Weak Attractive Ligand–Polymer and Related Interactions in Catalysis and Reactivity: Impact,Applications, and Modeling

The notion of weak attractive ligand–polymer interactions is introduced, and its potential application, importance, and conceptual links with “cooperative” ligand–substrate interactions are discussed. Synthetic models of weak attractive ligand–polymer interactions are described, in which intramolecular weak C? H???F? C interactions (the existence of which remains contentious) have been detected by NMR spectroscopy and neutron and X‐ray diffraction experiments. These C? H???F? C interactions carry important implications for the design of catalysts for olefin polymerization, because they provide support for the practical feasibility of ortho‐F???H_β ligand–polymer contacts proposed for living Group 4 fluorinated phenoxyimine catalysts. The notion of weak attractive noncovalent interactions between an “active” ligand and the growing polymer chain is a novel concept in polyolefin catalysis.     

Untersuchungen über Papaverin

Ohne Zusammenfassung     

Prädikatives und funktionales Denken in der Wahrscheinlichkeitsrechnung

In order to emphasize functional thinking in mathematical education, arguments are brought forward for an early and frequent use of tree diagrams in teaching stochastics. Since set and tree diagrams can be regarded as two sides of the same matter, Bayes’ theorem, which is strongly associated with predicative set diagrams, need not be dealt with explicitly any longer. Set diagrams are replaced by tree diagrams that are labelled in detail and by tree inversion as a functional instrument of dealing with conditioned probabilities. This technique is demonstrated by three typical problems in the context of conditioned probability. Finally, two letters by Pascal to Fermat are analysed in order to illustrate that predicative and functional approaches were already pursued in the early stages of probability calculus in the 17^th century.     

Synthesis and characterization of poly(higher‐α‐olefin)s with a nickel(α‐diimine)/methylaluminoxane catalyst system: Effect of chain running on the polymer properties

Homopolymerization of octadecene‐1 at different reaction conditions has been studied. Significant chain running can be seen at higher polymerization temperatures. Interestingly, insertion of octadecene‐1 into a sterically hindered nickel‐cation/carbon (secondary) bond is observed. The microstructure of the polymer was established using NMR spectroscopy. The effects of chain running on polymer melting, crystallization behavior, and dynamic mechanical thermal properties were studied using DSC and DMTA. The extent of chain running (i.e., 2,ω‐, 1,ω‐enchainments) decreases with an increase in the carbon number of α‐olefins. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 191–210, 2007     

4-Amino-imidazole durchThorpe-Cyclisierung

The alkylation of arylaminomethylenecyanamides1 or cyano-imidothiocarbamates2 with -halogen carbonyl compounds followed by base catalysed cyclization yields substituted 4-amino-imidazoles4. Imidazo[4,5-d]pyrimidones5, 6 and imidazo[4,5-b]pyridines7 can be obtained from4.     

The electrocapillarity of polyacrylates

Summary The electrocapillary properties of polyacrylic acid have been studied by two methods. Exploratory measurements have been made of the effect of the polymer on the differential capacity of a mercury drop in 0.1 m sodium perchlorate. They showed that the polymer was strongly adsorbed over a wide range of potentials but that it did not appear to form a monolayer. The surface excess of polymer obtained from drop weight data showed a maximum at very low concentrations and then a decline at higher concentrations. The bulk of the work was carried out by making surface tension measurements, using a sessile mercury drop, in solutions of a fraction of polyacrylic acid (mol. wt. 7.02×10⁴) in potassium chloride at 0.01, 0.1, 0.2, and 0.5 m at 25°C.The data have been used to evaluate the surface excesses of the polymer and of the inorganic ions. The distribution of K⁺ and Cl^– in the electrical double layer and the contact adsorption of Cl^– on the mercury were very little affected by the presence of the polymer. The surface excess of polymer was always found to be greatest at low concentrations, to decrease steeply at first as the concentration was increased and then to decrease more slowly at higher concentrations.Possible explanations of this behaviour are discussed and it is concluded that the rapid decrease is a consequence of molecular weight dispersion and the stronger adsorption of high molecular weight polymer. The slow decrease in surface excess at higher concentrations may be a result of configurational changes of the polymer molecules.Surface pressure data show that, despite this decrease in the surface excess, the surface coverage reaches a high level at very low polymer concentrations and then continues to increase slowly as the concentration of polymer is increased. This apparent contradiction is due to changes in configuration of the adsorbed polymer molecules. At higher bulk concentrations the chain configurations are more compact and each adsorbed molecule makes more contacts with and so occupies a greater area of the mercury surface than at low concentrations.The conclusion is reached that the surface excess of polymer is mostly contained in a layer probably more than 1000 Å thick. It consists of a concentrated and entangled mass of polymer chains. Relatively few of these chains are in contact with the mercury at any istant. The concentration in this surface layer decreases steadily with increasing distance from the mercury surface and it merges without discontinuity into the bulk solution.With 10 figures in 22 details     

Stereochemie von Metallocenen, 40. Mitt.

Starting from optically active methylferrocene-- and--carboxylic acids (1 a and1 b) of known absolute configuration and enantiomeric purity about 15 chiral ferrocenes (of each isomeric series— and ) were obtained by suitable ligand transformations. Thereby (almost) all possible chiral combinations of the ligands CH₃, COOH (COO^–), COOCH₃, CN and NH₂ (NH₃ ⁺) were accessible which are necessary for a potential test of approximations of chirality functions for compounds with basic symmetry C_5v. The chiroptical properties of these disubstituted ferrocenes are recorded.Preliminary tests using a shortened Ansatz revealed large discrepancies between calculated () and found [M]_D-values. Possible reasons for this failure are discussed.

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61. Mitt. über Ferrocenderivate

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39. Mitt.:A. Meyer, H. Neudeck undK. Schlögl, Chem. Ber.110, 1403 (1977).

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60. Mitt.:V. Rapi, K. Schlögl undB. Steinitz, J. Organometal. Chem.94, 87 (1975).