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Hello! I may be wrong, but doesn't neutral Cobalt tetranorbornyl have 13 valence electrons rather than the 11 mentioned under "Bulky ligands"? — Preceding unsigned comment added by Livedevilslivedevil ( talk • contribs) 16:26, 14 July 2012 (UTC)
M-M bonding (Mn2(CO)10, Fe3(CO)13 connected to cluster), agostic ligands, NO (linear, bent) and SO2 (planar, pyramidal). And much more.-- Smokefoot 21:52, 16 May 2006 (UTC)
I've renamed 'mismatch in ligand and metal orbital energy' to 'coordination compounds' and moved it to the end, so we can discuss organometallic examples that do not obey the 18-e rule first. TiCl4 has gone into this section - it will never obey the 18-e rule, being Ti(IV) and having weak-field ligands, so is a bad example to give under lower electron counts. Perhaps a better example is needed? This section should be compounds that might obey the 18-e rule, but don't, just as the higher electron counts section is compunds that should have 18-e but actually have more. Also, I expanded a bit and tideid up some of the English.-- Brichcja 08:43, 23 May 2006 (UTC)
Yeah, that sounds reasonable. I kinda feel that the 18-e rule is really only meant to apply to organometallic compounds (yeah, I know, what exctly constitutes an organometallic compound?), so maybe we could split it into organometallic and non-organometallic sections, and then split the former into more and fewer than 18 and give reasons? There's no point in having a huge debate about TiCl4 when the rule wasn't meant to apply to it anyway - it says at the top of the page which classes of compounds it works well for.-- Brichcja 09:28, 23 May 2006 (UTC)
No, I completely disagree with that. The 18-electron rule only applies to a relatively small percentage of TM compounds, so I see no point in introducing as a principle for all TM complexes and then pointing out that the majority of them don't obey it. To quote Elschenbroich and Salzer on the 18-e rule (p186, 2nd ed.): 'Thermodynamically stable transition metal organometallics are formed....' (my italics).-- Brichcja 11:20, 23 May 2006 (UTC)
Of course many non-organometallic compounds have 18-electrons. However, the 18-electron rule (which is what this entry is about) is only meant to apply to organometallic compounds (including the carbonyl compounds). I understand what you're saying, but I don't think you can go extending the rule to systems that it's not meant to cover even though your point is valid. I still think discussing it wrt organometallics is best, and then putting in non-organometallic (counter)examples. Housecroft and Sharp (1st ed., p591): low oxidation state organometallic complexes tend to obey the 18-electron rule. (My italics).-- Brichcja 16:03, 23 May 2006 (UTC)
Looking much better now. I tidied up generally, correcting the English etc, but rewrote the applciations section a bit to emphasise the pi-acid and low-oxidation state sentiments expressed above. I removed hydrides and alkyls from the list of typical ligands - they're not pi-acids, and often don't give 18e complexes (e.g. [WMe6]2-, {[ReH9]2-!). I replaced them with phosphines and olefins, which more often do. In this, I think the application of the 18e rule has been shifted away from specifically organometallics to pi-acid complexes in low ox states.
I think we shpould replace Cp and Cp* with eta5-C5H5 and eta5-C5Me5, but I can't be bothered right now. And also, I don't think "High spin metal complexes have orbitals half-occupied. These orbitals could be filled by lone pairs of electrons from donor ligands, when the ligand is capable of pairing (some of the) unpaired electrons." makes much sense. Anyhow, off to bed now.-- Brichcja 22:53, 23 May 2006 (UTC)
Compounds deviating from 18 VE indeed tend to be more reactive, nickelocene is a perfectly stable compound, as long as you don't feed it anything to react with .. just as with ferrocene, ferrocene will also react with oxygen, but it needs some activation.
Indeed, I think we are getting there more and more, we need some more examples (we have quite a number, already, I guess we need some 'difficult' ones (where the ligands are participating, e.g. bipy vs it's radical anion and dianion, or maybe the pyridine diimine ligand, also important in the electron counting article to show that counting is sometimes difficult or even ambiguous!!), and we need some references.
