Carboranyl system

Second, as a logical development of the first approach, polyphosphazenes have been synthesized that bear phosphine units connected to aryloxy side groups (37). The phosphine units bind organometallic compounds, such as those of iron, cobalt, osmium, or ruthenium (38). In several cases, the catalytic activity of the metal is retained in the macromolecular system (39). A similar binding of transition metals has been accomplished through nido carboranyl units linked to a polyphosphazene chain (40). 

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. 

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