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BRIDGE BONDING · ADVANCED CONCEPT

Al₂(CH₃)₆
Trimethylaluminium methyl bridges

Trimethylaluminium exists as the Al₂(CH₃)₆ dimer with two bridging methyl groups and four terminal methyl groups. Each Al–C–Al bridge distributes one electron pair across two aluminium atoms and one carbon centre.

3c–2e methyl-carbon bridgeChemical BondingInteractive 3D lab
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STRUCTURE REASONING

How Al₂(CH₃)₆ bridge bonding works.

The two methyl bridges form simultaneous three-centre two-electron units in the electron-deficient dimer. The complete model includes all six carbon and eighteen hydrogen atoms, allowing the longer bridge Al–C contacts to be compared directly with the four shorter terminal Al–C bonds.

BOND COUNT

2 × 3c–2e C bridges + 4 terminal Al–C + 18 C–H bonds

TERMINAL VS BRIDGE

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

ADVANCED CONCEPT CHECKLIST

Facts to read from the 3D model.

  1. The corrected molecular formula is Al₂C₆H₁₈, represented conventionally as Al₂(CH₃)₆.
  2. Two methyl groups bridge the Al centres; four methyl groups remain terminal.
  3. The dimer has a non-planar C₂h arrangement with staggered bridging CH₃ groups.
  4. The full bond count contains two 3c–2e bridges and twenty-two ordinary 2c–2e bonds.

SEARCHED QUESTIONS

Al₂(CH₃)₆ bridge-bonding FAQ.

What atom forms the bridge in Al2(CH3)6?

The carbon atom of each of two methyl groups bridges the two aluminium centres.

What type of bridge bond is present in trimethylaluminium dimer?

Each Al–C–Al methyl bridge is represented as a three-centre two-electron unit.

How many bridging methyl groups are present in Al2(CH3)6?

There are two bridging methyl groups and four terminal methyl groups in the dimer.

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.