Borane，also known as boron hydride, is the ageneraldesignation for a series of compounds formed by two elements of boron and hydrogen. Simple boranes are colorless, unpleasantly odorous and toxic. They are usually very unstable and spontaneous to generate boron oxide in air. With the increase of the number of boron atoms, boranes can be gaseous (e.g., diborane), liquid (e.g. pentaborane) and solid (e.g. decaborane). There have been more than 20 kinds of boranes ever prepared by human so far, which can be divided into two categories. The general formula of one of them is BnHR+4 (n≥2), such as diborane (B2H6), pentaborane-9 (B5H9) and sixteen borane (B16H20); the other is BnHR+6 (n≥3), such as triborane(B3H9), pentaborane-11 (B5H11), nonaborane (B9H15) and so on. Borane all have unpleasant odor. Simple borane (of relatively less boron atoms) is so chemically active that is spontaneous in air and easy for hydrolysis, halogenation and amination. Diborane is of the largest and most important usage. It is prepared from boron trifluoride with lithium hydride in ether in industry.
Other boranes can be prepared from the thermal decomposition of diborane at different temperatures.
Borane release a lot of heat when burned, therefore it can be used as high-energy fuel for rockets and missiles. It can also be used as the treatment agent of a metal or ceramic parts and rubber crosslinking agent. One of the important applications of diborane is reduction agent in the hydroboration reaction.
Borane is highly toxic, inhalation of diborane can cause lung damage, inhalation of decaborane can cause a heart recession, large boranes are toxic to the central nervous system and damaging to the liver and kidneys. Careful attention must be paid when using borane.