New cobalt trimethylacetate complexes with pyridine

The reaction of the tetranuclear trimethylacetate complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ with pyridine in acetonitrile was studied. Two new compounds, viz., the hexanuclear cobalt(ii) complex Co₆py₄(₃-OH)₂(-OOCCMe₃)₁₀ (25% yield) and the unusual ionic compound [Co₃py₃(₃-O)(-OOCCMe₃)₆]⁺[Co₄py(₄-O)(-OOCCMe₃)₇]^– (5% yield), were prepared. The structures of the new compounds were established by X-ray diffraction analysis.     

Reaction of the Hexa-1,3,5-triyne Me3SiC≡CC≡CC≡CSiMe3 with Ru4(CO)13(μ 3-PPh): Parallels with the Chemistry of Alkynes and Diynes

Reaction of Ru₄(CO)₁₃(₃-PPh) (1) with the 1,3,5-hexatriyne Me₃SiCCCCC CSiMe₃ under mild thermal conditions affords initially Ru₄(CO)₁₀(-CO)₂{₄-¹,¹,²-P(Ph)C(CCSiMe₃)C(CCSiMe₃) (2), via the facile formation of a P–C bond in a manner similar to that demonstrated previously with alkynes and diynes. The 62-CVE cluster 2 readily decarbonylates to give crystallographically characterised Ru₄(CO)₁₀(-CO)(₄-PPh){₄-¹,¹,²,²-Me₃SiCCC₂CCSiMe₃} (3). Attempts to further incorporate the pendant alkyne moieties in 3 into the Ru₄ coordination environment were partially successful with Ru₄(CO)₁₀(₄-PPh)(₄-¹,¹,³,³-RC₄R') (4, R/R'=SiMe₃/CCSiMe₃) being formed as a minor product together with the unusual toluene coordinated species Ru₄(CO)₇(⁶-C₆H₅Me)(₄-PPh)(₄-¹,¹,³,³-Me₃SiC₄CCSiMe₄) (5). Cluster 3 reacts with an excess of Me₃SiCCCCCCSiMe₃ to give the open chain cluster Ru₄(CO)₉(₃-PPh){₄-²,²,⁴,⁴,-C₄(CCSiMe₃)(SiMe₃)C₄(CCSiMe₃)₃} (6).     

A technique for capillary joining in capillary electrophoresis

Summary Aspects of cracking and joining capillaries have been investigated. Capillary coupling was achieved using various methods. The most successful used hydrofluoric acid-etched capillaries to form male and female ends which were then joined together. This type of joint was used to connect sections of capillary of similar and different internal diameters with minimal loss in resolution, peak width and number of theoretical plates. (Uridine and hypoxanthine was used as a test mixture). For hypoxanthine on a 50 m/50 m etched joined capillary 10 cm from the detector window the number of theoretical plates was 96.6% of that for hypoxanthine on an unbroken capillary. Following the relative success of capillary joining, a coupled capillary flowcell (50 m/200 m) was produced and evaluated.     

On the use of azo dyes for the spectrophotometric determination of uranium and thorium in mixed solvents

Summary Solochrome Black 6 BN in an acetate buffered medium containing methanol reacts with U(IV) to give a blue complex which permits photometric determination with 5g U/ml to 100g U/ml.In the presence of zinc acetate, uranyl ion also may be spectrophotometrically determined by means of the same dye. From 2g U/ml to 40g U/ml may be determined with a relative error of less than ± 0.05.

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Zusammenfassung Es werden zwei Methoden zur spektrophotometrischen Bestimmung von Uran mittels Solochromschwarz 6 BN beschrieben. Dieser Farbstoff bildet mit U(IV) in acetatgepuffertem, methanolhältigem Medium einen blaugefärbten Komplex, der die Bestimmung von 5 bis 100g U/ml erlaubt.Mit demselben Farbstoff lassen sich auch 2 bis 40g U/ml in Lösungen von Uranylchlorid bestimmen.

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Résumé Le noir solochrome 6 BN en milieu tampon acétique contenant du méthanol réagit avec U-IV en donnant un complexe bleu qui permet le dosage photométrique de 5 g U/ml à 100 g U/ml.En présence d'acétate de zinc, on peut aussi doser l'ion uranyle par spectrophotométrie avec le même colorant. On peut doser de 2 g U/ml à 40 g U/ml avec une erreur relative inférieure à ± 0,05.

