Binuclear iron(III) acetates

Summary The binuclear iron(III) compound, Fe₂Cl(OH)₂(MeCO₂)₃ 2 AcOH combines with pyridine, -picoline and 2,2-bipyridyl (B) to form Fe₂Cl(OH)₂(AcO)₃·B adducts. The secondary bases, pyrrolidine and diethylamine (RNH), on the other hand, combine with the complete elimination of chlorine to form, Fe₂(NR)(OH)₂(AcO)₃. These products have been characterised by molecular weight, i.r. spectra, magnetic susceptibility and Mössbauer measurements.     

Thermal conductivity of cemented carbides

The hypothetical salts Li₄SiN₂O and Li₇SiN₃O were sought in the course of studies on the reactions of Li₂SiN₂ and Li₅SiN₃ with lithium oxide, and of LiSiNO with lithium nitride.

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Zusammenfassung In einer Reihe von Studien der Reaktionen von Li₂SiN₂ und Li₅SiN₃ mit Lithiumoxid bzw. LiSiNO mit Lithiumnitrid wurde nach den hypothetischen Salzen Li₄SiN₂O und Li₇SiN₃O gesucht.

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Li₂SiN₂ Li₅SiN₃ LiSiNO Li₄SiN₂O Li₇SiN₃O.

     

Thermal decomposition of palladium-imidazole complexes

Two Pd-imidazole complexes have been synthesized following the reaction of PdCl₂ and imidazole at 12 and 14 metal ligand ratios. Elemental and thermogravimetric analytical data obtained from these compounds illustrate that they have the formulae Pd(IMDAH)₂Cl₂ · 4H₂O and Pd(IMDAH)₃Cl₂ (IMDAH = imidazole), respectively. The mechanism of thermal decomposition for these complexes in air involves initial dissociation of H₂O and IMDAH ligands in the 120–340 °C range, subsequent dissociation of the chloride atoms to form PdO in the 530–570 °C range, and finally formation of Pd metal at 820–840 °C.

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Zusammenfassung In einer Reaktion von PdCl₂ mit Imidazol wurde bei einem metall-Ligandenverhältnis von 12 bzw. 14 zwei Pd-Imidazolkomplexe dargestellt. Auf Grund der Ergebnisse von Elementaranalyse und Thermogravimetrieuntersuchungen besitzen die Verbindungen die Formeln Pd(IMDAH)₂Cl₂·4H₂O bzw. Pd(IMDAH)₃Cl₂ (IMDAH=Imidazol). Der Mechanismus der thermischen Zersetzung dieser Komplexe in Luft umschliesst eine anfängliche Dissoziation (Abgabe von Wasser und IMDAH-Liganden) im Temperaturbereich 120–340 °C, gefolgt von der Bildung von PdO unter Abspaltung der Chloratome bei 530–570 °C sowie die letztendliche Bildung von metallischem Pd bei 820–840 °C.

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, 12 14, . , d()₂l₂· 4₂ d()₃l₂. 120–340°, 530–570°. 820–840°.

     

Investigation of the interaction between zinc oxide and phosgene

It has been shown that in the interaction of zinc oxide and phosgene, the most active are the samples having oxygen vacancies. A mechanism for this process is suggested.

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, , . .

     

Thermal effects of contamination,adsorbed water and annealing on the DTA of powdered quartz

During the grinding of quartz, water is adsorbed from the atmosphere, but this water gave no detectable thermal effect on DTA because it was evolved uniformly up to 1000°. However, in conjunction with an iron contaminant, the adsorbed water was involved in an oxidation reaction causing noticeable thermal effects for quartz powdered in a vibration mill constructed of steel parts. When powdered so finely that the - inversion peak at 573° had disappeared, annealing caused a partial redevelopment of the peak but recrystallization of disrupted quartz was too small an effect to give any detectable exothermic peak on DTA.

