Configurations of the [Pd(NO2)4]2- Complex Anion: Crystal Structure of Ag4A2[M(NO2)4]3 (M = Pd, Pt; A = K, Rb)

An integrated Xray diffraction study was performed on polycrystals and single crystals of three new isostructural phases with general formula Ag₄A₂[M(NO₂)₄]₃ (M = Pd, Pt; A = K, Rb). Data on the crystal structure solution (CAD4 diffractometer, MoK radiation, graphite monochromator = 2–30° are presented. In one crystallographically independent [M(NO₂)₄]^2- complex anion, the planar square coordination of the central atom is completed to 4 + 2 by two oxygen atoms at a distance of 3.02–3.12 in the other anion, it is completed to 4 + 1 + 1 by an oxygen atom at a distance of 3.12–3.30 and an Ag⁺ cation at a distance of 3.04–3.11 . Part of the Ag⁺ cations form Ag - Ag dimers with a distance of 3.03–3.07. Crystalchemical analysis of known structures containing [Pd(NO₂)₄]^2- complex anions was performed. It has been established that in none of the cases do any of the possible limiting configurations occur.     

Hydrogenation of ethylene and propylene over MgO doped with alkali metals

The hydrogenation of ethylene and propylene over MgO doped with alkali metal vapors has been studied. All the catalysts examined are active in hydrogenation at 150 °C at atmospheric pressure. It is proposed that the catalytic activity of the systems investigated is connected with strong one-electron donor surface sites.

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MgO . 150°C . , .

     

Thermal decompositions of (NH4)2WSe4 and (NH4)3VS4 under normal and reduced nitrogen pressures

A method is devised by modification of the author's previous method. Thermoanalytical data are transformed to equivalent isothermal ones, and linear relations are utilized to elucidate the mechanism and the pre-exponential factor, instead of curvefitting. Advantages are illustrated by applying this method to the decomposition of polycaprolactam.

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Zusammenfassung Es wurde eine neue Methode durch Modifizierung der früheren Methode des Autors entwickelt. Bei der neuen Methode werden die thermoanalytischen Daten in isotherme umgewandelt und anstatt der Kurven-Anpassung der vorhergehenden Methode werden lineare Zusammenhänge zur Klärung des Mechanismus und des pre-exponentiellen Faktors eingesetzt. Die Vorteile der neuen Methode werden durch ihre Anwendung bei der Untersuchung der Zersetzung von Polycaprolactan veranschaulicht.

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Résumé La méthode précédemment proposée par l'auteur est modifiée. La nouvelle méthode qui est présentée transforme les données thermoanalytiques en données isothermes équivalentes et utilise des relations linéaires pour établir le mécanisme et le facteur pré-exponentiel au lieu de la méthode antérieure avec ajustement des courbes. Les avantages de cette nouvelle méthode sont illustrés en l'appliquant à la décomposition du polycaprolactane.

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, , , , , . .

     

Kinetic parameters of the thermal decompositions of nitritonickelates(II)

Kinetic parameters of thermal decomposition of compounds of general formulaM ₂ ^I M ^II[Ni(NO₂)₆], whereM ^I= K⁺, Rb⁺ or Cs⁺ andM ^II= Ca²⁺, Sr²⁺ or Ba²⁺, were investigated on the basis of the respective thermal curves. Calculations of the reaction order and activation energy carried out by the Coats-Redfern method and by Doyle's method (modified by Zsakó) gave similar results, The reaction order is 2 for all the compounds investigated. In the group of potassium salts the activation energy increases fromM ^II=Ca²⁺ toM ^II=Ba²⁺. In the groups of rubidium and caesium salts, the lowest activation energy is observed whenM ^II=Sr²⁺. Such behaviour of the nitritonickelates is explained in terms of structures and the principle of maximum density.

