Dicarba-closo-boranes

The discovery of polyhedral boranes and polyhedral heteroboranes, which contain at least one atom other than in the cage, initiated a new era in boron chemistry.1-4 Most commonly, of the three commercially available isomeric dicarba-closo-dodecaborane carboranes(l,2-, 1,7-, and 1,12-), the 1,2-isomer 1 has been used for functionalization and connection to organic molecules. The highly delocalized three-dimensional cage bonding that characterizes these carboranes provides extensive thermal and kinetic stabilization as well as photochemical stability in the ultraviolet and visible regions. The unusual icosahedral geometry of these species provides precise directional control of all exopolyhedral bonds. 

The incorporation of a large number of boron atoms into a tumor for boron neutron capture therapy (BNCT) has been accorded considerable interest over the last few years [67]. It is known that if boron-containing cells are exposed to a neutron flux, they are destroyed without causing irreparable harm to adjacent healthy tissue. In the context of SERMs, for example, Endo et al. have prepared complex 18 [ 1 - (hydroxymethyl) -12- (4-hydroxyphenyl) -1,12-dicarba-closo-dodeca-borane] in which the hydrophobic carborane cage mimics the C and D rings of estradiol (Scheme 3.7) [68]. 

C28H4iB2oClP2Pt, Chloro[1-diphenylphosphino-1,2-dicarba-closo-do-decaborane(12)-P][1-diphenylphosphino-1,2-dicarba-closo-dodeca-boran-3-yl-B, P]platinum, 46B, 1271... 

C22H39BF3NO3, Cyclohexyl(hydroxy)(trifluoroacetamido(dicyclohexyl)-methyl)-borane methanol solvate, 44B, 585 C22H68B2oN202Ti, Bis(tetramethylammonium) 4,4 -commo-bis(decahydro-1, 6-dimethyl-1,6-dicarba-4-titana-closo-tridecaborate) bis(acetone), 41B, 850... 

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