One remark, there is a statement "late transition metals often violate the 18 VE rule", because they have a d-orbital which is high in energy. I still believe that the same is true, if not more true, for ETM. These compounds tend to be happy with 16 VE or less, some examples:
It may be that I see things here the wrong way, but well. That's why it is on the talk-page ..
I'll have a look around in my personal library for some nifty references, though I think most will be about electron deficient compounds .. -- Dirk Beetstra 07:58, 24 May 2006 (UTC)
As Brichcja already mentioned, the description of making high-spin compounds low spin compounds (I changed it .. but) is not correct. What I mean is, that, e.g., coordinating CO to certain paramagnetic compounds makes all the energies of the ligands lower, resulting in spin pairing and hence diamagnetic (or better, low spin) compounds, I must confess, I don't know how the mechanism here goes (I guess the CO has to dock first, and hence, there has to be room for that, before the orbitals go to low spin, can somebody please try to rewrite that into something more scientifically correct?? -- Dirk Beetstra 09:26, 24 May 2006 (UTC)
I think what we need is a spectrochemical series page - there's link to a ligand-field page that also doesn't exist, and high vs low spin and pairing energy etc could go there Compounds that obey the 18-electron rule are all low-spin!. Apologies for [ReH9]2- - I obviously can't count!-- Brichcja 10:16, 24 May 2006 (UTC)
I agree to that, but maybe we could start that from this page, or from the ligand page (or start the ligand-field page with that list). Make a list of ligands sorted by field strength, and put in a small explanation why that list is important. The pages low_spin and high_spin do exist .. oh, wait, they redirect to ligand field theory .. that may be what we are looking for, then the spectroscopic series is better on the ligand-page (I'll make a redirect from ligand field to ligand field theory) -- Dirk Beetstra 10:32, 24 May 2006 (UTC)
have a look at the crystal field theory page - there's a lot there already.-- Brichcja 19:03, 24 May 2006 (UTC)
I have made a start with a table on Ligand containing ligands, sorted by Field strength. I don't have much time during the day, I will try to go on with it, please feel free to do some as well, I will save regularly. -- Dirk Beetstra 13:27, 24 May 2006 (UTC)
I propose removing the paragraph about the 32 electron rule near the top. There's no such thing - the only hits for this on Google come from this article (ie, whoever wrote it made it up), whereas you get millions for the 18 electron rule. I don't even think the concept is valid, as lanthanide ions (especially) show little if any covalency in their bonding, so they never have any electrons in their outermost s or d orbitals. If anything, it would be a 14 electron rule as the only valence orbitals (in the ions) are the f-orbitals. I challenge anybody to show me a compound that obeys this rule. Any thoughts?? —The preceding unsigned comment was added by Brichcja ( talk • contribs).
This is expected to be a thing, but only in the early actinides around uranium where the 5f orbitals are relativistically destabilised to the point that they participate on the same footing as 6d, 7s, and 7p. Double sharp ( talk) 15:39, 14 July 2016 (UTC)
Prof. Ged Parkin sent me an email with some references which, he thinks, could be used to upgrade this article. Please have a look:
(He is co-author in all three of them, it seems best that I suggest them here). -- Dirk Beetstra T C 15:22, 1 February 2008 (UTC)
I removed this hidden comment from the article:
In practice, of course, orbitals cannot directly accept electrons, otherwise one would encounter ions such as Fe10− and Pt8−. However,There are also some higher-energy anti-bonding orbitals). The complete filling of these nine lowest-energy orbitals with electrons, whether those electrons originate from the metal or from any ligands, is the basis of the 18-electron rule.
