Decarboxylierung cyclischer und acyclischer dicarboxylato-komplexe des platins

The interaction of (Ph₃P)₂PtO₂ (I) with the dicarboxylic acids HO₂C(CH₂)_nCO₂H (n = 1–3), phthalic acid and maleic acid gives the dicarboxylato complexes (Ph₃P)₂$\text{PtO(O)C(CH}{}_2\text{)}{}_{\mathrm{<mtext>n</mtext>}}\text{C(O)O}$ (II) (n = 1–3), (Ph₃P)₂$\text{PtO(O)CC}{}_6\text{H}{}_4\text{C(O)O}$ (III) and cis-[(Ph₃P)₂Pt(O(O)CCHCHC(O)OH)₂] (IV) in nearly quantitative yield. Thermal and photoinduced decarboxylation of III and IV yields the platina heterocycles (Ph₃P)₂$\text{PtC}{}_6\text{H}{}_4\text{C(O)O}$ (V) and (Ph₃P)₂$\text{PtCHCHC(O)O}$ (VI) with a carbon-platinum σ-bond. Complex VI has been characterized by an X-ray crystal structure determination.     

Elemento-Organic Amines and Imines

Amines with mixed substituents containing two or three El? N bonds

1 El = a higher IVa, Va, or VIa element; by IVa, Va, and VIa elements are meant elements of the IV, V, and VI main groups of the periodic system

. are relatively stable if one or two of these bonds are (CH₃)₃ Si? N bonds. IR and ¹H? NMR studies indicate that the (p → d)π bond components of the element-nitrogen bonds steadily decrease from silicon, phosphorus, and sulfur toward their higher homologs. Because of the differences in the polarities of the element-nitrogen bonds, these substances can be used for selective insertion and cleavage reactions. The reaction of metalated N-silylaminoarsines with methyl chloride as well as the reaction of metalated N-trimethyl(IVa)-element-substituted amino-tert-butylphosphines with halogenotrimethyl(IVa) element compounds open new, simple routes for the conversion of elemento-organic amine systems into imine systems. The problem of reversible and irreversible (CH₃)₃ El ligand migration (1,3 shift) is discussed for trimethyl(IVa)element-substitued benzamidines, diaminophosphines, aminoiminophosphoranes, sulfinamides, and aminosulfimines.     

Determination of testosterone in human hair by gas chromatography-selected ion monitoring mass spectrometry.

A method for the determination of testosterone in human hair by gas chromatography-mass spectrometry using d3-testosterone as internal standard is described. Our method consisted of alkaline digestion, fast liquid-liquid extraction, LH-20 chromatography and derivatization with heptafluorobutyric anhydride. Quantification was achieved by selected ion monitoring of m/z 680 (testosterone) and m/z 683 (d3-testosterone). Our method needed no complex corrections for isotope contributions. The procedure provided a sensitive and specific technique with good accuracy and precision. For the first time, testosterone has been quantified by gas chromatography-mass spectrometry in human hair. The concentrations (median, range, ng g-1 hair) reflected a significant (p = 0.05; t-test) sex difference with 2.7 ng g-1 (2.5-4.2) in male and 1.7 ng g-1 (1.0-3.4) in female hair.     

Composite alternatives in group decision support

Decision theory models of group decision processes usually assume a given set of alternatives, from which the group has to choose. In realistic group decision situations, however, alternatives are often not specified a priori, but are created during the group process from different components introduced by the group members. This paper develops methods for systematically creating such composite alternatives, also taking into account the necessity to keep both the computational effort and the cognitive load to group members within reasonable limits.Paper presented at the International Conference on Support Systems for Decision and Negotiation Processes DNS-92, Warsaw, 1992.     

Generalized Hückel treatment of a simple model of transannular interaction and excimer formation

The model of two interacting ethylene molecules having D _2h symmetry was studied using generalized Hückel method. The validity of - separation was tested on this model. The general character of the ground state and lower lying excited states of the model was discussed and the implications drawn concerning transannular interaction and excimer formation. The values obtained for the dissociation energy of the first excited state of our model and corresponding equilibrium intermolecular distance are of right order of magnitude.

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Zusammenfassung Mittels der verallgemeinerten Hückel-Methode wurde das Modell von zwei Äthylenmolekülen mit der Symmetrie D _2h studiert. An diesem Modell wurde die Gültigkeit der - -Separation geprüft. Der allgemeine Charakter des Grundzustandes und der niedriger liegenden angeregten Zustände des Modells wird erörtert und die Folgerungen in Bezug auf transannulare Wechselwirkung und Excimer-Entstehung diskutiert. Die erhaltenen Werte für die Dissoziationsenergie des ersten angeregten Zustandes von unserem Modell und den entsprechenden intermolekularen Gleichgewichtsabstand haben die richtige Größenordnung.

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Résumé Le modèle à symétrie D _2h de deux molécules d'éthylène en interaction a été étudié en utilisant la méthode généralisée de Hückel. On a examiné la validité de la séparation - sur ce modèle. Le caractère général de l'état fondamental et celui des états excités inférieurs du modèle furent discutés et on a fait des déductions sur l'interaction transannulaire et sur la formation d'«excimères». Les valeurs obtenues pour l'énergie de dissociation du premier état excité de notre modèle et la distance intermoléculaire d'équilibre corréspondante ont l'ordre de magnitude correct.

     

Komplexkatalyse : XI. Eine einfache synthese für chloro-nitrosyl-carbonyl-molybdän(0)-komplexe als neue hochaktive präkatalysatoren für die olefinmetathese

A simple preparation of the chloronitrosylcarbonylmolybdenum(0) complexes Mo(NO)(CO)₄(AlCl₄) and MoCl(NO)(CO)₂(PPh₃)₂ is described. The homogeneous system MoCl(NO)(CO)₂(PPh₃)₂/RAlCl₂ (R = Et, Me) represents a new highly active long-living catalyst for the metathesis of 2-pentene.     

Spontaneously formed trans-anethol/water/alcohol emulsions: mechanism of formation and stability

We studied the spontaneous emulsification and droplet growth mechanism in trans-anethol/water/ethanol solutions, also known as the beverage ouzo, using dynamic light scattering spectroscopy. This simple ternary mixture is a generic example of a system that forms microemulsions spontaneously when brought into the two-phase region. The volume fraction of the dispersed phase was found to profoundly affect the growth rates of the droplets, which is a new finding that has not been predicted by the Lifshitz-Slyozov-Wagner theory. Time-dependent measurements show that the droplet growth is governed by Ostwald ripening (OR), and no coalescence was observed. Furthermore, the OR rates increase with increasing oil concentration at low alcohol content. We attribute this behavior to enhanced droplet-droplet interactions. At high ethanol concentrations, we found that the measured rates decreased as the oil concentration increased. The OR growth mechanism completely correlates with changes in droplet size. The kinetics of droplet growth shows that the ripening has a saturation limit at a droplet radius of about 1.5 mum. Thus, formed emulsions remain stable for months.