Immobilized Metal Complexes as Catalysts

Transition metal complexes can be immobilized on organic polymers such as polystyrene-divinylbenzene, polypropylene, poly (vinyl chloride), etc., as well as on the surface of inorganic oxides such as silica, y-Al203, glass, and molecular sieves (cf. Section 3.1.1.3). The metal complexes are attached to the supports via phosphine (-PR2), amine (-NR2) or other groups (-SH, -CN) linked to organic or inorganic support, e. g. Structures 1 and 2, where M = Pt, Rh, Pd, Ru, or Ni. 

Early studies of the supported metal complexes utilized as hydrosilylation catalysts focused on the immobilization of H2PtCl6 on ion exchangers. Chloroplatinic acid and other Pt complexes have been used as efficient precursors of the catalysts anchored to silica or organic materials for the hydrosilylation of 1-alkenes, styrene, allyl derivatives, and acetylene [2, 84-87]. 

The sol-gel method was applied for the preparation of heterogenized complexes such as Structure 3 based on the polycondensation of suitable trialkoxy-silyl-substituted organosulphides, organophosphines, and organoamines bound as ligands to a given complex (Pt, Rh, Ir, Ru). They were employed in the hydrosilylation of allyl chloride and other olefins [88]. 

CH2CH2CH2—Sie CH2CH2CH2—Si CH2CH2CH2—Si CH2CH2CH2—Si CH2CH2CH2—Si CH2CH2CH2—Si Q— 

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Figure 15-3. Overview of immobilized metal complexes as catalysts.

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