Catalytic properties of nickel oxide and its solid solutions in magnesium oxide in hydrogen oxidation

Temperature dependence of the reaction rate of H₂ oxidation on nickel oxide and solid solutions of nickel ions in MgO prepared at 573–1373 K, has been studied. The variation of the catalytic properties with temperature is attributed to the presence of nickel ions in different oxidation states simultaneously, i. e. Ni(II) and Ni(III).

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H₂ MgO, 573–1373 K. — Ni(II) Ni(III).

     

Synthesis and structure of isomeric (μ-H)Os<Subscript>3</Subscript>(μ,η<Superscript>2</Superscript>-(O,N)-6,6-clusters of dimethyl-2-methylene-bicyclo[3.1.1]heptan-3-one oxime)(CO)<Subscript>10</Subscript>. Crystal structure of one of the isomers

(-H)₂Os₃(,²-(O,N)-6,6-dimethyl-2-methylene-bicyclo[3.1.1]heptan-3-one oxime)(CO)₁₀ isomeric clusters have been synthesized, separated chromatographically, and investigated by IR and NMR spectroscopy. The crystal structure of one of the isomers has been determined (Enraf-Nonius CAD-4 automatic diffractometer, graphite monochromator, MoK , /2 scan mode at a variable rate). The crystals are monoclinic with unit cell parameters: a = 9.125(2) , b = 13.629(3) , c = 10.098(2) , = 90.16(3)°, V = 1255.8(4) ³, space group P2₁, Z = 2, composition (-H)₂Os₃(,²-ONC₁₀H₁₄)(CO)₁₀, d _calc = 2.647 g/cm³. The structure is molecular; the planes of the Os₃ triangle and the OsONOs bridging ligand are linked according to the butterfly pattern with an angle of 102.0° between the planes. The Os-Os bonds vary within the range 2.840 –2.882 .Original Russian Text Copyright © 2004 by V. A. Maksakov, N. V. Pervukhina, S. V. Korenev, N. V. Podberezskaya, V. P. Kirin, and A. V. TkachevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 698–705, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Cationic β-diketonato molybdenum nitrosyl complexes: redox and structural properties

Summary -Diketones react with [Mo(NO){HB(dmpz)₃}I₂] [HB (dmpz)₃ = tris (3,5-dimethylpyrazolyl)borate] giving the cationic complexes [Mo(NO) {HB(dmpz)₃}{OC(R)CRC-(R)O}]⁺ (R = R = Me, R = H, Me or n-Bu; R = R = Ph, R = H; R = Me, R = n-Bu, R = H), isolated as triiodide salts. Electrochemical studies show that these complexes exhibit three electrode processes: two associated with oxidation of I _inf3 ^sup– and one with reduction of the metal-containing cation. Reduction of the cation where R = R = R = Me with cobaltocene afforded the neutral paramagnetic [Mo(NO) {HB(dmpz)₃} {OC(Me)CMeC(Me)O}], which was characterized by i.r. and e.p.r. spectroscopy. In contrast, 3-chloropentane-2, 4-dione reacts efficiently with [Mo(NO){HB(dmpz)₃}I₂] giving the known chloro-analogue, [Mo(NO)-{HB(dmpz)₃}Cl₂], and no -diketonate complex was detected. The X-ray crystal structure determination of [Mo(NO){HB(dmpz)₃} {OC(Me)CMeC(Me)O}]I₃ confirms that the cation is six-coordinate and shows that the 559-01 (diketonate) bonds are slightly longer than in comparable compounds, implying that the -diketonate ligand is not such a strong -donor as alkoxide groups.     