     

Determination of traces of sodium alkylbenzenesulphonate by high-performance liquid chromatography. Application to water

Summary For the trace determination of sodium alkylbenzenesulphonate (ABS) by HPLC the following conditions were employed: Shimadzu ZORBAX SIL Column (5 m, 4.6 mm i.d. x 150 mm) as stationary phase, 0.2% ammoniaethanol (v/v) as mobile phase, UV detector at 225 nm, injection volume 12 l. The chromatograms of ABS were simple and sharp (detection limit of ABS 0.02 g in 12 l of ethanol). The calibration curves of ABS were linear in a concentration range of 0.03 0.3 g in 12 l of ethanol. In the case of linear sodium dodecylbenzenesulphonate positive errors of 1 4% were caused by non-ionic surfactants or laurylsulphate (6 times excess), 10 50% positive errors were caused by 2 6 times excess of household detergents.Standard water samples containing ABS were treated with a weak base anion-exchange resin, the adsorbed ABS were eluted, and then determined either by HPLC or by the methylene blue spectrophotometric method. Recoveries of ABS in water were about 92 107% by HPLC.

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Bestimmung von Spuren Natriumalkylbenzolsulfonat mit Hilfe der HPLC. Anwendung auf Wasser

Zusammenfassung Für die Spurenbestimmung von Natriumalkylbenzolsulfonat (ABS) durch HPLC werden die folgenden Bedingungen empfohlen:Shimadzu ZORBAX SIL (5 m, 4,6 mm x 150 mm) als stationäre Phase, 0,2% Ammoniak/Ethanol als mobile Phase, UV-Detektor bei 225 nm, Injektionsvolumen 12 l. Die erhaltenen Chromatogramme sind einfach und scharf (Nachweisgrenze 0,02 g in 12 ml Ethanol). Die Eichkurven sind im Konzentrationsbereich von 0,03–0,3 g in 12 l Ethanol linear. Im Falle des linearen Natriumdodecylbenzolsulfonats werden bei Anwesenheit von nicht-ionischen oberflächenaktiven Substanzen oder von Laurylsulfat in 6fachem Überschuß positiver Fehler von 1–4% erhalten; bei 2–6fachem Überschuß von Haushaltswaschmitteln ergeben sich positive Fehler von 10–50%.Standard-Wasserproben werden zunächst einer Behandlung mit einem Anionenaustauscher unterzogen, die adsorbierten ABS eluiert und durch HPLC oder nach der Methylenblaumethode analysiert. Wiederfindungsraten liegen bei 92–107%.

     

Role of metal center in reactions of polynuclear nickel(ii) and cobalt(ii) trimethylacetates with 8-amino-2,4-dimethylquinoline

The reactions of 8-amino-2,4-dimethylquinoline (L) (1) with polynuclear nickel(ii) and cobalt(ii) hydroxotrimethylacetato complexes under anaerobic conditions were studied. The nonanuclear cluster Ni₉(₄-OH)₃(₃-OH)₃(_n-OOCCMe₃)₁₂(HOOCCMe₃)₄ gave the mononuclear complex Ni(²-L)(²-OOCCMe₃)₂ (2). The tetranuclear complex Ni₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆ produced the mononuclear complex Ni(²-L)(²-OOCCMe₃)(OOCCMe₃)L (3). At room temperature, the cobalt-containing polynuclear trimethylacetates, viz., the polymer [Co(OH) _n (OOCCMe₃)_2–n ] _x and the tetranuclear complex Co₄(₃-OH)₂(-OOCCMe₃)₄(²-OOCCMe₃)₂(EtOH)₆, were transformed into the trinuclear cobalt(ii) complex Co₃(₃-OH)(-OOCCMe₃)₄(²-L)₂(OOCCMe₃) (4). Meanwhile, at 80 °C these compounds generated the binuclear cobalt(iii) complex Co₂(₂²-(HN)C₉NMe₂)₂(-OOCCMe₃)(L)(OOCCMe₃)₃ (5). The structures of the resulting compounds were established by X-ray diffraction analysis. Compounds 2—4 exhibit the antiferromagnetic spin-spin exchange coupling, whereas compound 5 is diamagnetic.     

