acid and guluronic acid residues) and different molecular masses. Fucoidan preparations isolated from these parts of the plant differ slightly in the sulfate content. Their specific feature is a rather high galactose content comparable with the content of fucose. The sporophylls of A. fistulosa may be regarded as a rich source for practical isolation of fucoidan.

Ground-state multiplicity of acylnitrenes : computational and experimental studies

Abstract: The singlet—triplet energy splitting (ΔE ST = E S − E T ) was calculated for formylnitrene (5) and for the syn- and anti-rotamers of carboxynitrene HOC(O)N (6) by the CCSD(T) method. Extrapolation of ΔE ST to a complete basis set was calculated to be negative for 5 and strongly positive for 6. Similar results were obtained by the G2 procedure. The reason for the dramatic stabilization of the singlet state appeared to be a special bonding interaction between the nitrogen and oxygen atoms, which results in the structure intermediate between those of nitrene and oxazirene. It was found that the B3LYP/6-31G(d) method overestimates ΔE ST by ∼9 kcal mol−1 for 5 and by ∼7 kcal mol−1 for 6. Taking into account this overestimation and the results of DFT calculations, it was concluded that benzoylnitrene has a singlet ground state. It was proved experimentally using photolysis of benzoyl azide in an argon matrix at 12 K that benzoylnitrene has a singlet ground state and its structure is similar to that of oxazirene. Nevertheless, these singlet intermediates have low barrier to the aziridine formation, which is traditionally considered to be a typical singlet nitrene reaction.

Mechanism of Cp2ZrCl2-catalyzed olefin hydroalumination by alkylalanes

Abstract: The composition of intermediates of the Cp2ZrCl2-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBui 2, AlBui 3, ClAlBui 2) was studied by dynamic 1H and 13C NMR pectroscopy. The reaction of Cp2ZrCl2 with isobutylalanes affords the complex (Cp2ZrHCl·HAlBui 2)2 responsible for α-olefin hydroalumination.

Synthesis of hydroxyapatite by hydrolysis of α-Ca3(PO4)2

Abstract: Conditions for hydroxyapatite (HAP) synthesis in aqueous solutions by hydrolysis of α-Ca3(PO4)2 were studied. Temperature exerts a substantial effect on the rate of α-Ca3(PO4)2 hydrolysis and also changes the morphology of the reaction products. At 40 °C, the plate-like intersecting (perpendicular to the surface of the initial particles) crystals of HAP grow. Their maximum size after the 24-h hydrolysis is 1–2 µm. Needle like HAP crystals are formed upon boiling of the suspension. The morphology observed for the HAP particles agrees well with the conclusions obtained by analysis of the kinetics of tricalcium phosphate hydrolysis.

Synthesis and structures of C60 fullerene chlorides

Abstract: Systematic study of chlorination of fullerene C60 with inorganic chlorides SbCl5, VCl4, MoCl5, and KICl4 was carried out. Higher chlorofullerenes, viz., T h -C60Cl24, C60Cl28, C2-C60Cl30, and D3d-C60Cl30, can be prepared depending on the temperature and time of chlorination. The molecular and crystal structures of C60Cl24⋅VOCl3, C60Cl30⋅2CS2, and C60Cl30O1.22 were determined by single-crystal X-ray diffraction. Fullerenes C60Cl28 and C2-C60Cl30 were shown to be only kinetically stable, whereas D3d-C60Cl30 is a thermodynamically stable product. Transformations of less chlorinated fullerenes into more chlorinated products are accompanied by substantial changes in the addition patterns.

Synthesis of new chiral mono-, di-, tri-, and tetraalkylglycolurils

Abstract: Two general procedures were developed for the synthesis of chiral N-mono-, N, N′-di-, N, N′ N″-tri-, and N, N′, N″, N′″-tetraalkylglycolurils based on the reactions of 4,5-dihydroxy-imidazolidin-2-ones or glyoxal with one or two moles of alkylureas, respectively, by acid catalysis. The reactions of N-monoalkyl- and N, N′-dialkylureas with glyoxal proceed regioselectively. The mechanism of these reactions was suggested and partly confirmed by quantum-chemical calculations and experimental data. The enantiomeric separation of some chiral glycolurils by chiral-phase HPLC was carried out for the first time.

