Reduction requirements for Ru/(K)Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> catalytic activity in water-gas shift reaction

This paper is focused upon the influence of potassium on the reduction behavior and catalytic properties of Fe₂O₃, Ru/Fe₂O₃ and Ru/(K)Fe₂O₃ catalysts for the water gas shift (WGS) reaction. The effect of promotion by potassium is attributed to stabilization of a highly dispersed ruthenium phase on the iron oxide surface. The hydrogen reduction behavior of Fe₂O₃ catalysts is strongly influenced by time-pressure dependent processes and comprises two or three heavily overlapped TPR peaks which can be ascribed to the following stages of the iron(III) oxide reduction 3Fe₂O₃ 2Fe₃O₄ 6FeO 6Fe. The appearance of FeO as an intermediate phase was confirmed by XRD. The presence of ruthenium(IV) oxide substantially changes the kinetics of the reduction process. In the case of potassium-doped catalysts, the reduction of Fe₂O₃ is substantially different and is assigned to the reduction phase of KFeO₂. Both ruthenium and potassium have a promoting effect on the catalytic activity for the WGS reaction.From Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 930–941.Original English Text Copyright © 2004 by Jówiak, Maniecki, Basiska, Góralski, Fiedorow.This article was submitted by the authors in English.     

Vibrational linestrengths for the ground and first excited electronic states of HeH<Subscript>2</Subscript><Superscript>+</Superscript>

Together with recent improved potential-energy surface calculations for the ground (X) and first excited (Ã) electronic states of HeH₂ ⁺, the electric dipole moment surfaces for each state and the transition dipole moments connecting the two states were evaluated for the entire range of the energy calculations. Using these functions the linestrengths of all dipole-allowed transitions between the bound vibrational levels within each of the two states (XX) and (ÃÃ) as well as between them (ÃX) are evaluated here. These data are believed to be useful both in the experimental search for the yet unobserved molecular spectra of HeH₂ ⁺ and in evaluating theoretical rates for the radiative association or photodissociation processes involving the two lowest electronic states of the ion.Contribution to the Björn Roos Honorary Issue     

Crystal structure of the synthetic analog of radtkeite Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.00</Subscript>I<Subscript>1.00</Subscript>

The results of structural studies of the synthetic analog of the radtkeite mineral Hg₃S₂Cl_1.00I_1.00 are analyzed. The crystal structure of the compound has been refined; the unit cell parameters are a _m = 16.827(4) , b _m = 9.117(1) , c _m = 13.165(5) , = 130.17(2)°, V = 1543.3(8) ³, space group C2/m, Z = 8, R = 0.0527. A possible transition a ₀ = a _m; b ₀ = a _m + 2c _m; c ₀ = –b _m to the pseudo-orthorhombic F cell previously determined for radtkeite, where one of the angles ( ₀ ) is slightly different from 90° (89.55°), has been found. Each sulfur atom in the structure is bonded to three mercury atoms, forming SHg₃ umbrellas with distances 2.240(6) –2.474(8) and angles HgSHg 94.7(2)°–102.9(2)°. The SHg₃ fragments are linked through Hg vertices to form corrugated [Hg₁₂S₈] layers. The halogen atoms lie inside and between the [Hg₁₂S₈] layers; the distances are Hg-Cl and Hg-I 2.783(7) , 2.961(7) , and 3.083(4) –3.311(3) , respectively.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 755–758, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Phase equilibria in the CdI<Subscript>2</Subscript>-Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> system

The phase diagram of the system CdI₂-Bi₂O₃ is studied by means of X-ray diffraction, differential thermal analysis and measurements of the density of the material. As a result of the synthetic and peritectic interactions, two incongruently melting intermediate phases i.e. phase A — CdI₂·2Bi₂O₃ and phase B — CdI₂·4Bi₂O₃ (stable in the temperature interval 370–850°C) are formed.The phase A exists in two polymorphic forms with a temperature of the phase transition T =320–370°C. The unit cell parameters at low temperature modification of -CdI₂°2Bi₂O₃ were determined. (a=1.032 nm, b=1.046 nm, c=1.046 nm, =115.02°, =109.11° and =82.04°). The phases A and B have fields of homogeneity.The authors acknowledge thankfully the financial support for this work from the Ministry of Education and Science (Fond Scientific investigations — contract TN-1102).     

