Catalysts macromolecular, water soluble

The modified polyethylenimines described so far are only a few of many possibilities. It is obvious that this polymer provides a remarkably versatile macromolecular matrix for the attachment of a wide variety of different types of functional groups. Furthermore, the polymer framework makes it possible to juxtapose a binding site, a catalytic group, and an apolar-aqueous interface in a locally compact array. Thus a wide range of local environments can be created on this macromolecular water-soluble catalyst. We hope to be able to exploit these to obtain a series of synthetic macromolecules with tailor-made catalytic properties. 

Water-soluble hydrogenation catalysts with macromolecular ligands... 

Unmodified poly(ethyleneimine) and poly(vinylpyrrolidinone) have also been used as polymeric ligands for complex formation with Rh(in), Pd(II), Ni(II), Pt(II) etc. aqueous solutions of these complexes catalyzed the hydrogenation of olefins, carbonyls, nitriles, aromatics etc. [94]. The products were separated by ultrafiltration while the water-soluble macromolecular catalysts were retained in the hydrogenation reactor. However, it is very likely, that during the preactivation with H2, nanosize metal particles were formed and the polymer-stabilized metal colloids [64,96] acted as catalysts in the hydrogenation of unsaturated substrates. 

Higher (and supramolecular) ligands based on sugar, porphyrin, dendrimers, cyclodextrins, calix[4]arenes, etc., have also been tested for water-soluble conversions, the hydroformylation of water-insoluble olefins included [219]. In some cases the water-soluble, macromolecular cpds. act as inverse phase-transfer catalysts, e. g., when crown ethers are involved [269]. 

Enzymes are normally used as water-soluble homogeneous catalysts or immobilized onto water-insoluble solid supports. The many advantages of immobilized systems have been outlined in this chapter. Yet insoluble immobilized enzyme preparations can also have serious drawbacks. First, efficiency with macromolecular or insoluble... 

Water-soluble macromolecular metal complexes based on terminally functionalized ethylene oxides and ethylene oxide-propylene oxide block copolymers have been used as catalysts for hydroformylation, hydrogenation, Wacker oxidation of imsaturated compounds, hydroxylation of aromatic compounds, oxidation of saturated and alkylaromatic hydrocarbons, metathesis, Heck reaction, and some asymmetric reactions. 

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