Question

The correct statement about ${\mathrm{B}}_2{\mathrm{H}}_6$ is :

• A. All $\mathrm{B}-\mathrm{H}-\mathrm{B}$ angles are $120°$
• B. Its fragment ${\mathrm{BH}}_3$, behaves as a Lewis base.
• C. Terminal $\mathrm{B}–\mathrm{H}$ bonds have less p-character when compared to bridging bonds.
• D. The two $\mathrm{B}–\mathrm{H}–\mathrm{B}$bonds are not of the same length.

Answer 1

The correct option is C

Terminal $\mathrm{B}–\mathrm{H}$ bonds have less p-character when compared to bridging bonds.

The correct option is (C):

Explanation for the correct answer:

Diborane (${\mathrm{B}}_2{\mathrm{H}}_6$):-

1. It is actually a chemical that consists of the Hydrogen as well as the Boron atoms.
2. Basically, there is the presence of Banana bond in ${\mathrm{B}}_2{\mathrm{H}}_6$, which is a type of chemical bond where the hybridization state of the two atoms make up a chemical bond and then is further modified with the increased or decreased s-orbital character for accommodating a particular molecular geometry in 3-D.
3. It has a three center electron pair bond and also two types of Hydrogen that are the terminal Hydrogen as well as the bridging Hydrogen.
4. 
5. So here, $\mathrm{\theta }2>\mathrm{\theta }1$ and so the $\mathrm{B}-\mathrm{H}$ terminal will have the less p-character as compared to the bridge bond and so both the $\mathrm{B}-\mathrm{H}-\mathrm{B}$ bond will have the same bond length.
6. And so basically the $\mathrm{B}-\mathrm{H}-\mathrm{B}$ bond angle would be $90°$ and as the ${\mathrm{BH}}_3$ is the ${\mathrm{e}}^{-}$ deficient species so it will act as a Lewis base.

Explanation for the incorrect options:-

Option (A):-

All $\mathrm{B}-\mathrm{H}-\mathrm{B}$ angles are $120°$

1. In Diborane or ${\mathrm{B}}_2{\mathrm{H}}_6$, there is the presence of bond angle $120°$ among $\mathrm{H}-\mathrm{B}-\mathrm{H}$.
2. And in $\mathrm{B}-\mathrm{H}-\mathrm{B}$, there is the presence of bond angle as $90°$.

Option (B):-

Its fragment ${\mathrm{BH}}_3$, behaves as a Lewis base.

1. Basically there is the electron deficiency in ${\mathrm{BH}}_3$.
2. So, it will act as a Lewis acid and would be ready for accepting electron pairs as such it is an electron acceptor.

Option (D):-

The two $\mathrm{B}–\mathrm{H}–\mathrm{B}$bonds are not of the same length.

1. The bond angle between $\mathrm{B}-\mathrm{H}-\mathrm{B}$ is equal to $90°$.
2. And also the bond length among $\mathrm{B}–\mathrm{H}–\mathrm{B}$ bridge bond is same.

Therefore, the correct answer is (C):- Terminal $\mathrm{B}–\mathrm{H}$ bonds have less p-character when compared to bridging bonds.