Tri alkyl aluminium molecules exist as dimers which contain 3c – 2e bonds. The co –ordination number of bridged carbon is

Tri-alkyl aluminium (\( R_3Al \)) molecules:

• Tri-alkyl aluminium compounds exist as dimers (\( (R_3Al)_2 \)) to satisfy the electron deficiency of the aluminium atom.
• The dimeric structure contains 3-center-2-electron (3c-2e) bonds, where two aluminium atoms and one bridged carbon atom share a pair of electrons.
• Each bridged carbon atom is bonded to:
  • Two aluminium atoms through the 3c-2e bond.
  • Three other alkyl groups attached to the carbon atom.