Neutral hydrides of group 13 elements

  With three valence electrons, each group 13 element might be expected to form a hydride MH₃. Although the existence of BH₃ has been established in the gas phase, its propensity to dimerize means that B₂H₆ (diborane(6)) is, in practice, the simplest hydride of boron.

We have already discussed the structure of and bonding in B₂H₆ the reader is reminded of the presence of 3c-2e (delocalized, 3-centre 2-electron) B^_H^_B interactions.
 

Diborane(6) is an important reagent in synthetic organic chemistry, and reaction showen in below is one convenient laboratory preparation..

   Although this reaction is standard procedure for the preparation of B₂H₆, it is not without problems. For example, the reaction temperature must be carefully controlled because the solubility of Na[BH₄] in diglyme varies significantly with temperature. Secondly, the solvent cannot easily be recycled. Reaction that showen in below , which uses a triglyme adduct of BF₃ as precursor, produces B2H6 quantitatively and is an improvement on the traditional reaction showen in above . Reaction below can be applied to large-scale syntheses, and the triglyme solvent can be recycled. Tetraglyme can be used in place of triglyme in below reaction .

   Reaction 12.10 is the basis for an industrial synthesis of B₂H₆.

Diborane(6) is a colourless gas (bp 180.5 K) which is rapidly decomposed by wate). Like other boron hydrides  B₂H₆ has a small positive value of Δ_f H^o (‏36 kJ mol^_1); mixtures with air or O₂ are liable to inflame or explode.

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