Talk:Atomic carbon

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Dicarbene[edit]

How is this a dicarbene?? Isn't a carbene "a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons"? Atomic carbon has a valence of 0 and four unshared electrons.--Spmoura (talk) 05:51, 8 August 2012 (UTC)[reply]

Amphotericity[edit]

Specific evidence, preferably experimental, of atomic carbon behaving as a lewis base and lewis acid as stated is required. The statements appear dubious as atomic C has a triplet ground state. Axiosaurus (talk) 15:41, 20 August 2014 (UTC)[reply]

Carbon suboxide or the bis(carbonyl) adduct is formed in the gas phase within a combustion environment, by successive adduction:

C + CO → CCO

CCO + CO → C(CO)
₂

The reverse reaction is also possible through UV photolysis. The triple ground-state is not the sole important in determining atomic carbon's chemical behaviour at low temperature. Plasmic Physics (talk) 22:44, 20 August 2014 (UTC)[reply]

C₃O₂ is not normally described as a complex of atomic C with carbon monoxide. The short C-C bond lengths indicate double bond character and simple Huckel theory predicts C chains with odd numbers are more stable. The description of atomic carbon as a Lewis base and a Lewis acid still needs a reference. Axiosaurus (talk) 10:31, 21 August 2014 (UTC)[reply]

The definition of a coordinate bond does not exclude double bond character, it actually allows for it. Under carbonyl complexes it actually discusses case of it. I'll reference the definition of a Lewis base/acid tomorrow for your convenience. Plasmic Physics (talk) 12:09, 21 August 2014 (UTC)[reply]

thanks for reading the comment- I'll be interested to see what has lead to your conclusions about carbon. Axiosaurus (talk) 14:57, 21 August 2014 (UTC)[reply]

I can only see transition metals with the traditional description of back bonding into a CO antibonding orbital in the metal carbonyl article you refer to (an omission in this article is a discussion of main group metals- e.g. AlCl₃ which forms a weak CO complex- no back bonding). Have you a reference for C₂O₃ described as a carbonyl complex rather than as a relative of cumulene? Axiosaurus (talk) 10:13, 22 August 2014 (UTC)[reply]

That is besides my point, which is that a coordinate bond is not defined by any specific bond order. Rather it is a heuristic concept used to artificially subdivide a particular molecule to better understand it within a certain context. There is no defining characteristic which says that a bond must be coordinate. For instance, the ammonia-borane compound is sometimes viewed as a complex of ammonia coordinating to borane, alternatively, it is viewed as a zwitter-ionic molecule. There is no reason why it cannot be both. As it is a heuristic concept, it can be indiscriminately applied to any bond(s) within any molecule, and subject to symmetry conditions, as appropriate for the context. The consequence, is that carbon suboxide can be describe as both as a double carbonyl complex of carbon, and as a "relative of cumulene. Note the statement giving it as an example allows for either interpretation, but basically says that the electrophilicity of atomic carbon is satiated by reacting with two carbonyl groups, meaning that it reaches a full valence. Plasmic Physics (talk) 11:31, 22 August 2014 (UTC)[reply]

So this is not a referenceable description- it is your own interpretation. As such it is an interesting debating point, but should it be in an encyclopedia? My view is no- the problem with describing C₂O₃ as a carbonyl complex is that the C-C bond shortening is better described as a due to pi (p - p) overlap rather than a back bond into an anti bonding orbital. T metal carbonyl complexes are strong because of the d electrons which back bond ( the d electrons are at the right symmetry and energy to do this) whereas with C there are no d electrons. Looking at the other side of amphotericity - the example of the gold complex needs a reference. This complex cation contains 6 coordinate distorted octahedral C, a so-called hypervalent complex - not sure if this qualifies C as a lewis base - there are after all 6 adjacent gold atoms. Perhaps a description of atomic carbon in terms of electrophile/ nucleophile would be better than Lewis acid/base? Axiosaurus (talk) 13:48, 22 August 2014 (UTC)[reply]

What particularly is "not a referenceable description", because there are several statements being discussed? I'll restate - the statement does not explicitly state that carbon suboxide is a carbonyl complex, that is an inference. Furthermore, back-bonding can only occur for T metal complexes, and is not the sole explanation of bond shortening in complexes. For example, aluminium carbonyl complexes, which have no back-bonding, yet are described as "complexes".

Regarding the carbon-gold complex, I'll introduce you to the concept of bridging ligands, where it uses this complex as an example. Plasmic Physics (talk) 04:43, 23 August 2014 (UTC)[reply]

To sum up your evidence; lewis acid - your inference from the existence of C₂O₃; lewis base - central C atom in a cluster complex, where I guess you infer that the C has an electron pair or pairs that are donated. These appear to be "all your own work" and are interesting debating points, but there are other more pertinent models in chemistry for the behaviour of C atom in the cases you mention. Axiosaurus (talk) 09:30, 23 August 2014 (UTC)[reply]

I have flagged the gold complex as dubious. It is considered to be a gold(I) complex, i.e. involves ([AuPPh₃]⁺). To charge balance it has a carbide, C^4- at the centre. The complex was considered to be an analog of hypervalent CH₆²⁺, i.e. C^4- (H⁺)₆ Axiosaurus (talk) 07:12, 25 August 2014 (UTC)[reply]

It isn't clear what the ligand is in the amphotericity section lewis acid paragraph, could you clarify. This paper Daniel W. McPherson , Michael L. McKee , Philip B. Shevlin, J. Am. Chem. Soc., 1984, 106 (9), pp 2712–2713 DOI: 10.1021/ja00321a047 reports the production of an intermediate trimethylamine complex, LC:, which then rearranges. Axiosaurus (talk) 12:00, 25 August 2014 (UTC)[reply]

As the paragraph states, the ligand is any electron-pair donating molecular species. So, the ligand can be anything - carbon monoxide, dihydrogen, water, methylidene, etc. Plasmic Physics (talk) 13:44, 25 August 2014 (UTC)[reply]

Article Evaluation[edit]

This article seems to do a good job laying out the basic information about Atomic Carbon. It gives the basic information one should need to get a simple grasp on the subject after reading it. All of the links work, and all of the related links are credible articles. All of the information comes from reliable articles out of scientific books and journals that have been peer-reviewed. Given that a majority of this article is simply explaining scientific fact and where it originates, I find it to be a relatively unbiased article. Fordhuntington1 (talk) 02:34, 28 September 2019 (UTC) Ford[reply]