Catalysts 7-block organometallics

Fouling occurs by decomposition of organometallic compounds of the oil and deposition of the generated metals in the porous structure of the catalyst, blocking the active sites and plugging the pores. Long-term accumulation of these metals in the catalyst pores can result in permanent deactivation of the catalyst. 

Over the past 25 years, much effort has been put into investigating the use of r/-block organometallic clusters as homogeneous catalysts, and equations 26.23-26.25 give examples of small-scale catalytic reactions. Note that in reaction 26.23, insertion of CO is into the O—H bond in the Monsanto process using [Rh(CO)2l2] catalyst, CO insertion is into the C—OH bond (equation 26.12). 

The majority of ohgomerization-active catalysts involves organometallic species, most often metal-aUcyl complexes, which are considered to be prone to hydrolysis. Moreover, the coordination sites of the complexes can be blocked by the solvent. Nonprotic weakly coordinating solvents should therefore be preferred. In regard to these requirements, ILs provide good alternative solvents. 

Another application of hyperbranched polymers as supports for catalysts is their use as backbones for the covalent attachment of organometallic fragments. NCN-pincer complexes (NCN-pincer = 2,6-bis[(dimethylamino)-methyl] phenyl anion) are attractive building blocks for catalytic reactions [20,21], Covalent introduction of the transition-metal complexes can also be of interest for visualization and imaging of dendritic polymers by transmission electron microscopy (TEM). 

---