Question

Total number of \(2c-2e^{-}\) and \(3c-2e^{-}\) bonds present in diborane is _ _ _ _ _ .

Hint:

Diborane has 4 terminal (2c-2e) and 2 bridge (3c-2e) bonds → total = 6 bonds.

Answer 1

Correct Answer: 6

Step 1: Understanding the Concept:
Diborane ($B_{2}H_{6}$) has an unusual structure because boron does not have enough valence electrons to form conventional covalent bonds with all hydrogen atoms. It features multicenter bonding.
Step 2: Key Formula or Approach:
Structure of $B_{2}H_{6}$:
- 4 Terminal Hydrogen atoms.
- 2 Bridging Hydrogen atoms.
Step 3: Detailed Explanation:
1. Terminal Bonds: There are four $B-H$ terminal bonds. Each is a standard two-center two-electron ($2c-2e$) bond formed by the overlap of boron's $sp^{3}$ orbital and hydrogen's $1s$ orbital.
2. Bridging Bonds: There are two $B-H-B$ bridging bonds (often called banana bonds). Each bond involves three atoms (two borons and one hydrogen) but only two electrons. These are three-center two-electron ($3c-2e$) bonds.
3. Total Count:
- Number of $2c-2e$ bonds $= 4$.
- Number of $3c-2e$ bonds $= 2$.
- Total bonds $= 4 + 2 = 6$.
Step 4: Final Answer:
The total number of such bonds is 6.