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I'm perplexed as to why there is no mention of the importance/function of metal complexes in hemoglobin in this article whatsoever. Could someone please expand this article in that specific area? Ajaxkroon 11:02, 29 March 2006 (UTC)
Non-covalent bond? Aren't the bonds considered to be covalent since they are sharing? Olin 17:28, 31 March 2006 (UTC)
Are they not covalent once they are formed? I know they call them coordinate covalent bonds. This is what the article on CCBs has to say:
"A coordinate covalent bond...is a special type of covalent bond in which the shared electrons come from one of the atoms only." Expert needed. JohnJohn 17:16, 21 April 2006 (UTC)
Ligands (L:) in complexes use their lone pairs (if they have them) to form dative covalent bonds with the central metal atom.
Ben 15:24, 22 September 2007 (UTC)
I am removing some ambiguous statements in the Atomic structure of coordination compounds section of the article. Some are not untrue, but I think it is better to give real reasons (which have already been explained) instead of 'rule of thumb'-like statements. (As an example, the reason why late transition metals tend to have lower coordination numbers, is that (for a given oxidation state) late transition metal ions are smaller than the early transition metal ions (Sc3+ is much bigger than Co3+), so less ligands tend to fit around late transition metal ions. But, coordination is governed by overlap between orbitals (a thing also true for main group elements). -- Dirk Beetstra 15:44, 16 May 2006 (UTC)
I just took another look at this for the Wikipedia:WikiProject_Chemistry/Worklist, and it's certainly come a long way (it was only a "Start"), thanks a lot for adding all this content Smokefoot and Beetstra! I wanted to ask a few questions:
Is what has been described as Tri-capped trigonal prismatic actually a Triaugmented triangular prism ??? -- Dirk Beetstra 21:44, 22 May 2006 (UTC)
Reading this article I think that there are some changes required, which I think need some discussion as so many folk have contributed.For example:-
Axiosaurus 11:08, 27 February 2007 (UTC)
Would somebody mind to double check the nomenclature for the porphyrin complexes. www.iupac.org/publications/pac/1987/pdf/5906x0779.pdf It should be [5,10,15,20-tetrakisphenylporphyrinato]copper(II). Unless somebody prove me wrong. —Preceding unsigned comment added by Mandor ( talk • contribs) 14:43, 15 October 2008 (UTC)
The history section has no references. Also, it says Werner overthrew the theory that chirality was only for carbon compounds. Did anyone actually believe that? Crystal whacker ( talk) 02:03, 16 December 2008 (UTC)
Note to Smokefoot:
I see that you have relabeled the Fe(NH3)2F4 complex in the intro as Pt(NH3)2Cl4. I understand the point in the edit summary that you want to show a complex that really exists. However in that case the image needs to be re-drawn. At the moment readers are faced with a caption which says Pt and Cl, but the image shows Fe and F atoms! I think this is much more likely to confuse readers (especially those with little background in inorganic chemistry) than showing a correct image of a complex which doesn't really exist. Dirac66 ( talk) 14:08, 20 November 2009 (UTC)
The Structure of coordination complexes section currently notes: "Ligands are generally bound to said central atom by a coordinate covalent bond (donating electrons from a lone electron pair into an empty metal orbital), and are thus said to be coordinated to the atom." I believe the statement in brackets is false in the sense that it is not merely lone pairs donating, but pi bonds too. Later mentioned complexes exemplify this, and list ethene as ligand, which does not even have lone pairs. —Preceding unsigned comment added by 92.241.199.243 ( talk) 07:32, 17 April 2010 (UTC)
Complexation redirects to this article ... should the same be done with decomplexation? -- Andersneld ( talk) 19:01, 9 January 2011 (UTC)
To Smokefoot re today's edit:
1. Your edit summary reads "rvt naive edit by self-annointed expert Deng". I think it would have been more polite to write "rvt last edit and provide requested source".
