Molecular hydrides are classified as electron-deficient,

Molecular hydrides are classified into electron-deficient, electron precise and electron-rich compounds.

B2H6 is an electron-deficient hydride. These have an incomplete octet. They are formed generally by the group 13 elements like B, Al, etc.

An electron-precise hydride is a type of hydride which has the exact number of electrons required to form normal covalent bonds, no excess no deficient. These are formed generally by group 14 elements like Si and C which have 4 valence electrons.

Eg. CH4, SiH4, etc.