Talk:Asymmetric hydrogenation

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Achieved vs. enjoyed: "enjoyed" may be interpreted not to include the present, but "achieved" carries a slight connotation of permanence (or at least continuation until the present). You use "enjoyed" again later, but because you already used its stronger alternative in "achieved", it fits the pace and flow nicely. Hope the other changes seem reasonable to you, too. 69.196.168.117 (talk) 00:24, 30 October 2012 (UTC)

I suppose this may not be that important, but in the mechanisms, the bond angles for the carbon chains are a little off. It is difficult to show the correct bond angles when dealing with organometallic mechanisms, because of the bonding that tends to occur. I would also make the labels on the arrows consistent with the fonts used in the rest of the schemes in the article (looks like Arial or some other sans-serif font).

In the "Quadrant Model for Asymmetric Hydrogenation", the steric reasoning is correct, but the diagram I can see has the favoured and disfavoured orientations as being the same, when in reality, they should be inverted (i.e. the larger groups should be in the shaded boxes for the disfavoured orientation). .

The rest of the schemes are fine in terms of bond angles/visually (there is some leeway so that the functional groups can actually be seen). Some minor spelling issues, otherwise very nicely written with a good number of primary references to back up the material. It is a very important chemical process and one that should receive even more attention in the coming years as we move to more medical applications as well as industry. Gb105 (talk) 00:54, 30 October 2012 (UTC)

Glitches

role="presentation" class="wikitable mw-collapsible mw-collapsed"

| See discussion

My main and overriding disappointment about this article is the reliance on non-secondary references. Wikipedia's goal, like other encyclopedias, is to give time-honored overviews of topics. The highly detailed, (not to mention, Western academic oriented) references fail that standard. The reasoning for WP:SECONDARY and WP:RECENTISM, WP:NOTABILITY is to provide seasoned perspective and allow the overviewarticle to remain timely for many years, whereas this report (i) risks giving readers unbalanced perspective, (ii) becomes obsolete in a couple of years and (iii) encourages tiny players to vie for attention by citing their own tiny contribution, thus WP:COI. I say this as someone who humbly makes tiny contributions to my own field.

To put my criticism more sharply, the incremental referencing shows that the author is not here to serve readers of Wikipedia, but to use Wikipedia to showcase their agenda.

When I say someone else needs to look at it, I mean a professor or someone with deep experience. Images like this would not appear:

−

File:N-H Imine Hydrogenation.png

File:Noyori DiamineCatalyst.png

Thanks for asking for comments. The article is very nice.--Smokefoot (talk) 13:53, 28 November 2012 (UTC)

:*Thanks for the comments and I'm glad that you're pleased overall. The schemes should be fixed but some technical glitch is refusing to allow me to use the new, correct image for the Noyori catalyst. I will try to correct this again later today. The other doesn't appear in the article at all, so far as I can tell, but as I made it in the first place I have fixed it as well.

:*With regards to the comments about non-secondary references I would like to suggest the following:

::1. I have not published any work or performed any research in asymmetric hydrogenation nor do I know anyone who has. Thus, I have no conflict of interest nor agenda other than writing a FA-status worthy article in the field of chemistry. Asymmetric hydrogenation is merely the first topic I thought of that had not already been done.

::2. The wikipedia policy on secondary sources should be taken with a grain of salt since it is a blanket statement that must cover everything from Classics (where the Illiad/Odyssey are primary works) to modern science (where peer-reviewed primary articles are widely available). While bias and errors may still be present in peer-reviewed articles, the chance is much reduced compared to something like a news report. Additionally, I never offer my own interpretation of the data but rather use the citations as a means of recording where the data comes from. If I say a result is "good", "very good", or "excellent" I (attempt to) use those words to reflect numbers that fall into a range where those descriptors are commonly used in chemistry review articles in either than field or a related one. If I have failed to do that, or to offer a reasonable point of view in my reporting, then please suggest where this is the case and I will endeavor to correct it.

::3. Notability seems unquestionable in this case. Undue weight might be argued, though I have attempted to give both reasonable weight and reasonable coverage.

::4. On the issue of recentism, I can see where you are coming from, however, I believe that the more modern sources fall into the category of "well-sourced information that will remain notable over time" rather than simple clutter.