2. If you have Greenwood and Earnshaw handy, could you provide the page number for the fact that "virtually all compounds containing metals consist of coordination complexes"? It is not easy to find an explicit statement of this fact - I tried without success in Miessler + Tarr, Cotton + Wilkinson, and Jolly. Dirac66 ( talk) 16:33, 5 August 2011 (UTC)
The article currently states that "Virtually all compounds containing metals consist of coordination complexes", citing Greenwood & Earnshaw. What kind of compound containing a metal doesn't consist of coordination complexes? My understanding was that complexes are independent molecules or ions like [Ti(OH2)63+, whereas an extended structure like titanium dioxide is not a complex. Nonetheless, you see terms like "coordination geometry" in the literature, even when referring to extended structures like TiO2.
On page 912, Greenwood & Earnshaw give a summary of Alfred Werner's original coordination theory. They state that coordination number "may be defined as the number of donor atoms associated with the central metal atom or ion. For many years a distinction was made between coordination number in this sense and in the crystallographic sense, where it is the number of nearest-neighbour ions of opposite charge in an ionic crystal. Though the former definition applies to species which can exist independently in the solid or in solution, while the latter applies to extended lattice systems, the distinction is rather artificial, particularly in view of the fact that crystal field theory (one of the theories of bonding most commonly applied to coordination compounds) assumes that the coordinate bond is entirely ionic! Indeed, the concept can be extended to all molecules. TiCl4, for instance, can be regarded as a complex of Ti4+ with 4 Cl− ions in which one lone-pair of electrons on each of the latter is completely shared with the Ti4+ to give essentially covalent bonds."
What I gather from this paragraph is that the bonding in a molecular complex and in an extended structure can be pretty much the same. That doesn't mean that the names are the same, though. Would most chemists really call TiO2 a complex? We need some textbook quotes that explicitly state what defines a complex.
Ben ( talk) 19:47, 7 August 2011 (UTC)
I see your point, but I think it would mislead readers to use "virtually all metal compounds" when you really mean "a very high proportion of metal compounds". Probably better to say that an enormous number of molecular metal complexes exist and they are a major topic in chemistry. -- Ben ( talk) 21:07, 7 August 2011 (UTC)
It is definitely too broad to say that "virtually all compounds containing metals can be regarded as coordination complexes".
1) First of all, most chemists do not regard TiO2 as a coordination complex. Any atom in a crystalline ionic, metallic, or network solid can be analyzed with regard to its "coordination number". For example, the coordination number of carbon in diamond is 4. Does that make diamond a coordination complex? Of course not. Along those same lines, most chemists would not consider simple metal halides, oxides, sulfides, nitrates, carbonates, sulfates, etc. in the solid state as coordination complexes. They are simply ionic compounds (or covalent compounds, like TiCl4).
2) Secondly, most alkali and alkaline earth metals are very poor Lewis acids (with a few minor exceptions). Do potassium cations form coordination complexes as solids or in solution? Perhaps with a really good chelating ligand, but that's about it. I think it is safe to say that sodium chloride is not a coordination complex. Can we all at least agree about that? (Or are we going to throw away the concept of ionic compounds and just call everything a "coordination complex"?)
3) There are certainly similarities between different "types" of bonds, and of course all bonds boil down to electrostatic attractions. Nevertheless, there seems to still be some value in making distinctions between covalent compounds, ionic compounds, network solids, and coordination complexes, etc. This is perhaps my most important point, as Ben hinted at after his quote above. With the advent of MO theory, most chemists recognize the similarities of different bonds, but most chemists would still not call thousands of metal compounds "coordination complexes" because of the historical labels and the conceptual value of those distinctions. For example, I still teach my students about ionic compounds and covalent compounds, but I also explain that a bond is just a bond.