If it is correct, perhaps it should be included in the article. Biscuittin ( talk) 17:53, 29 December 2011 (UTC)
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![]() | The contents of the 16-Electron complex page were merged into 18-electron rule on 20 December 2009. For the contribution history and old versions of the redirected page, please see its history; for the discussion at that location, see its talk page. |
Hello! I may be wrong, but doesn't neutral Cobalt tetranorbornyl have 13 valence electrons rather than the 11 mentioned under "Bulky ligands"? — Preceding unsigned comment added by Livedevilslivedevil ( talk • contribs) 16:26, 14 July 2012 (UTC)
M-M bonding (Mn2(CO)10, Fe3(CO)13 connected to cluster), agostic ligands, NO (linear, bent) and SO2 (planar, pyramidal). And much more.-- Smokefoot 21:52, 16 May 2006 (UTC)
I've renamed 'mismatch in ligand and metal orbital energy' to 'coordination compounds' and moved it to the end, so we can discuss organometallic examples that do not obey the 18-e rule first. TiCl4 has gone into this section - it will never obey the 18-e rule, being Ti(IV) and having weak-field ligands, so is a bad example to give under lower electron counts. Perhaps a better example is needed? This section should be compounds that might obey the 18-e rule, but don't, just as the higher electron counts section is compunds that should have 18-e but actually have more. Also, I expanded a bit and tideid up some of the English.-- Brichcja 08:43, 23 May 2006 (UTC)
Yeah, that sounds reasonable. I kinda feel that the 18-e rule is really only meant to apply to organometallic compounds (yeah, I know, what exctly constitutes an organometallic compound?), so maybe we could split it into organometallic and non-organometallic sections, and then split the former into more and fewer than 18 and give reasons? There's no point in having a huge debate about TiCl4 when the rule wasn't meant to apply to it anyway - it says at the top of the page which classes of compounds it works well for.-- Brichcja 09:28, 23 May 2006 (UTC)
No, I completely disagree with that. The 18-electron rule only applies to a relatively small percentage of TM compounds, so I see no point in introducing as a principle for all TM complexes and then pointing out that the majority of them don't obey it. To quote Elschenbroich and Salzer on the 18-e rule (p186, 2nd ed.): 'Thermodynamically stable transition metal organometallics are formed....' (my italics).-- Brichcja 11:20, 23 May 2006 (UTC)
Of course many non-organometallic compounds have 18-electrons. However, the 18-electron rule (which is what this entry is about) is only meant to apply to organometallic compounds (including the carbonyl compounds). I understand what you're saying, but I don't think you can go extending the rule to systems that it's not meant to cover even though your point is valid. I still think discussing it wrt organometallics is best, and then putting in non-organometallic (counter)examples. Housecroft and Sharp (1st ed., p591): low oxidation state organometallic complexes tend to obey the 18-electron rule. (My italics).-- Brichcja 16:03, 23 May 2006 (UTC)
Looking much better now. I tidied up generally, correcting the English etc, but rewrote the applciations section a bit to emphasise the pi-acid and low-oxidation state sentiments expressed above. I removed hydrides and alkyls from the list of typical ligands - they're not pi-acids, and often don't give 18e complexes (e.g. [WMe6]2-, {[ReH9]2-!). I replaced them with phosphines and olefins, which more often do. In this, I think the application of the 18e rule has been shifted away from specifically organometallics to pi-acid complexes in low ox states.
I think we shpould replace Cp and Cp* with eta5-C5H5 and eta5-C5Me5, but I can't be bothered right now. And also, I don't think "High spin metal complexes have orbitals half-occupied. These orbitals could be filled by lone pairs of electrons from donor ligands, when the ligand is capable of pairing (some of the) unpaired electrons." makes much sense. Anyhow, off to bed now.-- Brichcja 22:53, 23 May 2006 (UTC)
Compounds deviating from 18 VE indeed tend to be more reactive, nickelocene is a perfectly stable compound, as long as you don't feed it anything to react with .. just as with ferrocene, ferrocene will also react with oxygen, but it needs some activation.
