The structure of diborane is determined by electron diffraction. Diborane has a total of six hydrogens. Four of them are terminal hydrogens and two of the hydrogen atoms are bridged with the boron atom. The boron atom and the four terminal hydrogen lie in the same plane. Two-hydrogen atom one above and one below, form bridge between the boron atoms. These hydrogens are called bridging hydrogens. Diborane is electron deficient because there are only 12 valency electrons. Three from each boron atom and six from the hydrogen atoms. Each bridged is bonded to the two-boron atom by sharing two electrons. Such three-centered covalent bond is called banana bonds