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Zusammenfassung Die kinetischen Parameter der thermischen Zersetzung von Verbindungen der allgemeinen FormelM ₂ ^I M ^II [Ni(NO₂)₆] (M ^I= K⁺, Rb⁺ oder Cs⁺ und M^II = =Ca²⁺, Sr²⁺ oder Ba²⁺) wurden auf Grund der entsprechenden thermischen Kurven untersucht. Die an Hand der Coats-Redfern Methode und der durch Zsakó modifizierten Doyleschen Methode durchgeführten Berechnungen der Reaktionsordnung und der Aktivierungsenergie ergaben ähnliche Resultate. Die Reaktionsordnung ist 2 für sämtliche untersuchten Verbindungen. In der Gruppe der Kaliumsalze steigt die Aktivierungsenergie vonM ^II=Ca²⁺ in RichtungM ^II=Ba²⁺ an. In der Gruppe der Rubidium- und Caesiumsalze wird die niedrigste Aktivierungsenergie beiM ^II=Sr²⁺ beobachtet. Dieses Verhalten der Nitritonickelate wird durch die Strukturen und das Prinzip der maximalen Dichte erklärt.

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₁ ^{2 II}[Ni(NO₂)₆], ^I= ⁺, Rb⁺Cs⁺,a ^II= ²⁺,8r²⁺²⁺. , - ( ), . 2. ^{+ 2+}. ^II=S²⁺. .

     

Thermal analysis of some complexes LH[Cr(NCS)4L2].xH2O (L=NH3 or organic base)

Data obtained by thermal analysis of K₃[Cr(NCS)₆].4H₂O and some derivatives, LH[Cr(NCS)₄L₂].xH₂O, where L=NH₃ or an organic base, are reported. The TG, DTG and DTA curves show common behaviour (SCN^– ligand decomposition) as well as specific behaviour for each complex due to the base L, which complicates the thermal decomposition of the complexes. Some weak bases with low boiling points are easily eliminated, which determines the common thermal behaviour of the complexes.A general mechanism of thermal decomposition is advanced involving dehydration and decomposition processes for both LH⁺ and [Cr(NCS)₄L₂]^–. The apparent activation energies of different processes confirm the thermal decomposition mechanisms of the complexes under study.

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Zusammenfassung Die thermische Analyse von K₃[Cr(NCS)₆].4H₂O und einigen Derivaten der allgemeinen Formel LH[Cr(NCS)₄L₂].xH₂O (L=NH₃ oder eine organische Base) betreffende Daten werden angegeben. Die TG-, DTG- und DTA-Kurven zeigen sowohl gemeinsame Charakteristika (Zersetzung des Liganden SCN^–) als auch für jeden Komplex spezifische, durch die Base L bedingte Züge, die die thermische Zersetzung der Komplexe komplizieren. Einige schwache Basen mit niedrigen Siedepunkten werden leicht eliminiert, was ein gleiches thermisches Verhalten dieser Komplexe zur Folge hat. Ein allgemeiner Mechanismus der thermischen Zersetzung wird angegeben, der die Dehydratisierung und die Zersetzungsprozesse sowohl für LH⁺ als auch für [Cr(NCS)₄L₂]^– in sich einschließt. Die scheinbaren Aktivierungsenergien der verschiedenen Prozesse sind mit dem Mechanismus der thermischen Zersetzung der Untersuchten Komplexe im Einklang.

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K₃[Cr(NCS)₆].4H₂O LH[Cr(NCS)₄L₂].x₂, L=NH₃ - . , - , , . , . , LH⁺ [Cr(NCS)₄L₂]^–. .

     

Phase equilibria in the FeVO4-Fe2(MoO4)3 system

Phase équilibria have been investigated in the FeVO₄-Fe₂(MoO₄)₃ system for the whole concentration range of the components. In this system there is one compound which melts incongruently: Fe₄V₂Mo₃O₂₀. The results are presented in the form of a phase diagram.

