Mono and dinuclear cationic rhodium(I) and iridium(I) complexes with sulphur donor and group Vb ligands

Summary Rhodium(I) and iridium(I) mixed complexes of the formulae [M(diolefin)LL]ClO₄, [M(diolefin)L₂L]ClO₄, [(diolefin)LIr(-L)₂IrL(diolefin)](ClO₄)₂, [(diolefin)LM(-L-L)ML'(diolefin)](ClO₄)₂, [(diolefin)Rh{-(L-L)}₂Rh(PPh₃)₂](ClO₄)₂ and [(diolefin)LIr{-(L-L)}₂IrL (diolefin)](C1O₄)₂, (L=monodentate sulphur ligand, L-L=bidentate sulphur ligand, L=group Vb ligand; M=Rh, diolefin=1,5-cyclooctadiene (COD) or 2,5-norbornadiene (NBD); M=Ir, diolefin=COD) are described.Author to whom all correspondence should be directed.     

Invariant sets for kinetic equations

Some sets in the space of compositions possessing an invariance property are considered for a closed system, where a complex chemical reaction of a known mechanism proceeds. If the vector of concentrations belongs to such a set at a certain moment of time, it will remain within it at any succeeding moment. Some possible applications are discussed.

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, , , : , . .

     

The application of XRF analysis in the determination of113mCd

The overall recovery of the separated^113mCd with added Cd carrier from 50 samples of natural water was determined by a secondarysource tube excited energy dispersive X-ray fluorescence spectrometer measuring the amount of cadmium in the final CdS+CuS coprecipitate on a 25 mm diameter Millipore filter. The method enables to determine 1–20 g Cd in 100 sec. with a limit of detection of 0.8 g.Presented at the 7th Czechoslovak Spectroscopic Conference and VIIIth CANAS, eské Budjovice, June 18–22, 1984.     

μSr studies of free radicals in the gas phase

Muonium (Mu=₊+e^-) is the bound state of a positive muon and an electron. Since the positive muon has a mass about 1/9 of the proton, Mu can be regarded as an ultra light isotope of hydrogen with unusually large mass ratios (MuHDT=1/9123). The muon spin rotation technique (SR) relies on the facts that (1) the muon produced in pion decay, ^{+ +} + , is 100% spin polarized and (2) the positron from muon decay is emitted preferentially along the instantaneous muon spin direction at the time of the muon decay.In transverse field SR (TF-SR), the precession of the muon spin in muonium substituted radicals is directly observed by detecting decay positrons time differentially. From observed radical frequencies, the hyperfine coupling constants (A ) of C₂H₄Mu, C₂D₄Mu,¹³C₂H₄Mu, C₂F₄Mu, and C₂H₃FMu are determined. In the longitudinal field avoided level crossing (LF-ALC) technique, one observes the resonant loss of the muon spin polarization caused by the crossing of hyperfine levels at particular magnetic fields. The LF-ALC method together with the information onA obtained from TF-SR allows one to determine the magnitude and sign of the nuclear hyperfine constants at - and -positions. Results are compared with hydrogen substituted ethyl-radicals and isotope effects are discussed.     

Le systeme eau-theophylline

The binary system water—theophylline was studied by DTA and radiocrystallography. The slow dehydration of theophylline monohydrate was observed at room temperature at relative humidities lower than 60%, without the formation of any other hydrate. The isochoric phase diagram was established. At 78 °C, a peritectic invariant occurred, owing to decomposition of the monohydrate. The existence of only one binary compound (theophylline H₂O) was confirmed by the.Tammann diagram.

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Zusammenfassung Mittels DTA und Radiokristallographie wurde das binäre System Wasser-Theophyllin untersucht. Bei einer relativen Luftfeuchtigkeit unter 60% wird bei Raumtemperatur eine langsame Dehydratation von Theophyllinemonohydrat ohne Formung anderer Hydrate beobachtet. Es wurde ein isochores Phasendiagramm entwickelt. Wegen der Zersetzung des Monohydrates tritt bei 78 °C eine peritektische Invariantheit auf. Die Existenz nur einer binären Verbindung (Theophyllin, H₂O) wird mittels eines Tammanndiagrammes bekräftigt.

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— . 60% - . . 78° , . -.

     

Kinetics and mechanism of oxidation of quinol by alkaline hexacyanoferrate(III)

The reaction between quinol and alkaline hexacyanoferrate(III) at constant ionic strength gives p-benzoquinone. The rate of the reaction was first order in the concentrations of substrate, oxidant and alkali. The slow step of the reaction involves the formation of the p-benzosemiquinone radical, which was detected by esr spectroscopy as a five-line spectrum with peak intensity ratios of 14641.

