Die Stabilität der Kobalt(II)- und Kupfer(II)-Komplexe mit α-, β- und γ-Aminobutyrat

Stability constants of cobalt(II) and copper(II) complexes with α-, β-, and γ-aminobutyrate as well as the protonation constants of these ligands have been determined by potentiometric titration. ΔG ^? values, computed from the stability constants, increase in the orderAABA. The increase in ΔG ^? AABA→BABA amounts approx. 15 per cent. The same difference was observed for α- and β-alaninato complexes with various transition metal ions.     

Darstellung und einige Eigenschaften von Kupfer(I)-Kupfer(II)-Selenocyanaten

Preparation and Some Characteristics of Copper(I)-Copper(II) Selenocyanates From the system Cu²⁺-H₂O-en-SeCN-in dependence on the conditions two new complexes have been prepared: Cu₃en₂(SeCN)(CN)₃· H₂O(I) and Cu₃en₂(SeCN)₂(CN)₂· H₂O(II). They were studied by the methods of infra-red and EPR spectra as well as by those of X-ray diffraction. It has been found that Cu₂₊ is coordinated in these complexes with two molecules of ethylene diamine and one molecule water. The anion ligands have a bridging function and coordinate the copper(I). The EPR spectra show that the two complexes exhibit around the atom Cu²⁺ have different ligand field symmetry. For complex (I) it is a typically axial spectrum with two values of the gfactor g⊥? 2.18 and g⊥? 2.05 while complex (II) has an asymmetrical isotropic spectrum with one g-factor value only g⊥? 2.07.     

Heterogeneous reactions of solid nickel(II) complexes

The influence of different modes of preparation on the stoichiometry of thermal decomposition of isothiocyanatonickel(II) complexes with ammonia was studied. It was found that the complex Ni(NCS)₂(NH₃)₄ (I) prepared by heterogeneous reaction undergoes decomposition in two steps (–2 NH₃, –2 NH₃), while for complex II, of the same composition but prepared by homogeneous reaction from solution, the decomposition proceeds in three steps (–1 NH₃, –1 NH₃, –2NH₃). Electronic and infrared absorption spectra were used for the study of the spectral properties of the starting complex. It was found that the different stoichiometries of thermal decompositions of complexes I and II do not cause differences in the bonding strength of the ammonia molecules (chemical factor); this effect is rather brought about by physical factors such as different imperfections of the crystal lattice.

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Zusammenfassung Der Einfluß der Herstellung auf die Stöchiometrie der thermischen Zersetzung von Amin-Komplexen des Isothiocyanatonickels wurde studiert. Der Zerfall des Komplexes Ni(NCS)₂(NH₃)₄ (I), hergestellt durch heterogene Reaktion, verlief in zwei Etappen (–2 NH₃, –2 NH₃). Beim selben Komplex (II), hergestellt durch homogene Reaktion in Lösung, wurden jedoch drei Etappen beobachtet (–1 NH₃, –1 NH₃, –2 NH₃). Die Eigenschaften des Ausgangsproduktes wurden durch Elektronen- und IR-Spektroskopie untersucht. Das unterschiedliche thermische Verhalten ist nicht auf eine verschiedene Bindungsstärke der NH₃ Moleküle, sondern auf physikalische Ursachen, wie z. B. Unregelmässigkeiten im Kristallgitter zurückzuführen.

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Résumé On a étudié l'influence des diverses méthodes de préparation sur la stoechiométrie de la réaction de décomposition thermique des complexes de l'isothiocyanate de nickel(II) avec l'ammoniac. On a établi que le complexe Ni(SCN)₂(NH₃)₄, (I), préparé rar réaction hétérogène, subit une décomposition en deux étapes (–2NH₃, –2NH₃), tandis que le complexe (II), de même composition, mais préparé par réaction homogène, à partir de solutions, se décompose en trois étapes (–1NH₃,–1NH₃, –2NH₃). Les propriétés spectrales du complexe initial ont été étudiées par absorption électronique et infrarouge. On a trouvé que les différences de stoechiométrie des réactions de décomposition thermique des complexes (I) et (II) n'apportaient pas de différences entre les énergies de liaison des molécules d'ammoniac (facteur chimique). C'est plutôt à des facteurs physiques, comme les différentes imperfections du réseau cristallin, que cet effet serait dû.

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(II) . , Ni(NCS)₂(NH₃)₄ (I), , (–2NH₃,–2NH₃). , II , , (–1 NH₃,–1 NH₃ –2NH₃). . , I II ( ), , .

     

Thermal and magnetization studies on Heusler alloys

Saturation magnetization measurements as a function of temperature were performed on Cu₂Mn(Al_1–xSn_x) Heusler alloys to study the existence of stable structures. The derivatograph was applied to study the thermal effects.