Mesophasic properties of low molecular weight analogues of nematogenic polycarbonates

The mesophasic behaviour of the following compounds has been investigated by DSC, X-ray diffraction and optical microscopy methods: CH₃(CH₂)₄-CO-R-A _n -R-CO-(CH₂)₄-CH₃,n=9 14, 16 CH₃(CH₂)₄-CO-R-B _n -R-CO-(CH₂)₄-CH₃,n=2, 3A _n=-CO-O-(CH₂)_n–4-O-CO-,B _n =-CO-(OCH₂CH₂) _n -O-CO-,R=-O-Ø-C(CH₃)=N-N=(CH₃)C-Ø-O-,Ø=-C₆H₄ They have been assumed to be low molecular weight models of homologous nematogenic polymers.All the examined compounds exhibit nematic mesomorphism. On complete analogy with the corresponding polymers, the thermodynamic data relative to the nematic-isotropic phase transition show a very reduced, if any, odd-even fluctuation. These data are compared with those obtained for very similar compounds, both polymeric and non-polymeric, containing ester linkages between the rigid and flexible groups, to provide evidence of the reliability of the dimeric compounds as models of the polymeric homologues.

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Zusammenfassung Das mesophasische Verhalten der folgenden Verbindungen wurde mittels DSC, Röntgendiffraktion und optischer Mikroskopie untersucht: CH₃(CH₂)₄-CO-R-A _n -R-CO-(CH₂)₄-CH₃;n=914, 16 CH₃(CH₂)₄-CO-R-B _n -R-CO-(CH₂)₄-CH₃;n=2, 3A _n =-CO-O-(CH₂)_n-4-O-CO-;B _n =-CO-(OCH₂CH₂)_n-O-CO-;R=-O-C₆H₄-C(CH₃)=N-N=(CH₃)C-C₆H₄-O-. Die Verbindungen wurden als Modelle homologer nematogener Polymere mit niedrigem Molekulargewicht angesehen. Alle untersuchten Verbindungen zeigen einen nematischen Mesomorphismus. Analog zu den entsprechenden Polymeren zeigen die sich auf den nematisch-isotropen Phasenübergang beziehenden thermodynamischen Daten eine, wenn überhaupt, sehr reduzierte ungerade-gerade Fluktuation. Diese Daten werden mit denen verglichen, die für sehr ähnliche, sowohl polymère als auch nicht-polymere Verbindungen mit Esterbindungen zwischen den starren und flexiblen Gruppen erhalten wurden, um Beweise für die Zuverlässigkeit der auf dimeren Verbindungen aufbauenden Modelle für polymère Homologe zu erhalten.

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, : CH₃(CH₂)₄-CO-R-A _n -R-CO-(CH₂)₄-CH₃ n=914,16 CH₃(CH₂)₄-CO-R-B _n -R-CO-(CH₂)₄-CH₃ n=2, 3A _n =-CO-O-(CH₂) _n–4-O-CO-;B _n =-CO-(OCH₂CN₂) _n -O-COR =-O--C(CH₃)=N-N=(CH₃)C--O- =C₆H₄ , . . — , , , - . , , ,

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The financial assistance of the Ministero Pubblica Istruzione is acknowledged.     

31P{1H}-n.m.r. as a tool for identification of ruthenium isomers containing PPh3 or 1,4-bis(diphenylphosphino)butane ligands. X-ray structures of the cis-{RuCl2(PPh3)2 [4,4′-(-X)2-2,2′-bipy]} complexes [X=-H, -Me, -SMe and (-Cl, -Me)]

A series of cis-{RuCl₂(PPh₃)₂[4,4-(X)₂-2,2-bipy]} [cis-chlorines; X=-H, -Me, -SMe, and (-Cl,-Me)] complexes have had their structures determined by single crystal X-ray diffraction. The geometry of these complexes, also determined in CH₂Cl₂ solution by ³¹P{¹H}-n.m.r. spectroscopy, showed that the chemical shifts for the phosphorus atoms are slightly dependent on the pKa of the 4,4-(-X)₂-2,2-bipy ligands.     

The relative permittivity of 1,2-dimethoxyethane and N,N-dimethylformamide mixtures from −10 to 40°C

Binary solutions of N,N-dimethylformamide and 1,2-dimethoxyethane have been investigated by means of dielectric measurements at temperatures ranging from –10 to +40°C, and for nine mixtures covering the whole miscibility field expressed by the mole fraction of one component (0X₁1). The experimental data were used to study the dependence of on T and X₁, of the type = (T), = (X₁), and = (T,X₁). Further, the excess mixing function _E has been evaluated in order to identify particular patterns of interaction between unlike molecules and any other factor that could modify such patterns. The minimum in the _E vs. composition plots suggests the formation of an adduct of stoichiometric ratio DMFDME=11 at all the investigated temperatures.     

