Heterogenized transition metal catalysts polystyrene

Aiming at easier workup conditions, immobilization of several transition metal catalysts, which show activity for the epoxidation of allylic alcohols, on polymer support has been investigated. For example, Suzuki and coworkers incorporated an oxo-vanadium ion into cross-linked polystyrene resins functionalized with iminodiacetic acid or diethylenetri-amine derivatives (Scheme 57), which afforded a heterogeneous catalyst that can promote... 

Syndiotactic polystyrene (SPS) can be readily polymerized using homogeneous or heterogeneous metallocene catalysts, based on group 4 metal compounds, especially titanium compounds like T1CI4, CpTiClj, and Cp Ti(OCH3)3 with methyl aluminoxane (MAO) as cocatalyst [1-3]. The recent developments of transition metal catalysts and reaction mechanisms are discussed in earlier chapters. This chapter will be focused on the quantitative aspects of SPS polymerization kinetics and related physical and chemical phenomena. 

There has been considerable recent research interest in the activation of carbon monoxide en route to more complex organic molecules. Among the various reactions that have been investigated and/or newly discovered, the transition metal catalyzed reduction of CO to hydrocarbons (Fischer-Tropsch synthesis) has enjoyed particular attention (l- ). Whereas most of the successful efforts in this area have been directed toward the development of heterogeneous catalysts, there are relatively few homogeneous systems. Among these, two are based on clusters (10,11) and others are stoichiometric in metal (12-17). In this report we detail the synthesis and catalytic chemistry of polystyrene ( ) supported... 

The alternative strategy for heterogenization has been pursued by Blechert and co-workers, for a polymer-supported olefin metathesis catalyst. A polymer-anchored carbene precursor was prepared by coupling an alkoxide to a cross-linked polystyrene Merrifield-type resin. Subsequently, the desired polymer-bound carbene complex was formed by thermolytically induced elimination of ferf-butanol while heating the precursor resin in the presence of the desired transition metal fragment (Scheme 8.30). 

The application of polymer-supported catalysts has now been extended to the synthesis of complexes between transition metal derivatives and structurally ordered macromolecular ligands to give catalytic systems exhibiting high activity and stereoselectivity. Polystyrene and polymethacrylate resin and polystyrene-divinylbenzene-polystyrene-polybutadiene block copolymers, as well as vinyl-functionalized polysiloxanes grafted onto silica, are very suitable polymers for heterogenization of mostly Pt and Rh complexes. Moreover, polyamides exhibit much higher thermal stability than conventional polystyrene supports (114). 

It is well known that atactic polystyrene (APS) is obtained with the catalyst such as radical initiater and IPS is obtained with Ziegler- Natta catalyst. SPS can be produced by a transition metal compound and MAO catalyst. As a transition metal, titanium(Ti) is excellent for the catalytic activity. We studied the stereospecific polymerization of styrene with homogeneous Ti and heterogeneous Ti compound and MAO catalyst. 

Almost all industrial catalysts are heterogeneous, with the reaction taking place on a solid surface. The polymeric catalysts are formed by chemically bonding a transition metal complex to an insoluble polymer they are then useful as heterogeneous catalysts. Cross-linked polystyrene-divinylbenzene gel, phosphonated polystyrene-divinylbenzene, ion-exchange resin, and silica are well-known insoluble polymers that have been used. Examples of polymer reactions are as follows [Eqs. (16-23)] ... 

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