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Zusammenfassung Während des Vermahlens von Quartz wird Wasser aus der Atmosphäre adsorbiert, jedoch ergab dieses Wasser keinen nachweisbaren thermischen Effekt in der DTA, da es bis zu 1000° gleichmässig freigesetzt wird. Im Zusammenhang mit einer Eisen-Verunreinigung wurde jedoch das adsorbierte Wasser in eine Oxidationsreaktion einbezogen, welche beim in einer aus Stahlteilen gefertigten Vibrationsmühle zerpulvertem Quartz nachweisbare thermische Effekte verursachten. Wenn so fein pulverisiert wurde, daß der --Inversions-Peak bei 573° verschwunden war, verursachte eine Wärmebehandlung eine teilweise Wiederentwicklung des Peaks, jedoch war die Rekristallisation des zerstörten Quartzes zu geringfügig um einen nachweisbaren exothermen Peak in der DTA-Kurve zu ergeben.

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Résumé Lors du broyage du quartz, il se produit une adsorption de l'eau atmosphérique mais cette eau ne donne pas d'effet thermique décelable par ATD car elle se dégage régulièrement jusqu'à 1000°. Cependant, en présence de fer comme contaminant, l'eau adsorbée intervient dans une réaction d'oxydation qui donne des effets thermiques perceptibles dans le cas de quartz pulvérisé dans un vibrobroyeur en acier. Si le quartz est en poudre assez fine pour que le pic d'inversion - à 573° disparaisse, le recuit provoque la réapparition partielle du pic. La recristallisation du quartz est cependant trop faible pour donner un effet exothermique décelable par ATD.

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, , 1000°. , , . - 573° , , , - .

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We are grateful to the Science Research Council for supporting this work.     

New Molybdenum(V) Complexes Prepared by the Oxidation of Dinuclear Quadruply-Bonded Molybdenum(II) Monothiocarboxylates

Oxidation of molybdenum(II) thiopivalate and thiobenzoate in the presence of -picoline or pyridine results in the formation of dinuclear molybdenum(V) complexes of the general formulae [Mo₂O₂(-O)₂(-SO₄)L₄] with L = -picoline or pyridine and [Mo₂O₂(-O)(-S)(-SO₄)L₄] with L = -picoline. As determined by X-ray structure analysis, two complexes with -picoline differ in their bridging cores: In one complex, two Mo atoms are doubly bridged through two oxygen atoms; in the other, one Mo atom is doubly bridged through oxygen and sulfur atoms. However, they both crystallize together. The product is solvated with -picoline and water molecules. Molybdenum atoms exhibit distorted octahedral coordinations. The same complexes were prepared also through direct reactions of [Mo₂O₃(O₂CCH₃)₄] with thiopivalic and thiobenzoic acid in the presence of -picoline or pyridine. The appearance of the oxo-oxygens and sulfido-sulfur as well as sulfato ligand is explained by the molybdenum-catalyzed oxidation of thiocarboxylates.     

Hydrodemetallation and the promoter effect of vanadium compounds on a Co?Mo/Al2O3 hydrodesulfurization catalyst

The effect of the vanadium compounds [VO(phthalocyanine)], [VO(salen)] [salen=N,N-ethylenebis(salicylideneiminate)], petroporphyrins, and metal-free phthalocyanine on the hydrodesulfurization of thiophene over a Co/Mo/Al₂O₃ catalyst (350°C, 1 atm) is described. The compound [VO(salen)], which decomposes, acts as a promoter at low V (0.1–0.2 wt. %); the other compounds deactivate the catalyst, an effect which is due to the whole molecule binding to the catalyst in the same way as a nitrogen base.

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[VO()], [VO()] [=N,N-- ()], , , Co–Mo/Al₂O₃ (350°C, 1). [VO()], , V (0,1–0,2 . %-); , , .