Influence of conjugated nitrogenous bases on the spectra and structure of mixed-ligand nickel(II) chelates containing β-diones

The infrared and electronic excitation spectra of a series of new nickel(II) chelates containing an-diimine (or nitrogenous base, enR) and the anion of a-dione (1,3-ketoenol or 1,3-ketoester,H) were obtained in the solid state and in solution. The composition and the overall structure of the new chelates in the solid state depends on ligand concentration, the substituents within the-dionato moiety and the counterion present. The IR and electronic excitation spectra of [Ni(enR)₂ ]NO₃ and [Ni(enR)(O₂NO)] indicate, in conjunction with other physicochemical measurements, bidentate coordination of the ligands, while the spectral shifts reveal replacement of the (O,O)nitrato group by basic solvents. The existence of the nickel(II) in an octahedral environment is confirmed by an X-ray structure analysis of [Ni(dpamH)₂acac]NO₃ · CH₃OH (monoclinic, space groupP2_l/n, a=17.296(1),b=7.462(1),c=21.604(3) å,=95.65(1),Z=4, R=0.0534,Rw=0.0600), where dpamH denotes the 2,2-dipyridylamine.     

Pressure-jump method in the dehydrogenation of propane over chromia-alumina-potassium oxide

The pressure-jump method was applied to the dehydrogenation of C₃H₈ over a Cr₂O₃–Al₂O₃–K₂O catalyst in a closed static reactor at 443°C. The rate equation proposed for initial kinetics was shown to apply to the dehydrogenation of C₃H₈.

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C₃H₈ Cr₂O₃–Al₂O₃–K₂O 443°C. , , , C₃H₈.

     

Ammonia Formation on (Ru + Cs)/C Catalysts by the Interaction of Adsorbed Nitrogen with Hydrogen That Diffused from the Bulk of Cesium–Ruthenium Particles

The high-temperature (T _max = 625 ) and (T _max = 750 ) states of ammonia and (T _max = 550–750 ), (T _max = 750–900 ), and (T _max > 900 K) states of hydrogen were detected on (Ru + Cs)/C catalysts for ammonia synthesis activated under the reaction conditions (P = 30 atm; T = 650 K; the initial pressure ratio P_{N 2}/P_{H 2} = 1/3). A mechanism was proposed for the formation of ammonia as a result of the interaction of chemisorbed nitrogen with hydrogen that diffused from the bulk of cesium–ruthenium particles.     

Peculiarities of formation of ZnO and CuO-based solid solutions

Low-temperature (623 K) treatment of hydroxocarbonate compounds of copper-zinc and copper-zinc-aluminium leads to the formation of phases with CuO and ZnO structures, which are solid solutions of the promoter ions. The formation of solid solutions is attributed to structural distortions (uniform or local) in the oxide lattice due to the incomplete removal of OH^– and CO ₃ ^2– groups at low temperatures.

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, (623 ) - -- CuO ZnO, . , ( ) - OH ₃ ^–– - .

     

Investigation of structural relaxation of Fe85B15 amorphous metallic alloy by thermomagnetization

Thermomagnetometry was used to determine the Curie temperature of Fe₈₅B₁₅ amorphous alloy. Measurements were made with a TGS-1 Perkin-Elmer thermobalance in a permanent magnetic field. Armosphous material with a thickness of 25 m was prepared by melt spinning.In the temperature region 300 to 800 K the sample is characterized by one Curie transformation in the amorphous matrix atT _c570 K. A broad region of primary crystallization of -Fe begins at approximately 660 K, followed closely by the rapid crystallization of Fe₃B phase with maximum atT _cr2 750 K. Amorphous material which is unstable due to quenching is relaxed by annealing. The structural relaxation causes ageing of the Curie temperature in the metallic glass.The observed phenomena might be explained in terms of certain changes in local atomic arrangement.