El Zarco 13:48, 5 November 2011 (UTC)
On first reading, it sounds like the coordination complex is just that atom or ion, rather than the whole thing - which I'm fairly sure is wrong. -- Chriswaterguy talk 02:29, 20 September 2012 (UTC)
The whole article currently is about transition metal complexes with short asides referring to other metals. This leads to a very misleading picture, particularly for lanthanide and actinide complexes. For example the electronic properties section is actually transition metal specific, but it reads as if it isn't. Lanthanides for example with tightly bound f orbitals are described reasonably well using LS coupling scheme unlike the spin only behavior of t metals. They are only subject to small crystal field effects - their pale colors, due to forbidden f-f transitions are virtually independant of the ligand. The magnetism section is similarly one sided. IMHO either new sections on lanthanides, early actininides and main group metals need adding with an appropriate rewrite of the whole article to remove the current "bias", OR we rename it. Axiosaurus ( talk) 09:37, 18 November 2013 (UTC)
The comment(s) below were originally left at Talk:Coordination complex/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Comment(s) | Press [show] to view → |
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The caption for the iron complex should read "trans-...." not "cis-..." The discussion of magnetism is ambiguous, and should include something like the following: Paramagnetism denotes no long-range ordering of the magnetic moments; it applies to gasses, liquids and many solids, comprising ensembles of magnetic moments that point in random directions. A weak interaction takes place between the random moments and an externally applied magnetic field, such that the strength of the field is attenuated. The attenuation arises from field lines moving into the paramagnetic sample, which is said to have a magnetic susceptibility, the symbol for which is the lower-case Greek letter chi [χ], and it can be measured many ways, for example by use of a Guoy balance, but the most sensitive instruments use a superconducting quantum interference device (SQuID). A plot of 1/χ as a function of temperature gives a straight line (a Curie plot), from which (by some simple calculations) the strength of the weak interaction between mostly random moments can be measured (the coupling constant). There should be a link to the respective Wiki pages on magnetism (do they exist? I haven't checked; I'm still learning how to insert links, so I apologize that there aren't any in this comment). The properties of many crystalline and amorphous solids containing magnetic complexes fit this model. Occasionally there are stronger, long-range interactions in solids (long-range as used here means more than the longest dimension of an individual complex, and typically on the order of 10's of nanometers, 10-9 meters, or more. One interaction is such that below a critical temperature (the Curie temperature), the randomly arranged moments all spontaneously line up in the same direction. This type of long-range order is called ferromagnetism. All other arrangements of magnetic moments fall into the broad category of antiferromagnetism. Paramagnetism and ferromagnetism are treated statistically and quantitatively by mean-field theory, an accessible description of which can be found in Kittel and Kroemer [1]. A somewhat less rigorous but easily readable treatment is present in many books on solid state physics [2]. Temperature-dependent antiferromagnetism is generally described by the Curie-Weiss Law, but there are so many variations of how to arrange a repeating pattern of magnetic moments, that a more precise and thorough description is to found in solid state physics textbooks intended for advanced undergraduate students and graduate students [3]. Everything above concerning magnetism is GK (General Knowledge), for which historical references are available in various textbooks, as cited. All of these forms of long-range order have counterparts in bi- and polymetallic complexes, in which the coupling among ions with magnetic moments (of the same or of different magnitudes) can be parallel, antiparallel, or anything in between. It is a fascinating subject and worthy of the many books that could be written on just the magnetism of known complexes, not to mention the difficulty of formulating a mathematical treatment of long-range antiferromagnetic ordering and prediction of the resulting susceptibility. Something more could be said in the article to that effect. Rowanw3 ( talk) 15:16, 14 October 2009 (UTC) |
Last edited at 15:16, 14 October 2009 (UTC). Substituted at 12:15, 29 April 2016 (UTC)
References
OverAll, considering CFT as well, how one can define coordination compound? Vanshita poddar ( talk) 16:58, 24 September 2019 (UTC)
Do halide ions form complexes in water? If yes, please provide some examples. Vanshita poddar ( talk) 17:21, 24 September 2019 (UTC)
The first paragraph currently describes ligands as molecules or ions. Can we add atoms to this list? I'm thinking of xenon in tetraxenonogold(II), but there might be other examples. -- Ben ( talk) 19:49, 18 December 2020 (UTC)
what is the coordination chemistry 2409:4089:119:22C7:B4A1:10FF:FED6:CB5D ( talk) 19:23, 9 January 2024 (UTC)
![]() | This ![]() It is of interest to the following WikiProjects: | ||||||||||
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I'm perplexed as to why there is no mention of the importance/function of metal complexes in hemoglobin in this article whatsoever. Could someone please expand this article in that specific area? Ajaxkroon 11:02, 29 March 2006 (UTC)
Non-covalent bond? Aren't the bonds considered to be covalent since they are sharing? Olin 17:28, 31 March 2006 (UTC)
Are they not covalent once they are formed? I know they call them coordinate covalent bonds. This is what the article on CCBs has to say:
"A coordinate covalent bond...is a special type of covalent bond in which the shared electrons come from one of the atoms only." Expert needed. JohnJohn 17:16, 21 April 2006 (UTC)
Ligands (L:) in complexes use their lone pairs (if they have them) to form dative covalent bonds with the central metal atom.