     

Syntheses and properties of mixed dinuclear copper(II) complexes with heterocyclic dithiocarbamates and a cyclic octadentate tertiary amine

Five new Cu^II complexes of general formula [Cu₂(Rdtc)tpmc](ClO₄)₃, (1)–(5), where tpmc and Rdtc ^– refer to N,N,N,N-tetrakis(2-pyridylmethyl)-1,4,8,11-teraazacyclotetradecane and piperidine- (Pipdtc), 4-morpholine- (Morphdtc), 4-thiomorpholine- (Timdtc), piperazine- (Pzdtc) or N-methylpiperazine- (N-Mepzdtc) dithiocarbamates, respectively, have been prepared. Elemental analyses, conductometric and magnetic measurements, u.v./vis, i.r., e.p.r. and mass spectroscopy have been employed to characterize them. The complexes adopt an exo coordination of Cu^II ions and tpmc. The dithiocarbamate ion joins both the sulphur and the copper atoms acting as a bridging ligand The presence of different heteroatoms in the piperidine ring influences the (C=N) and (C=S) vibrations which decrease in the order of the complexes: Pipdtc>N-Mepipdtc>Pzdtc>Morphdtc>Timdtc ligands. Attention has been paid to the detailed mechanism of the mass spectral fragmentation of the complexes. The g _eff factors of the complexes have been also estimated by e.p.r. spectra. Finally, the complexes obtained demonstrate microbiologycal activity against some bacteria.     

Image processing using the Briggs-Raucher oscillating chemical reaction

Some images obtained by illuminating the Briggs-Raucher oscillating chemical reaction are illustrated. This reaction gives more distinct and contrasty images than the Belousov-Zhabotinskii reaction.

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-. , , -.

     

Spectral dependence of photocatalytic CO oxidation on rutile

In the region of intrinsic rutile adsorption, CO oxidation follows a redox mechanism via the interaction of CO with O^– ion-radicals, and the photocatalytic activity is determined by the density of 2p states close to the top of the valence band.

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CO CO - O^–, 2- .

     

Inhomogeneity of strong Lewis acid centers on Al2O3 surface

Specificity of the bands at 1630–1620 cm^–1 in IR spectra of coordinatively bonded pyridine has been studied. Three strong Lewis-type acid centers have been revealed on Al₂O₃ surface.

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- 1630–1620 ^–1.

     

Thermal and calorimetric investigations on crystalline hydrates of barium hydroxide and their deuterated analogues

The thermal decompositions of Ba(OH)₂ · 8H₂O, Ba(OH)₂ · 8D₂O, Ba(OH)₂ · H₂O and Ba(OH)₂ · D₂O were studied and the phase transitions were identified by DSC and DTA methods. The corresponding enthalpy changes were determined and compared with those calculated from the thermodynamic data. A decrease of the thermal stability was demonstrated for the deuterated crystal hydrates in comparison with the normal ones.

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Zusammenfassung Die thermische Zersetzung von Ba(OH)₂ · 8H₂O, Ba(OH)₂ · 8D₂O, Ba(OH)₂ · H₂O und Ba(OH)₂ · D₂O wurde untersucht. Phasenübergänge wurden mittels DSC und DTA ermittelt. Die entsprechenden Enthalpieveränderungen wurden bestimmt und mit den aus thermodynamischen Daten berechneten Werten verglichen. Die deuterierten Kristallhydrate sind thermisch weniger stabil als die leichtes Kristallwasser enthaltenden Verbindungen.

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()₂ · 8₂, ()₂ · 8D₂O, Ba(OH)₂·H₂O Ba(OH)₂·D₂O. , . .

     

Thiocyanate bond mode determination on solid manganese(II) mixed ligand coordination compounds

Synthesized and in solid state characterized compounds correspond to the following types [Mn(NCS)₂L_mL'_n] · x D, [Mn(NCS)₂L_y]_z, and [MnX₂(CH₃SCN)(CH₃OH)] · x D (L=CH₃OH or O-donors; L=CH₃SCN or N-donors; D=solvent molecules; x=0, 1 or 2; m=0, 1 or 2; n=1, 2 or 3; y=0, 1, 2, 3 or 4; z2; X=Cl or Br). Derivatographic investigations confirm the formation of intermediates, especially for L=H₂O the existence of thermic stable partially dehydrated (hydrate poor) species (y=1/2 or 1/3) and -NCS-bonding with different ligating atoms. Solid state FT-IR analysis were carried out for band shapes, measurements of the integrated intensity, and correlations between located absorption maxima for v(CN), v(CS), (NCS), v(MnN), and v(MnS) and the thiocyanate bond mode.     

