Thermodynamics of silver-thiosemicarbazide complexation

The stability constants of the complexes formed by the silver ion with thiosemicarbazide (tsc) are determined by a potentiometric method using a silver electrode, in a wide range of silver-ion overall concentration (from 10^?4 to 9 × 10^?3 mol dm^?3). Calorimetric measurements gave access to the enthalpy changes accompanying the formation of the species Ag(tsc)⁺, Ag₂(tsc)₃²⁺, Agtsc)₂⁺, and Ag(tsc)₃⁺, and the corresponding entropy changes have been calculated.     

Approach to method development and validation in capillary electrophoresis for enantiomeric purity testing of active basic pharmaceutical ingredients

A chiral capillary electrophoresis system allowing the determination of the enantiomeric purity of an investigational new drug was developed using a generic method development approach for basic analytes. The method was optimized in terms of type and concentration of both cyclodextrin (CD) and electrolyte, buffer pH, temperature, voltage, and rinsing procedure. Optimal chiral separation of the analyte was obtained using an electrolyte with 2.5% carboxymethyl-beta-CD in 25 mM NaH2PO4 (pH 4.0). Interchanging the inlet and outlet vials after each run improved the method's precision. To assure the method's suitability for the control of enantiomeric impurities in pharmaceutical quality control, its specificity, linearity, precision, accuracy, and robustness were validated according to the requirements of the International Conference on Harmonization. The usefulness of our generic method development approach for the validation of robustness was demonstrated.     

Komplexbildung vontrans-Azobenzol und seinen Derivaten mit Akzeptorhalogeniden in 1,2-Dichloräthan

Zusammenfassung Die Bildung der Koordinationsverbindungen von SbCl₅, SnCl₄, AlCl₃, AlBr₃, GaBr₃ und GaCl₃ mittrans-Azobenzol, p-Chlorazobenzol und p-Nitroazobenzol wurde in 1,2-Dichloräthan quantitativ untersucht. Die UV-Spektren der Azoverbindung-Akzeptor-Komplexe sind auch in 1,2-Dichloräthan unabhängig von der Natur des AkzeptorhalogenidsMeX _n.

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Quantitative work is described on the formation of coordination compounds of SbCl₅, SnCl₄, AlCl₃, AlBr₃, GaBr₃ and GaCl₃ withtrans-azobenzene, p-chloroazobenzene and p-nitroazobenzene in 1,2-dichloroethane. The UV-spectra of the compounds in 1,2-dichloroethane are independent from the nature of the acceptor halideMeX _n.

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Growth and some properties of Sc2AlB6 crystal obtained from the solution in aluminum melt

Crystals of Sc₂AlB₆ were grown using scandium oxide and elemental boron as starting materials in a self-component aluminum solution under an argon atmosphere. The growth conditions for obtaining single crystals of relatively large size were investigated. Sc₂AlB₆ single crystals were obtained in the form of prisms extending in the b-axis direction. The largest Sc₂AlB₆ crystals prepared had maximum dimensions of about 0.4×0.4×4.2 mm³. The values of the Vickers microhardness and the electrical resistivity of Sc₂AlB₆ crystals are 12.7±0.8 GPa and 43±8 μΩ cm, respectively. The oxidation of Sc₂AlB₆ crystals starts at about 773°C, and the weight gain after TG determination is 12.9 mass% at 1200°C. The oxidation products of Sc₂AlB₆ crystals could not determined.     

Total assignment of the 1H NMR spectra of 5H-indolo[1,7-ab] [1]benzazepine,6,7-dihydro-5H-indolo[1,7-ab][1]benzazepine and pyrrolo[3,2,1-kl ] phenothiazine

The total assignment of the ¹H nmr spectrum of the three tetracyclic compounds: 5H -indolo[1,7-ab][1]benzazepine,6,7-dihydro-5H -indolo[1,7-ab ][1]benzazepine and pyrrolo[3,2,1-kl ]phenothiazine is described. Assignments were based on decoupling experiments and the spectrum of 1,10-dideuteriopyrrolo[3,2,1-kl]phenothiazine and the spectral parameters were verified by spin-simulation techniques. A temperature study of 6,7-dihydro-5H -indolo[1,7-ab][1]benzazepine was also performed.     

Hydrogendifluorokobaltate(II)

Zusammenfassung Aus Kobalt(II)perchlorat und Piperidiniumhydrogendifluorid entstehen in nichtwäßrigen Lösungsmitteln (L) Komplexe, welche HF₂-Einheiten als Liganden enthalten, nämlich [Co(HF₂)L ₅]⁺, [Co(HF₂)₂ L ₄], [Co(HF₂)₃ L ₃]^–, [Co(HF₂)₄ L ₂]^2– und [Co(HF₂)₆]^4–.

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Hydrogendifluorocobaltates(II)

Cobalt(II)perchlorate and piperidinium hydrogendifluoride in non-aqueous solvents (L) yield complex compounds containing an HF₂-group as ligand, e.g. [Co(HF₂)L ₅]⁺, [Co(HF₂)₂ L ₄], [Co(HF₂)₃ L ₃]^–, [Co(HF₂)₄ L ₂]^2– and [Co(HF₂)₆]^4–.

