Influence of lanthanum on K/Fe/silicalite-2 catalyst in CO+H2

The promotion of a K/Fe/silicalite-2 catalyst with lanthanum increases the selectivity of C₂–C₄ olefin and conversion of carbon monoxide. The influence of lanthanum on the catalyst has been characterized by TPR, TPD and XPS techniques. The suitable lanthanum content in the chemical composition of the catalyst is determined.

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K/Fe/-2 C₂–C₄ . , . .

     

A TPR study of SiO2-supported Ru?Ag catalysts

A H₂ chemisorption and TPR study of Ru–Ag/SiO₂ catalysts reveals that after oxidation at 373 K this systems behaves like Ru–Cu/SiO₂. High temperature oxidation, however, does not result in the separation of the metal like in the Ru–Cu case but in the redispersion of Ag on top of the Ru particles.

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H₂ Ru–Ag/SiO₂ , 373 Ru–Cu/SiO₂. , , , Ru–Cu, Ag Ru.

     

Thermische Eigenschaften und Aufschlussreaktionen von Natriummetaphosphat

Zusammenfassung Die thermischen Eigenschaften des Natriummetaphosphats sowie die Aufschlußreaktion zwischen Natriummetaphosphat und Natriumchlorid wurden durch Thermogravimetrie, Differentialthermoanalyse, Dilatometrie und Thermogasanalyse untersucht. Hierbei wurden die Zusammenhänge zwischen der Gewichtszunahme beim Schmelzen von NaPO₃, der Art der Atmosphäre und dem Verlauf der Reaktion zwischen Natriummetaphosphat und Natriumchlorid beobachtet.

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The thermal behaviour of sodium metaphosphate and the reaction thereof with sodium chloride have been investigated by thermogravimetry, differential thermal analysis, dilatometry and thermo-gas-analysis. Relationship has been established between the weight increase of NaPO₃ in the course of melting, the nature of the atmosphere and the proceeding of the reaction with NaCl.

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Résumé On a étudié par ATG, ATD, dilatométrie et analyse de la phase gazeuse les propriétés thermiques du métaphosphate de sodium et la réaction chlorure de sodium-métaphosphate de sodium. On a pu trouver une corrélation entre l'augmentation de poids de NaPO₃ lors de la fusion, la nature de l'atmosphère et la réaction NaPO₃-NaCl.

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NaPO₃-NaCl , , . NaPO₃, NaPO₃-NaCl.

     

Combined pulse microcatalytic and ESR studies of butylene oxidation on V-Mg oxide catalysts

Abstract The behavior of V–Mg oxide catalysts in both steady and non-steady state butylene oxidation has been examined.

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, .

     

Quality control of the cure process of thermosetting resins by means of differential scanning calorimetry

Calorimetric and rheological characterizations of thermosetting resin formulations containing a novalac epoxy resin hardened with 60 to 120 parts per hundred of methylated maleic acid adduct anhydride are described. The calorimetrically determined epoxy conversion has been related to the gelation limits theoretically calculated from Flory's non-linear copolymerization theory and experimentally verified in rheological tests.

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Zusammenfassung Die kalorimetrische und rheologische Charakterisierung der Ansätze von hitzhärtbarem Harz wird beschrieben. Die Ansätze enthalten ein mit 60–120% methyliertem Maleinsäure-Adduktanhydrid gehärtetes Novolackepoxidharz. Die kalorimetrisch bestimmte Epoxid-konversion wurde auf die theoretisch aus der nicht-linearen Flory'schen Kopolymerisationstheorie berechneten und experimentell durch rheologische Tests bestätigten Erstarrungsgrenzen bezogen.

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, - . -, , , .

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Financial and scientific support by the CNR Progetto Chimica Fine e Secondaria and the Societa Italiana Resine (SIR) is gratefully acknowledged.     