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Zusammenfassung Die thermomagnetometrische Methode wurde zur Bestimmung der Curie-Temperatur der amorphen Legierung Fe₈₅B₁₅ herangezogen. Die Messungen wurden mit einer Perkin-Elmer-Thermowaage des Typs TGS-1 unter Anwendung eines permanenten Magnetfeldes ausgeführt. Das 25 m dicke amorphe Material wurde nach dem Schmelzspinnverfahren dargestellt. Im Temperaturbereich von 300 bis 800 K ist für die Probe eine Curie-Transformation in der amorphen Matrix beiT _c570 K charakteristisch. Ein breiter Bereich der primÄren Kristallisation von -Fe beginnt bei etwa 660 K, dem sofort eine schnelle Kristallisation der Fe₃B-Phase mit maximaler Geschwindigkeit beiT _cr2 750 K folgt. Die durch Abschrecken eintretende InstabilitÄt des amorphen Materials wird durch Tempern aufgehoben. Die strukturelle Relaxation verursacht eine Alterung der Curie-Temperatur im metallischen Glas. Die beobachteten PhÄnomene können durch VerÄnderungen der lokalen Anordnung der Atome erklÄrt werden

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Fe₈₅B₁₅. -1 -, . 25 . 300–800 . -Fe 660 , Fe₃B T _cr2750 . , , . . .

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We wish to thank P. Duhaj for the preparation of glassy ribbons.     

New substrates in Belousov-Zhabotinsky reaction employing mixed media

Several substrates have been employed in different oscillatory systems. A serious limitation is the low solubility in water. This has been overcome by employing aqueous-organic mixed media in the iodate-system as well as the uncatalyzed and catalyzed [Ce(III) or Ferroin] systems. The present paper deals with the study of fifteen new substrates in the bromate-Mn(II) oscillatory system employing aqueous-organic mixed media.

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. . , - , (Ce(III) ), . -Mn(II) - .

     

Kinetics of the thermal decomposition of alkaline earth metal hydrofluorides

The thermal stability of alkaline earth metal hydrofluorides was studied by means of a Derivatograph. The values of the activation energy, reaction order and rate constant were determined. The comparison of the kinetic parameters of the decomposition process for the complete series of hydrofluorides studied led to a certain regularity in the differences in their thermal stabilities and its correlation with the strength of the hydrogen bond in their structure.

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Zusammenfassung Die thermische Stabilität von Erdalkalihydrofluoriden wurde mit Hilfe eines Derivatographen untersucht, die Werte der Aktivierungsenergien, der Reaktionsordnung und der Geschwindigkeitskonstanten bestimmt. Der Vergleich der kinetischen Parameter des Zersetzungsvorganges wies auf eine gewisse Regelmäßigkeit in ihrer verschiedenen thermischen Stabilität, die in Zusammenhang mit der Stärke ihrer strukturalen Wasserstoffbindung steht.

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Résumé On a étudié la stabilité thermique des hydrogénofluorures des métáux alcalinoterreux et déterminé les valeurs des énergies d'activation, des ordres de réaction et des constantes de vitesse de réaction à l'aide d'un Dérivatographe. Après comparaison des paramètres cinétiques on a pu établir une certaine régularité dans le changement de la stabilité thermique en corrélation avec la force de liaison de l'hydrogène dans la structure.

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. , . .

     

Eigenvalues of the real generalized eigenvalue equation perturbed by a low-rank perturbation