Ben 15:24, 22 September 2007 (UTC)
I am removing some ambiguous statements in the Atomic structure of coordination compounds section of the article. Some are not untrue, but I think it is better to give real reasons (which have already been explained) instead of 'rule of thumb'-like statements. (As an example, the reason why late transition metals tend to have lower coordination numbers, is that (for a given oxidation state) late transition metal ions are smaller than the early transition metal ions (Sc3+ is much bigger than Co3+), so less ligands tend to fit around late transition metal ions. But, coordination is governed by overlap between orbitals (a thing also true for main group elements). -- Dirk Beetstra 15:44, 16 May 2006 (UTC)
I just took another look at this for the Wikipedia:WikiProject_Chemistry/Worklist, and it's certainly come a long way (it was only a "Start"), thanks a lot for adding all this content Smokefoot and Beetstra! I wanted to ask a few questions:
Is what has been described as Tri-capped trigonal prismatic actually a Triaugmented triangular prism ??? -- Dirk Beetstra 21:44, 22 May 2006 (UTC)
Reading this article I think that there are some changes required, which I think need some discussion as so many folk have contributed.For example:-
Axiosaurus 11:08, 27 February 2007 (UTC)
Would somebody mind to double check the nomenclature for the porphyrin complexes. www.iupac.org/publications/pac/1987/pdf/5906x0779.pdf It should be [5,10,15,20-tetrakisphenylporphyrinato]copper(II). Unless somebody prove me wrong. —Preceding unsigned comment added by Mandor ( talk • contribs) 14:43, 15 October 2008 (UTC)
The history section has no references. Also, it says Werner overthrew the theory that chirality was only for carbon compounds. Did anyone actually believe that? Crystal whacker ( talk) 02:03, 16 December 2008 (UTC)
Note to Smokefoot:
I see that you have relabeled the Fe(NH3)2F4 complex in the intro as Pt(NH3)2Cl4. I understand the point in the edit summary that you want to show a complex that really exists. However in that case the image needs to be re-drawn. At the moment readers are faced with a caption which says Pt and Cl, but the image shows Fe and F atoms! I think this is much more likely to confuse readers (especially those with little background in inorganic chemistry) than showing a correct image of a complex which doesn't really exist. Dirac66 ( talk) 14:08, 20 November 2009 (UTC)
The Structure of coordination complexes section currently notes: "Ligands are generally bound to said central atom by a coordinate covalent bond (donating electrons from a lone electron pair into an empty metal orbital), and are thus said to be coordinated to the atom." I believe the statement in brackets is false in the sense that it is not merely lone pairs donating, but pi bonds too. Later mentioned complexes exemplify this, and list ethene as ligand, which does not even have lone pairs. —Preceding unsigned comment added by 92.241.199.243 ( talk) 07:32, 17 April 2010 (UTC)
Complexation redirects to this article ... should the same be done with decomplexation? -- Andersneld ( talk) 19:01, 9 January 2011 (UTC)
To Smokefoot re today's edit:
1. Your edit summary reads "rvt naive edit by self-annointed expert Deng". I think it would have been more polite to write "rvt last edit and provide requested source".