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Zusammenfassung Sättigungsmagnetisierungsmessungen als Funktion der Temperatur sowie Derivatographie wurden an Heusler-Legierungen der Formel Cu₂Mn(Al_1–xSn_x) zu Untersuchungen der Existenz einer stabilen Struktur vorgenommen.

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Résumé Etude de l'existence d'une structure stable dans les alliages de Heusler Cu₂Mn(Al_1–xSn_x), à l'aide d'un Derivatograph et par des mesures de magnétisation à saturation en fonction de la température.

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XecnepaCu₂Mn(Al_1–xSn_x), , , . .

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Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and Banco Nacional de Desenvolvimento Economico, Brasil.     

Electropolymerization of aminophthalic acids. I. Polymerization of 4-aminophthalic acid

4-Aminophthalic acid has been polymerized in almost quantitative yield to low molecular weight polymer by electrochemical initiation at a platinum anode. Systems involving the acid, amine salt, and the ammonium salt have been explored; the acid and/or the amine salt of the acid provides the best means of obtaining polymer. Maximum molecular weight is attained in a very short time at low current densities (～2 hr at 50 mA). Thermogravimetric data indicate a temperature stability comparable to polyamide-imide polymers (400°C). Long reaction times and high current densities decrease molecular weight and polymer yield.     

Studium des gegenseitigen Einflusses der Bindungen in Thiocyanat-Kupfer(II)-Komplexen mit Methyl- und Dimethylpyridinen mittels Infrarotspektroskopie

The infrared spectra of thiocyanato-copper(II) complexes of the type Cu(NCS)₂ L ₂ with all isomeric picolines and lutidines (L) as well as those of the type Cu(NCS)₂ L ₃ withL=3- and 4-picoline, 3,4- and 3,5-lutidine were measured. The behaviour of the (CN) stretching vibrations of the Cu(NCS)₂ L ₂ complexes led to conclusions on the different kind of coordination of the NCS groups in dependence on the ligandL. The mutually conditioned strength of the Cu–NCS and Cu–N(L) bonds in the equatorial plane, especially in the presence of ligandsL with the steric effect, was determined from the frequency shift of the Cu–NCS and Cu–N(L) stretching vibrations with regard to the vibrations for Cu(NCS)₂(pyridine)₂.

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Mit 1 Abbildung     

7-Benz[c] acridinemethanols as tetracyclic analogs of the 2-phenyl-4-quinolinemethanol antimalarials

A series of new 7-benz[c]acridinemethanols and 5,6-dihydro-7-benz[c]acridinemethanols was prepared as rigid, tetracyclic analogs of the antimalarial 2-phenyl-4-quinolinemethanols. Condensation of 5,7-dichloroisatin with 6-chloro-, 7-chloro-, and 6,7-dichloro-1-tetralone furnished halogenated 5,6-dihydro-7-benz[c]acridinecarboxylic acids, which were transformed into the corresponding acid chlorides, acyl malonates, α-bromomethyl ketones, and epoxides. Fully aromatic members of the series obtained via dehydrogenation of the 5,6-dihydro acids were likewise converted into epoxides via the acylmalonate route. Although all the epoxides studied proved to be exceptionally resistant to ring-opening by di-n-butylamine, probably on account of steric effects, they could be cleaved readily with piperidine or morpholine. Nmr spectra of the resulting amino alcohols suggest that these compounds exist in a single preferred conformation stabilized by internal O-H····N hydrogen bonding, and that free rotation about the side chain C-C bond does not occur at room temperature.     

Nuclear magnetic resonance studies of sulfur inversion in bis(cyclopentadienyl)-molybdenum and -tungsten complexes with dithioethers

The metallocene thioether derivatives [Cp₂M(MeSCH₂CH₂SMe)][PF₆]₂ (1, M = MO; 2, M = W), [Cp₂Mo(SCH₂CH₂SMe)][PF₆] (3) and [Cp₂M(SCH₂CH₂S)] (4, M = Mo; 5, M = W) exhibit temperature-dependent fluxional behavior in solution, owing to the pyramidal sulfur inversion process. The activation energies for this process were determined from proton band-shape analysis in the cases of 1 (54.9 ± 2 kJ mol⁻¹), 2 (51.2 ± 4.6 kJ mol⁻¹) and 3 (30.0 ± 3.1 kJ mol⁻¹). Extended Hückel calculations on related model complexes suggest that local inversion at the sulfur atoms, rather that an inversion of the complete S---C---C---S chain, is responsible for the observed fluxional behaviour.     

Separation of 23 dansylated amino acids by micellar electrokinetic chromatography at low temperature

Summary The baseline separation of 23 dansylated amino acids (including 3 didansylated species) is reported. Lowering of the analysis temperature and fine control of the surfactant concentration were essential in obtaining this result. Calibration graphs with good linearity were obtained.