Acyl- und Alkylidenphosphane. XXVII [I.]. Molekül- und Kristallstruktur des Methyl[(N-phenyl,N-tri-methylsilyl)thiocarbamoyl]trimethylsilylphosphans

Acyl- and Alkylidenephosphines. XXVII. Molecular and Crystal Structure of Methyl-[(N-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphine . Methyl[(N-phenyl, N-trimethylsilyl)thiocarbamoyl]trimethylsilylphosphine 1a formed via an addition of methylbis(trimethylsilyl)phosphine to phenyl isothiocyanate [1], crystallizes in the monoclinic centrosymmetric space group P2₁/n with following dimensions of the unit cell determined at a temperature of measurement of ?80±3°C: a=1041.2(4);b=1706.9(12);c=1001.1(6)pm; β=106.41(4)°; Z = 4. An X-ray structure determination (R_w = 0.039) confirms the constitution of the compound as already derived from its nmr spectra. One trimethylsilyl group is bound to the phosphorus atom, whereas the other is connected with the sp²-hybridized nitrogen atom. Characteristic rounded bond lenghts and angles are: P? Si 231, P? CH₃ 184, P? C(S) 187, C?S 167, N? C(S) 137, and N? Si 181 pm as well as P? C? S 122°, P? C? N 117°, and S? C? N 121°.     

Comparative studies of MCs+-SIMS and e–-beam SNMS for quantitative analysis of bulk materials and layered structures

For the quantification of heterostructure depth profiles the knowledge of relative sensitivity factors (RSF) and the influence of matrix effects on the measured profiles is necessary. Matrix dependencies of the measured ion intensities have been investigated for sputtered neutral mass spectrometry (SNMS) and MCs(+)-SIMS. The use of Cs as primary ions for SNMS is advantageous compared to Ar because the depth resolution is improved without changing RSFs determined under Ar bombardment. No significant amount of molecules has been found in the SNMS spectra under Cs bombardment. Using MCs(+)-SIMS the RSFs are matrix dependent. An improvement of depth resolution can be achieved by biasing the sample against the primary ion beam for SNMS due to a reduction of the net energy of the primary ions and a resulting more gracing impact angle.     

An alternative synthesis of 2-(N-arylhydrazono)-1-benzothiophen-3-ones

In the presence of triethylamine, 2-mercaptobenzoic acid readily adds onto acylhydrazonoyl chlorides (1a-c) (precursors of the reactive nitrile imine 1,3-dipolar species) to afford good yields of the corresponding 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto]benzoic acids (2a-c). The latter acyclic adducts, in THF in the presence of 1,1'-carbonyldiimidazole, undergo intramolecular cyclization involving the activated carboxy and the enol functionality to deliver the respective 2-(N-arylhydrazono)-3-oxobenzothiophenes (3a-c). In the solid state, the latter compounds adopt the (Z)-geometry around the C=N double bond as evidenced by single crystal X-ray structure determination for 3b.     

The determination of adsorbable organically bound halogens (AOX) in soil: interlaboratory comparisons and reference materials

The interlaboratory variability in the quantification of adsorbable organically bound halogens (AOX) in industrially contaminated soil is presented. Three consecutive rounds of a proficiency testing scheme, in which between 88 and 119 routine laboratories participated, yielded relative reproducibility standard deviations between 7 and 20% at AOX contents between 10.9 and 268 mg kg⁻¹. Nineteen laboratories with established proficiency were invited to participate in the certification of the AOX content in three soil reference materials meant for the internal quality control in analytical laboratories. The certified values are (1349 ± 59) mg kg⁻¹, (80 ± 7) mg kg⁻¹ and (102 ± 8) mg kg⁻¹, respectively.     

Tetrahydroepoxides and diol epoxides of benz[c]acridine

The chemical synthesis and NMR characterization of the benzo ring tetrahydro- and diol epoxides of the carcinogen benz[c]acridine are described.     

QUENCHING OF OXONINE EXCITED STATES BY EDTA VIA ELECTRON TRANSFER AND DEACTIVATION PROCESSES. A COMPARATIVE STUDY OF EXCITED SINGLET AND TRIPLET STATE REACTIVITY

The quenching of excited singlet oxonine by EDTA in aqueous solution leads mainly to deactivation of the dye to the ground state and, to a lesser extent, to electron abstraction. The rate constants for these processes have been measured and compared to those for the same reactions involving the oxonine triplet state. The rate constant of electron abstraction is about ten times greater via the singlet state than via the triplet state. However, the rate constant of deactivation to the ground state is 10³-10⁴ times greater for the excited singlet state than for the triplet state, so that the efficiency of electron transfer is much smaller for the singlet state.     

