Dendrimer-encapsulated metal nanoparticles and their applications to catalysis

This account describes the synthesis, characterization, and applications to catalysis of dendrimer-encapsulated metal nanoparticles (DEMNs). These materials are synthesized by a template approach in which metal ions are sorbed into the interior of dendrimers and then subsequently chemically reduced to yield nearly size-monodisperse, zero-valent metal particles having dimensions of less than 4 nm. The dendrimer component of these composites serve not only as a template for preparing the nanoparticle replica, but they also stabilize the nanoparticle, make it possible to tune solubility, and enhance catalytic selectivity. These materials have been used for a broad range of catalytic reactions, including hydrogenations, Heck coupling, and Suzuki reactions, in water, organic solvents, biphasic fluorous/organic solvents, and supercritical CO 2 . In many cases it is very simple to recycle the dendrimer-encapsulated catalysts. In addition to monometallic DEMNs, bimetallic materials have also recently been prepared and their catalytic properties are reported.