Boron is an element with one fewer electron than carbon, so it is prone to being destroyed by oxygen. This property makes boron particularly dangerous for pharmaceutical use, but it also gives the element special properties that make it useful in the nuclear industry (see thermal neutron cross section#Typical cross sections).
Borane and Carboranes
Borane is the simplest natural boron compound; it contains a single boron atom in a cage with a hydrogen atom on each end of the cage. It can be found in air as diborane B2H6 and as a series of pyrolysis products that are primarily pentaborane, B5H9, and decaborane, B10H14.
Carboranes, on the other hand, are polyhedral boron hydride clusters that include carbon atoms. They are most commonly encountered in icosahedral dicarbaborane, but there are also meta-carborane and para-carborane variants that include different carbon atoms.
Low-Valent Boron Compounds
For more than a century, scientists have been trying to develop boron compounds that don’t involve oxidation in the standard +3 oxidation state. This would allow researchers to use the boron atom as a Lewis acid and a nucleophile, which could open up new avenues for creating both organic and inorganic boron-containing materials.
But until recently, it wasn’t possible to use boron in this way. Instead, chemists mainly tried to coax boron into the standard +3 oxidation state by using boron halides as solvents.
But a few years ago, Makoto Yamashita and Kyoko Nozaki flipped the chemistry on its head by creating a new compound in which boron acts as a nucleophile instead of an electrophile. This was a breakthrough that opened up pathways to a lot of new chemical developments in the field, including boron-containing drugs.