chapter 2 palladium catalysts in suzuki cross- coupling reaction

• Complexes immobilized in zeolite super cages may have almost the same
activity as the free complexes in solution.
• The zeolite microstructure (micro-reactor) could help to overcome the
problems of metal leaching.
• Zeolites are capable of stabilizing intermediate active species retained in
their cavities and may show the product shape-selectivity.
• They should regenerate the catalyst after deactivation.
In the literature, [Pd]-loaded NaY zeolites were used for C-C coupling reactions
for the first time by Djakovitch and Koehler (Figure 3.15) (Djakovitch and Koehler
1999). They reported that the catalysts exhibited a high activity and selectivity toward
the Heck reaction of aryl bromides with olefins in low palladium concentrations (0.1
mol% of Pd). In another study, the Heck reactions were performed for industrially more
interesting chloroactophenone with styrene at 100 ºC (Djakovitch et al. 1999). The
authors observed that the catalysts could be separated from the reaction mixture.
However it could not be reused with same activity. The catalyst used in a first run at
100 ºC was regenerated by increasing temperature to 140 ºC under reaction conditions
(Djakovitch and Koehler 2001).
R
Br
+ [Pd] zeo
R = H, F, NO 2, CH 3CO
R
trans and cis-isomers
+
Figure 3.15. The Heck reactions of aryl bromides with olefins
(Source: Djakovitch and Koehler 1999)
The leaching test was also performed and it was found that only small amount of
palladium was leached, depending on temperature of the reaction and the nature of the
Pd species immobilized in the zeolite cage. For the [Pd(NH3)4] 2+ -NaY which we also
R
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