Chemistry

Boron Swap

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Science  25 May 2007:
Vol. 316, Issue 5828, pp. 1099
DOI: 10.1126/science.316.5828.1099d

In boron neutron capture therapy, the radioactive decay induced by neutron collisions with 10B nuclei is channeled toward tumor destruction. Implementation of the technique remains challenging because of the need to devise boron compounds that selectively concentrate in tumors while remaining relatively nontoxic overall. Moreover, 10B is one-fourth as abundant as the heavier 11B isotope, which is inert to neutron bombardment. Thus, synthetic routes to various candidate molecules are hampered by the need for isotopic enrichment.

In a step toward improved efficiency, Yinghuai et al. have found that ruthenium nanoparticles can catalyze the isotopic exchange of boron atoms from excess 10B2H6 to the larger B10H14 cluster. They prepared the catalyst by reduction of a metal-locene precursor in a biphasic mixture of ethylene glycol and a trialkylphosphonium ionic liquid (chosen because imidazolium systems can poison the catalysis). After six successive treatments of the decaborane with the catalyst and diborane, combined Raman and mass spectral analysis were consistent with ~90% 10B enrichment of the larger cluster. The mechanism is as yet unresolved. — JSY

J. Am. Chem. Soc. 129, 6507 (2007).

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