Future immobilized systems

This review will consist of three parts (i) rationale and need for immobilizing palladium on a solid support, (ii) comparison of various palladium immobilization systems and (iii) applications of these solid-bound palladium catalysts in organic chemistry. Some personal speculations about the future of this burgeoning field will also be included for the sole purpose of eliciting further interest and discussion. The term solid support will be... 

Immobilization of GpdQ on modified magnetite nanoparticles and of biomimetics attached to resins will be presented. Comprehensive characterization of activity and properties of the immobilized systems will be conducted as a starting point for future applications of these systems in bioremediation (Chap. 8). 

The wide variety of enzymes available gives for promise enzymatic derivatization to become a potent analytical tool in the future. Better understanding and theoretical formulations will lead to commercial availability of immobilized enzymes and consequently to more ready use of them. Since in such systems a low content of organic cosolvent in the mobile phase can only be tolerated (whereas a compromise has to be made as far as the optimum mobile phase pH is concerned), artificial enzymes, which are synthetic polymer chains having functional groups that mimic the biocatalytic activity of natural enzymes, are currently being synthesized and investigated as a means to overcome such limitations (276). 

In this chapter, we will present some contemporary results from our laboratory aimed toward blending the desirable properties of homogeneous and heterogeneous catalysts to create highly active, selective, and recoverable immobilized catalysts. The chapter covers organometaUic catalytic systems for polymerization reactions as well as small molecule reactions. Formation of single-site catalysts, recyclability, and stability/leaching issues will be addressed, as will studies on the effects of the immobilization procedure and the nature of the support structure on catalytic performance. Finally, a brief discussion on projected future directions for immobilized catalysts is presented. 

Future development work is needed to prove the possibilities of new concepts that have been created during recent years. The investigation of systems which work homogeneously but which can be separated easily [22] must be mentioned in this context (cf Section 3.1.1.1). The introduction of multidentate ligands and the evaluation of polymer systems containing more than one metal complex site, which cooperate eventually in the catalysis of parallel or sequential reactions [23-25], are among these concepts. In addition, the formation of new or normally unstable catalytic species [26, 27] attached to polymer supports, or the formation of immobilized metal complexes as intermediates of defined metal clusters [28], should be studied further (cf. Section 3.1.1.5). 

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