Dendrimers are well-defined hyperbranched macromolecules with characteristic globular structures for the larger systems. These novel polymers have inspired many chemists to develop new materials and several applications have been explored, catalysis being one of them. The recent impressive strides in synthetic procedures increased the accessibility of functionalized dendrimers, resulting in a rapid development of dendrimer chemistry. The position of the catalytic site(s) as well as the spatial separation of the catalysts appears to be of crucial importance. Dendrimers that are functionalized with transition metals in the core potentially can mimic the properties of enzymes, their efficient natural counterparts, whereas the surface-functionalized systems have been proposed to fill the gap between homogeneous and heterogeneous catalysis. This might yield superior catalysts with novel properties, that is, special reactivity or stability. Both the core and periphery strategies lead to catalysts that are sufficiently larger than most substrates and products, thus separation by modern membrane separation techniques can be applied. These novel homogeneous catalysts can be used in continuous membrane reactors, which will have major advantages particularly for reactions that benefit from low substrate concentrations or suffer from side reactions of the product. Here we review the recent progress and breakthroughs made with these promising novel transition metal functionalized dendrimers that are used as catalysts, and we will discuss the architectural concepts that have been applied.

Dendrimers are well‐defined hyperbranched macromolecules with characteristic globular structures for the larger systems. These novel polymers have inspired many chemists to develop new materials and several applications have been explored, catalysis being one of them. The recent impressive strides in synthetic procedures increased the accessibility of functionalized dendrimers, resulting in a rapid development of dendrimer chemistry. The position of the catalytic site(s) as well as the spatial separation of the catalysts appears to be of crucial importance. Dendrimers that are functionalized with transition metals in the core potentially can mimic the properties of enzymes, their efficient natural counterparts, whereas the surface‐functionalized systems have been proposed to fill the gap between homogeneous and heterogeneous catalysis. This might yield superior catalysts with novel properties, that is, special reactivity or stability. Both the core and periphery strategies lead to catalysts that are sufficiently larger than most substrates and products, thus separation by modern membrane separation techniques can be applied. These novel homogeneous catalysts can be used in continuous membrane reactors, which will have major advantages particularly for reactions that benefit from low substrate concentrations or suffer from side reactions of the product. Here we review the recent progress and breakthroughs made with these promising novel transition metal functionalized dendrimers that are used as catalysts, and we will discuss the architectural concepts that have been applied.

The synthesis of a series of diphosphine ligands having phosphorus donor atoms in the core of a carbosilane dendrimer and their use in palladium catalysed allylic alkylation is described.

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Dendrimere sind wohldefinierte hochverzweigte Makromoleküle, die bei hinreichender Größe charakteristische globuläre Strukturen aufweisen. Sie haben viele Chemiker zur Entwicklung von neuen Materialien angeregt, und eine Reihe von Anwendungen, auch in der Katalyse, wurde bereits untersucht. Die jüngsten Fortschritte bei den Syntheseverfahren haben den Zugang zu funktionalisierten Dendrimeren sehr vereinfacht, was zu einer raschen Entwicklung der Dendrimerchemie geführt hat. Sowohl die Lage der katalytischen Zentren als auch die räumliche Trennung der Katalysatoren scheinen hier wesentlich zu sein. Dendrimere, die im Kern mit Übergangsmetallen funktionalisiert sind, sind potentielle Enzymmimetika; die an der Oberfläche funktionalisierten hingegen könnten die Lücke zwischen homogener und heterogener Katalyse füllen. Dies könnte vorzügliche Katalysatoren mit neuartigen Eigenschaften – besonderer Reaktivität oder Stabilität – liefern. Sowohl die kern‐ als auch die peripherieorientierte Strategie ergeben Katalysatoren, die die meisten Substrate und Produkte an Größe deutlich übertreffen, sodass eine Abtrennung durch moderne Membrantrenntechniken möglich ist. Diese neuen homogenen Katalysatoren lassen sich in kontinuierlich betriebenen Membranreaktoren verwenden, was vor allem bei solchen Reaktionen sehr vorteilhaft wäre, die von niedrigen Substratkonzentrationen profitieren oder durch Nebenreaktionen des Produkts beeinträchtigt werden. Wir geben hier einen Überblick über die jüngsten Fortschritte auf dem Gebiet der Übergangsmetall‐funktionalisierten Dendrimere, die als Katalysatoren eingesetzt werden; auch die unterschiedlichen Konzepte für ihre Architektur werden besprochen.