ABSTRACT
Carboranes are a class of heteroboranes that contain both boron and carbon atoms in electron-delocalized clusters (Grimes, 1970). One of the most commonly encountered carborane clusters are the icosahedral dicarboranes (C2B10H12), as shown in Figure 26.1. There are three isomers, the 1,2C2B10H12 (ortho-), 1,7-C2B10H12 (meta-), and the 1,12-C2B10H12 (para-), all of which are commercially available. All three icosahedral carboranes are chemically and thermally very stable. In general, the ortho-carborane derivatives can be prepared from the reaction of decaborane with various acetylenes; the corresponding meta and para isomers can be obtained via thermal isomerization of the respective ortho-carboranes. The hydrogens attached to the cage carbons of the carboranes are acidic and can be removed by reaction with strong bases, which allows further derivatization of the clusters. Similarly, these icosahedral carboranes having electron-rich boron atoms can also be functionalized by Lewis acid-catalyzed Friedel-Craft-type reactions. All these factors make the icosahedral carboranes attractive as synthetic building blocks in materials science, medicine and catalysis (Valliant et al., 2002). In addition, there are a number of smaller cage dicarboranes that are in use (see Figure 26.1). (Russell et al., 2002). In this chapter we will highlight some recent works where carborane clusters have been incorporated into dendritic, nanostructured, and polymeric compounds.
