Metallo-dendrimers

Moss and Liao [182,183] reported a metallo-dendrimer built by a convergent strategy. An approach similar to that of Frechet was used to synthesize a fourth generation dendrimer containing 48 peripheral ruthenium atoms. 

CATALYSIS WITH (METALLO)DENDRIMERS CONTAINING CHIRAL LIGANDS... 

An interesting novel approach to the synthesis of (metallo)dendrimer catalysts could be the use of random hyperbranched polymers [38]. Obviously, these hyperbranched polymers have comparable but less defined structures, but to arrive at dendrimers with similar sizes, a larger number of preparative steps are required, which may be an economic disadvantage. Furthermore, materials involving heterogeneous supports with well-defined metallodendritic subunits [15] can be a promising future direction giving rise to new types of supramolecu-lar catalysts that can easily be recovered from production streams. 

The first account on the carbonylation of heterocyclic compounds with metallo-dendrimers was recently reported by Lu and Alper using Rh-complexed dendrimers on a resin [207]. The building-block techniques of solid-phase chemistry were used to synthesize dendrimers, followed by phosphonation of the dendrimers with diphenylphosphinomethanol. The resulting phosphonated dendrimers were then reacted with chloro(dicarbonyl)rhodium(I) dimer to give dendritic catalysts A and B (31P NMR, 8 - 25 ppm loading of rhodium A, 0.74 mmol g-1 B, 0.83 mmol g ). As a model study, the reaction of l-ferf-butyl-2-phenylaziridine with carbon monoxide in catalytic presence of A afforded the desired [3-lactam... 

Metallo-Dendrimers, Functionalised Nanoparticles and Surface Effects. 153... 

Scheme 2 Schematic synthetic pathway and structure of the carbosilane-based metallo-dendrimers Gq-1 and Grl...

Recently, different strategies have been studied to prepare enantiopure metallo-dendrimers. Constable [76] proposed a divergent strategy starting from a chiral... 

Togni et al.169 synthesized dendrimers using a cyclophosphazene core and 16 peripheral chiral ferrocenyl ligands (Figure 10.13). The periphery of these ferrocenyldiphosphine metallo-dendrimers was decorated with [Rh(COD)2][BF4] to instill the desired catalytic properties necessary to reduce dimethyl itaconate. These metalloconstructs showed 98% ee, which compared well with the 99% ee obtained with monomeric Rh-based josiphos catalyst. 

Macrocyclic metal complexes are the principal materials incorporated in the dendrimer structure (for reviews see [192,193]). Examples are metallo dendrimers with a porphyrin core [194-204], with a phthalocyanine core [205-209], with crown ethers in the repeat unit [210-212] or with a cyclic amine core [213],... 

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