Bmalbrecht (talk) 14:41, 28 November 2012 (UTC)

:Ah, the rules dont apply to you - it must be the guidelines that are wrongheaded. What other possible interpretation is there??? CAS reviews many tens of thousands of papers annually, and you have the insight into that microscopic fraction that should be highlighted. Delicious. --Smokefoot (talk)

::I have frustrated you and I apologize. It was not my intention. Rather my intention was to suggest why several featured articles within chemistry may make heavy use of the primary literature (Aldol Reaction, Atom, DNA Nanotechnology, Synthetic Diamonds, Oxygen Toxicity) without compromising their integrity or value. One compromise that has occurred to me is to include a "Further Reading" list of some sort where I can place a number of references to secondary literature. Anyone concerned could read these to help determine if the perspective given in the article is far off base. Another would be to remove some material on which limited research has been done (Furans and/or Thiophenes) in favour of the section I have promised Jimfbleak on asymmetric heterogeneous hydrogenation (which are a bit older and will present greater opportunity for cross-referencing with some secondary sources).Bmalbrecht (talk) 02:06, 29 November 2012 (UTC)

From looking at the references, it does look like quite a few review articles are cited, as well as reputable primary sources like Nobel prize speeches. I am puzzled by the comment about the bent towards western academics--what's missing? However, I agree about WP:COI. The most egregious example that I have no energy to deal with is in the Hajos-Parrish article...I feel certain it's wrong to write about your own work. We should go a little easier on Bmalbrecht--he's obviously put quite a bit of work into this, and has nothing to gain or lose by taking any particular perspective. Eugene Kwan (talk) 04:22, 9 December 2012 (UTC)

Comments regarding the "Metals" section of the article.

Hey there,

I noticed something and I will be working to clean it up over the coming days, but I just wanted to notify those who follow the page here first.

The section on metals needs to be re-worked in my opinion. The plan is to move a lot of the content already found on the page (formerly titled Noyori AH) Asymmetric transfer hydrogenation into the Platinum-group metals subsection. This will likely include a discussion of the mechanism (differences between different metals in the group) and substrate scopes. Additionally examples will be added to the industrial applications section which can be considered novel or noteworthy.

Balonlon (talk) 15:38, 28 November 2023 (UTC)

:@Smokefoot Can you please stop reverting my edits? Balonlon (talk) 16:03, 2 December 2023 (UTC)

::If something I write is wrong, please cite sources to the contrary, since I am clearly citing mine. Balonlon (talk) 16:04, 2 December 2023 (UTC)

::You dont know the area well. That much is clear from your edits. --Smokefoot (talk) 16:06, 2 December 2023 (UTC)

:::Again, you aren't providing evidence to the contrary for me to clearly see that I have misunderstood the literature. Smokefoot

:::Balonlon (talk) 16:10, 2 December 2023 (UTC)

::::If you want to learn, look at the practical apps in the Blacker reviews. One previous editor admired Andreas Pfaltz, who published on Ir and R2P-oxazolines. I dont know why.

::::One doesnt say that Ir operates this way and Ru operates that way because the behavior of these metals depends so much on their ligands. See Shvo catalyst vs RuCl2(PPh3)3. Or Ikariya Rh TsDPEN vs classical Rh-cod. Citing outer sphere ET is inappropriate, outer sphere in TH would be inner sphere in ET world. I have worked on this area for a long time (not that it matters here). I stopped previous editors from advancing the Noyori Asymmetric TH articles because the editor did not understand this complicated topic well. Sorry to be so awful and smug, I hate sounding like this but its a matter of broad truth vs superficial awareness. Or I can walk away and let you do your thing, then come back in a month and try to clean up. --Smokefoot (talk) 16:33, 2 December 2023 (UTC)

:::::Now we are getting somewhere.

:::::Look lets get the "inter-personal" part out of the way first. I respect your authority as a senior editor, again, it is the reason I was sure to get your attention from the get go on this. That said, I wish to contribute meaningfully. I would appreciate being treated in a professional manner rather then dismissed on assumed ignorance.

:::::Addressing the chemistry itself now:

:::::* As this article and Transfer hydrogenation are separate by design. As such, I believe your comment on the applicability of outer sphere ET is obsolete. Since we are dealing strictly with asymmetric hydrogenations here, it is appropriate to discuss in terms of inner/outer sphere transfers on the distinction that in inner a metal-substrate bond is formed and in the other it is not.

:::::* Yes, there is no denying that the specifics of each metal and each ligand play a major role here. That said, some overarching traits still exist, which would provide legitimacy to say that some metal complexes do in fact operate in a certain way. For example, regarding Shvo catalyst vs RuCl2(PPh3)3. Several papers show that for RuCl2(PPh3)3 to effectively carry out AH, it must first be converted into the hydrogen containing form, in fact the Wikipedia article about it specifically refers to it as a precatalyst when discussing its hydrogenation abilities. The chlorides have no active role in the catalytic cycle. Once in the dihydride form is generated, the reaction proceeds in an outer sphere mechanism, just like Shvo. [https://pubs.acs.org/doi/10.1021/ja016817p Ref 1] [https://pubs.acs.org/doi/10.1021/ja411374j Ref 2]

:::::I will start with these comments while I review the Ikariya Rh TsDPEN vs classical Rh-cod mechanisms. Balonlon (talk) 17:54, 2 December 2023 (UTC)

This will take a while. I am not trying to push you around because I am some sort of senior editor. There is no hierarchy here, and many long term editors are rank amateurs. A whole crowd of them swept through chemical articles at the inception of Wiki-chemistry, requiring years on repairs. I am trying to push you around because I am a subject expert and assume that you are not. Maybe I am wrong. There are so few organometallic chemists on wikipedia that my assumption has proven valid for years.

