Polymer-supported metal complex

While such a film format is not intended for routine use in e.g. soHd phase synthesis, it has proved useful for spectroscopic mechanistic investigation of polymer-supported metal complex catalysts [49] and we, with our collaborators, are employing such films as a component in nanosecond fluorescence sensing devices [50]. 

Sherrington, D. C. Polymer-supported metal complex alkene epoxidation catalysts. Catal. Toofay 2000, 57, 87-104. 

In the book, the section on homogeneous catalysis covers soft Pt(II) Lewis acid catalysts, methyltrioxorhenium, polyoxometallates, oxaziridinium salts, and N-hydroxyphthalimide. The section on heterogeneous catalysis describes supported silver and gold catalysts, as well as heterogenized Ti catalysts, and polymer-supported metal complexes. The section on phase-transfer catalysis describes several new approaches to the utilization of polyoxometallates. The section on biomimetic catalysis covers nonheme Fe catalysts and a theoretical description of the mechanism on porphyrins. 

TABLE XI Polymer Supported Metal Complexes as Catalysts for a Variety of Organic Reactions and Polymerizations... 

This monograph intends to acquaint the reader with the basic material available in the field of catalysis. Because this field was previously treated as a marginal area of polymer and catalytic chemistry, the authors mostly cite recent literature sources. It covers the catalytic properties of a broad class of functional polymers and their metal-ion complexes as well as ionite and heterogeneous (polymer-supported) metal-complex catalysis. 

Preparation of polymer-supported metal complex. An ethanol solution (20 mL) of palladium dichloride (0.42 mmol) was added to the polymer ligand (chloro-methylated polystyrene-bound porphyrin). The mixture was refluxed and stirred for 15 h. After cooling, the complex was filtered off, washed thoroughly with water and ethanol, and then dried in vacuo. 

Polymer-supported catalysts have been developed in order to better utilize their potential catalytic activity. With this purpose in mind, our laboratory has paid a great deal of attention to polymer-supported metal complexes, especially to those with 4f electrons, such as La, Nd, Pr, and Eu. Some polymer-supported catalysts with high catalytic activity have been developed (1-9). In this paper we will discuss in detail our recent results on polymer-supported catalysts for conjugated diene polymerization other work in this area will also be mentioned. 

Cyanomethylated polystyrene " and polyimide have also been investigated as Wacker catalyst carriers. A thorough review on polymer-supported metal complexes as oxidation catalyst is available. ... 

These siUca-supported catalysts demonstrate the close connections between catalysis in solutions and catalysis on surfaces, but they are not industrial catalysts. However, siUca is used as a support for chromium complexes, formed either from chromocene or chromium salts, that are industrial catalysts for polymerization of a-olefins (64,65). Supported chromium complex catalysts are used on an enormous scale in the manufacture of linear polyethylene in the Unipol and Phillips processes (see Olefin polymers). The exact stmctures of the surface species are still not known, but it is evident that there is a close analogy linking soluble and supported metal complex catalysts for olefin polymerization. 

Polymers play important roles in water photolysis. For multi-electron processes, polymer supported metal colloids or colloidal polynuclear metal complexes are very useful as catalysts. Unstable semiconductors with a small bandgap which photolyse... 

Polymers are attracting much attention as functional materials to construct photochemical solar energy conversion systems. Polymers and molecular assemblies are of great value for a conversion system to realize the necessary one-directional electron flow. Colloids of polymer supported metal and polynuclear metal complex are especially effective as catalysts for water photolysis. Fixation and reduction of N2 or C02 are also attractive in solar energy utilization, although they were not described in this article. If the reduction products such as alcohols, hydrocarbons, and ammonia are to be used as fuels, water should be the electron source for the economical reduction. This is why water photolysis has to be studied first. 

The functionalization of a polymer can be effected by numerous synthetic procedures and can be achieved chemically or by grafting onto a polymeric material that can, by itself, be used to support metal complexes. Often, the grafting occurs via radiation. 

In conclusion, we have shown that attachment of transition metal complexes to polymer supported triphenylphosphine leads to air stable, versatile immobilised catalysts that are as active as their homogeneous analogues and have the advantage that they can be re-used numerous times. Work is currently underway to exploit the activity of other polymer-supported organometallic complexes in metal-mediated organic synthesis. 

Aluminum chloride and its derivatives are the most familiar Lewis acids and are routinely employed in many Lewis acid-promoted synthetic transformations. The first polymer-supported metal Lewis acids to be studied were polymers attached by weak chemical or physical interactions to a Lewis acid. In the 1970s Neckers and coworkers reported the use of styrene-divinylbenzene copolymer-supported AlCl,- or BF3 as catalyst in condensations, esterifications, and acetalization of alcohols [11,12]. This type of polymer-supported AICI3 (1) is readily prepared by impregnation of a polystyrene resin with AICI3 in a suitable solvent. Subsequent removal of the solvent leaves a tightly bound complex of the resin and AICI3. The hydrophobic nature of polystyrene protects the moisture-sensitive Lewis acid from hydrolysis, and in this form the Lewis acid is considerably less sensitive to deactivation by hydrolysis. This polymer complex could be used as a mild Lewis acid catalyst for condensation of relatively acid-sensitive dicyclopropylcarbinol to an ether (Eq. 1) [13],... 

The use of polymer-supported metal catalysts for the hydrogenation of thiophe-nie substrates has recently been extended to Ru and Rh complexes anchored to silica via hydrogen bonding [23, 24]. 

With respect to the widely investigated metalloporphyrins for catalytic epoxidation, progress was made in the area of polymer-supported ruthenium porphyrins for asymmetric epoxidation. Manganese-porphyrin complexes attached via peptide linkers to organic polymers showed enhanced selectivity and catalyst stability due to donor atoms in the linker that could coordinate to the metal center. This shows that improvement can be achieved not only by optimization of the polymer or metal complex but also by appropriate choice of the linker. Furthermore, electropolymerization by anodic oxidation of suitable manganese-porphyrin complexes proved to be a promising technique for the preparation of efficient immobilized epoxidation catalysts. 

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