Definition

Electron deficient compounds are those in which the total number of atomic orbitals on all the atoms of the compound is more than the total number of valence shell electrons.

Boranes are electron deficient compounds:

B = 1s²2s²2p_x¹2p_y2p_z

H = 1s¹

B₂H₆

_{* number of orbitals from 2 B = 2 X 4 = 8}

    _{number of orbitals from 6 H = 6 X 1 = 6}

_{Therefore, total number of orbitals in diborane is 14, which can accommodate (14X2) = 28 electrons.}

_{But, the total valence shell electrons in diborane due to 2B and 6 H atoms is = 12.  According to definition of deficient compounds,}

B₂H₆ is an electron deficient compound.

Similarly, you can prove the following boranes are electron deficient compounds( Try Yourself)

B₅H₉, B₄H₁₀ and B₅H₁₁