Diborane undergoes unsymmetrical cleavage reactions with:

Options

A. dimethylamine
B. ammonia at low temperature
C. methylamine
D. carbon dioxide

Answer

To determine the substances with which diborane (B2H6) undergoes unsymmetrical cleavage reactions, we will analyze the reactions of diborane with various amines and carbon dioxide.

### Step-by-Step Solution:

1. **Understanding Diborane**:
- Diborane (B2H6) is a compound of boron that can react with different nucleophiles. It has unique bonding characteristics that allow it to undergo cleavage reactions.

2. **Reactions with Dimethylamine**:
- When diborane reacts with dimethylamine (N(CH3)2H), it undergoes unsymmetrical cleavage.
- The reaction can be represented as:
\[ B_2H_6 + N(CH_3)_2H \rightarrow BH_4^- + BH_2N(CH_3)_2 \]
- This reaction results in the formation of a borohydride ion (BH4-) and a dimethylamino-borane complex (BH2N(CH3)2).

3. **Reactions with Ammonia**:
- At low temperatures, diborane reacts with ammonia (NH3) also leading to unsymmetrical cleavage:
\[ B_2H_6 + NH_3 \rightarrow BH_4^- + BH_2NH_2 \]
- Here, a borohydride ion (BH4-) and a boron-ammonia complex (BH2NH2) are formed.

4. **Reactions with Methylamine**:
- Similarly, diborane reacts with methylamine (NH2CH3) to give:
\[ B_2H_6 + NH_2CH_3 \rightarrow BH_4^- + BH_2NHCH_3 \]
- This results in the formation of a borohydride ion (BH4-) and a methylamino-borane complex (BH2NHCH3).

5. **Reactions with Carbon Dioxide**:
- When diborane reacts with carbon dioxide (CO2), it does not undergo any cleavage:
\[ B_2H_6 + CO_2 \rightarrow \text{No reaction} \]
- Therefore, no unsymmetrical cleavage occurs in this case.

6. **Conclusion**:
- The substances with which diborane undergoes unsymmetrical cleavage are:
- Dimethylamine (A)
- Ammonia (B)
- Methylamine (C)
- Carbon dioxide (D) does not lead to unsymmetrical cleavage.

### Final Answer:
Diborane undergoes unsymmetrical cleavage reactions with:
- A) Dimethylamine
- B) Ammonia
- C) Methylamine