A differential thermal analysis study of phase transitions in some mercury(II) carboxylates

Data are presented on the heats of phase changes and heat capacities for the even chain number mercury(II) carboxylates from octanoate to octadecanoate. The octanoate and dodecanoate melt directly to the liquid, while the decanoate and octadecanoate pass through a solid solid transition before melting to the liquid. The tetradecanoate and hexadecanoate pass through a mesophase before finally melting. It is proposed that this mesophase is aG (smectic) phase. Addition of mercuric oxide to the tetradecanoate and hexadecanoate causes the appearance of an additional mesophase. The results are explained in terms of theR theory of fused micellar phases.

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Zusammenfassung Daten der Phasenübergangswärmen und Wärmekapazitäten der Quecksilber(II)karboxylate mit geradzahligen Kohlenstoffatomen vom Oktanat bis Oktadekanat angegeben. Oktanat und Dodekanat schmelzen unmittelbar zur Flüssigkeit, während Dekanat und Oktadekanat durch einen Fest-Fest-übergang in den flüssigen Zustand übergeführt werden. Tetradekanat und Hexadekanat werden über eine Mesophase endgültig geschmolzen. Es wird für diese Mesophase die Struktur einer smektischen G-Phase vorgeschlagen. Der Zusatz von Quecksilberoxid zum Tetradekanat und Hexadekanat verursacht das Auftreten einer zusätzlichen Mesophase. Die Ergebnisse werden durch die R-Theorie geschmolzener Micellarphasen erklärt.

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Résumé On présente des données sur les chaleurs des changements de phase et les chaleurs spécifiques des carboxylates de mercure(II), mÊme à longue chaÎne carbonée, de l'octylate à l'octadécanoate. L'octylate et le dodécanoate conduisent directement au liquide par fusion tandis que le décanoate et l'octadécanoate subissent une transition solide-solide avant de fondre. Le tétradécanoate et l'hexadécanoate passent par une mésophase avant la fusion finale. On propose pour cette mésophase une structure smectique (G). L'addition d'oxyde de mercure au tétradécanoate et à l'hexadécanoate donne une mésophase additionnelle. On explique les résultats en se référant à la théorie R des phases micellaires fondues.

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(II) . , - . . , () . . P .

     

Substituent effect and enthalpy-entropy compensation on the inclusion ofβ-cyclodextrin with 1-substituted naphthalenes

The inclusion complexation of-CD with 1-substituted naphthalenes has been investigated by fluorescence spectroscopy. It was observed that the association constants were influenced by the molar refraction (R _m), hydrophobic constant ( _x ), and Hammett constant ( _x ) of substituents in the guest compounds. The thermodynamic parameters G⁰, H ⁰, and S ⁰ determined by measuring the temperature-dependentK _a values shows that inclusion complex formation is enthalpy driven. The results are discussed in terms of enthalpy-entropy compensation.     

Dynamics of chemical reactions and nonphysical steady states

Data on the position of nonphysical (lying beyond the region of determination) steady states are shown to be of use for understanding the dynamic behavior of chemical reactions, in particular, the reasons for slow relaxations.

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, ( ) , , .

     

Ab initio investigation of the electron structure in bis-Cu+ acetylene and vinylidene complexes

[Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺ and [Cu(-C₂H₂) (-CCH₂]⁺ complexes have been studied by the ab initio double-zeta basis set method. It has been established that all calculated compounds are stable to decomposition into two C₂H₂ molecules and Cu⁺ cation and into one C₂H₂ molecules and the respective monocomplex. Calculation results suggest the possibility of intramolecular acetylene-vinylidene rearrangement in the coordination sphere of Cu⁺.

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ab initio : [Cu(-C₂H₂)₂]⁺, [Cu(-CCH₂)₂]⁺, [Cu(-C₂H₂) (-CCH₂)]⁺. C₂H₂ Cu⁺ C₂H₂ . - Cu⁺.

     

Influence of water on the heat of hydrogen adsorption on nickel

Water and hydrogen adsorption on Ni-black has been studied by a microcalorimetric method. The heat of hydrogen adsorption is considerably different on clean surfaces and on those covered with 20–50% chemisorbed water. In the former case it varies between 33 and 8 kcal/mol, and in the latter between 26 and 4.6 kcal/mol. The decrease in the heat of hydrogen adsorption is related to the energy requirement of water desorption. On the hydrogen-covered catalyst surface no water adsorption occurs.