Formation of a Hydroxo-bridged Dinuclear Ru(III)/Ru(III) Complex from <Emphasis Type="Italic">N</Emphasis>-Methylimidazole and [Ru<Emphasis Type="Italic">Cp</Emphasis>(CH<Subscript>3</Subscript>CN)<Subscript>3</Subscript>]<Superscript>+</Superscript>

Summary. The reaction of [RuCp(CH₃CN)₃]PF₆ with 1 equiv of N-Me-imidazole results in the quantitative formation of [RuCp(¹N-N-Me-imidazole)(CH₃CN)₂]PF₆ (1) featuring a ¹N rather than a ¹C bound N-Me-imidazole ligand. According to DFT/B3LYP calculations, ¹N coordination of N-Me-imidazole is preferred over ¹C coordination by 25.5kJ/mol. Upon exposure to air 1 reacts with oxygen and water to afford the novel hydroxo-bridged dinuclear complex of [Ru₂Cp₂(¹N-N-Me-imidazole)₂(-OH)₂](PF₆)₂ (2) featuring a metal-metal single bond. The dimeric nature of 2 was confirmed by a single-crystal X-ray structure analysis.     

The UV spectra of arsines and arsine selenides

Short-wavelength n_Se ^* and long-wavelength n_Se ^* bands are observed in the UV spectra of saturated trialkylarsine selenides in the near-UV region. The n_x ^* band in going from arsine selenides to arsine sulfide and then to arsine oxides is shifted hypsochromically, as in the corresponding phosphorus compounds. The n_x ^* band is only slightly sensitive to the chalcogen. Saturated trialkylarsines, in contrast to alkylphosphines, absorb in the near UV region (the n_As ^* band is at 208 nm).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 940–942, April, 1990.     

Laser-spectroscopic laboratory studies of atmospheric aqueous phase free radical chemistry

Nitrate radical (NO₃) reactions with benzene (R-1), toluene (R-2), p-xylene (R-3), p-cresol (R-4) and mesitylene (R-5) have been studied by laser photolysis/long path laser absorption (LP-LPLA) in aqueous solution. Rate constants of k₁=(4.0±0.6) 10⁸, k₂=(1.2±0.3)10⁹, k₃=(1.6±0.1)10⁹, k₄= (8.4±2.3)10⁸ and k₅=(1.3±0.3)10⁹ lmol^-1s^-1 were obtained at T=298 K. In addition, reaction rate coefficients for SO^-₅+Fe²⁺prod. (R-6) and SO^-₅+Mn²⁺prod. (R-7) of k₆=(4.3±2.4) 10⁷ lmol^-1s^-1 and k₇=(4.6±1.0)10⁶ lmol^-1s^-1 (T=298 K, I0) have been obtained by the application of laser photolysis/UV-VIS broadband diode array spectroscopy. A new laser photolysis/UV-long path laser absorption experiment has been applied to study the reaction of the Cl^-₂ radical anion with dissolved sulfur(IV). For the reactions Cl^-₂+HSO^-₃2Cl^-+H⁺+SO^-₃ (R-8) and Cl^-₂+SO^2-₃2Cl^-+SO^-₃ (R-9) rate coefficients of k₈=(1.7±0.2)10⁸ lmol^-1s^-1 (T=298 K, I0) and of k₉=(6.2±0.3)10⁷ lmol^-1s^-1 (T=279 K, I0) were obtained.     

Triterpene glycosides of Hedera taurica

From the leaves of Crimean ivy we have isolated the previously known glycosides 3-O--L-Ara_p-28-O-[O--L-Rha_p-(14)-O--D-Glc_p-(16)--D-Glc_p]hederagenin, 3-O-[O--L-Rha_p-(12)--L-Ara_p]-28-O-[O--L-Rha_p-(14)-O--D-Glc_p-(16)--D-Glc_p]oleanic acid and -hederagenin, and 3-O-[O--L-Rha_p-(12)--L-Ara_p]-28-O-[O--D-Glc_p-(16)--D-Glc_p]hederagenin and a new one: tauroside H₁ — 3-O-[O--L-Rha_p-(12)-O--L-Ara_p]-28-O-[O--L-Rha_p-(14)-O--D-Glc_p-(16)--D-Glc_p]echinocystic acid.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 522–528, September–October, 1992.     

Triterpene glycosides of Hedera taurica VI. Structures of hederosides G, H1, H2, and I from the berries of Crimean ivy

We have isolated from Crimean ivy berries in addition previously known triterpene glycosides — 3-O--L-arabinopyranosyl-28-O-[O--L-rhamnopyranosyl-(1 4)-O--D-glycopyranosyl-(1 6)--D-glucopyranosyl]hederagenin, 3-O-[O--L-rhamnopyranosyl-(1 2)--L-arabinopyranosyl]-28-O-[O--L-rhamnopyranosyl-(1 4)-O--D-glucopyranosyl-(1 6)--D-glycopyranosyl]hederagenin, the new triterpene glycosides hederoside H₂-3-O-[O--D-glycopyranosyl-(1 2)--D-glycopyranosyl-(1 2)--D-glucopyranosyl]-28-O-[O--D-glucopyranosyl-(1 6)--D-glucopyranosyl]oleanolic acid- and hederoside I-3-O-[O--D-glucopyranosyl-(1 2)--D-glucopyranosyl]-28-O-[O--D-glucopyranosyl-(1 6)--D-glucopyranosyl]hederagenin. Details of their¹³C NMR spectra are given.M. V. Frunze Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 779–783, November–December, 1990.     