The low-rank perturbation (LRP) method solves the perturbed eigenvalue equation (B +V) _k = _k (C +P) _k , where the eigenvalues and the eigenstates of the related unperturbed eigenvalue equationB _i = _i C _i are known. The method is designed for arbitraryn-by-n matricesB, V, C, andP, with the only restriction that the eigenstates _i of the unperturbed equation should form a complete set. We consider here a real LRP problem where all matrices are Hermitian, and where in addition matricesC and (C +P) are positive definite. These conditions guarantee reality of the eigenvalues _k and _i . In the original formulation of the LRP method, each eigenvalue _k is obtained iteratively, starting from some approximate eigenvalue _k . If this approximate eigenvalue is not well chosen, the iteration may sometimes diverge. It is shown that in the case of a real LRP problem, this danger can be completely eliminated. If the rank of the generalized perturbation {V, P} is small with respect ton, then one can easily bracket and hence locate to any desirable accuracy the eigenvalues _k (k = 1, ...,n) of the perturbed equation. The calculation of alln eigenvalues requiresO(² n ²) operations. In addition, if the perturbation (V, P) is local with the localizabilityl p, then onlyO(² n) operations are required for a derivation of a single eigenvalue.     

Origin of the conical intersection between the singlet ionic excited surfaces of twisted ethylene

The potential surfaces of the two valence ionic singlet excited states of twisted ethylene are known to exhibit a conical intersection for a twist angle of the double bond near 82°, and no pyramidalization of the CH₂ groups. The factors responsible for the stabilization of the symmetric excited state near 90° are shown to be ( )² and ( ^*)² double excitations. The analysis is performed in the Quasi Degenerate Perturbation Theory formalism. The analogy with the ¹ A _g ³ B _u ordering problem of the diradical ground and lower triplet states through a double spin polarization of the system is established.     

Kinetics of EDTA-catalyzed oxidation of Indigo Carmine by vanadium(V)

The reaction is first order both in vanadium(V) and substrate and is markedly inhibited by H⁺ ions. Kinetic evidence for the formation of a 11 complex of vanadium(V) and EDTA is obtained. The stability constant of this complex and its thermodynamic parameters were evaluated. A suitable mechanism is proposed.

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(V), H⁺. 11 (V) . . .

     

Naphthyl-(2-pyridylmethylene)amine complexes of silver(I) and ruthenium(II): synthesis,spectral studies and electrochemical behaviour

Pyridine-2-carboxaldehyde reacts with /-naphthylamine to give /-naphthyl-(2-pyridylmethylene)amine [-L (1), -L (2)]. L belongs to the unsymmetric diimine (—N=C—C=N—) family which can form five–membered chelate rings with metal ions. {donor centers are abbreviated as N[N(Py)] and N [N(nap)]} [Ag(L)₂]⁺ complexes were prepared and characterized by spectroscopic data. The reaction between L and RuCl₃ in boiling EtOH yielded green and blue–green compounds of composition RuCl₂(L)₂. I.r., u.v.–vis. and ¹H-n.m.r. data determined the stereochemistry of the complexes as trans-cis-cis (green) and cis-trans-cis (blue–green) according to the sequence of the coordination pair of Cl, N [N(Py)] and N [N(nap)]. Upon treatment of Ag(L)₂ ⁺ with Ru(bpy)₂Cl₂ in alcoholic suspension the ternary complexes, [Ru(bpy)₂(L)](ClO₄)₂, were isolated and characterized by spectroscopic data. [Ru(bpy)(L)₂](ClO₄)₂ complexes were synthesized similarly from ctc-Ru(L)₂Cl₂ and 2,2-bipyridine (bpy) in the presence of AgNO₃ and NaClO₄. These complexes show well-defined m.l.c.t transitions in the visible region. The sterochemistry of the complexes was established by ¹H-n.m.r. data. Cyclic voltammetry shows a high potential Ru^III/Ru^II couple and follows the order: [Ru(bpy)(L)₂]²⁺ > [Ru(bpy)₂(L)]²⁺ > Ru(-L)₂Cl₂ > Ru(-L)₂Cl₂.     