Reactions of ortho-Phenylenediamine with a Nickel Trimethylacetate Complex

Interaction of ortho-phenylenediamine with the nonanuclear nickel trimethylacetate cluster Ni₉(₄-OH)₃(₃-OH)₃( _n -OOCMe₃)₁₂(HOOCCMe₃)₄(I) in an amine deficiency yields the antiferromagnetic trinuclear complex [Ni₃{-N,N"-(NH₂)₂C₆H₄}₂(HCCOOCMe₃)₃(₃-OH)(-OOCCMe₃)₄]⁺(OOCCMe₃)^–(III) containing bridging diamine ligands. Reaction of excess diamine with Ior IIIleads to the formation of the paramagnetic monomer Ni{²-o-(NH₂)₂C₆H₄}₂(OOCCMe₃)₂(IV), which reacts with atmospheric oxygen to form the known bis(semiquinonediimine) complex Ni[1,2-(NH)₂C₆H₄]₂(V).     

Di-μ-hydroxo bridge-cleavage reactions between [Co(nta)(μ-OH)]2 2− and different monodentate ligands

The cleavage of the di--hydroxo bridges of [Co(nta)(-OH)]₂ ^2– by dimethylaminopyridine (dmap) and pyridine (py) has been investigated. [Co(nta)(-OH)]₂ ^2– equilibrates rapidly in aqueous basic solutions with a mono--hydroxo bridged Co^III species [pK _OH = 3.26(2)] and both these species react with the incoming ligand to form different ion associated species which react in the subsequent rate-determining steps (k ₁ and k ₂) to form presumably a ligand-substituted, mono-bridged species, [(nta)(OH)Co--OH-Co(nta)(L)]^2–. Values for k ₂, the preferred mono--hydroxo bridged substitution pathway for these reactions, vary between 6.8(2) × 10^–4 s^–1 (py) and 8.5(4) × 10^–2 s^–1 (dmap).     

Synthesis,characterization and crystal structures of heterometallic trinuclear carbonyl sulfido clusters (η5-Cp)MoFeCo- (CO)8(μ3-S) and [(η5-Cp)Mo]2Fe(CO)7(μ3-S)

HFe2Co(CO)9(3-S) reacts with (5-Cp)Mo(CO)3Cl in refluxing THF to give heterometallic trinuclear clusters (5-Cp)MoFeCo(CO)8(3-S) and [(5-Cp)Mo]2Fe(CO)7-(3-S), which have been characterized by elemental analyses, i.r., 1H- and 13C-n.m.r. and X-ray crystal structure determination. An electrophilic addition–elimination sequence is proposed for their formation.     

Effect of water on hydrogen desorption from the surface of Rh/C catalysts

An increase in the number of titration cycles results in a considerable decrease in H_T and O_T values, which in turn, brings about a decrease in the amount of desorbed hydrogen. This shows that water, being a product of titration reaction, is adsorbed on the oxidized surface of rhodium and represents a kinetic-diffusive barrier for hydrogen titration.

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, H_T O_T, , , . , , , , , - .

     

Calculation of spin densities in odd alternant hydrocarbon radicals

Spin densities in benzyl, allyl, pentadienyl and perinaphthenyl radicals have been calculated with some variants of the simplified McLachlan unrestricted SCF method based on Hückel-type and the SC Hückel-type molecular orbitals. The various estimations of the spin densities were compared one with each other and with the results of more sophisticated methods. It was shown that the SC Hückel basis and Zhidomirov and Schastnev's modification of the McLachlan approach give a best least square fit of the relation a ^exp Q ^calc .

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Zusammenfassung Die Spindichten von Benzyl-, Allyl-, Pentadienyl- und Naphtenyl-Radikalen werden mit einigen Varianten der uneingeschränkten SCF-Methode in der vereinfachten Form nach McLachlan, die auf den Hückel- und den SC-Hückel-Molekülorbitalen basiert, berechnet. Die verschiedenen Schätzungen der Spindichten werden miteinander sowie mit den Resultaten komplizierterer Methoden verglichen. Es wird gezeigt, daß die SC Hückel Basis und die von Zhidomirov und Schastnev eingeführte Modifikation der Näherung von McLachlan eine beste Näherung nach der Methode der kleinsten Quadrate an die Beziehung a ^exp Q ^calc ergeben.

