Übergangsmetallkomplexe : V. Über eine einfache synthese des phenyl-cyclooctatetraens und dessen liganden-eigenschaften gegenüber nullwertigem nickel

Butyl- and phenylcyclooctatetraene can be prepared in good yield by reaction of 2 equivalents of an organolithium complex with cyclooctatetraene followed by oxidation. In the case of phenylcyclooctatetrane, the intermediate dilithium salt could be isolated. The crystal structures of the 2:1 and 1:1 complexes formed by phenylcyclooctatetraene with zerovalent nickel have been determined by X-ray methods.     

Die Bestimmung des Chromgehalts in Laser-Rubinen mit Diphenylcarbazid

Ohne Zusammenfassung     

On the Relationship Between Macroscopic and Microscopic Time Constants in gas Discharges

The complicated relationship between macroscopic and microscopic time constants in gas discharges was given on the basis of the theory of the positive column of glow discharges.     

Asymmetric Syntheses with the Aid of Homogeneous Transition Metal Catalysts

The progress made in the field of homogeneous catalysis during the last five to six years has led, inter alia, to the development of highly selective catalysts for asymmetric syntheses. Homogeneous asymmetric hydrogenation, using well defined transition metal catalysts, may be achieved with optical yields of 85 to 90% or more. Catalytic reactions, in which the chiral centers are generated by C? C bond formation, can result in optical yields of 70 to 80%. The hydrogenation catalysts consist primarily of rhodium(I) complexes containing “Homer phosphanes”, phosphanes with chiral C atoms, or optically active amides. Catalysts which induce optical activity through the formation of C? C bonds have been developed from π-allylnickel halides, Lewis acids, and phosphanes containing chiral C atoms. The results obtained signify a breakthrough in an area of catalysis previously restricted to syntheses involving enzymes.     

Ligandeneigenschaften von Thiopyronen. I. Metallchelate von 2-Methyl-3-hydroxy-4-thiopyron (Thiomaltol)

Coordination Ability of Thiopyrones. I. Metal Chelates of 2-Methyl-3-hydroxy-4-thiopyrone (Thiomaltol) Metal chelates of 2-methyl-3-hydroxy-4-thiopyrone with a series of metals are prepared as solids, the constitution of the complexes is determined in solution, and the extraction ability of the ligand for copper, nickel, cobalt and palladium is studied. Stability constants of the zinc and cadmium chelates are compared with those of thiodibenzoyl-methane.     

Activated platinum electrodes as transducer for a glucose sensor using glucose oxidase in a photopolymer membrane

A planar platinum electrode was covered by a photopolymer membrane containing glucose oxidase (GOD) to construct an amperometric glucose sensor. The application of a photopolymer system in membrane formation gives the opportunity to manufacture cheap biosensors with good reproducibility by means of automated techniques and to miniaturise sensors using photolithography. The electrodes were pretreated mechanically and chemically resulting in a half-wave potential (E_1/2) of the H₂O₂ oxidation shifted towards more negative potentials. This shift allows the determination of glucose at a low working potential (300 mV vs. SCE) without addition of mediators. The important advantage of such applied potential decreasing lies in minimising the interference of oxidisable substances such as uric acid, bilirubin and paracetamol. The selectivity to ascorbic acid could also be proved without the application of additional protection layers. The glucose sensor developed has a high life-time, selectivity and sensitivity and a linear working concentration range from 0.05 up to 10 mmol/l of glucose. The sensor was used for the glucose determination in human serum samples with a very good correlation to a common photometric reference method. Received: 13 July 1996 / Revised: 11 September 1996 / Accepted: 14 September 1996     

Darstellung,Schwingungsspektren und Kristallstrukturanalyse von Di- und Trifluor-tetramethylammonium-Salzen

Synthesis, Vibrational Spectra, and Crystal Structure Analysis of Di- and Trifluoro-tetramethylammonium Salts The tetramethylammonium salts (CH₃)₃NCH₂F⁺ ( II ), (CH₃)₃NCHF₂⁺ ( III ), and (CH₃)₃NCF₃⁺ ( IV ) were prepared by quaternation of the corresponding fluoromethylamines. III was also generated from (CH₃)₃N and Zn/CF₂Br₂/KF in acetonitrile. II , III , and IV were characterized by NMR and vibrational spectroscopy, a normal coordinate analysis being undertaken for IV . The crystal structures of the iodides of III and IV have been determined. In both cations the N? CH₃ distances are on the average ( III 1.508(2) Å; IV 1.514(5) Å) longer than the N? CF valencies ( III 1.497(4) Å; IV 1.491(6) Å).