Carboranes chemical reactions

When nr/Ao-carborane, l,2-BioHioC2H2, is held at 465-500° for one day, it rearranges to the meta isomer neocarborane, 1,7-dicarbaclo-sododecaborane-(12), mp 264-266° (3.9b) which is less polar and even more thermally stable than the 1,2 isomer. The chemical reactions of the two compounds are similar. The para or 1,12 dicarba- compound, mp 259-261°, (3.9c) is obtained in 6% yield by the slow rearrangement of neocarborane at 615°. 

CARBORANE. A cry stalline compound composed of boron, carbon, and hydrogen. It can be synthesized in various ways, chiefly by the reaction of a borane (penta-or deca-) with acetylene, either at high temperature in the gas phase or in the presence of a Lewis base. Alkylated derivatives have been prepared. Carborancs have different structural and chemical characteristics and should not be conTused with hydrocarbon derivatives or boron hydrides. The predominant structures arc the cage type, the nest type, and the web type, these terms being descriptive of the arrangement of atoms in the crystals. Active research on cargorane chemistry has been conducted under sponsorship of the U.S. Office of Naval Research, http //www.onr.navy.mil/... 

Through this study we suggest a useful synthetic procedure for good candidate compounds of a new cage-cluster. The ort/io-carboranes are very stable chemicals in this research. Carboranyl acetic ester can be easily introduced to the ortho- carborane skeleton and then many types of cyclisation of carboranyl cluster can be made to occur. The reactivity and reaction mechanism for cyclisation of carborane cluster have been discussed. The mechanisms for boron cluster expansion reaction and cyclisation at carboranyl edge are summarized as follows. 

As carboranes are chemically stable and exhibit low toxicity to humans, biomedical applications of carborane systems, including cobaltacarboranes, have slowly emerged. The boron isotope °B accounts for about 20% of boron in nature, and it has the ability to capture a slow neutron and release an a-particle (equation 65). This reaction, if conducted in live tissue, will kill the immediate cell, but not its neighbors. Although early studies were done with toxic boron compounds, carboranes, with their low toxicities and high boron content, have been proven to be good substrates for boron capture neutron therapy (BCNT). Cobaltacarboranes have been employed in radioimmunodetection and radioimmunotherapy as well. ... 

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