Manfred Wahren

Nitridokomplexe des Technetium(V)

Folgende Komplexe des funfuertigen Tichnitiums wurden dargestellt und charakterisiert TcNCl2[P(C6H5)3]2 (A) Tc NCl2 (PR2C6H5)3 [R = CH3 (B) bzw. C2H5 (C)] TcN[(C2H5)2NCS2]2 (D) Die Darstellung von (A) erfolgt anlog der entsprechenden Rheniumkomplexes; (B), (C) und (D) wurden durch Reaktron von (A) mit uberschunssigem PR2C6H5 bzw. Na(C2H5)2NCS2 durch Substitutionsreaktionen orhalten. Die genannten Komplexe sind bomerkenswert hydrolysebestandig. Here IR- und 1H-NMR-Spektren warden diskutiert

Interaction of titanocene generated in the system Cp2TiCl2 + Mg in thf with benzyne and tolane. A novel route to titanaindene and titanacyclopentadiene complexes

Direct synthesis of the titanaindene complex Cp2Ti[o-C6H4C(Ph)C(PH)] through of reaction of tolane with Cp2Ti and benzyne, generated in the system Cp2TiCl2 + Mg + o-fluorobromobenzene in THF is described. Under similar conditions, reaction of Cp2TiCl2 with Mg in THF, in the presence of tolane only (ratio Cp2TiCl2/Mg/Ph2C2 ≈ 1/1/2) yields the titanacyclopentadiene complex Cp2Tic(Ph)C(Ph)C(PH)C(Ph).

HTc(N2)(dppe)2 as starting material for mixed-ligand complexes of technetium(I)

Abstract In the complex HTc(N2)(dppe)2 the nitrogen ligand is most labile and can be exchanged under mild conditions for CO, isonitriles and phosphites (L1), yielding neutral hydridocomplexes of Tc(1) HTcL1(dppe)2. HTc(CO)(dppe)2 is also formed from the title compound by CO abstraction from methanol. In the complexes HTcL1(dppe)2 the hydrido ligand can be exchanged for acetonitrile (L2), yielding cationic mixed-ligand complexes of Tc(I) TcL1L2(dppe)2+, which are isolated as hexafluorophosphates.

Deuterium labelled nonylphenols in an in-vitro model of percutaneous absorption of environmental xenoestrogens.

Abstract A technical mixture of isomeric nonylphenols NP is formed as rather persistent degradation product of nonionic surfactants and has become widespread in the environment, e.g., in surface waters. Information about possible pathways for incorporation is needed for risk assessments, as NP has estrogenic properties. NP uptake after skin contact was determined using isolated and perfused bovine udders as models for human skin. NP-d2 labelled in the positions ortho to the OH-group was prepared by an exchange procedure which did not measureably change the relative amount of isomers. Samples of udder perfusate, milk equivalent produced during the experiments and skin tissue were taken immediately before administration of 500 mg or 50 mg NP-d2 on an udder skin area of 200cm2 and then for 5 h. They were analyzed by GC-MS for NP and NP-d2 after cleanup by steam distillation and final extraction with SPME fibres. The results are an unambiguous proof of the penetration of NP into the capillary system of living mammals after skin contact.

Application of deuterated compounds for investigations of percutaneous absorption of chemical substances.

The percutaneous absorption of the xenoestrogen 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A) 1 has been studied and compared with results on dibenzoyl peroxide 2, a component of drug formulations for topical application. Isolated perfused bovine udders from slaughtered cows were employed as models for human skin. The deuterium labelled compounds 1-d14 and 2-d10 were applied to enhance the reliability of GC-MS trace determinations by use of reverse isotope dilution analysis. 1-d14 was found in perfusate and milk equivalent samples obtained between 60 and 300 min after topical application with maximum concentrations between 120 and 180 min. 1-d14 was enriched in the milk samples by a factor of about 300 compared with the perfusate. The results confirm a possible penetration of 1 from the environment through the skin into the capillary system. 2 studied on the same model system penetrated faster than 1 by a factor of about three.

IR-spektroskopische und mechanistische Untersuchungen an Technetiumkomplexen unter Einsatz von 15N

The formation of Technetium nitrido- and thionitrosyl-complexes was investigated by means of 15N labelled compounds. The course of the reaction is rather different with the elements technetium and rhenium in spite of quite analogous starting materials and products. A new feasible synthesis of nitridotechnetium (V) complexes was found from complexes of Te(III) and azide. By 15N-substitution an unambiguous assignment of characteristic infrared bonds in the complexes was achieved.

Catalytic activation of C–H bonds of alkanes, ethene and aromatic hydrocarbons by the adducts of active carbons with metallic potassium

Abstract It has been shown that the adducts of active carbons with metallic potassium are able to activate C–H bonds of alkanes, ethene and aromatic hydrocarbons and introduce these compounds into the hydrogen–deuterium exchange reactions at room temperature. This paper describes the reactions of the redistribution of hydrogen isotopes in CD3H, C6H5CD3 and C6D5CH3 catalysed by the potassium–carbon adducts as well as the similar isotope exchange reactions in the systems C2H4–C2D4, C6H6–C6D6, n-C6H14–n-C6D14 and CD4–n-C5H12. A study of the isotope exchange between C6H6 and C6D6 has shown that the efficiency of the process is strongly dependent on the potassium content in the catalyst passing through a maximum at the K:C molar ratio of 1:7.45.

H-D exchange on graphite–potassium intercalation compounds

Potassium graphite intercalation compounds are able to activate C–H bonds of hydrocarbons at room temperature. In this paper, the hydrogen–deuterium exchange of CHD3 in the presence of C8K, C24K and C36K is described.

Hydrogen Isotope Effects in Electrochemical Reductions of Organic Chloro Compounds

Abstract The kinetic hydrogen isotope effects in electrochemical reductions of CCl3COOD, CDCl2COOD, CCl4, CDCl3, benzyl chloride, 1-chloronaphthalene and 4-chlorobenzonitrile in deuterated reaction media were determined. The aliphatic chloro compounds are reduced with rather small isotope effects kH/kD = 1.2…1.7, as expected if anionic intermediates are formed and protonated. Benzyl chloride is reduced with an apparent kH/kD = 2.1, which is probably too high due to radical reactions. Aromatic chloro compounds are reduced with significant participation of a second mechanism via radical intermediates which abstract carbon-bound hydrogen atoms from the components of the reaction system. The resulting isotope effects are kH/kD = 1.2 for the part of the reduction which proceeds via anions and kH/kD ∼ 2.5 for the competing radical reaction.

Substitution of Hydroxyl Groups by Deuterium in the Electrochemical Reduction of Methanesulfonates

Abstract The electrochemical reduction of dodecyl methanesulfonate (ROMs; R = n-C12H25 −, Ms = CH3SO2 −) as model compound was studied in deuterated media. This reaction could be of potential use in syntheses of partially deuterated compounds by conversion of C‒OH-groups into C‒D-bonds in the presence of other reactive groups. In order to obtain detailed information about the origin of the introduced hydrogen all individual components (solvent, supporting electrolyte, substrate) of the reaction system were deuterium labelled in the model reaction. The experiments indicate, that this reduction does not proceed along a uniform pathway. Dodecyl anions play the dominating role in the reaction mechanism. Deuterium is transferred into the product dodecane-d 1 from all components of the reaction mixture in the order of their relative proton acidities Ms-d 3 > Bu4N+-d 36 > DMF-d 7 > R-1,1-d 2-OMs. In the presence of D2O a hydrogen isotope exchange was found with the methyl group of MsO−, catalyzed by electrogener...