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Ligand field theory

red_heat_cat - 1-12-2006 at 08:29

Does anybody know the name of the ligand " C2- " ?

Nerro - 1-12-2006 at 08:47

Can you give an example of a complex that contains this ligand?

red_heat_cat - 1-12-2006 at 08:54

I just know that the complex contains Cu2+ and C2- . The central atom is no problem for me but I am searching for a long time what ligand this is.

JohnWW - 1-12-2006 at 09:58

I think you mean the acetylide anion, -C[triplebond]C-

Dr. Beaker - 1-12-2006 at 11:15

alkilydene?
i.e metal carbene

Nerro - 1-12-2006 at 11:45

Are you sure its not C22- or CH22-?

If it really is C2- Then you have a carbon diradical...

[Edited on Fri/Dec/2006 by Nerro]

chemoleo - 1-12-2006 at 18:39

Eh, Nerro? Hardly a radical. Acetylene is an ever so weak acid, and does form, as JohnWW says, the acetylide anion -(C#C)-. Such as CuC2, or CaC2.

guy - 1-12-2006 at 21:34

I dont think Cu(2+) forms an acetylide, Cu(+) does. It should be Cu2C2, the explosive cuprous acetylide.

And how is this Ligand field theory?

Nicodem - 2-12-2006 at 02:08

Cu(2+) certainly can't form an acetylide since it oxidizes such anion to carbon. Cu2C2 has no acetylidic ligand since it is mostly a covalent compound (the Cu-C bonds barely have any ionic character at all). The only true ionic acetylides are the sodium acetylides and acetylides of other alkali metals, but still there is little in the context of ligands and complexes to discuss here. Besides the originator of the thread spoke of no acetylides, but of a certain C(2-) ion that I really can not imagine how could it exist and what weird hybridization would the outer orbitals form to allow something like that. All the two valent carbon species that I know of, have the carbon in the 2+ oxidation state.

Nerro - 2-12-2006 at 09:08

Quote:

Originally posted by chemoleo
Eh, Nerro? Hardly a radical. Acetylene is an ever so weak acid, and does form, as JohnWW says, the acetylide anion -(C#C)-. Such as CuC2, or CaC2.

What the hell...?

C22- is the acetilide ion, C2- would be a carbon with 2 aditional electrons which would give it an outer shell with 2s2 2p4 which is misses two electrons which would make it a radical.

I don't mean to bitch at mods here but please read my post before you accuse me of not knowing what the hell an acetilide ion is!

chemoleo - 2-12-2006 at 11:07

I see. I did think that post was a little out of character.... looks like because I misread it. Accept my humble apologies.

On the matter of copper I or II acetylide - For some reason I seem to remember that preps for both versions exist. Unfortunately I could find only one prep, that for Cu2C2. However, Philou writes on CuC2, which is obtained by disproportionation of Cu2C2.

Anyway, a related question to the original one - CO exists. Are there analogues, CS, CTe etc? Or even some stabilised variant such as C(phenyl)2?

The_Davster - 2-12-2006 at 11:22

Quote:

Originally posted by chemoleo
CO exists. Are there analogues, CS, CTe etc? Or even some stabilised variant such as C(phenyl)2?

The size difference for carbon compared to the lower chalcogens is too extreme for an effective bond to form. There is almost no stabilization by forming the CS bond, let alone for Te. I had to prove CS would not exist on an exam...I should dig that up. If you want to see a molecular orbital diagram explanation that is.

To bad they do not exist, they could be interesting...

guy - 2-12-2006 at 15:40

Quote:

Originally posted by The_Davster

Quote:

Originally posted by chemoleo
CO exists. Are there analogues, CS, CTe etc? Or even some stabilised variant such as C(phenyl)2?

THere is a 0.3 electronegativity difference between C and S. I wouldn't say they dont exist, but that they are extremely reactive. There is a very small stabilization due to the electronegativity differece, this would cause it to have a very weak bond.

Nerro - 2-12-2006 at 16:57

In CS, would the S bond with its 3p orbitals? And if it would, how substancial would the overlap between the C's p orbitals and the S's p orbitals be?

unionised - 3-12-2006 at 06:10

C(phenyl)2 exists, it's called diphenyl carbene but it isn't stable