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(III) -. , . - , , 14641.

     

Preparation of a Ru/Al2O3 catalyst from Ru3(CO)12 infrared and XPS study

A supported ruthenium catalyst on alumina prepared from Ru₃(CO)₁₂ has been studied by infrared and X-ray photoelectron spectroscopy (XPS). The triatomic cluster is retained on the support but breaks down at 150°C. Complete elimination of the carbonyl groups requires heating at 350°C under vacuum. XPS studies show that the decomposed catalyst does not change on further reduction in H₂ at 400°C. The ruthenium atoms remain trapped within the pores of the support.

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Al₂O₃, Ru₃(CO)₁₂, (XPS). , 150°C . 350°C . XPS , H₂ 400°C . .

     

Acid-base properties of Sn?Mo?Ox catalysts

The acidity and basicity of Sn–Mo–O_x catalysts with different Mo/Mo+Sn atomic ratios were measured by determining the adsorption isotherms of pyridine and acetic acid by chromatographic method. It was found that acidity and basicity go through a maximum at a Mo content of 15–20 at.%.

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Sn–Mo–O_x Mo/Mo+Sn, . Mo=15–20 at.%.

     

Kinetics of hydrogen isotope exchange in molecules with strong intramolecular hydrogen bonds

Rate constants and activation energies of hydrogen exchange in solution between methanol and molecules with intramolecular H-bonds have been measured. It has been established that the rate-determining step is the dissociation of this bond.

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H-. , .

     

Sensitization of the photoadsorption of O2 and NO on SnO2

Photoadsorption activity of SnO₂ with respect to O₂ and NO after CO chemisorption has been revealed to be drastically increased. Photoadsorption is suggested to be sensitized by surface carbonates formed due to CO chemisorption.

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. , .

     

Effect of iron on the behavior of Fe2O3?MoO3/SiO2 ammoxidation catalysts

Catalytic ammoxidation of propylene was studied using Fe₂O₃–MoO₃/SiO₂ catalysts, which have been prepared following a special method. Interaction of ammonia with the catalysts was studied by means of IR spectroscopy and gravimetrically using a McBain balance. Introduction of iron into MoO₃/SiO₂ catalysts modifies acidic as well as redox properties.

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Fe₂O₃–MoO₃/SiO₂ . . - . MoO₃/SiO₂ , .

     

ESR studies of Mo?Mg oxide catalysts

For 0.1–0.5 wt.% Mo–Mg oxide samples with high concentration of⁹⁵Mo isotopes two types of Mo⁵⁺ have been identified. Their role in the formation of O ₂ ^– anion-radicals in low-temperature oxygen adsorption on reduced samples has been established.

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, ⁹⁵Mo, Mo⁵⁺ Mo–Mg (0,1–0,5 .% Mo) - O ₂ ^– .

     

Catalytic oxidation of acrolein to acrylic acid over a molybdenum-vanadium catalyst

By the method of gas chromatography it has been found that the adsorption of acrolein takes place without dissociation whereas acrylic acid is adsorbed dissociatively. The adsorption of water vapor proceeds also dissociatively and results in increasing the number of the Brönsted acid centers. The presence of water vapor has a positive effect on the desorption rate of acrylic acid and a negative effect on the reoxidation rate of the catalyst.

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, , . , . , — .

     

Mechanism of methane photooxidation on V/SiO2 catalyst

CH₄ photooxidation on V/SiO₂ catalyst in the presence of gaseous oxygen has been studied by the mass-spectometric method. It has been established that CO₂ forms due to the interaction of CH₄ with surface oxygen anions bonded to vanadium ions. Photodecomposition of V⁴⁺O ₂ ^– species formed in O₂ adsorption on reduced vanadium ions leads to the reoxidation of the latter.

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- CH₄ V/SiO₂ . , CO₂ CH₄ , . V⁴⁺O ₂ ^– O₂ , .

     

Thermal properties of molten sulphur-oxyanionic salts

Lithium, sodium, potassium and ammonium bisulphate have been shown by detailed TG/DTA studies to have limited application as molten solvents. By contrast, the eutectic bisulphate systems, ammonium-potassium bisulphate and sodium-potassium bisulphate, appear to be excellent molten solvents in view of their low melting points, long liquid ranges and prolonged thermal stability at 200°. In contrast to previous studies, potassium pyrosulphate has been found to be an excellent molten solvent, provided rigorous preliminary drying procedures have been applied.