Lets start with hydrogenation,

AH is merely a perturbation on hydrogenation. Nothing fancy. Just chiral L's. We need consensus on hydrogenation.
All metal-based homogeneous hydrogenation catalysis involves metal hydrides. Shvo, RuHClP3, Wilkinsons, Ru-binap-amine, CymeneRu-DPEN, Crabtree, ... all of them. One can hydrogenate without metal hydrides but such reactions are not catalytic.
Lets just skip the arguments about inner vs outer sphere terminology, we can deal with definitions after we get the science worked out.
But the very idea that some metals are inclined toward TH vs normal hydrogenation is questionable IMHO and dangerously misleading to readers. The idea was inserted into this article by an organic chemist (the admirer of Pfaltz). Especially Ir: its an old favorite for MH2 mechansim (Crabtree) as well as pretty good for TH (Ikariya). So here's what worries me: some kid reads this article and comes away with the idea that Ir or Ru or Pt is inclined toward one mechanism or the other. There might be some trends, but its hardly a core concept. Yes, my impression is that more TH catalysts are based on Ru than on Rh, but I dont know if that intuition is correct or useful or documentable.
Hydrogenation of polar substrates (ketones, iminium, etc) is easier and more extensive with TH than MH2 and alkenes (except electrophilic ones) vastly favor MH2.

My 2 cents. --Smokefoot (talk) 21:20, 2 December 2023 (UTC)

:* If it wasn't something fancy, there would be no need for a separate page on it. It isn't trivial as just having chiral L's otherwise it would be much easier to carry out.

:* Yes, but the point is that the catalyst in question has the same underlying mechanism despite varying ligands.

:* Sure

:* Even if the specifics in some systems may differ, I would argue that having a more comprehensive overview of the mechanisms is necessary. The fact that Ir mechanism differs from the Rh mechanism is noteworthy. The fact that Ru as the most used metal (if your assertion is indeed correct) has a wildly different mechanism all together should be presented clearly. I still fail to see where you draw the conclusion that these metals don't in fact have specific mechanisms that they alternate on based on ligands. For Ir its 1/3 vs 3/4 and for Rh its dihydride vs unsat. The ligands "decide" which of the pair will happen, but Ir will not undergo the dihydride mechanism based on any current literature.

:Balonlon (talk) 09:09, 3 December 2023 (UTC)

:::OK, I'll stop arguing for a while, and you try out your versions.

:::Agreed chiral ligands are "fancy", but the underlying mechanisms are identical to normal hydrogenations.

:::In terms of "comprehensive mechanism", there is the quadrant model for MH2 processes but there is no comprehensive mechanism that is specific for AH by TH catalysts, although the ligands just happen to be chiral. I dont know why the ratio of MH2 vs TH pathways for various metals interests you. Almost all TH (and ATH) involve protic ligands (hydroxycyclopentadienyl (Shvo), TsDPEN, ethylenediamine, and more complicated versions).

::::Further comments:

:::*Somehow, it would be good to define bifunctional catalysis, which is somehow intertwined into TH.

:::*The long list of so many substrate classes should be removed IMHO. Its ridiculous to attempt this cataloguing because the literature is vast, the list is strangely selective (seeWP:UNDUE), the refs are obsolete, and primary (WP:SECONDARY or even WP:TERTIARY). Also importantly, the long listing detracts from readability.

:::*One approach to identifying ligands would be to look at the applications (not those defined as "useful" by academic, but by real $-making apps). My guess is that Josiphos ligands will be up there. Good luck, I'll shut up for a while.

--Smokefoot (talk) 15:00, 3 December 2023 (UTC)

:I will be signing off for today in a moment. Just wanted to reply quickly.

:I very much agree with the second bullet point, it is something I hope to work on soon. I feel like a very clear way to discuss ligands and substrates is in direct relation to one another in a similar way as [https://pubs.rsc.org/en/content/articlelanding/2021/cs/d0cs00082e this paper] has done with first row metals, but instead subdividing each underlying functional group by complexes (metal + ligands) which illustrate "why it works" in each case.

:I haven't had time today but the $-making apps are also something worth paying attention to moving forward.

:Feel free to leave comments. I do find them very helpful in the writing process. Balonlon (talk) 20:44, 3 December 2023 (UTC)