2. If you have Greenwood and Earnshaw handy, could you provide the page number for the fact that "virtually all compounds containing metals consist of coordination complexes"? It is not easy to find an explicit statement of this fact - I tried without success in Miessler + Tarr, Cotton + Wilkinson, and Jolly. Dirac66 ( talk) 16:33, 5 August 2011 (UTC)
The article currently states that "Virtually all compounds containing metals consist of coordination complexes", citing Greenwood & Earnshaw. What kind of compound containing a metal doesn't consist of coordination complexes? My understanding was that complexes are independent molecules or ions like [Ti(OH2)63+, whereas an extended structure like titanium dioxide is not a complex. Nonetheless, you see terms like "coordination geometry" in the literature, even when referring to extended structures like TiO2.
On page 912, Greenwood & Earnshaw give a summary of Alfred Werner's original coordination theory. They state that coordination number "may be defined as the number of donor atoms associated with the central metal atom or ion. For many years a distinction was made between coordination number in this sense and in the crystallographic sense, where it is the number of nearest-neighbour ions of opposite charge in an ionic crystal. Though the former definition applies to species which can exist independently in the solid or in solution, while the latter applies to extended lattice systems, the distinction is rather artificial, particularly in view of the fact that crystal field theory (one of the theories of bonding most commonly applied to coordination compounds) assumes that the coordinate bond is entirely ionic! Indeed, the concept can be extended to all molecules. TiCl4, for instance, can be regarded as a complex of Ti4+ with 4 Cl− ions in which one lone-pair of electrons on each of the latter is completely shared with the Ti4+ to give essentially covalent bonds."
What I gather from this paragraph is that the bonding in a molecular complex and in an extended structure can be pretty much the same. That doesn't mean that the names are the same, though. Would most chemists really call TiO2 a complex? We need some textbook quotes that explicitly state what defines a complex.
Ben ( talk) 19:47, 7 August 2011 (UTC)
I see your point, but I think it would mislead readers to use "virtually all metal compounds" when you really mean "a very high proportion of metal compounds". Probably better to say that an enormous number of molecular metal complexes exist and they are a major topic in chemistry. -- Ben ( talk) 21:07, 7 August 2011 (UTC)
It is definitely too broad to say that "virtually all compounds containing metals can be regarded as coordination complexes".
1) First of all, most chemists do not regard TiO2 as a coordination complex. Any atom in a crystalline ionic, metallic, or network solid can be analyzed with regard to its "coordination number". For example, the coordination number of carbon in diamond is 4. Does that make diamond a coordination complex? Of course not. Along those same lines, most chemists would not consider simple metal halides, oxides, sulfides, nitrates, carbonates, sulfates, etc. in the solid state as coordination complexes. They are simply ionic compounds (or covalent compounds, like TiCl4).
2) Secondly, most alkali and alkaline earth metals are very poor Lewis acids (with a few minor exceptions). Do potassium cations form coordination complexes as solids or in solution? Perhaps with a really good chelating ligand, but that's about it. I think it is safe to say that sodium chloride is not a coordination complex. Can we all at least agree about that? (Or are we going to throw away the concept of ionic compounds and just call everything a "coordination complex"?)
3) There are certainly similarities between different "types" of bonds, and of course all bonds boil down to electrostatic attractions. Nevertheless, there seems to still be some value in making distinctions between covalent compounds, ionic compounds, network solids, and coordination complexes, etc. This is perhaps my most important point, as Ben hinted at after his quote above. With the advent of MO theory, most chemists recognize the similarities of different bonds, but most chemists would still not call thousands of metal compounds "coordination complexes" because of the historical labels and the conceptual value of those distinctions. For example, I still teach my students about ionic compounds and covalent compounds, but I also explain that a bond is just a bond.
