Talk:Three-center two-electron bond

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General question[edit]

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[edit]

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)[reply]

Octet rule?[edit]

@Dirac66: 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)[reply]

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)[reply]
Thanks for helping to check. I have done as specified. Is the wording OK?--Officer781 (talk) 02:04, 1 March 2019 (UTC)[reply]
Yes, fine. Thank you.Dirac66 (talk) 03:21, 1 March 2019 (UTC)[reply]

Inorganic Chemistry[edit]

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)[reply]

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)[reply]

General/parent-topic article[edit]

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)[reply]