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Mit 3 Abbildungen     

Diverse ring-opening reactions of rhodium η4-azaborete complexes

Sequential treatment of [Rh(COE)₂Cl]₂ (COE = cyclooctene) with PⁱPr₃, alkyne derivatives and ^tBuN BMes (Mes = 2,4,6-trimethylphenyl) provided functionalized rhodium η⁴-1,2-azaborete complexes of the form (η⁴-azaborete)RhCl(PⁱPr₃). The scope of this reaction was expanded to encompass alkynes with hydrogen, alkyl, aryl, ferrocenyl, alkynyl, azaborinyl and boronate ester substituents. Treatment of these complexes with PMe₃ led to insertion of the rhodium atom into the B–C bond of the BNC₂ ring, forming 1-rhoda-3,2-azaboroles. Addition of N-heterocyclic carbenes to azaborete complexes led to highly unusual rearrangements to rhodium η²,κ¹-allenylborylamino complexes via deprotonation and C–N bond cleavage. Heating and photolysis of an azaborete complex also led to rupture of the C–N bond followed by subsequent rearrangements, yielding an η⁴-aminoborylallene complex and two isomeric η⁴-butadiene complexes.

Rhodium η⁴-azaborete complexes can be transformed into a variety of species with ring-opened, BN-containing ligands by treatment with Lewis bases.     

Solvent effects on the redox potentials of tetraethylammonium hexacyanomanganate(III) and hexacyanoferrate(III)

Tetraethylammonium hexacyanomanganate(III) was studied in formamide, N-methylformamide, methanol, propylenecarbonate, N,N-dimethylthioformamide, N-methylthiopyrrolidinone(2), butyrolactone, acetonitrile, dimethylsulfoxide, N,N-dimethylformamide, N-methylpyrrolidinone(2), nitromethane and tetramethylenesulfone employing polarographic and voltammetric techniques. Reversible or nearly reversible behaviour for the reaction Mn(CN)₆^3?/Mn(CN)₆^2? was observed in most solvents on the stationary platinum electrode. The reaction Mn(CN)₆^3?/Mn(CN)₆^4? was studied on both the dropping mercury electrode and the stationary platinum electrode. Besides the reaction Mn(CN)₆^3?/Mn(CN)₆^4? several anodic waves due to successive reactions of mercury with the cyano-ligand of the complex occurred at the dropping mercury electrode. No redox reaction for (et₄N)₃Mn(CN)₆ was found in nitromethane. The polarographic behaviour of tetraethylammonium hexacyanoferrate(III) was studied in formamide, N-methylformamide, N-methylpyrrolidinone(2) and butyrolactone. The variation of E_1/2 and 1/2 (E_pa+E_pc) values versus bisphenylchromium(I)/bisbiphenylchromium(0) as reference redox system of the processes Mn(CN)₆^3?/Mn(CN)₆^2?, Mn(CN)₆^3?/Mn(CN)₆^4? and Fe(CN)₆^3?/Fe(CN)₆^4? with the nature of the solvent is discussed within the donor-acceptor concept. Correlations between the E_1/2 and 1/2(E_pa+E_pc) values and the acceptor properties of the solvent have been observed. The preparation of tetraethyl- and tetrabutylammonium hexacyanomanganate(III) is described.     

Halogen-und Pseudohalogenkomplexe von Kobalt(II) in Nitromethan

Zusammenfassung Die neutralen Halogenide und Pseudohalogenide von Kobalt(II) sind in Nitromethan kaum dissoziiert. Bei Zusatz entsprechender Anionen zu Kobalt(II)-perchloratlösungen werden in Nitromethan folgende Koordinationsformen leicht gebildet: CoCl₂, CoCl₃ ^–, CoCl₄ ^2–, CoBr₂, CoBr₃ ^–, CoBr₄ ^2–, CoJ₂, CoJ₃ ^–, CoJ₄ ^2–, Co[N₃]₂, [Co(N₃)₄]^2–, Co[NCS]₂, [Co(NCS)₄]^2–, Co[CN]₂ [Co(CN)₄]^2– und [Co(CN)₅]^3–.

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The neutral halides and pseudohalides of cobalt(II) are nearly undissociated in nitromethane. On addition of the appropriate anion to a solution of cobalt(II)-perchlorate in nitromethane the following coordination forms are easily produced: CoCl₂, CoCl₃ ^–, CoCl₄ ^2–, CoBr₂, CoBr₃ ^–, CoBr₄ ^2–, CoJ₂, CoJ₃ ^–, CoJ₄ ^2–, Co[N₃]₂, [Co(N₃)₄]^2–, Co[NCS]₂, [Co(NCS)₄]^2–, Co[CN]₂, [Co(CN)₄]^2– and [Co(CN)₅]^3–.

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Mit 10 Abbildungen     

Spektrophotometrische Untersuchungen über Chlorokomplexe von Co++, Ni++ und Cu++ in acetonitril und Trimethylphosphat

Zusammenfassung Mit steigendem Chloridionenangebot lassen sich auf spektrophotometrischem Wege in Lösungen von Acetonitril und Trimethylphosphat folgende Cl-Koordinationsformen nachweisen: CoCl₂, CoCl₃ ^–, CoCl₄ ^–;K ₁<K ₂>K ₃>K ₄; NiCl₂, NiCl₃ ^–, NiCl₄ ^–; in TrimethylphosphatK ₂K ₃>K ₄; in AcetonitrilK ₃>K ₄; CuCl⁺, CuCl₂, CuCl₃ ^–, CuCl₄ ^–;K ₁>K ₂K ₃>K ₄. Die Löslichkeit des NiCl₂ steigt mit der Basizität des Lösungsmittels.Mit 9 Abbildungen