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BRIDGE BONDING · ADVANCED CONCEPT

Al₂Cl₆
Aluminium chloride bridge bonding

Two electron-deficient AlCl₃ units form Al₂Cl₆ through reciprocal chlorine bridges. Each bridging chlorine retains an original shared pair and directs another lone pair toward the neighbouring aluminium acceptor orbital.

3c–4e chlorine bridgeChemical BondingInteractive 3D lab
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STRUCTURE REASONING

How Al₂Cl₆ bridge bonding works.

The two bridges form simultaneously and create the Al₂Cl₂ bridge core. In the classroom multicentre description, each Al–Cl–Al path contains four electrons distributed across three centres. The dimer does not require an additional Al–Al bond.

BOND COUNT

2 × 3c–4e bridges + 4 × terminal 2c–2e Al–Cl bonds

TERMINAL VS BRIDGE

Bridge Al–Cl contacts are longer and weaker per contact than terminal Al–Cl bonds.

ADVANCED CONCEPT CHECKLIST

Facts to read from the 3D model.

  1. AlCl₃ is trigonal planar as a monomer, while each Al becomes approximately tetrahedral in the dimer model.
  2. The two chlorine bridges are reciprocal: each donor chlorine supports the neighbouring electron-poor Al centre.
  3. A maximum of six atoms—two Al and four terminal Cl—are coplanar in the displayed model.
  4. Do not add a separate Al–Al bond when counting the dimer’s bonding units.

SEARCHED QUESTIONS

Al₂Cl₆ bridge-bonding FAQ.

Why does AlCl3 form Al2Cl6?

AlCl₃ is electron deficient. Two units can reduce that deficiency by reciprocal chlorine lone-pair donation through two Al–Cl–Al bridges.

What type of bridge bond is present in Al2Cl6?

The simulation describes each chlorine bridge as a three-centre four-electron Al–Cl–Al unit.

Is Al2Cl6 planar?

The complete Al₂Cl₆ model is non-planar, although a maximum set of six atoms can lie in one plane.

MOLECULE-BY-MOLECULE GUIDES

Study every bridge-bonding system.

Open a focused structure guide, then use the shared 3D lab to rotate the complete molecule and compare bridge formation.