Catalysts homogeneous multi-component

The known catalyst systems for olefin metathesis can be grouped into heterogeneous catalysts, homogeneous multi-component catalysts, and homogeneous single-component catalysts. 

During this process, the layer thickness of three catalyst components on a titer-plate was simultaneously varied in such a way that 48 single catalyst mixtures were obtained in a one-step process. Thus, the amount of each catalyst component in the mixture could either be decreased or increased, resulting in a homogeneous multi-component layer. 

Table 3.14. Examples of multi-component catalysts for homogeneous-phase alkene metathesis.

This chapter is concerned with highlighting some of the more notable advances that have come to light as a result of identifying key factors that influence catalyst performance, particularly those related to precatalyst structure. The importance of the initiator and the role played in chain fransfer is probed. Current mechanistic understanding is examined from both a spectroscopic and a computational viewpoint while efforts to prepare well-defined iron or cobalt alkyl catalysts are discussed. Efforts to heterogenize these homogeneous catalysts are briefly reviewed, as is their use in multi-component catalysis. 

Due to their ready availability and excellent catalytic properties, this type of catalyst has been extensively used in cycloolelin polymerization for several decades, resulting in important industrial applications such as manufacture of hydrocarbon resins [3, 17, 18], They are used mainly in homogeneous systems with adequate solvents but also heterogeneous catalysts are very active and promote cycloolefin polymerization to different reaction products, depending on the operation conditions. Generally, they are unicomponent, binary, ternary and multi-component catalytic systems and their final composition is strongly dependent on the nature and quality of the solvent, the reaction conditions and the monomer type and structure [1],... 

On the other hand, hi- or multi-metallic supported systems have been attracting considerable interest in research into heterogeneous catalysis as a possible way to modulate the catalytic properties of the individual monometalUc counterparts [12, 13]. These catalysts usually show new catalytic properties that are ascribed to geometric and/or electronic effects between the metalUc components. Of special interest is the preparation of supported bimetallic catalysts using metal carbonyls as precursors, since the milder conditions used, when compared with conventional methods, can render catalysts with homogeneous bimetallic entities of a size and composition not usually achieved when conventional salts are employed as precursors. The use of these catalysts as models can lead to elucidation of the relationships between the structure and catalytic behavior of bimetalUc catalysts. 

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