Carboranes from Alkylboron Hydrides.
CALIFORNIA STATE COLL LOS ANGELES DEPT OF CHEMISTRY
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Both one-carbon and two-carbon carboranes have been prepared from the flow pyrolysis of several alkylboronhydrides. Carbahexaborane7 and 2-carbahexaborane9 have been prepared from methylpentaborane9 and the corresponding C-methyl derivatives of these carboranes are obtained from ethylpentaborane9. Pyrolysis of 1,2-dimethylpentaborane gives a modestly high yield of 1,5-C2B3H5 and, suprisingly, no detectable quantity of B-methyl derivatives of CB5H7. The four-carbon carborane C4B2H6 is obtained in low yield from 1,2-tetramethylenediborane6. Temperature dependent nuclear magnetic resonance studies on CB5H7 and its C-methyl derivative reveal a bridge hydrogen tautomerism with a Free energy of ca. 14 and 12 kcal, respectively. Author
- Organic Chemistry