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Ni-. 20–50% . 33 8 /, - 26 4,6 /. . , , .

     

Effect of substituents on ionization potentials of phosphorus compounds. Conjugation in radical cations

The first vertical ionization potentials (I) of phosphorus compounds P(X_i)₃, OP(X_i)₃, SP(X_i)₃, (4-XC₆H₄)₃P, and PCX are related to the inductive, resonance, and polarizability parameters of inorganic, organic, and organometallic substituents X by dependences of the type I = I _H + a_I + b_R ⁺ + c, where I _H is the I value for X = H. The I values are also affected by hyperconjugation. The ratio of the contributions of the resonance (b_R ⁺) and polarizability (c) effects to the I value is determined by the degree of delocalization of the unpaired electron and the positive charge in the radical cations formed upon ionization of neutral molecules. The _R ⁺ resonance parameters of organosilicon, organogermanium, and organotin substituents bound to the P ^·+ radical cation center were calculated for the first time.     

Thermal analysis of heterocyclic thione donor complexes. Part 1

The thermal decomposition of the Co(II) complexes of 1-methylimidazoline-2(3H)-thione (MImt), general formula Co(MImt)₂X₂ (X=Cl, Br & I), have been studied in air and argon by means of TG and DTG as well as in nitrogen by DTA. Quantitative DTA has been used to derive reaction enthalpies (H _R) from the melting and decomposition endotherms in nitrogen. Decomposition processes have been proposed for the complexes in air and in inert atmospheres. A mean coordinate bond dissociation energy (¯D) has been estimated for the Co-MImt bond in Co(MImt)₂Cl₂.Reaction end products in air have been identified by X-ray powder diffraction.

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Zusammenfassung Die thermische Zersetzung von Kobaltkomplexen des 1-Methylimidazolin-2(3H)-thions (IMmt) der allgemeinen Formel Co(MImt)₂X₂ (X=Cl, Br, J) wurde in Luft und Argon mittels TG und DTG und in Stickstoff mittels DTA untersucht. Reaktionsenthalpien (H_r) wurden durch quantitative DTA aus den in Stickstoffatmosphäre erhaltenen endothermen Schmelz- und Zersetzungspeaks erhalten. Es wurden Mechanismen für die Zersetzungsprozesse der Komplexe in Luft und inerter Atmosphäre vorgeschlagen. Die mittelere Dissoziationsenergie (¯D) der koordinativen Bindung Co—MImt in Co(MImt)₂Cl₂ wurde bestimmt.In Luft erhaltene Reaktionsendprodukte wurden durch Röntgenpulverdiffraktometrie identifiziert.

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1- -2()- () ()₂₂, X=l, I, , . (H _R) . . - ()₂l₂. , , - .

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The author is grateful to Mr. J. R. Creighton, Newcastle upon Tyne Polytechnic, for technical assistance with this work and to Dr. F. Buttler, Teesside Polytechnic for mass spectral data and helpful discussion.     

Thermal decomposition of Cu(I) phosphine complexes

The thermal decomposition of Cu(I) phosphine complexes of the general types (CuXPPh₃)₄, [CuX(PPh₃)₂] and [CuX(PPh₃)₃] was investigated.The thermal decomposition of (CuXPPh₃)₄, where X denotes Cl^–, Br^–, I^–, NO ₃ ^– and PPh₃=P(C₆H₅)₃, occurs with formation of a phosphine oxide intermediate. For the remaining complexes this intermediate was not proved in the thermal decomposition.