Mechanism and structural aspects of thermal Curtius rearrangement. Quantum chemical study

Abstract: The electronic and geometric structures of formyl, acetyl, and benzoyl azides were studied and fragments of the potential surfaces for the thermal Curtius rearrangement of these azides into the corresponding isocyanates were calculated by density functional theory at the PBE/TZ2P level. Acyl azides adopt two stable, conformations syn and anti, with respect to the C-N bond. The syn conformers are more stable than their anti analogs. The activation energies of the syn-anti isomerization in the series under study are 9.4, 7.0, and 9.2 kcal mol−1, respectively, and the activation energies of the reverse reaction are 8.5, 6.1, and 2.5 kcal mol−1. The rearrangement of syn-acyl azides is a one-step process, in which elimination of N2 occurs synchronously with the rearrangement of atoms and bonds to form isocyanates. The activation energies of the rearrangements of syn-HC(O)N3, syn-MeC(O)N3, and syn-PhC(O)N3 are 28.0, 32.9, and 34.5 kcal mol−1, respectively. The rearrangement of the anti conformers of the above-mentioned azides involves the formation of singlet acylnitrene. The activation energies of the latter process are 34.6, 32.9, and 32.3 kcal mol−1, respectively. The activation energies of the rearrangement of acylnitrenes into isocyanates are 20.9, 18.9, and 13.6 kcal mol−1, respectively. The energy characteristics of the process and the structural data for the starting compounds, final products, and transition states provide evidence that the thermal Curtius rearrangement occurs predominantly by a concerted mechanism.

Synthesis and some properties of 6-di(tri)fluoromethyl- and 5-di(tri)fluoroacetyl-3-methyl-1-phenylpyrano[2,3-c]pyrazol-4(1H)-ones

Abstract: Condensation of 4-acetyl-5-hydroxy-3-methyl-1-phenylpyrazole with RFCO2Et (RF = CF2H, CF3) in the presence of LiH affords 4-di(tri)fluoroacetoacetyl-5-hydroxy-3-methyl-1-phenylpyrazoles from which 6-di(tri)fluoromethyl-and 5-di(tri)fluoroacetyl-3-methyl-1-phenylpyrano[2,3-c]pyrazol-4(1H)-ones were synthesized. The reactions of pyrano-pyrazoles with hydrazine hydrate, ethyl mercaptoacetate, or aromatic amines proceed at the C(6) atom with pyrone ring opening and formation of aminoenones, pyrazoles, or thiophenes with the 5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl fragment.

Synthesis of organochalcogen compounds in basic reducing systems

Abstract: The review surveys the data on the synthesis of organosulfur,-selenium, and-tellurium compounds in basic reducing systems. Good prospects of the hydrazine hydrate—alkali system are demonstrated.

Synthesis and crystal structure of a supramolecular adduct of trinuclear molybdenum oxocluster with macrocyclic cavitand cucurbit[5]uril containing the included ionic associate Na+...Cl...Na+

Abstract: The compound of composition [{Mo3O4(H2O)6Cl3}2(Na2Cl⊂ C30H30N 20O10)]Cl3⋅14H2O (1) was prepared by evaporation of a hydrochloric acid solution containing NaCl, the trinuclear aqua complex [Mo3O4(H2O)9]4+, and the macrocyclic cavitand cucurbit[5]uril (C30H30N20O10). X-ray diffraction analysis demonstrated that the cucurbit[5]uril molecule is closed on both sides by the cluster cations through hydrogen bonding between the CO groups of the cucurbit[5]uril portals and the aqua ligands of the oxo cluster. The inner cavity of the supramolecular adduct includes an unusual ionic associate Na+...Cl...Na+. The sodium cations are coordinated by five carbonyl oxygen atoms of each portal of the macrocycle. Compound 1 is the first structurally characterized complex, in which the macrocyclic cucurbit[5]uril ligand is directly coordinated to the alkali metal cation.