Copper(I) Acetylenide π-Complexes. Synthesis and Structure of Cluster Compound HAmp[Cu9Cl8(C≡CCH2OH)2] (HAmp is 4-Aminopyridinium Cation)

Crystals of the HAmp[Cu₉Cl₈(CCCH₂OH)₂] cluster compound (HAmp is the 4-aminopyridinium cation (NH₂–C₅H₄NH)⁺) were obtained through ac electrochemical synthesis and their structure was determined using X-ray diffraction analysis (DARCh autodiffractometer, /2 scan mode, 3435 independent reflections with F 4(F), R = 0.047). The crystals are triclinic: space group P , a = 12.547(5) Å, b = 12.502(4) Å, c = 8.201(2) Å, = 75.93(2)°, = 82.21(3)°, = 76.05(3)°, V = 1207(2) ų, Z = 2. Two crystallographically independent moieties ^–(CCCH₂OH) were detected in the complex structure. Each moiety acts as a double bridging ,-ligand and binds four or five Cu(I) atoms, thus forming the [Cu₄(CCCH₂OH)] and [Cu₈(CCCH₂OH)₂] clusters. The shortest Cu···Cu distance is equal to 2.337(4) Å.     

3- and 4-Pyridinecarboxylic acidN-oxide complexes with manganese(II), cobalt(II) and nickel(II) chlorides

Summary During interaction of ethanol-triethyl orthoformate solutions of nicotinic or isonicotinic acidN-oxides (LH and LH, respectively) with MCl₂ (M = Mn, Co, Ni), only one true adduct, of the Ni(LH)₃Cl₂ · 2 H₂O type was obtained. In all other cases, partial substitution of Cl^– ions with the corresponding pyridinecarboxylateN-oxide anionic ligands (L or L) occurred. As a result, mixed ligands (LH-L or LH-L) were precipitated, as follows: Mn(LH)₂LCl, Co(LH)LCl, Mn(LH)LCl · 4H₂O, Co(LH)LCl · H₂O and Ni₂(LH)LCl₃ · 6 H₂O. The insolubility of the new complexes in all common solvents, combined with the pronounced tendency of the 3- and 4-pyridinecarboxylates and theirN-oxides to function as bidentate bridging ligands, favours bi- or polynuclear structures. Spectral data suggest that Ni(LH)₃Cl₂ · 2 H₂O is hexacoordinate, and the rest of the new complexes pentacoordinate. Bi- or polynuclear structures, involving double -M-(L)₂-M- or-M-(LH)₂-M- and single -M-(L)-M- or-M(L)-M-(LH)-M- bridges, were proposed on the basis of the overall evidence; additional features of the proposed structural types are: exclusively coordinated chloro ligands, in all cases; aqua ligands [Co(LH)LCl · H₂O]; lattice water [Ni(LH)₂Cl₂ · 2H₂O]; both lattice and coordinated H₂O [Mn(LH)LCl · 4H₂O, and Ni₂(LH)LCl₃ · 6H₂O]; and, with the exception of Ni₂(LH)LCl₃ · 6 H₂O, terminal, unidentate, N-O oxygen-bonded LH or LH ligands.Abstracted in part from the Ph.D. Thesis (in preparation) of L. S. Gelfand, Drexel University.     

Thermal decomposition of decavanadates of bivalent metals

The thermal decomposition of Cd₃V₁₀O₂₈ · 16H₂O and Mg₃V₁₀O₂₈ · 18H₂O has been investigated. It was found by means of IR spectroscopy and X-ray phase analysis that the final products of decomposition of the given compounds are V₂O₅, the corresponding metavanadates and the vanadium bronzes of cadmium and magnesium. Present and previous results allow conclusions on the thermal decomposition of decavanadates of bivalent metals.

