Optisch aktive übergangsmetall-komplexe XX. Optisch aktive cyclopentadienyl-perfluoropropyl-kobalt-komplexe mit zweizähnigen schiff-basen

In the reaction of C₅H₅ Co(C₃F₇)(CO)I with the Schiff base NN′, derived from S-(-)-?-phenylethylamine and pyridine carbaldehyde-2, the salt [C₅H₅Co(C₃F₇)NN′]⁺ I^? (Ia,b) is formed, which can be transformed to [C₅H₅ Co(C₃F₇)NN′]⁺ PF₆^? (IIa,b). The sodium salt Na⁺ [NN″]^? of the Schiff base, derived from S-(-)-α-phenylethylamine and pyrrol carbaldehyde-2, in the reaction with C₅H₅ C0(C₃F₇)(CO)I yields the neutral complex C₅H₅ Co(C₃F₇)NN″ (IIIa,b). The diastereoisomeric pairs IIa,b and IIIa,b are separated by fractional crystallisation and chromatography respectively into the optically pure components which differ in their ¹H NMR spectra. The IR, UV, CD, mass spectra and optical rotations of the new compounds IIa, IIb, IIIa and IIIb are compared.     

A Highly Stereoselective Synthesis of C(11)-Functionalized Aromatic Steroids by an Intramolecular Benzocyclobutene-Olefin -Cycloaddition. Preliminary Communication

The racemic cis-anti-trans-steroids 9 to 11 have been synthesized in a highly stereoselective manner starting from 4-methoxybenzocyclobutene carboxylic acid via the key step 8 → 9 . (cf. Scheme 2).     

The hyperbolic n-space as a graph in Euclidean (6n−6)-space

We construct for each n2 an isometric C-imbedding HⁿE^6n–6 of the n-dim. hyperbolic space into the Euclidean space E^6n–6 whose image is the graph of a C-map RⁿR^5n–6. This generalizes a well known result of D. Blanusa 1955 (the case n=2).     

Local limits and harmonic functions for nonisotropic random walks on free groups

Summary Nearest neighbour random walks on the homogeneous tree representing a free group withs generators (2s) are investigated. By use of generating functions and their analytic properties a local limit theorem is derived. A study of the harmonic functions corresponding to the random walk leads to properties that characterize ther-harmonic function connected with the local limits.     

Integer points on hypersurfaces

Very general hypersurfaces in ⁴ contain r ^2+(4/9) integer points in any ball of radiusr>1. As a consequence, an irreducible algebraic hypersurface in ⁿ (wheren4) which is not a cylinder and is of degreed, contains c(d, n)r ^{n–1–(5/9)} integer points in a ball of radiusr. This improves on the known boundc(d, n)r ^n–(3/2).Meinem verehrten Lehrer Professor E. Hlawka zum siebzigsten Geburtstag gewidmetWritten with partial support from NSF-MCS-8211461.     

Electronic Structure and Photophysical Properties of Isoindole and its Benzo[f]- and Dibenzo[e,g]-Derivatives

The synthesis of N-methyl-benz[f]isoindole ( 2 ) and N-methyl-dibenz[e,g]isoindole ( 3 ) is reported. The NMR. spectra of N-methyl-isoindole ( 1 ) and of 2 have been analysed and the implications concerning the alternation of bond lengths are discussed. The photophysical properties of 1 to 3 have been investigated by the following methods: HeI photoelectron (PE.) spectroscopy, UV./VIS. absorption (polarization measurements by the stretched-foil technique) and emission spectroscopy (fluorescence spectra, lifetimes and quantum yields, phosphorescence spectra), and flash spectroscopy (triplet-triplet absorption spectra). The discussion of the results is based on HMO. and PPP SCF CI. calculations and points to the relationship between the heterocycles 1 to 3 and the corresponding benzenoid hydrocarbons obtained by replacement of the ? NMe? subunit by ? CH?CH? . Some comments concerning the ground state properties of isoindole and related compounds are derived from the analysis of their electronic structure.     

Organometallic Syntheses with Diazoalkanes

In recent years, aliphatic diazo compounds have proved to be more and more versatile as reagents in the preparative chemistry of organometallic complexes. As readily accessible compounds, they are not only suitable for the synthesis of known kinds of metal complexes but also open fresh routes to novel complex systems. The comparatively new field of diazoalkane complex chemistry exhibits numerous unexpected and novel reactions, and introduces interesting and promising aspects into the chemistry of carbonylmetal compounds.     

Übergangsmetall-substituierte phosphane,arsane und stibane : XXV. C5H5(CO)2[P(OMe)3]M-substituierte dioxaphospholane und dioxarsolane; stereochemische evidenz für den intermolekularen ablauf einer isomerisierung unter methylgruppenverschiebung

2-C₅H₅(CO)₂[P(OMe)₃]Mo(W)-substituted 4,4,5,5-tetramethyl-1,3,2-dioxarsolanes and -dioxaphospholanes (Ia–Ic) are obtained from C₅H₅(CO)₃M derivatives via CO/P(OMe)₃ exchange. In all cases the phosphite ligand appears trans to the σ-bonded arsenic heterocycle, which prefers a conformation with the transition metal group in an axial position. The dioxaphospholane-metal (Ia) undergoes isomerization with alkyl migration at 0°C, which due to stereochemical reasons can only occur by an intermolecular mechanism.     

Chlor-dimethylaminosulfonium-Salze Darstellung und IR-Spektren

Chloro-dimethylaminosulfonium Salts. Preparation and I. R. Spectra By reaction of bis-dimethylamino-mono- resp. -disulfane with a mixture of chlorine/antimony(V) chloride the chloro dimethylaminosulfonium hexachloroantimonates(V) [(CH₃)₂N]₂SCI^⊕SbCl₆^? (I) and (CH₃)₂NSCI₂^⊕SbCl₆^? (II) are yielded. The i. r. spectra of these compounds were measured and assigned.     

Quantitative goldbestimmung in filmmaterialien mittels flammenloser atomabsorption

A graphite rod electrothermal atomizer has been used for the AAS determination of traces of gold in hydrochloric and in hydrobromic acid solutions, and also after extraction into HBr-saturated methyl isobutyl ketone. Photographic film samples were decomposed first by enzyme action then by nitric acid/peroxide oxidation, and the gold was extracted into MIBK. For 10-μl aliquots of solution the 3s limits of detection were 3 × 10^?10g for aqueous solutions, 7 × 10^?10g for MIBK, and 7 × 10^?9 g/cm² for film.