Liquid-phase noncatalytic butene oxidation with nitrous oxide

Abstract: The kinetics and mechanism of noncatalytic liquid-phase oxidation of but-1-ene and but-2-ene with nitrous oxide in a benzene solution in the temperature range from 180 to 240°C were studied. Oxidation proceeds via the 1,3-dipolar cycloaddition mechanism to form carbonyl compounds. Both of these reactions occur with close rates and activation energies and have the first orders with respect to the alkene and N2O. A considerable fraction (39%) of but-1-ene involved in oxidation undergoes cleavage at the double bond yielding propanal and an equivalent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but-2-ene proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation of terminal and internal alkenes C2—C8 with nitrous oxide were analyzed using the previously published data.

New subvalent bismuth telluroiodides incorporating Bi2 layers : the crystal and electronic structure of Bi2TeI

Abstract: Two new subvalent bismuth telluroiodides, Bi2TeI and Bi4TeI1.25, were prepared by the gas-phase synthesis. The compositions of these phases were determined by energy-dispersive X-ray spectroscopy. X-ray diffraction study of melt grown Bi2TeI single crystals demonstrated that the compound crystallizes in the monoclinic system (space group C/2m) with the unit cell parameters a = 7.586(1) A, b = 4.380(1) A, c = 17.741(3) A, β = 98.20°. The layered crystal structure of Bi2TeI consists of weakly bonded two dimensional blocks with a stoichiometry of the title compound. The blocks are stacked along the c axis. Each block consists of eight atomic layers alternating in the Te-Bi-I-Bi-Bi-I-Bi-Te order and includes a double layer of bismuth atoms. Based on the results of ab initio quantum-chemical calculations, the title compound is expected to possess a pronounced anisotropy of conductivity.

Synthesis of bithiophenesilane dendrimer of the first generation

Abstract: The synthesis of tris{5′-[methylbis(2-thienyl)silyl]2,2′-bithienyl-5-yl} methylsilane, a first-generation bithiophenesilane dendrimer, is described. The conditions of effective formation of methyltrithienylsilane were found; methyltris(5-bromo-2-thienyl)silane and a number of other monofunctional derivatives of methyltrithienylsilane were synthesized for the first time. The advantages and drawbacks of the Suzuki and Kumada reactions for the formation of bithienyl fragments in the synthesis of oligothienylsilane dendrimers are discussed.

Adsorption and catalytic conversion of hydrocarbons on nanosized gold particles immobilized on alumina

Abstract: Gold and nickel particles immobilized on alumina were prepared by the metal vapor synthesis and anionic adsorption methods. The dispersion of metals was determined by X-ray diffraction and transmission electron microscopy. The activity of nanoparticles, tested in model catalytic reactions of CCl4 addition to multiple bonds and allyl isomerization of allylbenzene, changes in a wide range (from 1 to 3000 (mole of product) (mole of Au)−1 h−1) and is parallel to the chromatographically measured heats of adsorption of the corresponding unsaturated substrates. The heat of adsorption of unsaturated hydrocarbons can serve as a criterion for the efficiency of the gold-containing catalyst in olefin conversion.

Quinone imines and aminophenols as precursors of new heterocycles

Abstract: Cyclization of substituted quinone imines and diazabutadiene derivatives of aminophenols affords 4aH-phenoxazine or 4H-1,4-benzoxazine derivatives, which are finally transformed into the following fused heterocycles: the stable 1,4,6,8-tetra(tert-butyl)phenoxazin-10-yl radical and 7a,14a,15a, 15b-tetrahydro-14,16-dioxa-5,9-diaza-8,15-ethenohexaphene and 5a,6,11a, 12-tetrahydro[1,4]benzoxazino[3,2-b][1,4]benzoxazine derivatives. The influence of the substituents on the pathways of the reactions of intermediate benzoxazines and phenoxazines, such as oxidation, [2+4] dimerization, and the closure of the second ring, was studied. The structures of the fused heterocycles were determined by X-ray diffraction, NMR spectroscopy, and ESR.

