Question

What are electron deficient compounds? Explain with examples.

Answer 1

There are two types of compounds when we focus on the electron compositions i.e. electron rich compound and electron deficient compounds. As their name suggests that one will have more electrons than general criteria and other will have less.

Complete answer:
Let us study the phenomenon in detail-
Electron deficient compounds –
The compounds in which the central atom does not have eight electrons in its valence shell or it have eight electrons but can expand the valency due to presence of vacant d – orbitals. Thus, in short electron deficient compounds have insufficient number of electrons to complete the octet of the central atom.
There are many examples to describe the electron deficiency; most common are the compounds formed by Boron family i.e.$B{{H}_{3}},Al{{H}_{3}},B{{F}_{3}},SiC{{l}_{4}},etc.$(some of them). To describe, consider $BC{{l}_{3}}$ which has 6 electrons (3 electrons of boron and other 3 which got involved by chlorine to form covalent bond) in its valence shell i.e. incomplete octet.

Note:
Do note that even if having less electrons than required i.e. the octet is incomplete of that compound, it will be stable as any other compound will be. Though sometimes they will dimerise (sometimes polymerise) but will be stable in any form of existence.