The structure of diborane ($\mathrm{B}_{2} \mathrm{H}_{6}$) contains

(A) four $2 \mathrm{c}-2 \mathrm{e}$ bonds and two $3 \mathrm{c}-2 \mathrm{e}$ bonds

(B) two 2 c -2e bonds and four 3 c -2e bonds

(C) two $2 \mathrm{c}-2 \mathrm{e}$ bonds and two $3 \mathrm{c}-3 \mathrm{e}$ bonds

(D) four $2 \mathrm{c}-2 \mathrm{e}$ bonds and four $3 \mathrm{c}-2 \mathrm{e}$ bonds

JEE Main · 2005 · 08 May 2005 · Offline · Chemical Bonding and Molecular Structure

The structure of diborane (

B_{2} H_{6}

) contains

Answer: (A)

Diborane,

B X_{2} H X_{6}

, famously cannot be drawn with ordinary two-electron bonds everywhere. Its four terminal

B - H

bonds are normal two-centre two-electron bonds, but the two bridging hydrogens each sit in a

B - H - B

three-centre two-electron bond, where a single pair of electrons is shared across three atoms. So the structure holds four

2 c - 2 e

bonds and two

3 c - 2 e

bonds.

JEE Main · 2005 · 08 May 2005 · Offline · Single correct option