Stereospecific solid-state [2+2] autophotocycloaddition of a styryl dye containing a 18-crown-6 fragment

Abstract: A procedure was developed for the synthesis of a 18-crown-6-containing styryl dye of the pyridine series Phototransformation products of the dye that formed upon irradiation with visible light in solution, films, and crystals were studied by 1H and 13C NMR spectroscopy and spectrophotometry Irradiation of solutions of this dye in acetonitrile leads only to reversible E-Z photoisomerization of the C=C bond Irradiation of a film of the dye induces stereospecific [2+2] photocycloaddition to form exclusively the rctt isomer of tetrasubstituted cyclobutane The latter was found to undergo base-catalyzed isomerization giving rise to the rcct isomer X-ray diffraction study showed that photocycloaddition occurs in single crystals without their destruction The structures of the E isomer of the dye and the resulting rctt isomer of the cyclobutane derivative were established The characteristic features of the molecular packing of the dye favorable for topochemical photocycloaddition in the crystal and the structural changes that accompany the cyclobutane formation are discussed

Substrate and positional selectivity in electrophilic substitution reactions in pyrrole, furan, thiophene, and selenophene derivatives and related benzoannelated systems

Abstract: Data on the relative reactivities (substrate selectivity) of five-membered heterocycles in electrophilic substitution reactions and positional selectivity (α : β ratio) in these reactions were analyzed. Unlike the substrate selectivity (pyrrole ≫ furan > selenophene > thiophene) determined by the position of heteroatoms in the Periodic Table, the positional selectivity decreases in the order corresponding to the change in the relative stability of the onium states of the elements (O+ < Se+ ≤ S+ < N+) and reflects the predominant role of heteroatoms in the stabilization of σ complexes formed upon β-substitution. These differences in the positional selectivity of the parent heterocycles have a substantial effect on the orientation in electrophilic substitution reactions in their derivatives and the corresponding benzoannelated systems. This interpretation was confirmed by ab initio quantum chemical calculations (RHF/6–31G(d) and MP2/6– 31G(d)//RHF/6–31G(d)) and density functional theory calculations (B3LYP/6–31G(d)). Quantum chemical calculations were performed by the above-mentioned methods for model N-R-pyrroles (R = Me, Et, Pri, But, CH=CH2, C≡CH, Ph, PhSO2, and 4-O2NC6H4) and their α- and β-protonated σ complexes. The results of these calculations demonstrated that it is the steric factors and charges on the β-C, α-C, and N atoms and the substituents at the N atom (the kinetic control), as well as the nature of the electrophile, rather than the difference in the relative stabilities of the onium states of N+ (which depends on the nature of the substituent at the N atom and reflects the role of the heteroatom in stabilization of σ complexes formed via β-substitution; the thermodynamic control) that are responsible for the type of orientation (α or β) that prevails.