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Zusammenfassung An Hand eingehender TG/DTA-Untersuchungen wurde gezeigt, daß die Bisulfate von Lithium, Natrium, Kalium und Ammonium nur eine begrenzte Anwendung als geschmolzene Lösungsmittel finden können. Die eutektischen Bisulfat-Systeme Ammonium/ Kalium Bisulfat und Natrium/Kalium Bisulfat scheinen wegen ihrer niedrigen Schmelzpunkte, ihres weiten Flüssigkeitsbereichs und ihrer dauerhaften Thermostabilität bei 200° ausgezeichnete geschmolzene Lösungsmittel zu sein. Im Gegensatz zu früheren Untersuchungen erwies sich Kaliumpyrosulfat als ein ausgezeichnetes geschmolzenes Lösungsmittel, vorausgesetzt daß vorangehend strenge Trocknungsverfahren angewandt wurden.

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Résumé On montre par une étude TG/ATD approfondie que les hydrogénosulfates de lithium, de sodium, de potassium et d'ammonium n'ont qu'une application limitée en tant que solvants fondus. Les systèmes eutectiques des hydrogénosulfates ammonium/potassium et sodium/potassium paraissent, au contraire, être des solvants fondus excellents, en raison de leurs points de fusion bas, de leurs larges intervalles d'existence à l'état liquide et de leur stabilité thermique prolongée à 200°. Contrairement à des études antérieures, on a trouvé que le pyrosulfate de potassium est un solvant fondu excellent, à la condition d'appliquer un mode opératoire rigoureux lors du séchage préliminaire.

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/ , , , . , - - , 200°. , , , - .

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The authors would like to thank Dr. C. Barraclough and Mr. M. Beyer of the Physical Chemistry Department, Melbourne University, for assistance with the Raman spectra.     

Kinetic study of the thermally initiated cyclocondensation of some 1,3-dimethyl-4-alkylamino-5-nitrosouracils

The isothermal and non-isothermal DSC method was used to investigate the influence of changes in structure of 1,3-dimethyl-4-alkylamino-5-nitrosouracils on the 8-substituted theophyllines originating in the cyclocondensation reaction. The evaluation of the optimum reaction mechanism obtained on the basis of the corresponding model functions by using the integral method of Coats and Redfern is discussed. Significant differences, depending on the nature of the substituents, were observed in the course of the reaction.

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Zusammenfassung Der Einflu\ von VerÄnderungen in der Struktur von 1,3-Dimethyl-4-alkylamino-5-nitrosouracilen auf die in einer Zyklokondensationsreaktion gebildeten, 8-substituierten Theophylline wurde mittels isothermer und nicht-isothermer DSC untersucht. Die optimalen, basierend auf entsprechenden Modellfunktionen bei Anwendung der Integralmethode von Coats und Redfern erhaltenen Reaktionsmechanismen werden diskutiert. Im Verlaufe der Reaktion wurden signifikante, von der Natur der Substituenten abhÄngende Unterschiede festgestellt.

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1,3--4--5- 8- , . , , - . .

     

A gradientless airtight glass reactor with a detachable catalyst chamber

A gradientless airtight glass reactor supplied with a detachable chamber for the catalyst has been developed. It is designed for investigations on the kinetics of heterogeneous catalytic processes and the determination of catalytic activities at atmospheric and reduced pressures by the flow-circulation and quasi-static techniques.

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. - . , .

     

Study of the adsorption properties of a natural Hungarian mordenite and its ion-exchanged derivatives

The texture and adsorption properties of a natural, Hungarian mordenite were investigated by electron microscopy and BET adsorption measurements. The properties of the ion-exchanged adsorbents were characterized by CO₂ and SO₂ isotherms. The measurements were evaluated on the basis of the pore-filling theory of Dubinin. We have found that at 20°C the H⁺-form of mordenite interacts preferably with CO₂, while on the Na⁺- and Ca²⁺-derivatives stronger adsorption of SO₂ takes place. This fact accounts for their applicability as selective adsorbents.

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, . CO₂ SO₂. . , 20°C H⁺- CO₂, Na⁺- Ca²⁺- SO₂ . .

     

Oxidation of divalent manganese by peroxodiphosphate in acetate buffers. A kinetic study

Bivalent manganese in oxidized to the tervalent state in 4.0–5.3 pH (acetate buffers) when treated with an excess of peroxodiphosphate (PDP). Kinetic evidence for the formation of a 11 complex between manganese(II) and PDP was obtained. The reaction exhibits first order dependence on [Mn(II)] and fractional order dependence on [PDP]. The reaction is markedly inhibited by H⁺ ions. A plausible mechanism consistent with the observed data is proposed.

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pH=4,0–5,3 (). (II) 11. [Mn(II)] []. H⁺ . , .