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Résumé Les densités de spin ont été calculées dans les radicaux benzyle, allyle, pentadiényle et perinaphthényle à l'aide de variantes de la méthode SCF sans restrictions de spin simplifiée de Mac Lachlan, en utilisant des orbitales de type Hückel et SC Hückel. Les différentes évaluations de densité de spin sont comparées entre elles et avec celles obtenues par des méthodes plus élaborées. On montre que la base SC Hückel et la modification de Zhidomirov et Schastnev à la théorie de Mac Lachlan donnent le meilleur accord au sens des moindres carrés avec la relation a ^exp Q ^cal .

     

Determination of trace heavy metals associated with suspended particulate matter in pond water by microscale anodic stripping voltammetry

Summary Less than 1 milligram of suspended particulate matter in a 50-ml water sample was separated by centrifugation, decomposed with 22l of 21010 perchloric-nitric-hydrofluoric acid mixture, and analyzed for copper, lead, cadmium and zinc by microscale differential pulse anodic stripping voltammetry with a hanging mercury drop electrode in 300l of 0.06M perchloric acid. The procedure was simple and rapid, because a single Teflon microvessel was used throughout the whole procedure.

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Bestimmung von Schwermetallspuren in suspendierten Teilchen in Teichwasser durch Anodic Stripping Voltammetry im Mikromaßstab

Zusammenfassung Weniger als 1 mg suspendierter Teilchenmaterie wurde durch Zentrifugieren abgetrennt, mit 22l eines Gemisches HClO₄HNO₃HF (21010) zersetzt und darin Cu, Pb, Cd und Zn durchDifferential-Pulse-Anodic-Stripping-Voltammetrymit hängender Hg-Tropfelektrode in 300 l 0.06M Perchlorsäure bestimmt. Das Verfahren ist einfach und schnell, es bedarf dazu nur eines Mikrokölbchens aus Teflon.

     

Propos sur l'interpretation de l'energie d'activation experimentale

Résumé Les résultats de divers travaux montrent que la valeurE _e de l'énergie activation expérimentale tirée des diagrammes d'Arrhénius varie avec la pression, dans le cas de réactions de décompositions endothermiques.L'analyse de divers modèles permet d'expliquer cette constatation en montrant que la grandeurE _e n'a pas le sens d'une énergie d'activation mais est une fonction de nombreux paramètres. Deux d'entre eux ont été retenus dans le cadre de cette étude: le terme d'écart à l'équilibre et le terme de gradient thermique, provoqué par l'endothermicité du phénomène.Cette analyse permet d'établir une prévision de la fonctionE _e (P) conforme aux résultats expérimentaux.

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The results from various investigations show that the experimental activation energy valueE _e derived from the Arrhenius diagrams varies with pressure for endothermic decomposition reactions.The analysis of various models allows this fact to be accounted for by showing thatE _e should be regarded not in its fundamental formulation, but as being a function of numerous parameters. Two of these were taken into account in the present study, i.e. deviation from equilibrium and a thermal gradient due to the fact that the phenomenon is endothermic.FunctionE _e (P) fitting the experimental results may be predicted by such an analysis.

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Zusammenfassung Die Ergebnisse verschiedener Untersuchungen zeigen, dass die aus den Arrhenius-Diagrammen abgeleiteten experimentellen Werte der AktivierungsenergieE _e bei endothermen Zersetzungsreaktionen mit dem Druck variieren.Die Analyse verschiedener Modelle ermöglicht eine Erklärung dieser Tatsache, indem gezeigt wird, dassE _e nicht in ihrer grundliegenden Formulierung betrachtet werden darf, sondern als Funktion einer Anzahl von Parametern. Zwei dieser Parameter wurden in der vorliegenden Untersuchung berücksichtigt d.h. die Abweichung von dem Gleichgewicht und der thermische Gradient, welcher infolge der endothermen Beschaffenheit der Erscheinung auftritt.Eine den Versuchsergebnissen entsprechende FunktionE _e (P) kann mittels einer solchen Analyse vorausgesagt werden.

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, _e, , . , _ee , . , : , , . _e (), , .

     

Kinetics of oxidation of acrolein on a vanadium-molybdenum oxide catalyst

A kinetic study has shown that, in the range of low conversions, the reaction rate depends only on the partial pressure of oxygen. Comparison of the oxidation of acrolein and I-deuteroacrolein suggests that the splitting of the H–CO bond is not rate-limiting.

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, , , . 1- , H–CO .

