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Can the structure of an azide ion ($\ce{N3-}$) be $\ce{N#N\bond{->}N^-}$?

I know the actual structure but was asking whether the single bond can be shifted to a N to make it a triple bond and a coordinate bond with other Nitrogen.

This is not a duplicate of Hybridization in azide ion? because I am asking whether it can have a coordinate bond or not while the other question asks what the hybridization of centre nitrogen in $\ce{N3-}$ is.

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Satyajeet
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2 Answers2

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You can’t really tell a dative bond from a ‘normal’ covalent bond until you break the bond. A dative bond will then dissociate heterolyticly while a covalent bond will dissociate homolyticly.

Just using that simplified way of putting it, you could say that there are many reactions of azides wherein $\ce{N2}$ is liberated leaving a nitrene or related structure; just one of many examples would be the Curtius rearrangement. However, that is not what is meant in the definition above; the definition talks about supplying the bond dissociation energy.

The BDE is not typically supplied in chemical reactions except in coordination compound ligand exchange and radical generation. If you were to apply it to $\ce{N3-}$, I predict homolytic dissociation. Thus, the bond between the nitrogens is more of a typical single bond.

Of course, aside from the chemical implications of dative versus covalent bond you may just have decided to use an arrow notation rather than formal charges. Technically nobody can stop you but still you shouldn’t call it a true dative bond.

Jan
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No.

The issue with using your proposal is very simple: $\ce{N_2}$ sucks at being reactive. It doesn't want to give up or share its electrons with any other atom. In fact, the azide ion is usually explosive because it keeps trying to form nitrogen gas. $\ce{N_2}$ has no real polarity and no particular motive to coordinate to anything, a single N included.

Breaking Bioinformatics
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    Sorry. you're wrong - structures with additional formal charges are more important in azide than those without them. – Mithoron Jun 19 '15 at 16:35
  • Formal charge of the azide has nothing to do with the stability of gaseous nitrogen. Azide is not formed directly from diatomic nitrogen and azide ions are terribly explosive. Sodium azide is used in airbags because it explodes so well, mercury azides detonate if you do nothing with them, etc. Nitrogen gas is extremely stable and will not try to coordinate to anything. Azide can adopt formal charges, yes, but that's distinct from a nitrogen coordinating to a nitride. – Breaking Bioinformatics Jun 19 '15 at 16:42
  • Thanks that was pretty much good answer but is ther any other way to think about its formation rather than just thinking it will be unstable. – Satyajeet Jun 19 '15 at 16:46
  • see annswers to questions I linked, also one pair of N2 electrons can certainly be donated. – Mithoron Jun 19 '15 at 16:47
  • Can be? Sure, technically, I suppose an electron pair can usually be coordinated. But it's energetically unfavorable to the point of ridiculousness. The second question you linked has no answer, and I'm already very aware of the resonance in an azide (in which the most stable contributor is N=N=N). – Breaking Bioinformatics Jun 19 '15 at 16:53
  • This is the second important contributor and it is there in answer to hybridizatio.. - http://chemistry.stackexchange.com/a/19911/9961 – Mithoron Jun 19 '15 at 16:58
  • The resonance structure is distinct from the coordination shown here. That resonance structure is a direct covalent bond. This structure proposes that nitrogen gas will directly coordinate with $\ce{N^-}$. – Breaking Bioinformatics Jun 19 '15 at 17:02
  • yes , yes sorry thank you Breaking Bioinformatics now I deeply realized that how can $\ce{N2}$ being thermodynamically extremely stable be co-ordinating with N , it will be a freaking dangerously unstable molecule then and will not actually represent the $\ce{N3-}$ molecule which is lot different from the one I mentioned above. – Satyajeet Jun 19 '15 at 17:13
  • As @Jan points out in comment it's the same Satyajeet simply wrote another mesomeric structure and probably thought it's another compound – Mithoron Jun 19 '15 at 18:57
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    That definitive no is just very wrong. If one accepts donor-acceptor-bonds to be part of the Lewis formalism, then the indicated structure is indeed a resonance contributor. There is no such thing as a most stable resonance structure, as they are only present when coexistent. It is possible to have a highest contributor, but it is not the same thing. I am sorry, but since this is wrong (and accepted) I had to down vote it. – Martin - マーチン Jun 20 '15 at 06:26