Transition metal complexes, catalyst

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

Coordination-catalyzed ethylene oligomerization into n-a-olefins. The synthesis of homologous, even-numbered, linear a-olefins can also be performed by oligomerization of ethylene with the aid of homogeneous transition metal complex catalysts [26]. Such a soluble complex catalyst is formed by reaction of, say, a zero-valent nickel compound with a tertiary phosphine ligand. A typical Ni catalyst for the ethylene oligomerization is manufactured from cyclo-octadienyl nickel(O) and diphenylphosphinoacetic ester ... 

W02005/080456 Al, Lanxess Inc. Process for the preparation of low molecular weight hydrogenated nitrile rubber EP2028194 Al, Lanxess Deutschland GmbH Metathesis of nitrile rubbers in the presence of transition metal complex catalysts Press release Lanxess - New York Conference, New York City, USA, Monday August 28, 2006, Address by Dr. Ulrich Koemm LANXESS Concepts in Rubber ... 

Dimerization, oligomerization, and similar reactions of olefins have been reported to be catalyzed by systems involving the majority of the Group VIII metals (3). The reasons for the particular interest in nickel-containing catalysts are their exceptionally high catalytic activity (catalytic reactions have been performed at temperatures as low as - 100°C), the diversity of catalytic reactions of obvious synthetic value, as well as the possibility to direct the course and control the selectivity of a catalytic reaction by tailoring the catalyst which are perhaps without parallel among transition metal complex catalysts. 

Transition metal complexes, catalysts based on, 20 193 Transition-metal compounds cause of color, 7 326t, 328-331 Transition-metal coordination compounds, 7 582-584... 

It is very clear that the field of supported transition metal complex catalysts is a rapidly expanding field. Indeed, only their application to hydrogenation, hydrosilylation, and hydroformylation reactions have received more than a preliminary skirmish. Already a number of points are becoming clear. 

In conclusion it is fair to say that, although supported transition metal complex catalysts have only recently been investigated, a sufficient number of encouraging results have been obtained already to allow us to predict that they clearly have an important future. 

For reviews of chiral transition metal complex catalysts, see Brunner Top. Stereochem. 1988, 18. 129-247, Hayashi Kumada Acc. Chem. Res. 1982, 15, 395-401. 

Michalska ZM, Rogalski L, Rozga-Wijas K, Chojnowski J, Fortuniak W, Scibiorek M (2004) Synthesis and catalytic activity of the transition metal complex catalysts supported on the branched functionalized polysiloxanes grafted on sUica J Mol Catal A Chem, 208 187-194... 

A titanium complex with a pyrazolylborate ligand was studied by Campbell and Malanga [19]. Similarities between the cyclopentadienyl ligand and the hydridotris(pyrazolyl)borate ligand have been noted for transition metal complexes. Catalyst efficiencies are much lower than those of the analogous penta-methylcyclopentadienyl complexes. 

Compounds 1-4, 7-13, and 16 should be appropriate as monomeric precursors for modified PA-MPs, whereas the derivatives 17, 20, and 23 must be polymerized previously. The polymerization can be carried out either dehydrogenative (compounds 20 and 23) by the use of transition metal complex catalysts or by intermolecular hydrosilylation of Si-H to the -C=C- unit (compound 17) to yield crosslinked polymeric precursors for Si-alloyed PA-MPs. 

Pyrolysis of dihalocyclopropanes was studied along with the effects of electrophilic reagents, and confirms the foregoing results (33-37). In many cases, those authors observed that polymeric residues, in addition to ally lie and diene-type products, were present at the end of pyrolysis. The formation of these polymers confirms the hypothesis that the dihalocyclopropanes are monomers that can be polymerized either by cationic processes or by the action of transition-metal complex catalysts. 

Polymerization by Transition-Metal Complex Catalysts. Mlly M12, and M13 have been polymerized by Et3Al/TiCl4 catalysts between 50° and 80 °C in n-hexane, the reaction times ranging from a few hours to several days. The polymers obtained have the same structure as those obtained by cationic polymerization. By analogy with mechanisms proposed in the literature (38, 39), the structure shown in Equation 24 may be proposed for the active center. 

Cationic Polymerization. In the compounds of Equation 25, the pseudoconjugation between the phenyl and the cyclopropane is maximum when the two rings are perpendicular (40). Polymerization, cationic or by transition-metal complex catalysts, indicates the participation of the phenyl group. 

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