Abstract
Soluble polysiloxanes of various architectures (linear, star-shaped and hyperbranched), having vinyl, 2-butylthioethyl and 2-diphenylphosphinoethyl side groups have been used as supports for palladium(II) catalysts. Catalytic activity of such immobilized palladium complexes was tested in model Mizoroki–Heck reactions. The activity of the complexes in terms of yield and turnover number was comparable to that of PdCl 2(PhCN) 2. Polysiloxane-supported catalysts show good stability and can be reused several times. Catalysts immobilized on linear polymers show generally better stability than those immobilized on branched structures. Mercury poisoning test indicated that the true catalytic species is the supported complex. According to XPS analysis, palladium in the complexes with polysiloxanes is present as Pd(II). XRF shows however a significant metal leaching after 5–10 reaction cycles.
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