Talk:Non-coordinating anion
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Images
I've made a few images of BArF based on a crystal structure - see Commons:Category:Tetrakis(3,5-bis(trifluoromethyl)phenyl)borate ion for details.
If they're any use to this article, or if BArF gets its own article at some stage, the images exist.
Ben (talk) 14:06, 11 June 2008 (UTC)
Contrast to strongly coordinating anions.
I assume that "interacts weakly", "non-coordinating", and "weakly coordinating" are intended to mean that the anions do not form coordination bonds with their cations, and maybe also that they don't react chemically to decompose the cations and change them into something else.
My problem is that I don't feel like this article clearly states what these terms are supposed to mean, despite the fact that this is the first place many people would look to find that out. I think the problem is that at no point does the article explain what these terms are in contrast to, i.e., what a "strongly interacting", "coordinating", or "strongly coordinating" anion would be.
It is true that it isn't that hard to figure out, because it does use the word "coordinating" which implies "coordination complex", and "coordination bond", and much of the article discusses anions bonding to metals; and the word "interacting" seems pretty likely to refer to, or at least include, chemical reactions in the context of chemistry; but it still feels like I'm guessing. I think it should be more clear right at the beginning of the article.
Moreover, given how much the term "weakly coordinating anion" shows up in Wikipedia pages about anions, I think it's worth putting at least a sentence in the blurb at the top that will inform readers who don't know what a coordination complex is that that's what this is about, if that actually is what this page is about. (I'm still not sure.) Similarly, if the fact that weakly interacting anions don't decompose delicate cations is part of the issue, than some note should be made of the fact that many salts are not stable because the anion would react chemically with the cation.
As a final sidenote, it seems to me like this is closely related to the idea of strong acid, or even a superacid, as those can be seen as anions that react very weakly with protons. If that is true, it might be worth noting.
DubleH (talk) 16:17, 20 October 2020 (UTC)
- @DubleH:A table could be added about the contrasts that you are recommending.
| feature | strongly coordinating anion |
weakly coordinating anion |
|---|---|---|
| charge | 1-, 2-, 3- | 1- |
| size | small, often monatomic | polyatomic |
| symmetry (applies to polyatomic ions) |
lower symmetry | high symmetry, often Td or Oh |
| pKa of conjugate acid | high (weak acids) | low (strong acids) |
| substituents (applies to polyatomic ligands) |
electron-releasing | electronegative |
--Smokefoot (talk) 23:19, 20 October 2020 (UTC)
I think that helps, but it would probably be even more helpful if the definition at the top was just made a little bit more clear and specific. The closest thing to a definition I see now is, "Anions that interact weakly with cations are termed non-coordinating anions." I think my actual problem is not so much the lack of contrast as the fact that I think the word "interact" requires more explanation. I think most of those properties you've listed are things which determine how much an anion "interacts" with cations, and acidity is a result of how much it "interacts" with cations, but there isn't an explicit statement of exactly what kind of "interactions" matter, since there is more than one way that an anion and a cation might interact: bumping into each other, chemically bonding to each other, switching atoms between each other, switching electrons between each other, catalyzing each other's decomposition or polymerization, catalyzing reactions of the other with other chemicals, bonding together into low solubility salts, affecting fluid properties of solutions through electrical attraction, affecting the spectrum of each other (most likely via one of the preceding types of interaction), etc.DubleH (talk) 10:18, 27 October 2020 (UTC)