Hydrides

The most simple hydrogen compounds are salts of the tetrahydroborate ion BH₄^- that is isoelectronic and tetrahedral with methane. LiBH₄ is ready by reducing BF₃ with LiH. It is more extensively used as the sodium salt, that is a powerful reducing agent with enough kinetic stability to be employed in aqueous solution. Reaction of NaBH₄ with either I₂ or BF₃ in diglyme (CH₃OCH₂)₂O provides diborane B₂H₆, the most simple molecular hydride. Its structure along with bridging hydrogen atoms needs three-center two-electron bonds:

Heating B₂H₆ above 100°C leads to pyrolysis and makes several more complex boranes of that tetraborane (10) B₄H₁₀ and decaborane(14) B₁₀H₁₄ are the most stable. Another reactions can lead to anionic species, like the icosahedral odecahydrododecaborate(2^-) [B₁₂H₁₂]^2-, get ready at 180°C:

The structural classification and bonding in boranes is explained in Topic C7; particularly  striking are the anions [B_nH_n]^2- with closed polyhedral structures. Boranes with heteroatoms can also be prepared, like B₁₀C₂H₁₂, that is isoelectronic with [B₁₂H₁₂]^2-. Boranes are strong reducing agents and the neutral molecules inflame impulsively in air, even though the anions [B_nH_n]^2- have significant kinetic stability. Diborane itself responds with Lewis bases. The most simple results can be considered as donor-acceptor complexes with BH₃, that is a 'soft' Lewis acid and forms adducts with soft bases like CO (1). More complex results frequently result from unsymmetrical cleavage of B₂H₆, for instance,