Chelating Ruthenium Phenolate Complexes: Synthesis,General Catalytic Activity,and Applications in Olefin Metathesis Polymerization

Cyclic Ru‐phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring‐closing metathesis (RCM), enyne and cross‐metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat dicyclopentadiene (DCPD) and show good applicability in ring‐opening metathesis polymeriyation (ROMP) of this monomer.     

Preparation of Allylstannanes and Distannanes Using Zinc in Liquid Ammonia

Abstract

Barbier-type reductive coupling of allylic bromides and organotin compounds can be carried out in liquid ammonia (?33°C) using commercial zinc powder. This procedure provide a new simple and environment-friendly method for the synthesis of allylstannanes and distannanes.     

Einige neue,für die chemisch-technologische Forschung geeignete radioaktive Leitsubstanzen

Zusammenfassung Für Traceruntersuchungen mit Alumosilikaten werden Derivate der Alumokieselsäure, in denen das Al durch Ga substituiert wurde, vorgeschlagen. Es wurden einige so substituierte Zeolithe und Kaolinite synthetisiert.Für ähnliche Untersuchungen in der organische Rohstoffe verarbeitenden Industrie werden⁷⁷Ge-markierte Germaniumkohlenwasserstoffe vorgeschlagen. Es werden die Synthese und die Eigenschaften solcher Verbindungen angegeben.Am Beispiel des Germaniumtetramethyls und Germaniumtetraäthyls wurden die Ausbeuten und chemischen Formeln der bei der Aktivierung im Kernreaktor entstehenden Verbindungen ermittelt.

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Some new radioactive labelled substances suitable to investigations in chemical technology

For tracer studies with aluminosilicates, derivatives of aluminosilicic acid in which aluminium is wholly or partially replaced by gallium, are proposed. Several zeolites and kaolinites substituted in this manner have been prepared.For related studies in the organic sector of the chemical industry the use of organogermanes labelled with⁷⁷Ge is suggested. The synthesis and properties of such compounds are described.Using tetramethyl- and tetraethylgermane as models, the yields and chemical structures of compounds formed during activation within a nuclear reactor have been determined.

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Mit 4 Abbildungen

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Herrn Professor Dr.Engelbert Broda aus Anlaß seines 60. Geburtstages gewidmet.     

Absolute cross sections for pion reactions on light nuclei at the (3,3) resonance

Absolute cross sections for pion-induced neutron knockout reactions and some more complex reactions on ¹⁴N, ¹⁶O, ¹⁹F and ³¹P were determined by activation at 190 MeV. Results are consistent with existing spallation models as modified by the recent final-state interaction theory of Sternheim and Silbar.     

Cross section of (π+, π+n+π° p) reaction on 12C at the (32, 32) resonance

The absolute cross section for the neutron-knockout reaction on ¹²C with π⁺ particles has been measured at the ($\text{3}\text{2}\text{,}\text{3}\text{2}$) pion-nucleon resonance. A value of 50 ± 4 mb was obtained.     

Cross sections for (π, πn) reactions on 14N and 19F at the (32,32) resonance

Neutron knockout cross sections induced by π⁺ mesons on ¹⁴N and by π⁺ and π^? mesons on ¹⁹F were measured at 190 MeV relative to ¹²C. Results are compared to both qualitative and rigorous theoretical models.     

In an attempt to provide a user's guide to the galaxy of benzylidene, alkoxybenzylidene, and indenylidene ruthenium olefin metathesis catalysts

The data reported in this paper demonstrate that great care must be taken when choosing an appropriate catalyst for a given metathesis reaction. First-generation catalysts were found to be useful in the metathesis of sterically unhindered substrates. Second-generation catalysts (under optimised conditions) showed good to excellent activities toward sterically hindered and electron-withdrawing group (EWG)-substituted alkenes that do not react using the first-generation complexes. A strong temperature effect was noted on all of the reactions tested. Interestingly, attempts to force a reaction by increasing the catalyst loading were much less effective. Therefore, when possible, it is suggested that metathesis transformations should be carried out with a second-generation catalyst at 70 degrees C in toluene. However, different second-generation catalysts proved to be optimal for different applications and no single catalyst outperformed all others in all cases. Nevertheless, some empirical rules can be deduced from the model experiments, providing preliminary hints for the selection of the optimal catalysts.