Beiträge zur Chemie der Pyrrolpigmente, 38. Mitt.: Zur Assoziation von Gallenpigmenten

The long standing problem of solvent dependent absorption spectra of certain bile pigments such as bilirubindimethylester has been solved by measurement of molecular masses by means of vapour pressure osmometry. Using this method and the investigation of the concentration and temperature dependence of the absorption spectra on several model compounds an association equilibrium for pigments of the rubinoid structural type could be confirmed. Moreover the optical properties of the coexisting species and the corresponding equilibrium constants could be deduced by spectroscopic techniques. Verdinoid pigments lacking free carboxylic functions on the other hand tend to be monomeric in solution. A heteroassociated species involving equimolar amounts of a verdinoid and a rubinoid pigment could be verified existing on adsorbents like silicagel.

37. Mitt.:Falk, H., Thirring, K., Tetrahedron, im Druck.     

Metallorganische Verbindungen der Lanthanoide, 60. Mitt.: Synthese und Röntgenstrukturanalyse von Cyclooctatetraenyl(methylcyclopentadienyl)-(tetrahydrofuran)yttrium(III)

Summary The reaction of (C₈H₈)YCl(THF) with NaC₅H₄CH₃ in tetrahydrofuran leads to (C₈H₈)Y(C₅H₄CH₃)(THF). The X-ray structural analysis shows the compound to be orthorhombic witha=1157.5 (2),b=1553.2 (5),c=1718.9 (6) pm, space group Pbca,Z=8, andD (calcd)=1.48 g/cm^–3. The structure was solved from 1643 observed reflections withF _o4 (F _o) and refined to a finalR factor of 0.058. The expected sandwich structure is bent according to the ring centroid-Y-ring centroid angle of 149° caused by theTHF molecule coordinated to Y.

Herrn Prof. Dr. E. Hengge mit den besten Wünschen zum 60. Geburtstag gewidmet.     

1,1-Addition von Zinn- und Bleiverbindungen an Isonitrile Umsetzungen von Isonitrilen mit Halogeniden der IV. und V. Gruppe, 1. Mitt.

Zusammenfassung Isonitrile reagieren mit Zinntetrahalogeniden unter Einschiebung in Zinn-Halogen-Bindungen zu Halogencarbimino-zinnhalogeniden. Bei Umsetzungen mit organosubstituierten Zinnhalogeniden reagieren bevorzugt die Zinn-Halogen-Bindungen; nur Phenylisonitril wurde (unter forcierten Bedingungen) auch in Zinn-Kohlenstoff-Bindungen eingeschoben. In manchen Fällen entstehen dimere oder polymere Produkte. Triphenylbleibromid reagiert mit Phenylisonitril zur entsprechenden Tetracarbiminobleiverbindung.

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1,1-additions of tin and lead compounds to isonitriles

The reaction of isonitriles with tin(IV) halides yields halogenocarbiminotinhalides by insertion into tin-halogen bonds. In organosubstituted tin halides the tin-halogen bonds are more reactive towards insertion of isonitriles than the tin-carbon bonds. Under forced conditions however, phenylisonitrilisonitril also inserts into Sn–C bonds. A tetracarbimino-lead compound was obtained by reacting phenylisonitrile with triphenyllead bromide.