Diborane Structure

Preparation:

• 4BH₃ + 3LiALH₄ → 2B₂H₆ + 3LiF + 3AlF₃
• 2NaBH₄ +I₂ → B₂H₆ + 2NaI + H₂
• 2BF₃ + 6NaH → B₂H₆ + 6NaF

Structure:

• Diborane contains four terminal and two bridging hydrogen atoms
• The terminal H atoms and B atoms lie in one plane. The bridging H atoms lie above and below the plane

Properties:

• Colourless highly toxic gas
• B.P : 180 K
• Catches fire instantly in air
• Burns in oxygen releasing energy.
  B₂H₆ + 3 O₂ → B₂O₃ + 3 H₂O; Δ_cH^Θ = -1976 kJ/ mol
• Hydrolyze in water to give boric acid
  B₂H₆ + 6H₂O → 2B(OH)₃ + 6 H₂
• Borane adducts:
  B₂H₆ + 2NMe₃ → 2BH₃.NMe₃
  B₂H₆ + 2CO → 2BH₃.CO
• On reaction with ammonia and subsequent heating, gives borazine also known as inorganic benzene.
  3B₂H₆ + 6NH₃ → 3[BH₂(NH₃)₂]⁺[BH₄]^– → 2B₃N₃H₆ + 12H₂

Borazine