Examples of Immobilized Catalyst Systems

Bliimel et al. [22-32] presented a strategy where previously successful homogeneous molecular catalysts are covalently bound to oxidic supports. Subsequent analysis and investigation was performed by conventional and suspension solid-state NMR spectroscopy. 

Silica was used as support material for the immobilization of phosphine ligands. As the surface of the silica is able to react with the phosphine ligands, an improved spacer/linker system had to be applied in order to shield the substituents and to prolong the lifetime of the catalyst. The spacer/linker system is therefore designed to prevent entirely the contact of the catalysts with the aggressive surface. Two new linker systems were tested to achieve this goal. 

A very elegant approach was developed by Hoveyda et al. [37], where NHC-based catalysts have been immobilized by sol-gel chemistry. The thus-obtained 

In 2011, Trapp etal. [38] presented a strategy for bonding 2-(pentafluorophenyl) imidazolidine to a polysiloxane and permanently coating this modified polymeric matrix on the inner surface of fused-silica capillaries (id 250 pm) to obtain thin films of defined thicknesses (50-1000 nm). 

The immobilized NHC preligands obtained by this strategy were then converted to free carbene ligands by flushing these capillaries with suitable reagents. 

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