El Zarco 13:48, 5 November 2011 (UTC)
On first reading, it sounds like the coordination complex is just that atom or ion, rather than the whole thing - which I'm fairly sure is wrong. -- Chriswaterguy talk 02:29, 20 September 2012 (UTC)
The whole article currently is about transition metal complexes with short asides referring to other metals. This leads to a very misleading picture, particularly for lanthanide and actinide complexes. For example the electronic properties section is actually transition metal specific, but it reads as if it isn't. Lanthanides for example with tightly bound f orbitals are described reasonably well using LS coupling scheme unlike the spin only behavior of t metals. They are only subject to small crystal field effects - their pale colors, due to forbidden f-f transitions are virtually independant of the ligand. The magnetism section is similarly one sided. IMHO either new sections on lanthanides, early actininides and main group metals need adding with an appropriate rewrite of the whole article to remove the current "bias", OR we rename it. Axiosaurus ( talk) 09:37, 18 November 2013 (UTC)
The comment(s) below were originally left at Talk:Coordination complex/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.
Comment(s) | Press [show] to view → |
---|---|
The caption for the iron complex should read "trans-...." not "cis-..." The discussion of magnetism is ambiguous, and should include something like the following: Paramagnetism denotes no long-range ordering of the magnetic moments; it applies to gasses, liquids and many solids, comprising ensembles of magnetic moments that point in random directions. A weak interaction takes place between the random moments and an externally applied magnetic field, such that the strength of the field is attenuated. The attenuation arises from field lines moving into the paramagnetic sample, which is said to have a magnetic susceptibility, the symbol for which is the lower-case Greek letter chi [χ], and it can be measured many ways, for example by use of a Guoy balance, but the most sensitive instruments use a superconducting quantum interference device (SQuID). A plot of 1/χ as a function of temperature gives a straight line (a Curie plot), from which (by some simple calculations) the strength of the weak interaction between mostly random moments can be measured (the coupling constant). There should be a link to the respective Wiki pages on magnetism (do they exist? I haven't checked; I'm still learning how to insert links, so I apologize that there aren't any in this comment). The properties of many crystalline and amorphous solids containing magnetic complexes fit this model. Occasionally there are stronger, long-range interactions in solids (long-range as used here means more than the longest dimension of an individual complex, and typically on the order of 10's of nanometers, 10-9 meters, or more. One interaction is such that below a critical temperature (the Curie temperature), the randomly arranged moments all spontaneously line up in the same direction. This type of long-range order is called ferromagnetism. All other arrangements of magnetic moments fall into the broad category of antiferromagnetism. Paramagnetism and ferromagnetism are treated statistically and quantitatively by mean-field theory, an accessible description of which can be found in Kittel and Kroemer [1]. A somewhat less rigorous but easily readable treatment is present in many books on solid state physics [2]. Temperature-dependent antiferromagnetism is generally described by the Curie-Weiss Law, but there are so many variations of how to arrange a repeating pattern of magnetic moments, that a more precise and thorough description is to found in solid state physics textbooks intended for advanced undergraduate students and graduate students [3]. Everything above concerning magnetism is GK (General Knowledge), for which historical references are available in various textbooks, as cited. All of these forms of long-range order have counterparts in bi- and polymetallic complexes, in which the coupling among ions with magnetic moments (of the same or of different magnitudes) can be parallel, antiparallel, or anything in between. It is a fascinating subject and worthy of the many books that could be written on just the magnetism of known complexes, not to mention the difficulty of formulating a mathematical treatment of long-range antiferromagnetic ordering and prediction of the resulting susceptibility. Something more could be said in the article to that effect. Rowanw3 ( talk) 15:16, 14 October 2009 (UTC) |
Last edited at 15:16, 14 October 2009 (UTC). Substituted at 12:15, 29 April 2016 (UTC)
References
OverAll, considering CFT as well, how one can define coordination compound? Vanshita poddar ( talk) 16:58, 24 September 2019 (UTC)
Do halide ions form complexes in water? If yes, please provide some examples. Vanshita poddar ( talk) 17:21, 24 September 2019 (UTC)
The first paragraph currently describes ligands as molecules or ions. Can we add atoms to this list? I'm thinking of xenon in tetraxenonogold(II), but there might be other examples. -- Ben ( talk) 19:49, 18 December 2020 (UTC)
what is the coordination chemistry 2409:4089:119:22C7:B4A1:10FF:FED6:CB5D ( talk) 19:23, 9 January 2024 (UTC)