Catalysts from metal complexes with organic ligands

This review primarily focuses on the numerous reactions catalysed by water soluble transition metal complexes with emphasis on their implications for development of new environmentally benign processes in aqueous media based on the easy and quantitative separation of products from the catalyst as well as the avoidance of organic solvents. Moreover it contains, to our knowledge, the first comprehensive overview of water soluble ligands which play a key role for the development of efficient organometallic catalysis in aqueous media. 

The regeneration of deactivated immobilized catalysts is not as easy as with conventional supported metal catalysts, where combustion of the deposited material is frequently used. Because such a procedure would destroy the organic ligands, one must resort to washing procedures. However, when this method fails, attempts must be made to recover the metal and the ligand, and to prepare a fresh catalyst. In principle, it is possible to recover the metal complexes from physically and ionically immobilized catalysts. This can also be done from covalently bound catalysts by using an easily hydrolyzable linker. 

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