Ruthenium-based metallodendrimer

The ruthenium-based metallodendrimer Go-8 was applied as catalyst in a ring-closure metathesis reaction. The activity per metal center of the dendritic catalysts was found to be comparable to that of the corresponding mononuclear catalyst. Unfortunately, the metathesis reaction conditions were not compatible with the nanofiltration membrane set-up used, since a black precipitate was formed in the vessel containing the catalyst. It was found that the conversion to diethyl-3-cyclopentene dicarboxylate product stopped... 

Some metallodendrimers with one or more stereogenic centers have been prepared without control of the chirality. Vogtle and Balzani [74] have tried several strategies to prepare dendrimers in which a ruthenium cation is the core of the final compound. In these compounds, the only centre of chirality is that of the metal, but as it was not controlled racemic mixtures were obtained. Controlling the stereochemistry of the starting complex would have allowed the authors to prepare a optically pure metallodendrimer. Denti, Campagna, Balzani, and their co-workers have studied polymetallic dendrimers based on bipyridine and 2,3- 7s -(2-pyridyl)pyrazine (2,3-... 

In parallel, it was reported by Housecroft and coworkers a completely different metalloden-dritic system based on a pentaerythritol, as a core molecule, and four carboranyl-functionalized complexes of 2,2 6, 2"-terpyridine ruthenium. The reaction of pentaerythrytol with 4 -Cl-2,2 6, 2" -terpyridine in dimethyl sulfoxide (DMSO) in the presence of KOH gave a molecule that contains four tpy metal-binding sites, the crucial point for the formation of the metallodendrimer. The reaction of this with the carboranyl-functionalized Ru complex [Ru 4 -[2-(tert-butyldimethylsilyl)-l,2-carboranyl]-2,2 6, 2"-ter-pyridine Cl3], [Ru(sicarbtpy)Cl3], in ethane-l,2-diol at 120°C led to the formation of the first generation of a cationic tetranuclear metallodendrimer (Scheme 27.12), confirmed by NMR and MALDI-TOF. 

---