Pentaborane, BSHS

Boranes are usually named by indicating the number of B atoms with a latin prefix and the number of H atoms by an arabic number in parentheses, e.g. B5H9, pentaborane(9) B5H11, pentaboranefl 1). Names for anions end in ate rather than ane and specify both the number of H and B atoms and the charge, e.g. BsHs" octahydropentaboratefl—). Further information can be provided by the optional inclusion of the italicized descriptors closo-, nido-, arachno-, hypho- and conjuncto-, e.g. ... 

Many of the boron hydrides have been shown to function as Brdnsted acids (See 34 for references). The bridging hydrogens are acidic. Pentaborane(9) is a monoprotic acid in the presence of a variety of bases (35,36,37). An example of such a reaction (38) is given in Scheme I, Reaction (4). By removing the bridging proton to give BsHs , a boron-boron bond is formed which is susceptible to insertion of electrophillic agents. 

The synthesis and characterization of the [BsHs]- ion 15,16,17) js one of the most important developments in recent years in the chemistry of pentaborane(9) and its derivatives. Several examples of a new class of pentaborane(9) derivatives have been prepared in which substituents occupy bridging sites 172-175) and significant yields of hexa-borane(lO) 16>17>, hexaborane(12) 17>, or decaborane(14) 16>17> have been obtained from the reaction of B5H8 with B2H6 by careful control of the reaction conditions. 

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