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Zusammenfassung Die thermische Zersetzung der Cu(I)-Phosphinkomplexe vom allgemeinen Typ (CuXPPh₃)₄ und [CuX(PPh₃)₂], wie auch [CuX(PPh₃)₃] wurde untersucht. Die thermische Zersetzung von (CuXPPh₃)₄, wobei X=Cl^–, Br^–, I^– und NO ₃ ^– bedeutet und PPh₃=P(C₆H₅)₃, verläuft unter Bildung eines Phosphinoxid Zwischenproduktes, bei den übrigen Komplexen konnte dieses im Laufe der thermischen Zersetzung nicht nachgewiesen werden.

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Résumé On a étudié la décomposition thermique des complexes phosphine-Cu(I) de formule générale (CuXPPh₃)₄, [CuX(PPh₃)₂], [CuX(PPh₃)₃]. La décomposition thermique de (CuXPPh₃)₄, où X désigne Cl^–, Br^–, I^– et NO ₃ ^– , et PPh₃=P(C₆H₅)₃, s'effectue avec formation d'un oxyde de phosphine intermédiaire; avec les autres complexes, cet intermédiaire n'a pas été mis en évidence au cours de la décomposition thermique.

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(CuXPPb₃)₄ [CuX(PPh₃)₂] [CuX(PPh₃)₃]. (CuXPPh₃)₄, X=Cl^–, Br^–, I^–, NO ₃ ^– , PPh₃=(₆₅)₃ . .

     

Quantum-chemical study of allylic compounds with two bonded heavy atoms

It has been shown by the CNDO method that the bathochromic shift of the long-wave absorption band in the transition from allylstannane to compounds of the type C=C-C-Sn-X and C=C-Sn-X (where X is a heavy atom) is connected with the formation of a low-energy vacant *_S-X orbital, localized mainly in the region of the Sn-X chemical bond, and of an occupied _Sn-X orbital, the energy of which is somewhat higher than of the _C-Sn orbital. The dependence of the position of the long-wave absorbance region on conformation is related to the fact that, in planar and nonplanar conformers, the long-wave transitions are of a different type ( * and *, respectively); the bathochromic shift is determined to a large degree by the difference in the energies of the highest occupied MO ( - ) in the s-trans form. In the nonplanar conformers the heavy atom orbitals interact with the -orbital of the ethylene moiety through the bridge group; this leads to a significant delocalization of the HOMO and to a considerable change in its energy. On the other hand, their interaction with the *-orbital in compounds of the C=C-C-Sn-X type is very low and does not favor the delocalization of lower vacant MO. In vinyldistannane the *-orbital is noticeably delocalized, due to the interaction with the *_Sn-Sn orbital in planar and with the *_Sn-Sn orbital in nonplanar conformers.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 636–641, March, 1992.     

Thermal behaviour of transition metal complexes of dithiocarbazic esters. II

A thermal study (simultaneous TG and DTA measurements) was carried out on the dithiocarbazic ester complexes M[N³CH₂R₁N²C¹(S)SCH₃]₂, where M=Ni, Pt; R₁=C₆H₅. The following disproportionation reaction occurs in the solid state: II is formed through deprotonation of the CH₂ group bound to N³, whereas III is formed through protonation of N³.The influence of inductive and/or steric effects on the mechanism of this reaction is discussed, taking into account the electrochemical and X-ray data on the complexes Pt[NRNC(S)SR']₂ with differentR substituents: R=H, Ph, CH₂Ph, CH₂C₅H₁₁, CH(CH₃)₂, C(CH₃)₃; R=CH₃, CH₂Ph.These results accord with the behaviour of the same complexes in solution.

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Zusammenfassung Dithiokarbamidsäureesterkomplexe M[N³CH₂R₁N²C¹(S)SCH₃]₂ mit M=Ni, Pt und R₁=C₆H₅ wurden thermisch untersucht. Im festen Zustand spielt sich folgende Disproportionierungsreaktion ab: II wird durch Deprotonierung der an N³ gebundenen CH₂ Gruppe und III durch Protonierung des Atoms N² gebildet. Unter Zuhilfenahme der elektrochemischen und Röntgendaten der Komplexe Pt[NRNC(S)SR']₂ mit verschiedenen Substituenten R: R=H, Ph, CH₂Ph, CH₂C₅H₁₁, CH(CH₃)₂, C(CH₃)₃ und R=CH₃ bzw. CH₂Ph wurde der Einfluß von induktiven und/or sterischen Effekten auf den Reaktionsmechanismus diskutiert. Diese Ergebnisse stehen in Übereinstimmung mit dem Verhalten der Komplexe in Lösung.

