Talk:Hapticity

Hapto - where does it come from?

I removed this sentence here: [1] -- "eta is the first letter of the Greek word pronounced "hapto", meaning "held" in Greek". According to some Wikipedians on the language reference desk, this isn't the case. Does IUPAC have anything interesting about the history of this symbol? --HappyCamper 18:55, 23 July 2006 (UTC)

Delighted to see interest in this article, even if the focus is off the chemistry. Here's the source: "Proposed nomenclature for olefin-metal and other organometallic complexes" F. Albert Cotton J. Am. Chem. Soc.; 1968; 90(22); 6230-6232. Here is the key except: "The adjectival prefix hapto (from the Greek haptein, ηαπτειν, to fasten, denoting contact or combination^2a) is placed before the name of the olefin." {I think that I transcribed the Gk correctly from the PDF journal article}

"(2a) “Webster’s Third New International Dictionary,” unabridged, 1961, G. and C. Merriam Co., Springfield, Mass."

So I will reinsert a modification of this information into the article. Thank you for the suggestion and keep checking up - WE needs that!--Smokefoot 20:11, 23 July 2006 (UTC)

Ah :-) Is this the same person who wrote the little book on group theory and chemistry? --HappyCamper 21:25, 23 July 2006 (UTC)

ηαπτειν isn't a word though...eta is not an H, the H in English comes from the alpha pronounced with an h-like sound in front of it, which is not marked by any letter but by a "breathing mark". Adam Bishop 21:37, 23 July 2006 (UTC)

Then, what is Cotton referring to in his original paper? Hm...I should get a hold of a copy to see more closely what is happening. I don't know Greek, so if I sound silly, my apologies in advance. I will ask a classics colleague about this, and if I find anything interesting, I'll let everyone know. --HappyCamper 21:44, 23 July 2006 (UTC)

Apparently hapto is derived from the same root as used for hapten in biology and apparently it is supposed to mean 'fasten" more than "hold" which I used in an early draft of this article. Organometallic chemists sound out the "h" in hapto. Very possibly imperfect from the perspective of classics professor, but this nomenclature is pervasive and indelible. --Smokefoot 22:22, 23 July 2006 (UTC)

I assume Cotton just transliterated "haptein" and assumed the H was an eta, or it's just a typo. It's pronounced "hapto-" in Greek too, they just don't have a H in the spelling. Adam Bishop 00:25, 24 July 2006 (UTC)

Thanks for the clarification. It's really helpful! --HappyCamper 05:02, 24 July 2006 (UTC)

What has Zeise got to do with this?

1) I recommend relocating the fascinating bits on Zeise's salt and the associated personalities possibly to the history of organometallic chemistry or history of Zeise's salt. The hapto thing directly comes from organometallics as practiced in the 60's with polyolefins that gave really complicated molecules. Novices might say, η²-alkene, and this terminology is formally valid, but this is also quite obvious because virtually no other bonding modes are known for alkenes. 2) "The term was introduced in organometallic nomenclature in during the mid-1950s" Hapticity for organometallic chem was introduced by Cotton in the 60's, I thought we settled this. 3) We might revise the subtitle on molecules with "hapticity" molecules dont have hapticity any more than they have "stereochemistry". Ligands do.--Smokefoot 01:04, 25 July 2006 (UTC)

The business on Zeise's salt and Dunitz X-ray structure seems like a giant non sequitur. Yes, these are facts - but pertinent or cruft?--Smokefoot 04:52, 26 July 2006 (UTC)

Well, I like that sort of information, but you're right, in a sense, it's a bit too esoteric for what is needed here. We need something like History of Hapticity to place all these things perhaps. Not sure what to do really. --HappyCamper 21:24, 26 September 2006 (UTC)

Two questions

1. Can a reaction be degenerate? Check out the degenerate page.
2. I think "imaginary symmetry axis" is a little bit wrong, because the symmetry axis is definitely there, it's not imaginary. There is no axle, but I think there is an axis of symmetry. Thoughts??--Chris 20:45, 26 September 2006 (UTC)

I don't understand the first question. Could you rephrase it? As for the second one, well, it's semantics I think. There isn't a "stick" that the two sandwiches rotate around, but it's definitely there. Maybe we should change that to "rotating around the principle axis of symmetry". That would be more precise. --HappyCamper 21:22, 26 September 2006 (UTC)

For the first, I think what is meant is that it is a 'nonreaction reaction' .. hence, it does not generate a new species (but it does generate another species, one can prove that the metal is hopping to another carbon using nifty labeling experiments, e.g. via NMR). I am not good enough in the definition of degeneracy to see if it is indeed a proper term here. For the second, HappyCampers suggestion might be a good one. --Dirk Beetstra ^{T C} 21:43, 26 September 2006 (UTC)

I just meant that degeneracy applies to energy levels, not reactions.--Chris 06:21, 27 September 2006 (UTC)

I made this edit here [2], but turns out principal axis doesn't have a definition for what we are thinking of right now. What's a good one to use? The principle axis is the group element which has the highest symmetry, or something like that? --HappyCamper 00:13, 27 September 2006 (UTC)

I put a link to rotational symmetry, which has the definition you were looking for.--Chris 06:21, 27 September 2006 (UTC)

Proposal

I like the page but I think it could use a quick reference to a simlipifed deffinition of the term Hapticity. Somthing like "In most cases Hapticity is the number of times a ligand unit binds to the traget molecule". Lets face it most pepole who will come to this page will be students wanting a collage level difinition. Bsanchez 12:20, 9 August 2007 (UTC)

Well the spirit of WE-chem is that you could try out a simplified definition - even an imperfect one - and await the edits, but the one you suggest is incorrect. Then again, the term is routinely misused even by professional scientists, who confuse it with denticity. —The preceding unsigned comment was added by Smokefoot (talk • contribs) 03:13, 10 August 2007.

