Heterogeneous Metal Complex Catalysis

In the sixties of past century, a few patents issued to Bergbau Chemie [5,48,49] and to Mobil Oil [50-52], respectively described the use of CFPs as supports for catalytically active metal nanoclusters and as carriers for heterogenized metal complexes of catalytic relevance. For the latter catalysts the term hybrid phase catalysts later came into use [53,54], At that time coordination chemistry and organo-transition metal chemistry were in full development. Homogeneous transition metal catalysis was expected to grow in industrial relevance [54], but catalyst separation was generally a major problem for continuous processing. That is why the concept of hybrid catalysis became very popular in a short time [55]. 

Before any catalysis can occur, at least one of the substrates must coordinate to the catalyst. This means that the catalyst must have a vacant active site. In homogeneous metal complex catalysis and biocatalysis, this will be a vacant coordination site at the metal atom. In heterogeneous catalysis, the vacant site could be a metal crystallite or an ion on the surface. For the latter, we speak of desorption and adsorption instead of dissociation and coordination. Remember that our reactions are not in vacuum, so there is no vacant site . Thus, before any chemical species can coordinate to the metal complex (or to the active site in heterogeneous catalysis or biocatalysis) the species already occupying this space must first vacate it. This happens constantly, as the system is dynamic (Figure 3.3) [15]. At any given moment... 

Abstract Recent progresses in molecularly imprinted metal-complex catalysts are highlighted in this chapter. Molecular imprinting is a technique to produce a cavity with a similar shape to a particular molecule (template), and the molecularly imprinted cavity acts as shape-selective reaction space for the particular reactant. The application of the molecular-imprinting technique to heterogeneous metal-complex catalysts is focused in the viewpoint of a novel approach in the design of shape-selective catalysis mimicking enzymatic catalysis. 

Key words inorganic ion exchanger, titaniiun tungstate, metal complex catalysis, anchored ion exchangers, heterogenized homogeneous catalysis. 

The internal coordination sphere of Ni(II), Co(II), Rh(III), Pd(II), Pt(II,IV) and Ir(III, IV) complexes is maintained during ion exchange. However, Ru, Os, and Pd(IV) complexes break down thereby causing heterogenized metal complexes (HMC) based on them to lose their catalytic activity. Catalysis in the presence of HMC proceeds directly on ionic group sites. 

This monograph intends to acquaint the reader with the basic material available in the field of catalysis. Because this field was previously treated as a marginal area of polymer and catalytic chemistry, the authors mostly cite recent literature sources. It covers the catalytic properties of a broad class of functional polymers and their metal-ion complexes as well as ionite and heterogeneous (polymer-supported) metal-complex catalysis. 

In comparison with traditional biphasic catalysis using water, fluorous phases, or polar organic solvents, transition metal catalysis in ionic liquids represents a new and advanced way to combine the specific advantages of homogeneous and heterogeneous catalysis. In many applications, the use of a defined transition metal complex immobilized on a ionic liquid support has already shown its unique potential. Many more successful examples - mainly in fine chemical synthesis - can be expected in the future as our loiowledge of ionic liquids and their interactions with transition metal complexes increases. 

The past fifteen years have seen evidence of great interest in homogeneous catalysis, particularly by transition metal complexes in solution predictions were made that many heterogeneous processes would be replaced by more efficient homogeneous ones. There are two motives in these changes—first, intellectual curiosity and the belief that we can define the active center with... 

This chapter focuses exclusively on microwave heterogeneous catalysis. Microwave homogeneous catalysis by transition metal complexes is treated in Chapt. 11, phase transfer catalysis in Chapt. 5, catalytic reactions on graphite in Chapt. 7, photocataly-tic reactions in Chapt. 14, and catalytic synthesis oflabeled compounds in Chapt. 13. 

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