Organometallic catalysts, supported

Recently some information became available on a new type of highly active one-component ethylene polymerization catalyst. This catalyst is prepared by supporting organometallic compounds of transition metals containing different types of organic ligands [e.g. benzyl compounds of titanium and zirconium 9a, 132), 7r-allyl compounds of various transition metals 8, 9a, 133), 7r-arene 134, 185) and 71-cyclopentadienyl 9, 136) complexes of chromium]. 

Mesoporous Silica Supported Organometallic Catalysts by Grafting... 

Exploiting Surface Chemistry to Prepare Metal-Supported Catalysts by Organometallic Chemical Vapor Deposition... 

This reaction was one of the first examples of catalysis by a supported organometallic compound. In 1964 it was observed that Mo (CO) 6/ A1203, after activation by heating in vacuo at 120°C, catalyzed the conversion of propylene into ethylene and 2-butene (82). The nature of the active site in this catalyst system is still not fully defined (83). Since the initial discovery many heterogeneous and homogeneous catalyst systems have been reported (84, 85), the latter being more amenable to kinetic and mechanistic studies. 

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. 

C. Coperet, and J.-M. Basset, Strategies to Immobilize Well-Defined Olefin Metathesis Catalysts Supported Homogeneous Catalysis vs. Surface Organometallic Chemistry, Adv. Synth. Catal. 349, 78-92 (2007). 

The catalytic activity of zeolites in alkane to olefin reactions, photochemical conversion reactions, Fischer-Tropsch hydrogenation, isocyana-tion, carbonylation, and related chemistry make up the last theme. An important focus of this is to explore the utility of zeolites as selective heterogeneous catalysts for reactions that involve Group VIII metals. The mechanistic nature of some of this chemistry is presented, along with the characterization of supported organometallic transition metal complexes. 

Warzelhan and Burger proposed to remove the cocatalyst before the introduction of C02 to avoid the possible influence of the cocatalyst on polymer radioactivity. However, two conditions have to be fulfilled to obtain correct data on Cp i) the life-time of an active metal-polymer bond has to be sufficiently long ii) the polymer must not contain Al—C bonds able to interact with a quenching agent. The possibility to use CO and CO2 for the quantitative determination of Cp was illustrated in the case of one-component catalysts (titanium dichloride supported organometallic catalysts when Cp values were independently determined by the use of other inhibitors including radioactive alcohol. 

Due to the good solubility of organometallic compounds, ionic liquids have been used as reaction media, replacing traditional molecular solvents, or as the catalyst-supporting phase in a biphasic system. Influences of the ionic liquid on the reaction rate and selectivity can mostly be explained by the reactivity of the anion, which can be noncoordinating or coordinating as well as Lewis-acidic, Lewis-basic or neutral. The cation, in contrast, is considered to be essentially noncoordinating and innocent. 

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