9.4 Microscopic Catalytic Mechanism of Supported Palladium Clusters
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Fig. 9.6 Stability cluster covalently of Pd n bond to defected graphene. a The binding energy of
Pd n , n = 1–4 on different sized graphene defects. b The average atomization energy of free Pd n
clusters and Pd n on defected graphene
The Suzuki reaction follows a three-step pathway of oxidative addition, transmetalation, and reductive elimination [65, 67, 68]. Figure 9.7 shows the model Suzuki
reaction for different supported and free Pd clusters to gain a qualitative insight
into the origin of the variations in catalytic activity. For the oxidative addition step,
the Br-C bond of 4-bromobenzoic acid is cleaved by a Pd cluster/atom, indicating
that this step requires a charge donation from the catalyst and support (Fig. 9.7,
blue arrow). During the trans-metalation step, it was proposed that the charge flows
Fig. 9.7 Full reaction cycle of Pd catalyzed Suzuki reaction using Pd 4 . Charge flow from catalyst
to reagent is indicated by blue arrows, and charge flow from reagent to catalyst is indicated by red
arrows