Arjunolic acid derivative glycoside from the stems of <Emphasis Type="Italic">Hedera colchica</Emphasis>

Five triterpenoid saponins were isolated from the stems of Hedera colchica K. Koch, Araliaceae. Two of them are new natural substances. HCSt-A (1): 3-O--D-arabinopyranoside; 28-O--L-rhamnopyranosyl-(1 4)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl-arjunolic acid. HCSt-B (2): 3-O--D-xylopyranoside; 28-O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl-hederagenin. The derivative of arjunolic acid is described for the first time in Araliaceae family. The chemical structures of isolated compounds were established on the base of chemical and 1D and 2D NMR experiments.Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 461–463, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

<Emphasis Type="Italic">Ab initio</Emphasis> structural study of M(mda)<Subscript>2</Subscript> complexes (M = Be,Mg, Ca; mda = C<Subscript>3</Subscript>O<Subscript>2</Subscript>H<Subscript>3</Subscript>)

The structure of M(mda)₂ (M = Be, Mg, Ca; mda = C₃O₂H₃) bis-complexes was investigated by the ab initio Hartree-Fock method and by including electron correlation in terms of second order Möller-Plesset perturbation theory; for calculations we used triple-zeta valence basis sets complemented with polarization functions. Two most probable geometrical nuclear configurations (D _2h and D _2d ) are considered for each molecule. The structure with two mutually orthogonal chelate ligands (D _2d symmetry) corresponds to the potential energy surface (PES) minimum. The planar D _2h configuration corresponds to the first order saddle point on PES; consequently, its relative energy determines the height of the barrier to the D _2d D _2h D _2d intramolecular rearrangement. Correlation equations that relate the calculated values of equilibrium internuclear distances, force constants, and rearrangement barrier heights to the value of the ionic radius of the metal atom have been obtained. These correlations were employed to evaluate the molecular constants for Sr(mda)₂ and Ba(mda)₂. The theoretical data are compared with the available experimental literature data.Original Russian Text Copyright © 2004 by V. V. Sliznev, S. B. Lapshina, and G. V. GirichevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 611–623, July–August, 2004This revised version was published online in April 2005 with a corrected cover date.     

Triterpene glycosides from Pulsatilla chinensis

Four triterpene glycosides were isolated from the roots of Pulsatilla chinensis (Bunge) Regel (Ranunculaceae). Two new glycosides, chinensiosides A (1a) and B (2), were identified as 3-O-[-L-rhamnopyranosyl-(12)--L-arabinopyranosyl]-28-O-[-L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranosyl]-3,23-dihydroxylup-20(29)-en-28-oic acid and 3-O-{-L-rhamnopyranosyl-(12)-[-D-glucopyranosyl-(14)]--L-arabinopyranosyl}-28-O-[-L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranosyl]-3,23-dihydroxylup-20(29)-en-28-oic acid. The other two glycosides were identified as previously known hederasaponin C (3) from Hedera helix and glycoside III (4) from Pulsatilla cernua.     

Triterpene glycosides ofPatrinia scabiosofolia; II

Conclusions The triterpene glycosides scabiosides D, E, F, and G have been isolated from the roots ofPatrinia scabiosofolia Fisch. et Link. It has been established that scabioside D is O--D-glucopyranosyl-(1 4)-O--L-arabopyranosyl-(1 3)-O-oleanoloyl-(28 1)--D-xylopyranose, and scabioside E is O--D-glucopyranosyl-(1 4)-O--L-arabopyranosyl-(1 3)-O-oleanoloyl-(28 1)-O--D-xylopyranosyl-(4 1)--L-rhamnopyranose.     

Surface acid sites of H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> as studied by the adsorption of stable nitroxyl radicals

The surface acidity of H₃PW₁₂O₄₀ and Na_xH_3-xPW₁₂O₄₀(x = 1-3) was studied using the adsorption of 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (TEMPON) and 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (TEMPOL) radicals. It was found that the amount of surface proton sites determined from the adsorption of TEMPON decreased with the degree of substitution of Na⁺ cations for protons. A correlation between amount of strong surface proton sites and catalytic activity of Na_xH_3-xPW₁₂O₄₀(x = 0-3) in the dealkylation reaction of 2,6-di-tert-butyl-4-methylphenol was found.Translated from Kinetika i Kataliz, Vol. 46, No. 1, 2005, pp. 131–136.Original Russian Text Copyright © 2005 by Timofeeva, Ayupov, Volodin, Pak, Volkova, Echevskii.     

