Solutions of pentaborane(9) in tetrahydrofuran (THF) were found to be indefinitely stable under inert conditions and relatively stable to dry air. Solutions exposed to the air were found to decompose slowly to boric acid. Similar stabilities were also found for other pentaborane(9) organic solvent systems including diglyme, diethyl ether, and hexane. No vigorous reactions with air or moisture, including pyrophoric or shock-sensitive behavior, were observed for any of the solutions investigated. The reaction of pentaborane(9) with triethylamine and either 3-hexyne or phenylacetylene in THF at room temperature was found to produce up to 80% of nido-2,3-(CH3CH2)2C2B4H6 and 20% of nido-2,3-(C6H5)HC2B4H6, respectively. In addition, the reaction of diphenylacetylene with the pentaborane(9)-THF solution and triethylamine was also explored to determine if the preparation of the synthetically very difficult nido-2,3-(C6H5)2C2B4H6 carborane could be achieved. The reaction was found to give a 21% yield of the nido-2,3-(C6H5)2C2B4H6 carborane after 1 day at room temperature. The nature of the interaction between pentaborane(9) and THF has been investigated by ambient- and low-temperature 11B NMR studies.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry