Polymeric Supports in Homogeneous Catalysis

Homogeneous catalysis with a dendrimer supported catalyst was introduced by van Koten et al. in 1994 [68] and since then has rapidly expanded [5, 64—67]. The advantage of dendrimers over linear or irregular polymeric supports is their well- 

Generally these globular dendritic architectures offer several advantages over other kinds of organic polymers, such as the full exposure of the catalytic centers to the environment. In contrast to linear or cross-Hnked polymeric supports, which can partially hide catalytic centers, the functional groups are located on the surface of the dendritic nanoparticle and diffusional Hmitations are less relevant Furthermore the close proximity of the catalytic centers on the surface of the dendritic polymer can enhance the catalytic activity by multiple complexation or even cooperativity. This behavior is described as positive dendritic effect. However, in some cases a negative dendritic effect was observed, which is caused by an undesired interaction or electron transfer between the neighboring catalytic centers on the surface of the dendrimer [70]. 

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