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Zusammenfassung Phasengleichgewichte im System FeVO₄-Fe₂(MoO₄)₃ wurden über den ganzen Konzentrationsbereich der Komponenten hinweg untersucht. Eine Verbindung des Systems, Fe₄V₂Mo₃O₂₀, schmilzt inkongruent. Die Ergebnisse sind in Form eines Phasendiagramms angegeben.

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FeVO₄-Fe₂(MoO₄)₃ . Fe₄V₂Mo₃O₂₀, . .

     

Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

Lewis-Base Adducts of Group 11 Metal(I) Compounds. LXXVI Structural Studies in the Copper(I) Halide : Norbornadiene System

The structural characterizations of some copper(I) halide (CuX) adducts with norbornadiene (nbd) are recorded. CuCl : nbd (1:1)₄ (a redetermination), (2:1)_2(|), are systems both based around Cu₄Cl₄ cubane-type cluster arrays. CuBr : nbd (7:3)_(|)( 0.5 MeOH), a complex polymer with 3-symmetry, is believed to be the complex previously described as an adduct of 2:1 stoichiometry. Attempts to obtain an iodide counterpart have resulted in the definition of an ephemeral adduct CuI : MeCN (3:2)_(|). 0.5 C₇H₈ in which, remarkably, the nbd is uncoordinated; the complex is a polymer, related to the [AgX(quinoline)]_(|) (X = Cl, Br) saddle polymer.     

Thermal Behaviour of some dioxane adducts ofM(C6F5)2 (M=Pd,Pt)

The thermal treatment of the pentafluorophenyl derivativesM(C₆F₅)₂Dx_n [M=Pd (n=2, 3) or Pt (n=2); Dx=dioxane] leads to the formation of the new dioxane adducts M(C₆F₅)₂Dx (M=Pd, Pt) and Pt(C₆F₅)₂Dx_1.5. Calculations of the order of reaction and the activation energy of some of the decomposition reactions are described. The values were determined by the Coats-Redfern and Freeman-Carroll methods. Structural data on the isolated intermediates were obtained by infrared spectroscopy and magnetic susceptibility measurements.

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Zusammenfassung Die thermische Behandlung der PentafluorphenylderivateM(C₆F₅)₂Dx_n [M=Pd (n=2, 3) oder Pt (n=2); Dx=Dioxan] führt zu der Bildung der neuen DioxanaddukteM(C₆F₅)₂Dx (M=Pd, Pt) und Pt(C₆F₅)₂Dx_1.5. Die Berechnungen der Reaktionsordnung und der Aktivierungsenergie einiger Zersetzungsreaktionen werden beschrieben. Die Werte wurden durch die Methoden von Coats-Redfern und Freeman-Carroll bestimmt. Die Strukturangaben der isolierten Zwischenprodukte wurden durch Infrarotspektroskopie und Messung der magnetischen Suszeptibilität erhalten.

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(₆F₅)₂, M=Pd n=2, 3 Pt _n=2, - , -M(C₆F₅)₂ (=Pd, Pt) (₆F₅)_21,5. , — —. .

     

Ce(IV)-Komplexe mit α,α'-Bipyridin und 1,10-Phenanthrolin

Zusammenfassung Es wurden die Verbindungen (H_of)₂CeCl₆, (H_bip)₂CeCl₆ sowie Ce_{of 2}Cl₃OCH₃·CH₃OH (of=1,10-Phenanthrolin,bip=,-Bipyridin) isoliert. Die ersten zwei Verbindungen sind isomorph und kubisch, die letzte ist röntgenamorph. Beim Erhitzen tritt in allen drei Fällen mit Abspaltung eines aktiven Chlors verbundene Pyrolyse ein. Es wurden auch die IR-Spektren aufgenommen. Das dritte Präparat stellt einen Cer(IV)-Komplex mit einem N-Liganden dar.

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Ce(IV)-complexes with ,'-bipyridine and 1,10-phenanthroline

The following compounds were isolated: (H-of)₂CeCl₆, (H-bip)₂CeCl₆, and Ce-of ₂Cl₃OCH₃·CH₃OH (of =1.10-phenanthroline,bip =.-bipyridine). The first two are isomorphous and cubic, the latter is X-ray amorphous. On heating all compounds pyrolyze with loss of active chlorine, IR spectra are reported. The third compound mentioned is a Ce(IV)-complex with a N-ligand.

