Question

What do you understand by electron-deficient? Provide justification with a suitable example.

Answer 1

Molecular hydrides are classified on the basis of the presence of the total number of electrons and bonds in their Lewis structures as:

Electron-deficient hydrides:

An electron-deficient hydride has very few electrons, less than that required for representing its conventional Lewis structure e.g. diborane (B₂H₆). In B₂H₆, there are six bonds in all, out of which only four bonds are regular two centered-two electron bonds. The remaining two bonds are three centered-two electron bonds i.e., two electrons are shared by three atoms. Hence, its conventional Lewis structure cannot be drawn.