Solid supported catalysis, atom

A third technique that has been used to study colloidal nanocatalysis is the Colhnan test or the 3-Phase Test [16]. One reactant is chemically bound to a solid support (Phase 1) and the catalyst is chemically bound to a second solid support (Phase 2). Phases 1 and 2 are suspended in solution (Phase 3), into which a second reactant is also dissolved (not substrate bound). Direct contact between Phase 1 and Phase 2 is restricted due to the fact they are both substrate bound. If the heterogeneous catalyst in Phase 2 is required for the reaction to proceed there will not be any product formation. If the heterogeneous catalyst (Phase 2) leaches homogeneous complexes into solution (Phase 3), the reaction will proceed and in this way the nature of the active catalyst can be investigated. However, there are limitations to this experimental setup since the formation of products does not rule out heterogeneous catalysis. The formation of secondary particles from leached species is possible, so at best, this test supplies evidence for atomic leaching. 

This reaction has been extended to the Michael Addition on a,)0-unsaturated nitrile by temporarily chelating the Grignard reagent to y-hydroxy unsaturated nitrile. An alternative route involving a free-radical )0-alkylation of nonactivated carbon atoms and subsequent anionic cyclization has been developed as a complementary route of the Robinson annulation. In addition, this reaction has been modified to occur under antibody catalysis" or with the combination of a lithium enolate with aluminum tris(2,6-diphenylphenoxide). Further modifications include the Robinson annulation in supercritical C02, the reaction promoted by K2CO3 under ultrasound,and the solid-supported reaction under microwave irradiation. ... 

In contrast to supported homogeneous catalysis, surface organometallic chemistry (SOMC) uses an inorganic oxide (ExOy) as a solid ligand, on which the metal is directly attached by at least a bond with a surface atom, usually an oxygen, through a M-OE bond. 

Our view that in chemisorption and catalysis one has to look at the properties of the individual atoms at the surface rather than at parameters of the continuum (3) has received decisive support from recent advances in solid state physics. 

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