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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Francopper on March 25, 2010, 09:56:07 AM

Title: [Co(edta)]- enantiomers resolution?
Post by: Francopper on March 25, 2010, 09:56:07 AM

Hi
This is my first post in the forums. I'd like to know if anyone has ever heard of how the edta-cobaltate(III) anion, [Co(edta)]-, is resolved into enantiomers. I mean, what is the procedure that has to be carried out to get the enantiomers separated?
Thank you all.

Title: Re: [Co(edta)]- enantiomers resolution?
Post by: sjb on March 25, 2010, 02:20:15 PM

Probably no different to resolving other enantiomeric pairs, so in short forming diastereomeric pairs somehow that can be separated, then reforming the original enantiomers

Title: Re: [Co(edta)]- enantiomers resolution?
Post by: Francopper on March 25, 2010, 06:27:11 PM

Thanks sjb. Do you know of any reaction that could produce the diastereomeric pair and in what conditions they can be separated? Difference in melting points, perhaps?

Title: Re: [Co(edta)]- enantiomers resolution?
Post by: sjb on March 27, 2010, 01:31:53 PM

Not specifically in this case, no, sorry.

However, I have for instance resolved a complex amino acid with a chiral amine, by preferential crystallisation of one of the salts.

Anything in priniciple goes, so you may be lucky in getting diasteromers that are well separated by TLC or similar.

Title: Re: [Co(edta)]- enantiomers resolution?
Post by: nj_bartel on March 27, 2010, 02:54:46 PM

I haven't taken inorganic chem, but out of curiosity, how is that complex chiral?

Title: Re: [Co(edta)]- enantiomers resolution?
Post by: Francopper on March 27, 2010, 07:06:25 PM

Thanks, I guess preferential crystallisation is the key. I'll do a little bit of research on that.
nj:bartel, here's a picture of one of the enantiomers (Let M be Co)
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fa%2Fae%2FMedta.png&hash=c83af4232a6a059f74e34daf9e8b3fcbb9f8e0f3)
If you imagine the mirror image of this enantiomer, it would be the one that has (looking from this angle) the front nitrogen atom bonded to an acetate which would be bonded to the top of the complex (the one in the picture in bonded to the bottom), and the back nitrogen atom bonded to an acetate which would be bonded to the bottom of the complex (the one in the picture is bonded to the top).
This may sound quite difficult to understand, but the the easi est way to see it is: draw the mirror image of the  complex of the picture, and turning it around in all the ways that you can imagine, convince youself that they're not the same complex.

Title: Re: [Co(edta)]- enantiomers resolution?
Post by: nj_bartel on March 27, 2010, 07:37:02 PM

That does make sense.  Very clear explanation.  Thanks a bunch :)