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Mit 2 Abbildungen     

Use of differential calorimetry for characterization of hydration processes in the system Ca4(Al6O12) (SO4)-CaSO4.2H2O-H2O

Differential calorimetry was used to determine the heat evolution and kinetics of hydration processes of the calciumsulphatealuminate phase Ca₄(Al₆O₁₂)(SO₄) with gypsum CaSO₄ · 2H₂O at room temperature with one mole of water added to the solid phase. An increasing content of sulphate ions in the sytem results in substitution of the monosulphate Ca₄(Al₂O₆)(SO₄) · 12H₂O in the reaction products by ettringite, Ca₆(Al₂O₆)(SO₄)₃ · 32H₂O. Higher contents of ettringite influence the rates of hydration reactions and the values of the evolved heat.

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Zusammenfassung Die Wärmeentwicklung und ihr zeitlicher Ablauf bei der Hydratation des Calciumsulfat-aluminats Ca₄(Al₆O₁₂)SO₄ mit Gips CaSO₄ · 2H₂O bei Zimmertemperatur und einem Wasser/Feststoff-Massenverhältnisw/s=1 wurde durch isotherme Differenzkalorimetrie untersucht. Bei erhöhtem Sulfatgehalt wird das Monosulfat Ca₄(Al₂O₆)SO₄ · 12H₂O im Reaktionsprodukt durch Ettringit Ca₆(Al₂O₆)(SO₄)₃ · 32H₂O ersetzt. Der erhöhte Ettringitgehalt beeinflusst die Beschleunigung der Hydration und die abgegebene Wärmemenge.

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₃( l₆₁₂) (SO₄) . - ₆(l₂₆)(S₄)₃·32₂, .

     

Thermal decomposition of some imidazole and N-methyl substituted imidazole complexes of palladium(II)

We describe in this paper the thermal decomposition in air of several complexes of palladium(II) chloride with imidazole and N-methylimidazole. Although the final process of the decomposition gives (PdCl₂)_n which then decomposes to pa ladium which oxidizes to PdO, there are interesting differences in the initial decomposition path. The reasons for these differences appear to be related to the trans-effect and to the presence in the imidazole complexes of hydrogen bonds which break down at temperatures of around 220.

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Zusammenfassung In diesem Beitrag wird die thermische Zersetzung verschiedener Komplexe des Palladium(II)chlorids mit Imidazol und N-Methylimidazol in Luft beschrieben. Obwohl der Endvorgang der Zersetzung (PdCl₂)_n ergibt, welches dann zu Palladium zersetzt und zu PdO oxidiert wird, bestehen interessante Unterschiede im Anfangsschritt der Zersetzung. Die Ursachen dieser Unterschiede scheinen mit dem Trans-Effekt und der Anwesenheit von Wasserstoffbindungen in den Imidazolkomplexen verbunden zu sein, welche bei Temperaturen um 220 zerstört werden.

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Résumé La décomposition thermique dans l'air de plusieurs complexes du chlorure de palladium(II) avec l'imidazole et le méthyl-4-imidazole est décrite. Bien que l'étape finale de la décomposition donne (PdCl₂)_n qui se décompose ensuite en palladium qui s'oxyde en PdO, des différences intéressantes apparaissent dans les étapes initiales de la décomposition. Les causes de ces différences sont en rapport avec l'effet trans et la présence, dans les complexes avec l'imidazole, de liaisons hydrogÊne qui se rompent vers 220.

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(II) -. (PdCl₂)_n, , PdO, . , - , 220.

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One of us (M.C. Navarro Ranninger) would like to thank the D.G.E.S.I. for a grant that allowed her to work on this research.     