Indeed, I think we are getting there more and more, we need some more examples (we have quite a number, already, I guess we need some 'difficult' ones (where the ligands are participating, e.g. bipy vs it's radical anion and dianion, or maybe the pyridine diimine ligand, also important in the electron counting article to show that counting is sometimes difficult or even ambiguous!!), and we need some references.
One remark, there is a statement "late transition metals often violate the 18 VE rule", because they have a d-orbital which is high in energy. I still believe that the same is true, if not more true, for ETM. These compounds tend to be happy with 16 VE or less, some examples:
It may be that I see things here the wrong way, but well. That's why it is on the talk-page ..
I'll have a look around in my personal library for some nifty references, though I think most will be about electron deficient compounds .. -- Dirk Beetstra 07:58, 24 May 2006 (UTC)
As Brichcja already mentioned, the description of making high-spin compounds low spin compounds (I changed it .. but) is not correct. What I mean is, that, e.g., coordinating CO to certain paramagnetic compounds makes all the energies of the ligands lower, resulting in spin pairing and hence diamagnetic (or better, low spin) compounds, I must confess, I don't know how the mechanism here goes (I guess the CO has to dock first, and hence, there has to be room for that, before the orbitals go to low spin, can somebody please try to rewrite that into something more scientifically correct?? -- Dirk Beetstra 09:26, 24 May 2006 (UTC)
I think what we need is a spectrochemical series page - there's link to a ligand-field page that also doesn't exist, and high vs low spin and pairing energy etc could go there Compounds that obey the 18-electron rule are all low-spin!. Apologies for [ReH9]2- - I obviously can't count!-- Brichcja 10:16, 24 May 2006 (UTC)
I agree to that, but maybe we could start that from this page, or from the ligand page (or start the ligand-field page with that list). Make a list of ligands sorted by field strength, and put in a small explanation why that list is important. The pages low_spin and high_spin do exist .. oh, wait, they redirect to ligand field theory .. that may be what we are looking for, then the spectroscopic series is better on the ligand-page (I'll make a redirect from ligand field to ligand field theory) -- Dirk Beetstra 10:32, 24 May 2006 (UTC)
have a look at the crystal field theory page - there's a lot there already.-- Brichcja 19:03, 24 May 2006 (UTC)
I have made a start with a table on Ligand containing ligands, sorted by Field strength. I don't have much time during the day, I will try to go on with it, please feel free to do some as well, I will save regularly. -- Dirk Beetstra 13:27, 24 May 2006 (UTC)
I propose removing the paragraph about the 32 electron rule near the top. There's no such thing - the only hits for this on Google come from this article (ie, whoever wrote it made it up), whereas you get millions for the 18 electron rule. I don't even think the concept is valid, as lanthanide ions (especially) show little if any covalency in their bonding, so they never have any electrons in their outermost s or d orbitals. If anything, it would be a 14 electron rule as the only valence orbitals (in the ions) are the f-orbitals. I challenge anybody to show me a compound that obeys this rule. Any thoughts?? —The preceding unsigned comment was added by Brichcja ( talk • contribs).
This is expected to be a thing, but only in the early actinides around uranium where the 5f orbitals are relativistically destabilised to the point that they participate on the same footing as 6d, 7s, and 7p. Double sharp ( talk) 15:39, 14 July 2016 (UTC)
Prof. Ged Parkin sent me an email with some references which, he thinks, could be used to upgrade this article. Please have a look:
(He is co-author in all three of them, it seems best that I suggest them here). -- Dirk Beetstra T C 15:22, 1 February 2008 (UTC)
I removed this hidden comment from the article:
In practice, of course, orbitals cannot directly accept electrons, otherwise one would encounter ions such as Fe10− and Pt8−. However,There are also some higher-energy anti-bonding orbitals). The complete filling of these nine lowest-energy orbitals with electrons, whether those electrons originate from the metal or from any ligands, is the basis of the 18-electron rule.
If it is correct, perhaps it should be included in the article. Biscuittin ( talk) 17:53, 29 December 2011 (UTC)