New approaches to synthesis of tris[1,2,4]triazolo[1,3,5]triazines

Abstract: Thermal cyclization of 3-R-5-chloro-1,2,4-triazoles (R = Cl, Ph) afforded 2,6,10-tri-R- tris[1,2,4]triazolo[1,5-a:1′,5′c:1″,5″-e][1,3,5]triazines 5 (R = Ph) and 7 (R = Cl). These compounds are first representatives of this class of heterocycles, whose structures were unambiguously established. Treatment of these compounds with nucleophiles (H2O/NaOH, NH3) results in the triazine ring opening to give compounds consisting of three 1,2,4-triazole rings linked in a chain. For example, treatment of cyclic compound 5 with aqueous alkali affords 3-phenyl-1-3-phenyl-1-(3-phenyl-1H-1,2,4-triazol-5-yl)-1,2,4-triazol-5-yl-1H-1,2,4-triazol-5-one. Treatment of 3,7,11-triphenyltris[1,2,4]triazolo[4,3-a:4′,3′c:4″,3″-e][1,3,5]triazine (2) with HCl/SbCl5 leads to the triazine ring opening giving rise to 5-(3-chloro-5-phenyl-1,2,4-triazol-4-yl)-3-phenyl-4-(5-phenyl-1H-1,2,4-triazol-3-yl)-1,2,4-triazole. Thermal cyclization of the latter produces 3,7,10-triphenyltris[1,2,4]triazolo[1,5-a:4′,3′c:4″,3″-e][1,3,5]triazine (13). Thermolysis of both cyclic compound 2 and cyclic compound 13 is accompanied by the Dimroth rearrangement to yield 3,6,10-triphenyl-tris[1,2,4]triazolo[1,5-a:1′, 5′-c:4″,3″-e][1,3,5]triazine (14). Compounds 13 and 14 are the first representatives of cyclic compounds with this skeleton. 13C NMR spectroscopy allows the determination of the isomer type in a series of tris[1,2,4]triazolo[1,3,5]triazines.

Synthesis and electrochemical study of complexes of 2-methylthio-5-(pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-ones with transition metals (Co, Ni, and Cu). Molecular structures of CuIIL1Cl2 (L1 is (5Z)-2-methylthio-3-phenyl-5-(α-pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-one) and CoIIL2Cl2 (L2 is (5Z )-3-methyl-2-methylthio-5-(α-pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-one)

Abstract: New transition metal (NiII, CoII, and CuII) complexes with 2-methylthio-5-(pyridyl-methylidene)-3,5-dihydro-4H-imidazol-4-ones were synthesized by the reaction of 5-(α-, β-, or γ-)pyridyl-substituted 2-methylthio-3,5-dihydro-4H-imidazol-4-ones with MCl2· nH2O. In the complexes with α-Py-substituted ligands, the metal atom has a tetrahedral coordination environment and is coordinated by the nitrogen atoms of the pyridine and thiohydantoin rings and two chloride anions. The results of electronic spectroscopy and magnetic susceptibility measurements suggest that the complexes with the β-and γ-Py-substituted ligands have polymeric structures, and the metal atoms in these complexes are in an octahedral environment. The molecular and crystal structures of CuIIL1Cl2 (L1 is (5Z)-2-methylthio-3-phenyl-5-(α-pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-one) and CoIIL2Cl2 (L2 is (5Z)-3-methyl-2-methylthio-5-(α-pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-one) were established by X-ray diffraction. Semiempirical quantum-chemical calculations were performed for 2-methylthio-5-(pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-ones. The complexes, starting ligands, and metal chlorides were studied electrochemically. The mechanism of electro-oxidation and electroreduction of 2-methylthio-5-(pyridylmethylidene)-3,5-dihydro-4H-imidazol-4-ones and their cobalt, nickel, and copper complexes was proposed.

Synthesis of nitro, nitroso, azo, and azido derivatives of (4-R1-5-R2-1,2,3-triazol-1-yl)-1,2,5-oxadiazoles by oxidation and diazotization of the corresponding amines

Abstract: Nitro-, nitroso-, and azo-1,2,5-oxadiazoles with 4-R1-5-R2-1,2,3-triazol-1-yl substituents were synthesized by oxidation of amino-(1,2,3-triazol-1-yl)-1,2,5-oxadiazoles (aminotriazolylfurazans). Azido-1,2,5-oxadiazole was prepared by diazotization of amino(triazolyl)furazan followed by treatment of the diazonium salt with sodium azide. Depending on the nature of the substituents and the reagent, triazolylfurazans can undergo destruction to give amino-R-furazans (R = NO2, N3, aminofurazanylazo), the amino group being formed from the triazole ring.