Some Pharmaceutical Properties of a New Branched Cyclodextrin, 6-O-α-(4-O- α-D-Glucuronyl)-D-glucosylβ-cyclodextrin

Some physicochemical and biological properties of a new branched cyclodextrin, 6-O--(4-O--d-glucuronyl)-d-glucosyl--cyclodextrin GUG--CyD) were investigated. Further, theinteraction of GUG--CyD with several drugs was studied by the solubility and spectroscopic methods, and compared with those of parent -CyD and 6-O--maltosyl--CyD(₂--CyD).The hemolytic activity of GUG--CyD on rabbit erythrocytes was lower than those of -CyD and ₂--CyD. GUG--CyD and ₂--CyD showed negligible cytotoxicity on Caco-2 cells up to at least 0.1 M. The inclusion ability of GUG--CyD to neutral and acidic drugs was comparable to or slightly smaller than those of -CyD and ₂--CyD, probably because of a steric hindrance of the branched sugar. On the other hand, GUG--CyD showed greater affinity for the basic drugs, compared with -CyD and ₂--CyD, owing to the electrostatic interaction of its carboxylate anion with positive charge of basic drugs. Thus GUG--CyD may be useful as a safe solubilizing agent particularly for basic drugs.     

Molecular Recognition Based on Roof-shaped Diol Hosts. X-Ray Crystal Structures of Inclusion Compounds with Methanol, Pyridine and Toluene

Three crystalline inclusion compounds of roof-shapedtrans-11,12-bis(diaryl-hydroxymethyl)-9,10-dihydro-9,10-ethanoanthracene host molecules [where aryl is 4-methyl-phenyl (3) or4-t-butylphenyl (4)] have been studied by X-ray diffraction.The crystals of both the 3methanol (2 : 1) [a = 10.755(1),b = 11.571(1), c = 14.697(2) Å, = 75.12(1), = 89.67(1), = 87.13(1) °] and the 4-pyridine (2 : 3) compounds[a = 14.045(3), b = 14.366(3), c = 15.607(3) Å, = 91.62(1), = 103.65(1) and =116.05(1)°] are triclinic (P–1),while the 3toluene (1 : 1) complex has orthorhombic (Fddd) symmetry [a = 16.041(1), b = 25.008(1), c = 40.440(4) Å]. The host–guest interactions in both triclinic crystals are characterised by hydrogen bonds, with different patterns however. The determined crystal structures indicate a compromise between the requirement of hydrogen bonding on the one hand and close packing on the other. The highly symmetrical host framework in the toluene (1 : 1) complex of 3 seems to be the result of shape recognition, although atendency towards weak (C_methyl)H _arylinteractions [C_methyl = 3.533(7) and 3.674(6) Å] between the hosts was observed. The present roof-shaped diol hosts give excellent examples of molecular recognition by exhibiting two significantly different conformations, mostly depending on the proton donor/acceptor ability of the guest component. (O)H O intramolecular bonding between the two alcoholic groups characterises the so-called active form, whereas weaker (O)H and interactions stabilise the `inactive'conformation.     

Entropy in dissimilarity and chirality measures

Within the prospect of quantifying the geometrical dissimilarity of molecular models on the basis of a thermodynamical formalism, the algebra of stereogenic pairing equilibria is reviewed and applied to molecular geometry: developing Rassat's proposition, an interaction energy of two figures F and F is taken as proportional tod _H ^Emphasis>/2 (F, F), whered _H denotes the Hausdorff distance. IfG is a group of rotations in E _n the geometrical version of the general equation (E) of the chemical algebra defines a distance extensionD _p(F,F) ofd _H(F,F), which is independent of the orientations of F and F, and where the coefficientp is interpreted as the reciprocal of a temperature-like parameter:p 1/T. At K (p = ), no formal entropy contributes to the definition of the uniform distanceD . At K (p = 0), the discrimination between homo- and hetero-pairing of figures by the harmonic distance Do is averaged over orientation states. Temperature-dependent chirality measuresc _p are derived fromD _p, andc is analogous to Mislow's chirality measure. If T and oT are normalized enantiomorphic triangles with coincident centroids inE ₂,c _p(T) =D _p (T, T) is calculated forp = 0 andp = , and discussed for 0 <p < . Finally, the Hausdorff interaction model is putatively related to energy profiles versus dihedral angle inmeso- anddl-molecules.     