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Zusammenfassung Die thermische Zersetzung von Cd₃V₁₀O₂₈ · 16 H₂O und Mg₃V₁₀O₂₈ · · 18 H₂O wurde untersucht. Durch IR-Spektroskopie und Röntgen-Phasenanalyse wurde festgestellt, daß die Endprodukte der Zersetzung der gegebenen Verbindungen V₂O₅ ist, entsprechend den Metavanadate und den Vanadiumbronze von Cadmium und Magnesium. Die gegenwärtigen und früheren Ergebnisse gestatten Folgerungen bezüglich der thermischen Zersetzung von Dekavanadaten zweiwertiger Metalle.

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Résumé On a étudié la décomposition thermique de Cd₃V₁₀O₂₈ · 16 H₂O et Mg₃V₁₀O₂₈ · · 18 H₂O. A l'aide des techniques de spectroscopie IR et de rayon X, on a établi que les produits finaux de la décomposition de ces composés sont V₂O₅, les métavanadates correspondants et les bronzes au vanadium, de cadmium et magnésium. Les résultats présents et antérieurs permettent de tirer des conclusions sur la décomposition thermique des décavanadates des métaux divalents.

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d₃V₁₀₂₈ · 16₂ Mg₃V₁₀O₂₈· 18H₂O. , , V₂O₅, . , , .

     

Synthesis and properties of some chromium(III) β-diketonate complexes

Summary Equimolar quantities of CrCl₃ · 3THF and-diketones, -dkH, react to yield CrCl₂(-dk) · 2THF and CrCl₂(-dk) · THF complexes in coordinating and noncoordinating solvents respectively. For 1 : 2 and 1 : 3 molar ratios of reactants, derivatives of general formulae CrCl(-dk)₂ and Cr(-dk)₃ (where-dkH = acerylacetrrnc, benzoylacetonc and dibenzoylmethane) have been isolated. All complexes have been characterized by elemental analysis, molecular weights and by i.r. spectra.     

The thermal decomposition of Plutonium (IV) oxalate hexahydrate

The thermal decomposition of Pu(C₂O₄)₂ · 6H₂O has been studied in both argon and oxygen using a combination of thermogravimetry and infrared spectroscopy. Decomposition in an inert atmosphere involves reduction of the cation to the trivalent state and its subsequent reoxidation to form PuO₂. In an oxidizing atmosphere, with unrestricted access of oxygen, reduction of the cation does not take place and decomposition to PuO₂ is through the oxycarbonate. The reduction of Pu(IV) appears to take place by a carbon monoxide catalyzed mechanism and the presence of carbon in the PuO₂ decomposition product is attributed to the disproportionation of CO.

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Zusammenfassung Die thermische Zersetzung von Pu(C₂O₄)₂ · 6 H₂O wurde sowohl in Argon als auch in Sauerstoff unter Anwendung einer Kombination der Thermogravimetrie und der Infrarotspektroskopie untersucht. Die Zersetzung in einer inerten Atmosphäre umfaßt die Reduktion des Kations zur Dreiwertigen Form und seiner darauffolgenden Reoxidation zu PuO₂. In einer oxidierenden Atmosphäre mit unbeschränktem Sauerstoffzutritt findet die Reduktion des Kations nicht statt und die Zersetzung in PuO₂ erfolgt über das Oxycarbonat. Die Reduktion von Pu(IV) scheint durch einen kohlenmonoxidkatalysierten Mechanismus zu erfolgen und die Gegenwart von Kohle in dem PuO₂-Zersetzungsprodukt wird der Disproportionierung von CO zugeschrieben.

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Résumé On a étudié la décomposition thermique de Pu(C₂O₄)₂ · 6 H₂O dans l'argon et dans l'oxygène à la fois par thermogravimétrie et par spectroscopie infrarouge. La décom-position dans une atmosphère inerte met en jeu la réduction du cation à l'état trivalent et sa réoxydation subséquente pour donner PuO₂. En atmosphère oxydante, avec accès nonlimité d'oxygène, la réduction du cation n'a pas lieu et la décomposition en PuO₂ s'effectue par l'intermédiaire de l'oxycarbonate. La réduction de Pu(IV) semble avoir lieu par un mécanisme catalysé par le monoxyde de carbone et on attribue la présence du carbone dans le produit de décomposition PuO₂ à la dismutation de CO.

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Pu(C₂O₄)₂ · 6₂ ,