What you say its true, that pepole sould use denticity, however i'm currently at a good uni doing my thesis and every one uses the term hapticity. I'm going to mull it over for a few days to see if I can find a nice way of putting it.Bsanchez 07:31, 16 August 2007 (UTC)

Oh my! Folks at so-called "good uni's" are mortal: maybe you should edit their usage, not the article! Anyway, it's only nomenclature and not a deeply significant principle.--Smokefoot 12:50, 16 August 2007 (UTC)

Graphical Examples

For a topic that is trying to cover a concept that is necessary because of the problems that arise when taking a structure and turning it into a formula, there is a suprising lack of structures shown. Not everyone learns by text and graphical examples in my opinion would help. Even simple ones such as Ferrocene, an η³ propylene, Cp/Cp* etc. Along with this, in the fluxional section maybe show η⁵ Cp and η³ Cp as an illustration of WHY this became so important, I feel that it is easier to understand via an image than text. What can I say, I am just a lowly masters student. PedroDaGr8 (talk) 16:41, 20 November 2008 (UTC)

Wikipedia is not written by professors only, I am sure you can help us with some improvements on this article! --Dirk Beetstra ^{T C} 16:47, 20 November 2008 (UTC)

Edited my above post because of a typo η³ Cp not η⁴ PedroDaGr8 (talk) 18:37, 20 November 2008 (UTC)

Nice addition Smokefoot. I also posted some two on Dirk Beestra's talk page (actually one reaction, a substitution reaction, but one has the haptic bonds colored and one does not). —Preceding unsigned comment added by PedroDaGr8 (talk • contribs) 01:53, 23 November 2008 (UTC)

Misleading sentence

This sentence: "In general the η-notation is only used when there is more than one atom coordinated (otherwise the κ-notation is used, see also hapticity vs. denticity)"

While accurate I feel this is a bit of a misleading sentence, as it is true that if there is only one bond, then dentate is used, but its position in the first paragraph makes it seem as if this is the most important difference.

Maybe it would be better written as:

"In general, the η-notation is only used when two or more contiguous atoms are coordinated (otherwise the κ-notation is used, see also hapticity vs. denticity)." (Maybe substitute adjacent or continuous for contiguous)

Feel free to disagree, I just feel this drives both points home better. More than anything this just stuck out at me in the first paragraph and I feel that the adjacent/contiguous atoms concept should be included in the first paragraph as well.PedroDaGr8 (talk) 01:40, 23 November 2008 (UTC)

Hapticity v. Denticity edit

I want to make an edit to the Hap v. Dent. section but since it is a larger edit, I didn't want to do it without input. Here is the text:

Polydentate Ligand	Haptic Ligand

Hapticity must be distinguished from denticity. While both haptic and polydentate ligands coordinate via multiple coordination sites within the ligand, haptic ligands coordinate via adjacent atoms and polydentate ligands coordinate via non-contiguous atoms. For example, in the coordination of 1,2-bis(diphenylphosphino)ethane (Ph₂PCH₂CH₂PPh₂), to NiCl₂ as dichloro[ethane-1,2-diylbis(diphenylphosphane)-κ²P]nickel(II), above on the right. While the ligand coordinates via two atoms, the coordination is interrupted by the atoms in red. Therefore, the ligand is polydentate and the κ-notation is used. . If the coordinating atoms are contiguous (connected to each other), the ligand is haptic and the η-notation is used, as in titanocene dichloride: dicholorobis(η⁵-2,4-cyclopentadien-1-yl)titanium, above on the left.

Tell me what you think and if I should post it.PedroDaGr8 (talk) 00:48, 8 December 2008 (UTC)

I salute your intentions and admire your willingness to submit your ideas for review - that's thoughtful and gutsy. Your proposed edit makes sense to you and me because we know the rules of hapticity and denticity, but your words and your artwork are incorrect in detail as well as practically speaking. The article is fine as it stands, except that it is obviously authored by those who dont use the terminology in real life and dont know how to draw very carefully. For example, the article as currently (12-2008) implies that the hapticity terminology is used for very simple ligands (like dihydrogen and ethylene, where the bonding is usually unambiguous - not many examples of other bonding modes for these things). In general if you want pictures to illustrate your chemical ideas, you can take the artwork from other articles. For example you could take the M(edta) picture and relabel the caption to indicate that it is kappa-6. I hope that these comments help. The area of real-world nomenclature requires knowing the rules of the nomenclature and knowing the culture in which it is used. My advice, if you want to edit in the chem space, would be to find a more important topic (than nomenclature) less bound to cultural knowledge.

Structure of M(κ⁶-EDTA).

--Smokefoot (talk) 04:13, 8 December 2008 (UTC)

Would you mind explaining what you mean by my words are incorrect in detail? (So I may learn :) )PedroDaGr8 (talk) 04:43, 8 December 2008 (UTC)

If you want to learn factoids, then talk to your chem teacher (although most good instructors will view this area of nomenclature unimportant and would encourage you to focus on something meaty). If you want to learn culture, then critique this awful thing:

--Smokefoot (talk) 05:26, 8 December 2008 (UTC)

References