Metallization, complex polymers

A chiral diphosphine ligand was bound to silica via carbamate links and was used for enantioselective hydrogenation.178 The activity of the neutral catalyst decreased when the loading was increased. It clearly indicates the formation of catalytically inactive chlorine-bridged dimers. At the same time, the cationic diphosphine-Rh catalysts had no tendency to interact with each other (site isolation).179 New cross-linked chiral transition-metal-complexing polymers were used for the chemo- and enantioselective epoxidation of olefins.180... 

Modification of electrode surfaces by macrocyclic transition metal complexes, polymers, upd layers, etc. has provided considerable enhancement of activity and selectivity of electrode reactions, but still the poor stability of many modified electrodes is a serious limitation and extensive research is being carried out at the present time. 

In this chapter we will review the recent advances of supramolecular photon chirogenesis in various confined media, excluding micelles, chiral solvents, liquid crystals, metal complexes, polymer matrices, clays, and crystals. Micelles are typical supramolecular assembly with an internal hydrophobic core which shows a unique boundary effect, e.g., enhanced radical recombination of geminate radi-cal pairs produced by ketone photolysis [26], but essentially no asymmetric photon-... 

Using Co as the metal centre, 1-vinyl imidazole as the functional monomer and amino acids as the templates, Leonhardt and Mosbach prepared imprinted metal-complexing polymers [14]. These polymers were aimed at being used as enzyme-like substrate specific catalysts (for more details, see Section 6.5.3.). 

Leonhardt and Mosbach prepared metal-complexing imprinted polymers by polymerising Co " complexes of N-vinyl imidazole and A-protected amino acids [14]. After work-up of the polymer and removal of the amino acid templates, the catalytic activities of the resulting imprinted metal-complexing polymers were evaluated by following the hydrolysis of the p-nitrophenyl esters of various amino acids. Assessment of the rate of hydrolysis revealed a clear preference for the substrates used as the templates. The polymers could be used several times without any deterioration of the catalytic activities and true turnover was observed. 

Fig. 6.7. Molecularly imprinted metal-complexing polymer as a glucose sensor.

Dhal PK, Arnold FH (1991) Template-mediated synthesis of metal-complexing polymers for molecular recognition. J Am Chem Soc 113 7417... 

Whereas phosphine-functionalized polymer supports are generally prone to oxidation, especially after attachment of a metal complex, polymers containing phosphite ligands are oxidatively stable. A disadvantage of the latter supports, however, is their greater susceptibility to hydrolysis. 

K. E. Geckeler, Metal Complexation Polymers, in Advanced Functional Molecules and Polymers (H.S. Nalwa, Ed.), Vol. 4, Physical Properties and Applications, Chap. 9, Gordon and Breach Science Publ., Tokyo, Japan, 2001, pp. 323-347. 

Kamai, G., and Kukhtin, V.A., Polymerization of some unsaturated esters of phosphonocarboxyhc acids, Zh. Obshch. Khim., 24, 1855, 1954 J. Gen. Chem. USSR (Engl. Transl.), 24, 1819, 1954. Kennedy, J., Lane, E.S., and Robinson, B.K., Synthesis of metal-complexing polymers. Part 1. Phosphorylated polymers, J. Appl. Chem., 8, 459, 1958 Chem. Abstr., 53. 3032h, 1959. 

Elliott, C. M., Baldy, C. J., Nuwaysir, L. M., and Wilkins, C. L., "Electrochemical Pol3mieiization of 4-Methyl-4 -vinyl-2,2 -bipyridine-Containing Metal Complexes Polymer Structure and Mechanism of Formation," Inorg. Chem., 29, 389-392, 1990. 

M. Kancko and E. Tsuchida, Formation, characterization, and catalytic activities of polymer-metal complexes, / Polym. Sci. Macromol. Revs. 16, 397 (1981). 

Type II polymers with pendant metal complexes Polymers containing bipyridyl and terpyridyl metal-binding sites... 

Several chelating or metal-complexing polymers were reported in Volume 1 of the series (p. 362). There is still considerable activity in this area and polystyrene remains one of the most widely-used supports. Selective chelate-forming ion-exchange resins were prepared from polystyrene by nitration followed by reduction, diazotization then coupling with aromatic amines and derivatives of phenol. Poly(styryl-l,8-naphthyridine) (7) also functions as a chelating agent with Cu ,... 

---