Kinetics of Anodic Dissolution of Gold in Cyanide Solutions Containing Thallium Ions: Potentiostatic Measurements

Effective reaction order by cyanide ions, p, effective transfer coefficient _ef, and exchange current i ₀of the gold dissolution process are measured at a constant surface coverage by thallium adatoms _Tl. The constancy of _Tlis ensured by constant time tof the electrode's contact with solution after renewal of its surface and before starting the measurements. Solutions containing 2.5 × 10^–6to 10^–5M TlNO₃, 0.1 M KCN, and 0.1 M KOH are studied. With an increase in t, quantities p, _ef, and i ₀increase from values typical for pure KCN solutions (0.17, 0.1, and 10^–5A/dm², respectively) to p 1.1, _ef 0.4, and i ₀ 3 × 10^–4A/dm². The increase in pby nearly unity is interpreted as indicating a change in the limiting stage in the presence of thallium ions: in the latter case, it involves not only adsorbed cyanide ions (as in pure cyanide solutions), but also those located beyond the adsorption layer. A possible mechanism explaining the acceleration of gold dissolution in the presence of thallium adatoms is put forward.     

Possibilities of applying the piloyan method of determination of decomposition activation energies in the differential thermal analysis of polynitroaromatic compounds and their derivatives

Piloyan activation energiesE as well as initals of exothermT _D of sevenN-monoalkyl and fiveN,N-dialkyl-2,4-dinitroanilines were determined. Relationships were found between the T_D values and R_f factors as well asE values and those R_M functions and also theET _D ^–1 term and R_M functions.

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Zusammenfassung Die AktivierungsenergienE nach Piloyan sowie die Anfangswerte der ExothermenT _D wurden für siebenN-Monoalkyl- und fünfN,N-Dialkyl-2,4-dinitroaniline bestimmt. Die Zusammenhänge zwischen denT _D-Werten und den papierchromatographischenR _f-Faktoren der gemessenen Dinitroaniline wurden abgeleitet und erörtert. Desgleichen wurden auch die Zusammenhänge zwischen denE-Werten und denR _M-Funktionen der Papierchromatographie abgeleitet und erörtert. Auch zwischen dem AusdruckE ·T _D ^–1 und denR _M-Funktionen wurde ein Zusammenhang gefunden.

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Résumé On a déterminé les températures initialesT _D de l'effet exothermique ainsi que les énergies d'activationE d'après la méthode de Piloyan, de sept N-mono alcoyl et cinqN,N-dialcoyl-2, 4-dinitroanilines. Une corrélation entre les valeursT _D et les facteursR _f de la Chromatographie sur papier des dinitroanilines étudiées a été trouvée et discutée, ainsi qu'entre les valeursE et les fonctionsR _M de la Chromatographie sur papier. Une relation entre le termeE ·T _D ^–1 et les fonctionsR _M a également été trouvée.

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E T _D N- N,N- -2,4- . _D R _f , E R _M. E. _D ^–1 R _M.

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The authors would like to thank Mrs. Anna Collàkovà for careful DTA measurements, and Dr. Ladislav Smolka for help in treatment of the measured results with the Wang 600 computer.     

On theC v toC p conversion for solid linear macromolecules

TheC _v toC _p conversion for solid linear macromolecules via the Nernst-Lindemann equationC _p -C _v =A ₀,C _p ² T/T_m is discussed on hand of data for 10 crystals and seven glasses. An average value ofA ₀=(5.11±2.41) · 10^–3 mol K J^–1 was calculated if the mole is assumed to refer to heavy atoms only. ThisA ₀ is numerically equal to the original Nernst—Lindemann constant.

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Zusammenfassung An Hand von sich auf 10 Kristalle und 7 Gläser beziehenden Daten wird die Umrechnung vonC _v -inC _p -Werte für feste lineare Makromoleküle mittels der Nernst-Lindemann-GleichungC _p -C _v =A ₀ C _p ² T/T _m diskutiert. Ein Durchschnittswert vonA ₀=(5.11±2.41) · 10^–3 mol K J^–1 wurde unter der Annahme berechnet, daß sich das Mol nur auf schwere Atome bezieht. DieserA ₀-Wert ist numerisch gleich der ursprünglichen Nerns-Lindemann-Konstanten.

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10 , - C _v C _p , —C _p –C _v = _{0 p} ² / . , , ₀ (5.11±2.41) · 10^–3 · ^–1. ₀ — .

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Support by the National Science Foundation, Polymers Program (Grant No. DMR 83-17097) is gratefully acknowledged.