Untersuchungen der Symmetrieverhältnisse in äquatorial koordinierten 2:1-Arylazo-CoIII-Komplexen mit Hilfe der Protonenresonanz

The magnetic equivalence of ligand protons was examined with aid of NMR. spectroscopy for a large number of 1:2 Co^III-complexes of tridentated azo dyestuffs forming a representative cross section of the whole class of substances. It was established by this investigation that ligands with a moderately polarised azo group have a particular inclination to form asymmetrical complexes in which the protons of the two ligands are not magnetically equivalent. On the other hand, ligands having a non-polarised or a strongly polarised azo group tend to form symmetrical complexes. In three cases both symmetrical and asymmetrical complexes were isolated. As in previous investigations [1], up to a total of 5 complexes were again observed, which indicates at least two causes governing the symmetry conditions. The phenomena described here could be explained with an alternative coordination of the two azo nitrogen atoms. On the basis of the NMR. results, however, preference is given to an exchange of the azo with the hydrazone form.     

Die Kristallstruktur der Verbindung Li2ZnGeO4

The crystal structure of dilithiumzine orthogermanate, Li₂ZnGeO₄, has been determined and refined byFourier syntheses and least-squares, using three dimensional single-crystal data. A finalR-value of 5.7% was obtained. The monoclinic unit cell (Pn–C_s ²) with the dimensionsa=6.40,b=5.45,c=5.04 Å and =90.2° contains two formula units Li₂ZnGeO₄. The crystal structure is built up by [GeO₄] tetrahedra, which are linked together by [LiO₄] and [ZnO₄] tetrahedra. The average interatomic distances are found to be: Ge–O=1.77, Li–O=2.01 and Zn–O=1.93 Å.     

Die Neubestimmung der K2CuF4-Struktur

Redetermination of the K₂CuF₄ Structure The structure of K₂CuF₄ was redetermined by x-rays. An enlarged tetra-gonal unit cell of dimensions a = 5.858, c = 25.42 Å was found. The refinement in spacegroup D–I4c2 yielded R = 0.06. Contrary to former findings the JAHN-TELLER- distortion of the CuF₆-octahedra corresponds to a tetragonal elongation with distances Cu–F = 1.92 Å (4 ×) and 2.22 Å(2×).     

Die absolute Konfiguration von 1-2H1-Äthanol

(S)-l-²H₁-Ethanol (6) has been prepared in three steps from (–)-erythro-(2R,3S)-3-²H₁-butan-2-ol (2) , itself available from cis-butene by asymmetric hydroboration. In enzymatic tests with yeast alcohol dehydrogenase this deuterated ethanol proved to be indistinguishable from the laevorotatory isomer. This establishes the (S)-chirality of the latter and at the same time defines the stereospecificity of the yeast alcohol dehydrogenase.     

Beitrag zur Aufklärung der Beziehungen zwischen der Zusammensetzung,der Struktur und den Redox-Veränderungen der Komplexverbindungen von CuCl2 mit aliphatischen Aminen als Liganden

Contribution to the Study of the Correlations between Composition, Structure, and Redox Changes of Complex Compounds of CuCl₂ with Aliphatic Amines as Ligands Complex compounds of the composition CuCl₂L₂L₄(L = methylamine and ethylamine) and CuCl₂L₂ (L = methylamine, ethylamine, ethylamine and diethylamine) were prepared. The structure of these complexes was studied by means of electronic, infrared and e:p.r. spectra. The results of the applied methods showed that the degree of distortion of the coordination polyhedra of Cu^II increased with the basicity and dimension of The ligands. The thermal stability of the complexes as well as the reduction temperature of the Cu^II decreased in the same order. These results are discussed with respect to the mutual influence of ligands in Cu^II complexes and to its effects on the course of their redox reactions.     

Die Stereochemie der fragmentierenden Enthalogenierung von 1-Chlor-1-fluor-2-(1-halogenalkyl)cyclopropanen

The Stereochemistry of the Fragmentative Dehalogenation of 1-Chloro-1-fluoro-2-(1-halogenalkyl)cyclopropanes A number of model substrates were submitted to zinc-promoted fragmentation, and the composition of the resulting mixture of isomeric fluorodienes was determined. The exocyclic reaction center, bearing the electrofugal leaving group, was found to undergo almost complete stereochemical randomization in the course of the reaction. On the other hand, the ring-opening proceeds stereoselectively. The rotation, which brings the substitutents of the halogen-free ring position into the plane of the new, fluorine-bearing double-bond, occurs mainly in that sense to move the electrons of the breaking ring linkage into the rear of the departing chlorine atom.     