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M[N³CH₂R₁N²C¹(S)SCH₃]₂, M= Ni, Pt,R ₁=C₆H₅. : II CH₂ , N³, III N². () , Pt[NRNC(S)SR]₂, R= , aR= . .

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We thank prof. A. La Ginestra for many helpful discussions on the various aspects of this work.     

Donor properties of the nitrone function in copper(II) complexes of some 2-hydroxy-1-naphthylnitrones

Summary Copper(II) complexes of the type CuL₂, 2H₂O and CuL₂. Py where L=-(2-hydroxy-1-naphthyl)-N-R-nitrone (R= methyl, phenyl and variously substituted phenyls) have been isolated and characterised. They have normal magnetic moments. Their ligand field spectra indicate an octahedral geometry for the dihydrates and a five-coordinate environment for the pyridine adducts. Increased (C=N) and considerably decreased (N-O) frequencies in these complexes reveal the presence of - and -interactions of the ligand with copper through nitrone oxygen. The effect of pyridine adduct formation is to increase the Cu-O -interaction.     

Studies on thermal decomposition of rare earth element complexes with glycolic acid

The rare earth complexes with glycolic acid were prepared as crystalline solids with general formula [Ln(CH₂OHCOO)₃H₂O]·nH₂O, wheren=0 for La-Gd andn=2 for Y and Tb-Lu. During heating the monohydrates of La and Pr-Gd decomposed in two steps to Ln₂O₃ and Pr₆O₁₁, with intermediate formation of Ln₂O₂CO₃; monohydrated Ce(III) glycolate decomposed directly to CeO₂. The trihydrated glycolates of Y and Tb-Lu first lost two water molecules and the monohydrated complexes then decomposed to Ln₂O₃ and Tb₄O₇ through Ln₂O₂CO₃.

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Zusammenfassung Komplexe der Seltenerden mit Glykolsäure wurden in Form von kristallinen Substanzen mit der allgemeinen Formel [Ln(CH₂OHCOO)₃·H₂O]·nH₂O mitn=0 für La-Gd undn=2 für Y und Tb-Lu dargestellt. Die Monohydrate von La und Pr-Gd zersetzen sich beim Erhitzen in zwei Stufen über die Zwischenstufe Ln₂O₂CO₃ in Ln₂O₃ und Pr₆O₁₁. Das Monohydrat von Ce(III) glykolat zerfiel direkt in CeO₂. Die Trihydrate der Glykolate von Y und Tb-Lu gaben zunächst zwei Moleküle Wasser ab und die so entstandenen Monohydratkomplexe zersetzen sich dann über Ln₂O₂CO₃ in Ln₂O₃ bzw. Tb₄O₇.

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[Ln(CH₂OHCOO)₃·₂]·n₂, =0 La-Gd =2 Tb-Lu. Pr-Gd Ln₂O₃ r₆₁₁ Ln₂O₂CO₃. ₂. Tb-Lu , Ln₂O₃ b₄₇ Ln₂O₂CO₃.

     

Molecular isotope exchange of14CO in surface carbonyl complexes of rhodium

Molecular isotope exchange of CO with¹⁴CO for Rh₆(CO)₁₆/Sn(II)–SiO₂, Rh₆(CO)₁₆/Al₂O₃, Rh(I)(CO)₂/Al₂O₃, Rh₄(CO)₁₂/Al₂O₃ carbonyl complexes of rhodium has been studied. Estimates of the activation energies and a mechanism of the CO exchange are suggested.

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, (Rh₆(CO)₁₆/Sn(II)–SiO₂, Rh₆(CO)₁₆/Al₂O₃, Rh^I(CO)₂/Al₂O₃, Rh₄(CO)₁₂/Al₂O₃), ¹⁴CO. CO .

