What is the behavior of organometallic compounds on TLC? What is the best method for their detection?
It really depends if your compound is air or moisture sensitive. I know ferrocene and acetoferrocene behave as organic compounds on TLC and can be separated. Without knowing more about your complex, I say, just give it a go. never hurts to experiment.
It definitely depends on the complex, but it can work well. As Charles said, ferrocene and its derivatives can be TLC'ed (I actually did that way back when I was TA'ing ochem lab... it was in the ochem labs for the students I was TA'ing).
If it is non-poliar, it will flow pretty well on silica. If its sensitive, try basic aliumina. If its a very polar complex, you will need more polar solvents. I know some Re and Mo complexes can be TLC'ed.
Ionic complexes generally don't flow, but I know some acetontrile adducts can be eluted with pure acetonitrile.
Detect them using iodine vapors.Use an iodine chamber for this purpose with some iodine crystals inside the chamber. Also concentrated sulfuric acid can be used for organic compounds.
Behavior of organometallic compounds on TLC is simple : stable to H2O compounds can be separated; non-stable will decomposed. Most popular sorbents contain -OH groups on surface ( Al-OH for alumina, Si-OH for silicagel, C-OH for cellulose), and after calcination have lost this groups simultaneously with sorption capacity.
However, RP-silicagel, florisil (magnesium silicate) and activated carbon can be used in organometallics separation in inert atmosphere.
Detection is specific : non-reactive can be detected as usually, reactive organometallics are good reductants so to UV-indication will be added color reactions.
Most compounds survive TLC or even column chromatographic work-up even though they might be sensitive to H2O or oxygen. It is important to heat the TLC plates for at least 12 h at 120 °C to remove most of the H2O that is bound in the silica gel. After that, put them into a glove box and do your separation. Usually, organometallic stuff should have some colour so you can easily see what happens on the plate. After you seperated the mixture, you can cut the coloured bands with a scissor. Cut these separated bands into small pieces and add THF or dicholomethane to redissolve the desired compounds. However, that method will only work for small amounts of product since the amount of silical gel on the plates is rather small. If you want to separate larger amounts you should use coloumn chromatography with Schlenk technique to purify your product.
Good luck...
@Christoph Schwarzmaier... Heating the plates at 120°C for 12 h is going to burn the plate I believe. As far as TLC is concerned, heating the plates for 30 min at 110°C is sufficient to activate the plates (for removal of moisture and air entrapped in the capillary pores). In case the plates are made manually using glass plates, after spreading silica gel-G as a layer, they are allowed to air dry and then prior to use these plates are activated at 110°C for 30 min. If you are using pre-prepared plates with silica gel coated on aluminium sheets or glass plates, they are supplied as a ready to use material. Just an activation is required with the same protocol of 30 min heating at 110°C. I am a little confused with the time and temperature you have mentioned.
Regards
I did the purification of organometallic and coordination compounds with TLC and Column chromatography quite regularly. For TLC, I used commercially available TLC plates with silica gel on aluminium. Drying at 120 °C over night has never been a problem so far. In my experience, you need that long drying times to remove as much water traces as possible. Ideally you put the hot TLC plates directly into the glove box, since the evacutaion process removes even more H2O. In case of silica gel for column chromatography, I heat it up to 120 °C for 2 days in high vacuum to get it sufficiently dry.
Regards
Heating plates at 120 oC will not damage the aluminium metal backed plates, I know that some plates are plastic or glass backed but I have always found that aluminium backed ones work well.
When I worked for Tony Hill (AF Hill) I did use chromatography sometimes on organometallics, Tony had a system for doing column chromatography at -40 oC to reduce the decomp of the compounds on the silica. Also the chromatography was done under inert conditions.
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