First and second thermodynamic mixing properties of ethylbenzene +n-alkanes: Experimental and theory

Isobaric expansibilities _P and isothermal compressibilities _T have been determined at 25 and 45°C for binary mixtures of ethylbenzene + n-tetradecane and + n-hexadecane and the corresponding excess functions (V ^E /T)_P and (V ^E /P)_T have also been obtained. With these data and supplementary literature values, the following second order mixing properties are also reported at 25°C: _S ^E , (V ^E /P)_T, C_V and (VT). All mixing quantities have been compared with the results obtained at 25°C by using the Prigogine-Flory-Patterson theory of liquid mixtures. The predicted values suggest that the ability of ethylbenzene as a breaker of the pure n-C_n orientations is similar to what we found for toluene and higher than for p-xylene.     

Inclusion Complexes of Cyclodextrins with Tetrakis(4-carboxyphenyl)porphyrin and Tetrakis(4-sulfonatophenyl)porphyrin in Aqueous Solutions

In neutral and alkaline solutions, tetrakis(4-carboxyphenyl)porphyrin (TCPP) and tetrakis(4-sulfonatophenyl)porphyrin (TSPP) form 1:1 and 2:1 host–guest inclusion complexes with -cyclodextrin (-CD), -cyclodextrin (-CD), and 6-deoxy-6-diethylamino--CD (DEA--CD), except for DEA--CD in alkaline solution. On the other hand, TCPP and TSPP form only 1:1 inclusion complexes with 6-deoxy-6-dihexylamino--CD (DHA--CD). The limited solubilities of DEA--CD in alkaline solution and DHA--CD are likely responsible for no observation of the 2:1 inclusion complex containing DEA--CD in alkaline solution and that containing DHA--CD. The equilibrium constants (Ks) of TCPP and TSPP for the formation of the inclusion complexes have been estimated from the absorption and/or fluorescence intensity changes in neutral and alkaline solutions. The K₂ values, which are the equilibrium constants for the formation of the 2:1 host–guest inclusion complex from the 1:1 inclusion complex, are about one tenth the corresponding K₁ values, except for the -CD–TSPP system in alkaline solution. In neutral solution, where DEA--CD and DHA--CD are in protonated forms, the electrostatic force operates between DEA--CD (DHA--CD) and TCPP (TSPP), leading to the greater K values than those in alkaline solution, where DEA--CD and DHA--CD exist as neutral species.     

NMR studies of the interaction between tris-acetylacetonates of Fe(III), Cr(III) and diethyldichloride of Sn (IV)

Paramagnetic relaxation rate of CH₂ protons has been found to be higher than that of CH₃ protons of SnEt₂Cl₂ in the presence of tris-acetylacetonate of Cr(III) in chloroform at 298 K, which supports the specific interactions between these compounds. The revealed ligand exchange between Cr(AA)₃, Fe(AA)₃ and SnEt₂Cl₂ takes place with the equilibrium shifted to the side of initial reactants.

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, -CH₂ CH₃- SnEt₂Cl₂ - Cr(III) 298 K, . Cr(AA)₃, Fe(AA)₃ SnEt₂Cl₂, .

     

Kinetics of oxidation of adonitol by manganese(III) pyrophosphate

Adonitol is oxidized to ribose by Mn(III) pyrophosphate under the conditions [adonitol] [Mn(III)]. The oxidation rate is first order with respect to both oxidatn and substrate and decreases inversly with [pyrophosphate]_free. Thermodynamic parameters are reported and a suitable mechanism involving free radicals is proposed.

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(III) [] [Mn(III)]. , - []. - .