Question

Which of the following is the electron deficient molecule?

• A. $B _{2} H _{6}$
• B. $C_{2} H_{6}$
• C. $PH _{3}$
• D. $SiH _{4}$

Answer 1

Answer: (A)

$B _{2} H _{6}$

Answer 2

$B_{2} H_{6}$ is electron deficient molecule because boron atom has three half-filled orbitals in excited state. The structure of $B_{2} H_{6}$ is represented as follows:

In it two electrons of a $B-H$ bond are involved in formation of three centre bond, these bonds are represented as dotted lines.