Talk:Octahedral molecular geometry

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[edit] Recent changes (July 3, 2006)

A number of revisions were made to this article by me today and I welcome discussion or debate of any of them. Such a discussion would probably teach each of us some chemistry and some lessons on communicating. So please look at the difference in the previous and current editions and make comments.

• I replaced the example of nickel sulfate hydration. The paragraph begins with a statement about many complexes reacting in water. Non-sequitur aside, so what. And the depolymerization of nickel sulfate does not bear particularly on the reactivity of octahedral complexes. etc. My experience is that molecular transformations are far easier to explain and the facts are usually clearer. Of course the section does not really highlight anything peculiar to octahedral cmpxs, right?
• some residual ideas about low field ligands only absorbing low E photons is tempting but too simplistic - all sorts of charge transfer and other bands occur. Also weak field ligands relax the selection rules through allowing high spin states that opens the way for lots of action as seen in Tanabe Sugano diagrams. etc.
• The section on CFT is tricky. I rephrased it focusing on which orbitals bump into ligands.
• Octahedral tend to be more stereochemically rigid than say tetrahedral complexes, perhaps we should mention that.
• Bailar twist of M(en)3 species is a typical topic under this heading.

I also replaced "this" with more definite subjects, which are easier to understand. Dig in! --Smokefoot 00:20, 4 July 2006 (UTC)

Hi Smokefoot, communication is very important indeed. Some edits ago one of the editors requested expert help for some reason and proposed to merge the junker, the why and where unexplained. I am unfamiliar with the phrase junker, i can only hope it is not cursing or derogating because that would be impolite.

My comments:

• what happened with the centence are arranged around a central atom with 4 of them in the same plane as the central atom at the corners of a square (basal positions) and two more at either side of the plane forming a straight line with the central atom (the apical postions). should be basic stuff
• the nickel sulfate hydration bit is how Werner started the whole thing in the first place, unfortunatly I no longer have the reference.
• My Atwood tells me that most Werner type reactions take place in water, I should add a citation..
• the topics you mention above Tanabe Sugano diagrams,Bailar twist etc I would love to see in this article!

V8rik 16:32, 4 July 2006 (UTC)

[edit] Chirality?

Hi all, I would like to state one question, is that the delta/lambda convention in chirality section is reversed? I have read some ref. books as well as lecture notes and I found that they are revered, do you guys think so? Kelix 11:07, 6 October 2007 (UTC)

You have good eyes.--Smokefoot 15:45, 6 October 2007 (UTC)

[edit] Molecular geometry infobox

I agree with Smokefoot (Jan.19) that the new infobox needs discussion. One problem is that this box is really at a first-year chemistry level (except for the phrase "symmetry group") whereas the rest of the article is more advanced. However if an elementary summary is deemed useful, then the information could be more accurate. Here are some comments and suggestions:

1. Symmetry group O_h: True only when the six ligands are identical (and monoatomic). If the example molecule is placed at the beginning (before the symmetry group), then it will be clearer that the subsequent information is for that example.

2. "Electron directions". Not a recognized term. If you are thinking of the VSEPR model, I suggest "Electron pairs about central atom". But in this case SF₆ is not the best example since modern quantum calculations show that most of the bonding is due to only 4 electron pairs. A better example would be WF₆ for which there is no doubt that 6 electron pairs participate in bonding.

3. "Atom directions". Perhaps "Ligands about central atom"

4. Polarity. Some octahedral molecules are polar, some are not. An example with six identical ligands (SF₆, WF₆, etc) is nonpolar so we can put zero.

5. Hybridization: For SF₆ Pauling (circa 1932) proposed sp³d² but modern calculations show that d participation is minimal. Again a better example is WF₆ which is generally agreed to be d²sp³ (with d first as its energy is lower). Dirac66 (talk) 02:00, 20 January 2008 (UTC)

Changes 1-3 have been applied to the infobox template. Change 4 is conditional to the molecule (as you stated) and thus only applies to this page and not other molecular geometry pages (some of them don't have a listed polarity). The hybridization syntax has been temporarily removed from the template, but the page syntax has been left intact. I'm reading on molecular orbital theory right now (not here because this article didn't exactly provide the information I was hoping for).·· TVO_talk 22:14, 20 January 2008 (UTC)

This is much better, thank you. For polarity I think it is understood that 0 refers to WF₆ because this example is now specified at the top. I am also glad to see that the infobox is now a little smaller so that the first screen shows the more advanced text as well as the elementary infobox. Other geometries can be done similarly, and it is always best to choose an example with identical ligands (AX_n). Dirac66 (talk) 02:47, 21 January 2008 (UTC)

Then should the infoboxes for trigonal pyramidal, tetrahedral, and square planar be readded (they've been commented out)?·· TVO_talk 16:55, 21 January 2008 (UTC)

I think that with revisions similar to those made for octahedral, the infoboxes now have value as an elementary introduction. We have to remember that Wikipedia is intended for a general readership, and that not everyone has the background to understand the rest of the article which is at a higher level. Some readers will just want a one-minute definition of each geometry. However it seems not everyone agrees with me. Dirac66 (talk) 22:24, 21 January 2008 (UTC)

That effectively sums up my line of thinking. It's likely that many of the readers of these pages (the geometry ones) are first or second year students of chemistry. Right now I'm removing hybridization syntax from the geometry pages based on a third opinion from User:Bduke. Since the revisions were made to the template, they apply automatically to all the pages.·· TVO_talk 22:49, 21 January 2008 (UTC)