Polyanionic Carbosilane and Carbosiloxane Metallodendrimers Based on Cobaltabisdicarbollide Derivatives

Carbosilane and carbosiloxane metallodendrimers that contain one, four, and eight peripheral cobaltabisdicarbollide derivatives have been synthesized using regiospecific hydrosilylation of vinyl-terminated dendrimers with Cs[1, 1'-mu-SiMeH-3,3'-Co(1,2-C2B9H10)(2)], 1. A methodology to synthesize a trifunctional molecule containing one cobaltabisdicarbollide and three vinylsilane moieties, 2, has been developed starting with tetravinylsilane. The first- and second-generation of anionic metallacarborane-containing metallodendrimers, 3, 4, and 5, were constructed via hydrosilylation of carbosilane dendrimers functionalized with four or eight vinyl functions, by using 1 as the hydrosilylation agent. Furthermore, it has been possible to apply this methodology to vinyl-terminated cyclocarbosiloxane dendrimers to yield metallodendrimers, 6, 7, and 8, which contain four (6) and eight (7, 8) peripheral cobaltabisdicarbollide units. Products are fully characterized by FTIR, NMR, and UV-vis spectroscopies. For metallodendrimers, the UV-vis absorptions have been a good tool for estimating the experimental number of cobaltabisdicarbollide moieties attached to the periphery and consequently to corroborate the good level of functionalization of the dendrimers. In addition, UV-vis spectroscopic measurements have also allowed the study of the solubility and behavior in water/DMSO solutions of these metallodendrimers.