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Dimer of Aluminum Chloride

How are the bridge bonds in $\ce{Al2Cl6}$ different from the terminal bonds?

We could have just mentioned the bridge bond formed by $\ce{Cl}$ as a coordinate bond. Why introduce this extra concept?

I can understand why 3 center-2 electron bond would have been introduced but not this one.

My guess is that during the formation of the molecule vacant orbitals take part in hybridisation which is different from usual but after formation of the bond, there is no difference.

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    $\begingroup$ It's showcasing ionic component of bonds and their symmetry. $\endgroup$ – Mithoron May 28 at 21:52
  • $\begingroup$ Sir, I did not understand your statement much, would you mind elaborating it. Like why does it have ionic character, if it has ionic character then why not just call it ionic bond(My guess:as Cl gets distributed between two Al, thus it has less distortion so it has less covalent/more ionic character by Fazan's rule). How does 3 centre 4 electron signify symmetry? $\endgroup$ – satyam kumar jha May 29 at 1:35
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    $\begingroup$ There are no 3c4e bonds in Al2Cl6 chemistry.stackexchange.com/questions/34842/… $\endgroup$ – Mithoron May 29 at 14:45