     

Pt(II) complexes in activation of saturated hydrocarbons

The rate constants of deuterium exchange for cyclohexane in CH₃COOD/D₂O have been measured in the presence of 12 complexes of Pt(II) with various ligands (Cl, H₂O, NH₃, Br, NO₂, py, DMSO, PPh₃, etc.). The change in the rate constant is shown to follow the reverse series of the trans-effect of Pt(II) ligands. The rate constant of the interaction of PtCl₂S_n (S is H₂O, CH₃COOH, n=1, 2) with cyclohexane in CH₃COOD/D₂O (11), k, equals 2.5×10⁸ exp (–18200/RT) 1 mol^–1 sec^–1 (at 354–385 K). The ratio of rate constants for PtCl₂S₂, PtCl₃S^– and PtCl ₄ ^2– is 10060.5 at 100°C.

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CH₃COOD–D₂O 12- Pt(II) (Cl, H₂O, NH₃, Br, NO₂, , DMCO, PPh₃ .). , Pt(II). PtCl₂S_n (S–H₂O, CH₃COOH, n=1,2) 11 CH₃COOD–D₂O k=2,5·10⁸ exp(–18200/RT). ^{–1 –1} (354–385°). 100°C PtCl₂S₂, PtCl₃S^– PtCl ₄ ^2– 10060,5.

     

Thermal studies on metal complexes of 5-nitroso-pyrimidine derivatives

The following cadmium(II) complexes of deprotonated 6-amino-5-nitroso-uracil (AH), deprotonated 6-amino-3-methyl-5-nitroso-uracil (BH) and neutral 6-amino-1-methyl-5--nitroso-uracil (CH) have been prepared and their thermal behaviour studied by TG and DSC techniques: CdA₂ · 3 H₂O, CdB₂ · 2 H₂O, CdB₂ and CdCl₂(CH)₂ · 2 H₂O.Dehydration processes of these complexes take place in only one step and the enthalpy values associated with them are comprised in the 42.7–80.5 kJ · mole^–1 H₂O range. The pyrolytic reactions finish in the 630–900 C temperature range, remaining as final residue in the case of CdA₂ · 3 H₂O, CdB₂ · 2 H₂O and CdB₂ complexes, cadmium oxide. The pyrolytic decomposition of CdCl₂(CH)₂ · 2 H₂O complex does not yield any residue, due to the elimination of cadmium chloride.

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Zusammenfassung Folgende Cadmium(II)-Komplexe von deprotoniertem 6-Amino-5-nitrosouracil (AH), deprotoniertem 6-Amino-3-methyl-5-nitroso-uracil (BH) und neutralem 6-Amino-1-methyl-5-nitroso-uracil (CH) wurden hergestellt: CdA₂ · 3 H₂O, CdB₂· 2 H₂O, CdB₂ und CdCl₂(CH)₂ · 2 H₂O. Das thermische Verhalten dieser Komplexe wurde mittels TG und DSC untersucht. Die Dehydratisierung der Komplexe verlÄuft in nur einem Schritt. Die Enthalpiewerte für diese Prozesse liegen im Bereich von 42.7–80.5 kJ · mol^–1 H₂O. Die pyrolytischen Reaktionen verlaufen im Temperaturbereich von 630–900C zu Ende, wobei im Falle der Komplexe CdA₂ · 3 H₂O, CdB₂ · 2 H₂O und CdB₂ Cadmiumoxid als Rückstand zurückbleibt. Die pyroytische Zersetzung von CdCl₂(CH)₂ · 2 H₂O verlÄuft wegen der Flüchtigkeit von CdCl₂ rückstandslos.

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CdA₂ · 3 H₂O, CdB₂ · 2 H₂O, CdB₂ CdCl₂(CH)₂ · 2 H₂O, A — 6--5-, B — 6--3--5- CH — 6--1--5- . . 42.7–80.5 · ^–1. 630–900, . CdCl₂(CH)₂ · 2 H₂O - , .