Excited Π states of divinyl chalcogenides and chalcophenes

Electron transitions in divinyl chalcogenides (CH₂=CHXCH=CH₂, where X is S, Se, or Te) have been analyzed using UV absorption spectra of dialkyl and alkyl vinyl chalcogenides. The following relations for the orbital energies are found: ^* < ^* < ^* < ^* for Te and ^* < ^* < ^* < ^* for S and Se. For chalcophenes, a correlation between the energy of the excited state (E ^*) of specific symmetry, the ionization potential (I) and the electron affinity (EA) is obtained:E ^*=const+(I+EA)/2. The electron affinity of divinyl chalcogenides is estimated. The correlation between the excited ^* states of divinyl chalcogenides and chalcophenes is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–835, May, 1994.     

Über die Wirkungen von Aldehyden auf gesunde und maligne Zellen, 2. Mitt.: Synthese von homologen 4-Hydroxy-2-alkenalen,I

Zusammenfassung 4-Hydroxy-2-alkenale verschiedener Kettenlänge (C₅–C₁₀) werden in einer mehrstufigen Synthese hergestellt: Alkanal 2-Bromalkanaldimethylacetal 2-Alkenaldimethylacetal 4-Brom-2-alkenaldimethylacetal 4-Hydroxy-2-alkenaldimethylacetal 4-Hydroxy-2-alkenal.     

Ionic conduction of a high-temperature modification of Lu<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript>

A nanoceramic product of the composition Lu₂Ti₂O₇ is synthesized by a coprecipitation method with a subsequent sublimation drying and an annealing at 650–1650°C. The conduction of Lu₂Ti₂O₇ synthesized at 1650°C is ionic (10^–3 S cm^–1 at 800°C). Thus, a new material with a high ionic conduction has been discovered. The ordering in Lu₂Ti₂O₇ is studied by methods of RFA, RSA, IK spectroscopy, electron microscopy, and impedance spectroscopy. The existence of a low-temperature phase transition fluorite-pyrochlore at 800°C and a high-temperature conversion order-disorder at 1650°C are established.Translated from Elektrokhimiya, Vol. 41, No. 3, 2005, pp. 298–303.Original Russian Text Copyright © 2005 by Shlyakhtina, Ukshe, Shcherbakova.     

Density Functional Theory and Low-Temperature Matrix Investigations of CO-Loss Photochemistry from [(C<Subscript>5</Subscript>R<Subscript>5</Subscript>)Ru(CO)<Subscript>2</Subscript>]<Subscript>2</Subscript> (R = H,Me) Complexes

The photochemical CO-loss products of the diruthenium complexes [CpRu(CO) ₂]₂ (5; Cp = ⁵-C₅H₅), [Cp*Ru(CO)₂]₂ (5*; Cp* = ⁵-C₅(CH₃)₅) and CpCp*[Ru(CO)₂]₂ (5) have been studied experimentally in low-temperature (96 K) matrices in 3-methylpentane by using IR spectroscopy. It is proposed that all three complexes undergo single-CO-loss chemistry but that the products have different structures. The single-CO-loss product from 5 is proposed to have one bridging and two terminal carbonyl ligands, whereas 5* and 5 generate triply bridged CO-loss products similar to that observed from [CpFe(CO)₂]₂ and [Cp*Fe(CO)₂]₂. Double-CO-loss from 5* and 5* 9 is also apparently observed. Relativistic DFT calculations have been carried out on various isomers of the starting materials and on potential CO-loss products from 5. The calculations suggest that the triply bridged product Cp₂Ru₂(-CO)₃ (6) might have a singlet ground state in contrast to the corresponding diiron complex Cp₂Fe₂(-CO)₃ (3), which has a triplet ground state.     

Calculations of electronic spectra of Fe and Co porphyrins and their anionic forms

Energies and intensities of electronic transitions of a number of Co and Fe porphyrins and their anionic forms have been calculated by the INDO/S-CI method in the Zerner parametrization. The results from the theoretical analysis are consistent with the basic relationships observed in the change of electronic spectra within the limits of isoelectronic series of compounds characterized by identical total number of -electrons and identical filling of the pair of d orbitals. It has been established that in the spectra of compounds of an isoelectronic series corresponding to the neutral state of the porphyrin ligand, the allowed electronic transitions are described by superpositions of two ^* configurations (la_1u 4e_g) ) and (3a ^2u 4e_g ) , two configurations of intermolecular charge transfer 3 (d 2b_1u) and (d 3b_2u), and two types of doubly excited configurations (la_1u, d 4e_g, 4e_g) and (3a _2u, d 4e_g, 4e_g). Data have been obtained on the energies and orbital nature of the even electronic states that are responsible for rapid exchange of excitation energy of the porphyrin molecules with the transition metals.Leningrad. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 2, pp. 144–151, March–April, 1991. Original article submitted September 28, 1989.