sites for CO. This suggests that a trace amount of a cocatalytic metal leads to a
significant improvement in catalytic performance [143].
Yamamoto et al. successfully prepared an atom-specified bimetallic Rh 32 Fe 28
cluster using a fourth-generation phenylazomethine dendrimer derivative (DPAG4)
[144]. The DPA enables the number and composition of different metals to be
defined at the atomic level thorough layer-by-layer stepwise complexation of
imine sites with metal ions (Fig. 41). The Rh 32 Fe 28 cluster showed synergistic
catalysis toward the hydrogenation of olefins and nitroarenes and demonstrated
enhanced activity that surpassed that of a single Rh catalyst [145] and Wilkinson
catalysts.
Multimetallic hybrid clusters with three elements were also prepared using a
DPAG4-TPM template. Heterometal assemblies of AuCl 3 , PtCl 4 , and CuCl 2 in an
Fig. 39 (a) Procedure for the synthesis of the AuCu and AgCu alloys within a click dendrimer. (b)
Catalytic activity of the alloys and Cu NPs in the catalytic AAC reaction. Adapted with permission
from [140]. Copyright 2017 The Royal Society of Chemistry
162
M. Tanabe and K. Yamamoto