Neuere Entwicklungen der flammenphotometrischen Analysenverfahren

Zusammenfassung Es wird gezeigt, daß man durch Einsatz von reduzierenden Flammen, durch Einsatz von Chemiluminescenzvorgängen in Flammen, durch Atomabsorptionsverfahren, durch Modulations- und Differentiations-operationen eine Reihe von weiteren Elementen mit den schnellen und spezifischen Flammenmethoden analytisch gut erfassen kann. Hierbei wird insbesondere auf die Bestimmung von Spurenelementen in Mikroproben mit möglichst einfachen Mitteln eingegangen.

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Summary It is demonstrated that one can grasp analytically well a series of further elements with the quick and specific flame methods by use of chemiluminescence processes in flames, by atomic absorption methods, by operations of modulation and differentiation. Hereby the determination of trace elements is specifically treated in microprobes with the most possible simple means.

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Unterstützt mit Mitteln der Deutschen Forschungsgemeinschaft.

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Herrn Prof. Dr. Bohnstedt zum 65. Geburtstag gewidmet.

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Meinen Mitarbeitern, insbesondere Herrn Dipl. Phys. W. Lang und Frau B. Gutsche, die an den zuletzt besprochenen Ergebnissen einen maßgeblichen Anteil hatten, als auch der Deutschen Forschungsgemeinschaft sei an dieser Stelle herzlichst gedankt.     

Exploring CH-activation pathways in bifunctional zirconocene/borane systems

The dimethylsilanediyl-bridged ansa-zirconocene dichloride 1, that contains a pendent allyl substituent at a Cp-ring, adds HB(C(6)F(5))(2) to the vinyl group to yield the bifunctional zirconocene/borane complex 2. Substituted benzimidazoles were added to the strongly electrophilic borane moiety as protective groups, which allowed subsequent chloride versus -CH(2)SiMe(3) exchange at zirconium to take place by treatment with the respective alkyllithium reagent. Alternatively, the introduction of active sigma-ligands at zirconium is carried out first, followed by the hydroboration reaction. This route was followed for the synthesis of the diphenyl-ansa-zirconocene/borane complex 12. Complex 12 reacts slowly in solution by intramolecular electrophilic attack of the borane at its adjacent Cp-ring, followed by deprotonation using a [Zr]-Ph group to yield the zwitterionic complex 14 featuring a borata-tetrahydroindenyl moiety as part of the ansa-metallocene framework. Complex 14 was characterized by X-ray diffraction. It adds PMe(3) at zirconium to yield 15. Thermolysis of 12 with excess PMe(3) leads to the formation of the (aryne)zirconocene complex 18, which is stabilized by PMe(3) coordination to zirconium and PMe(3) addition to boron. N-Methylbenzimidazole adds to the -B(C(6)F(5))(2) unit of 12 to give the 1:1 adduct 19. Thermolysis of 19 at 80 degrees C in benzene solution in the presence of one additional equivalent of N-methylbenzimidazole results in deprotonation of the substrate to yield the sigma-N-methylbenzimidazolyl zirconium complex 20 (as a mixture of two diastereoisomers). An additional N-methylbenzimidazole ligand is bonded to the B(C(6)F(5))(2) unit in this product.     

Time-resolved investigations of singlet oxygen luminescence in water, in phosphatidylcholine, and in aqueous suspensions of phosphatidylcholine or HT29 cells

Singlet oxygen was generated by energy transfer from the photoexcited sensitizer, Photofrin or 9-acetoxy-2,7,12,17-tetrakis-(beta-methoxyethyl)-porphycene (ATMPn), to molecular oxygen. Singlet oxygen was detected time-resolved by its luminescence at 1270 nm in an environment of increasing complexity, water (H2O), pure phosphatidylcholine, phosphatidylcholine in water (lipid suspensions), and aqueous suspensions of living cells. In the case of the lipid suspensions, the sensitizers accumulated in the lipids, whereas the localizations in the cells are the membranes containing phosphatidylcholine. By use of Photofrin, the measured luminescence decay times of singlet oxygen were 3.5 +/- 0.5 micros in water, 14 +/- 2 micros in lipid, 9 +/- 2 micros in aqueous suspensions of lipid droplets, and 10 +/- 3 micros in aqueous suspensions of human colonic cancer cells (HT29). The decay time in cell suspensions was much longer than in water and was comparable to the value in suspensions of phosphatidylcholine. That luminescence signal might be attributed to singlet oxygen decaying in the lipid areas of cellular membranes. The measured luminescence decay times of singlet oxygen excited by ATMPn in pure lipid and lipid suspensions were the same within the experimental error as for Photofrin. In contrast to experiments with Photofrin, the decay time in aqueous suspension of HT29 cells was 6 +/- 2 micros when using ATMPn.     

Organometallic reactions of α-haloimines as a useful tool in organic synthesis

The reaction of organometallic reagents, e.g. alkyllithiums, cuprates and alkylcoppers, with α-haloimines gave selectively a variety of synthetically useful reactions, including coupling to 1,4-diimines, homologation, and production of heterocycles.