Diborane

Diborane is the boron hydride with the chemical formula B2H6. It is a colorless, highly reactive gas at room temperature that is typically handled under inert conditions due to its air sensitivity. In solution or in complexes it can be more stable, but as a pure substance it readily reacts with moisture and oxygen.

The molecule is best described as an electron-deficient boron cluster in which two boron centers are connected through two three-center, two-electron B–H–B bridges. Each boron bears terminal hydrogen atoms, and the two bridging hydrogens form multicenter bonds that stabilize the species. There is no conventional two-center, two-electron B–B bond; the boron–boron interaction is mediated by the bridging hydrogens.

Diborane is typically generated in situ, often by reductive coupling of boron halides or by decomposition of boron hydride precursors in the presence of suitable hydride donors. It has a very low boiling point (around −92 °C) and is usually collected as a gas or used immediately in solution or adduct form, such as the borane–THF complex, for practical handling.

In chemistry, diborane serves as a versatile source of BH3 equivalents. It is widely used in hydroboration-oxidation reactions, where alkenes are rapidly converted into organoboranes and ultimately into alcohols after oxidation. It also participates in the synthesis of boron-containing compounds and can act as a reducing agent in certain reactions.

Safety and handling are important due to its reactivity and volatility. Diborane is toxic, reacts with water and oxygen, and can form flammable mixtures; it is stored and used under strictly controlled, inert conditions.

See also: borane, hydroboration, borohydride chemistry.