     

Analysis of the fusariotoxins zearalenone and vomitoxin (deoxynivalenol) in human foods and animal feeds by high-performance liquid chromatography (HPLC)

Summary HPLC procedures for analyses of the fusariotoxins zearalenone and vomitoxin in individual food- and feedstuffs as well as in mixed feed are described. Zearalenone is separated on a column with polar stationary phase (25 cm × 4.6 mm i.d., particle size 7 m), eluted with a chloroform-isooctane (75/25, v/v)+1.5% methanol mixture and detected fluorometrically. The quantitative determination was possible in all analyzed samples with a detection limit of 2g/kg with 70–80% recovery. Vomitoxin is fractionated by HPLC (C ₁₈ ¹ column, 25 cm×4 mm i.d., 5 m particle size) with water-methanol (60/40, v/v) mobile phase and determined by combining GLC or TLC with UV detection. The detection limit in mixed feed with interfering substances was 25 g/kg (recovery 25–35%). The separation by HPLC makes preparation of pure vomitoxin possible. The described methods are fast, simple and low cost and are suitable for routine analyses.     

Thermal decomposition of some homobinuclear dihalide-bridged iron(III) complexes

Thermal studies by TG and DTG on some homobinuclear dihalide-bridged iron(III) complexes of the general type [Fe(S₂CNR₂)₂X]₂(}-X ₂) were carried out in air and nitrogen atmospheres. The apparent activation energies were determined by graphical methods and the TIN temperatures were calculated from the TG profiles. Finally, a possible mechanism of the decomposition is suggested on the basis of the pyrolysis and mass spectral data.

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Zusammenfassung Einige homobinukleare Eisen(III)-Komplexe mit Dihalidbrücken der allgemeinen Formel [Fe(S₂CNR₂)₂X]₂(–X₂) wurden mittels TG und DTG in Luft und Stickstoffatmosphäre untersucht. Die scheinbaren Aktivierungsenergien wurden nach graphischen Methoden aus den TG-Profilen bestimmt. Ein möglicher, auf pyrolytischen und massenspektrometrischen Daten basierender Zersetzungsmechanismus wird vorgeschlagen.

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[Fe(S₂CNR₂)₂X]₂ (-₂) . , . - .

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Thanks are due to Dr. G. Karagiannidis, Laboratory of Organic Chemical Technology, Aristotelian University, for technical assistance.     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

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, 423 743 CH₄/O₂ 1 9, . . .

     

Crystal structure and spectroscopic study of di-μ(1,1)-azido-di-μ(0,0-nitrato)tetrakis(3,5-lutidine)dicopper(II), [Cu(N3) (NO3) (3,5-lutidine)2]2

A mixed ligand 12 complex of copper(II) azide with 3,5-lutidine, namely di-(1,1)-azido-di(0,0)-nitrato)tetrakis(3,5-lutidine)dicopper(II) has been prepared and characterized by X-ray crystallographic and spectroscopic methods. The dimeric molecule, which possesses a crystallographic inversion center, contains two(1,1) bridging azido ligands. Each copper(II) atom in the cyclic Cu₂N₂ unit is further coordinated by two oxygen atoms from two(0,0-nitrato) bridges at Cu-O distances of 2.465(3) and 2.568(3) Å and two nitrogen atoms from the lutidine molecules [Cu-N=2.003(3) and 2.012(3) Å] to give a distorted tetragonal bipyramid. Both azido ligands are linear [N-N-N angle=179.0(4) and asymmetric N-N=1.207(4) and N-N=1.135(5) Å]. The azido bridges produce a rather short Cu Cu distance of 3.013(2) Å. Infrared and electronic data are presented and discussed.     

Extractive spectrophotometric determination of dioxouranium(VI) with the sodium salt of hexamethyleneiminecarbodithioate

The optimum conditions for the extractive spectrophotometric determination of dioxouranium(VI) with hexamethyleneiminecarbodithioate(HMICdt) have been established. Dioxouranium(VI) reacts with this ligand at pH 4.5 to form a yellowish-orange uncharged 12 metal-ligand complex which can be extracted by chloroform. The calibration graph was linear in the range of 1–20 g ml^–1 of dioxouranium(VI) at 335 nm. The molar absorptivity of the extracted species is 5.952×10³ l mol^–1 cm^–1 with Sandell's sensitivity of 0.04 g cm^–2. The average of 10 determinations of dioxouranium was 49.75 g for the samples containing 50 g of U(VI) and the variation from the mean at 95% confidence limit was 49.75±0.5955.