Talk:Three-center two-electron bond

General question
So what does 2-centre-2-electron bond mean and when is it used? :S Im just a little confused about this...
 * A 2-centre-2-electron bond is a ordinary, every-day bond, the simplest example being H2. 2 centre means there are two nuclei (the two protons) and 2-electron means, well, there are two electrons. -Exomnium

Diborane bond lengths
Can we restore the experimental bond lengths in diborane (removed today) which demonstrate from simple evidence that the bridge B-H-B bonds for all their complexity are longer and therefore weaker than the terminal B-H bonds? Dirac66 (talk) 21:18, 11 January 2013 (UTC)
 * Done! V8rik (talk) 10:55, 12 January 2013 (UTC)

Octet rule?
It seems we have a bit of disagreement here. I admit I have difficulty understanding how a 3c-2e bond satisfies the octet rule. Recently a user linked the electron-deficient pages to Wade's rules and I can see how Wade's rules provides an additional justification for why such molecules are stable. You see, the issue I have with 3c-2e bonds satisfying octet rule is this: in hypervalent molecules, each resonance structure obeys the octet rule. However, I cannot see that with the resonance structures for diborane for instance (there's always hydrogen or boron being short of full valence). I imagine these molecules to be somewhat metal-like, which are stable and yet which are not commonly considered to obey the octet rule. If 3c-2e boranes satisfy the octet rule, then why are so many carbocations (with 3c-2e/hyperconjugated/etc bonding) unstable? Thoughts?--Officer781 (talk) 08:52, 28 February 2019 (UTC)


 * The octet rule says that a p-block atom has 8 electrons in its valence shell. Electrons shared with 1 other atom are included, so the question is whether electrons shared with 2 other atoms should be included also. Normally we would look for reliable references to answer the question, but you said in an edit summary 3 days ago that you found nothing useful on the Internet, and my Google search found nothing either. I also checked the discussions of diborane in several textbooks, which all seem to avoid specifying whether or not diborane obeys the octet rule.
 * So perhaps Wikipedia should follow the literature and leave the question unanswered. I will agree to the removal of the statement that diborane obeys the octet rule, but I would also like to delete the words despite not having a full octet. This would leave the sentence as The molecule achieves stability because each B participates in a total of four bonds and (therefore) all bonding molecular orbitals are filled, although two of the four bonds are 3-centre B−H−B bonds. I think this claim is on firmer ground. Perhaps the word therefore should be deleted also. Dirac66 (talk) 01:53, 1 March 2019 (UTC)
 * Thanks for helping to check. I have done as specified. Is the wording OK?--Officer781 (talk) 02:04, 1 March 2019 (UTC)
 * Yes, fine. Thank you.Dirac66 (talk) 03:21, 1 March 2019 (UTC)

Inorganic Chemistry
What about I2Cl6 ,there is no word mentioned for it. I2CL6 have 3c -2e bond or not BaibhavBittuTiwaari (talk) 05:18, 13 June 2021 (UTC)


 * We have an article on iodine trichloride, which exists in the solid state as the planar chlorine-bridged dimer I2Cl6. The structure in that article shows that two of the chlorines form I-Cl-I bridges, so the molecule does have three-center bonding. However halogens such as I and Cl contribute more valence electrons to the bonding (compared to B and H in B2H6 which is the typical 3c-2e molecule), so the I-Cl-I bridges are very probably Three-center four-electron bonds (3c-4e). Can anyone find a reference which says so? Dirac66 (talk) 00:45, 26 June 2021 (UTC)

General/parent-topic article
Thinking about Dirac66's comment above, do we have a top-level article for all these sorts of "Xc–Ye" covalent bonding other than classical 2c–2e? I found an example described as 8c–2e (!), and while that mode probably doesn't merit an article itself, it seems worthy of mention in some general article. DMacks (talk) 01:05, 26 June 2021 (UTC)