Mit der Anwendung organischer Reazenzien und Komplexverbindungen in der analytischen Chemie

Ohne Zusammenfassung     

Die Veresterungsgeschwindigkeiten der Monoaminobenzoesäuren und der 1- und 2-Pyridinkarbonsäuren in Glykol und Glyzerin

Zusammenfassung Es werden die Veresterungsgeschwindigkeiten der Monoaminobenzoesäuren und der 1- und 2-Pyridinkarbonsäuren bei 25° mit Chlorwasserstoff als Katalysator sowohl in wasserfreiem als auch in wasserhaltigem Glykol und in wasserfreiem Glyzerin gemessen, die derm- und derp-Aminobenzoesäure und der 2-Pyridinkarbonsäure (Nikotinsäure) auch in wasserhaltigem Glyzerin. Die Abhängigkeit der monomolekularen Geschwindigkeitskonstanten vom Wassergehalt (w) des Mediums und dem Überschuß der Konzentration der Salzsäure über die der organischen Säure, bzw. ihres Esters (C) wird für die drei zuletzt genannten Säuren durch Formeln dargestellt. Diese Geschwindigkeitskonstanten nehmen durchwegs sowohl in wasserfreiem als auch in wasserhaltigem Glykol und Glyzerin nicht nur rascher als die Konzentration der gesamten Salzsäure, sondern auch als die des obigen Überschusses, d. h. der freien Salzsäure, zu.FürC=1/3 sind beiw=0.03 die Geschwindigkeitskonstanten derm- und derp-Aminobenzoesäure und der Nikotinsäure in Äthylalkohol um 20–30 %, die der Anthranilsäure um 70%, die der Pikolinsäure um 130% größer als in Glykol, beiw=0.7 dagegen die der drei ersteren Säuren um 35–50% kleiner.In Glykol sind die Konstanten bei der Anthranilsäure und den Pyridinkarbonsäuren kleiner als in Glyzerin, bei den übrigen wie bei den früher untersuchten Säuren aber größer.Die sterische Wirkung der Aminogruppe in Orthostellung ist in Glykol größer, in Glyzerin kleiner als in Äthylalkohol.Unter gleichen Bedingungen Bind die Konstanten der Veresterungsgeschwindigkeit der Nikotinsäure in Glykol und Glyzerin etwa viermal, in Äthylalkohol nur etwa zweimal größer als die der Pikolinsäure.     

Kinetik und Mechanismus der Substitutionsreaktionen von Komplexverbindungen. XXIII. Die Wasserstoff-bis-nyoximato-diselenocyanatokobaltiat(III)-Säure und die Kinetik der Aquotisierung des [Co(NioxH)2(NCSe)2]-Ions

A new monobasic complex acid has been obtained by oxydizing a mixture of 1,2-cyclohexane-dione-dioxime (nyoxime), cobalt(II)-acetate and KCNSe. It is the hydrogen-bis-nyoximato-diselenocyanato cobaltiat: H[Co(NioxH)₂(NCSe)₂]. A number of 34 new complex salts of this acid have been isolated in crystalline form. In order to clear up some structural problems, a spectrophotometric study has been made in UV, and IR region. In aqueous solutions of the complexion takes place an aquation reaction, which leads to the substitution of a selenocyanation by water. Kinetics of this reaction has been followed at different temperatures (Activation energy of the reaction E_a = 32.5 ± 0.9 kcal/mole, pre-exponential factor in ARRHENIUS' equation lg Z = 15.5 ± 2.5). Results are compared with the kinetic parameters of the aquation of the analogous bis-dimethyl-glyoximato-diselenocyanato-cobalt(III)-ion.     

Die Strukturen der mittleren Ringverbindungen. XI. Cyclooctan-1, 2-trans-dicarbonsäure

Crystals of 1, 2-trans-cyclooctane-dicarboxylic acid are monoclinic, a = 14.76 Å, b = 11.89 Å, c = 12.98 Å, β = 111.25°, space group C/2c with 8 molecules in the unit cell. The structure has been solved by direct methods and refined by full-matrix least squares analysis of three-dimensional intensity data. The cyclooctane ring is found to occur in an approximately mirror-symmetric (‘boat-chair’) conformation.     

Isomeriefälle bei CrIII- und CoIII-1:2-Komplexen aus 8-(2′-Carboxyphenyl)-amino-chinolinen: Zur Frage der pyramidalen Struktur des koordinierten,dreibindigen Stickstoffatoms von Metallchelaten

8-(2′-Carboxyphenyl)-aminoquinolines are tridentate ligands. They form on complexation with Co^III or Cr^III singly negatively charged 1:2 complexes by loss of two protons. In these octahedral complexes the ligands are very probably coordinated equatorially. Nevertheless up to 3 isomeric 1:2 complexes are formed. According to the NMR.-spectra two of them an symmetrical the third is asymmetrical. The basis of our assumption is that a trivalent N-atom which is co-ordinated to a metal ion and which is a link of two annelated rings can possess pyramidal valence structure. The ligand in the complex would thus be bent, which renders the possibility to form three conformers.     

Die Tropfzeitabhängigkeit der polarographischen Halbstufen-potentiale von 2-Phenylchinoxalin

Reversible redox reactions which are followed by irreversible steps give often polarographic waves with drop life dependent shapes. A mathematical model is proposed which is capable to describe the change of the polarographic waves of quinoxalines, even at short drop lives and slow reactions of the irreversible step.