Polymer-supported ligand-metal

N. E. Leadbeater, M. Marco, Preparation of polymer-supported ligands and metal complexes for use in catalysis, Ghent. Rev. 102 (2002) 3217. 

Figure 1. Preparation of polymer-supported transition metal complexes by ligand exchange.

Few other asymmetrie reactions have been performed using insoluble or soluble polymer-supported ligands. The first example is a Mukaiyama-aldol condensation between silyl ketene acetal and different aldehydes using polymeric Box analog of 99 as chiral ligands and Cu(OTf)2 as metal soiu ce in water (Scheme 147) [216]. When using benzaldehyde as substrate, yields were very low (12-34%) and ee were moderate (40-62%) whatever the polymer-supported Box. The same level of enantioseleetivity was observed with other aldehydes while the yield was better with all the ligand/Cu complexes used. 

Flow Reaction with an Immobilized Catalyst Metal Catalysts Coordinated by a Polymer-Supported Ligand... 

IV. 10. N.E. Leadbeater, M. Marco - Preparation of Polymer-Supported Ligands and Metal Complexes for Use in Catalysis, Chem. Rev. 102,3217,2002. 

Polyquiaolines have been used as polymer supports for transition-metal cataly2ed reactions. The coordinatkig abiUty of polyqukioline ligands for specific transition metals has allowed thek use as catalysts ki hydroformylation reactions (99) and for the electrochemical oxidation of primary alcohols (100). 

Electropolymerization is also an attractive method for the preparation of modified electrodes. In this case it is necessary that the forming film is conductive or permeable for supporting electrolyte and substrates. Film formation of nonelectroactive polymers can proceed until diffusion of electroactive species to the electrode surface becomes negligible. Thus, a variety of nonconducting thin films have been obtained by electrochemical oxidation of aromatic phenols and amines Some of these polymers have ligand properties and can be made electroactive by subsequent inincorporation of transition metal ions... 

Another metal-catalyzed microwave-assisted transformation performed on a polymer support involves the asymmetric allylic malonate alkylation reaction shown in Scheme 12.4. The rapid molybdenum(0)-catalyzed process involving thermostable chiral ligands proceeded with 99% ee on a solid support. When TentaGel was used as as support, however, the yields after cleavage were low (8-34%) compared with the corresponding solution phase microwave-assisted process (monomode cavity) which generally proceeded in high yields (>85%) [30],... 

In this context, it was shown that polymer-supported triphenylphosphine as a ligand for metal-based oxidation is an alternative catalytic system [72]. 

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