I'm reacting a schiff base from salicylaldehyde and p-chloroaniline and trying to react it with mangan(II) salts. I've tried mangan(II) chloride and mangan(II)acetate but both likely produce the same result: blackish brown solid, and the ligand had always precipitated in the end. What should I reconsider in this trial ? Thank you
You may try one-pot-synthesis.
Use dry toluene, anhydrous manganese (II)chloride and your Schiff base forming components in a single pot and then heat at an appropriate temperature under stirring. This method should produce the complex directly.
Hope, your luck favours you in this.
With best wishes,
ARB
Devina Wijaya Mn chemistry is very much sensitive to the pH of the solution. If you add 2-3 drops of aq. Et3N in your reaction medium, the solution color becomes light reddish and pH remains below 8. If you add more Et3N, Mn precipitates out as Mn(OH)2 (brownish-black). Et3N makes the solution basic and the Schiff base -OH becomes -O-(alkoxide). Alkoxide easily forms the Mn complex. If you filter the solution and kept for slow evaporation, you will find the single crystals of Mn complex.
Reference: A. Jana et al., Polyhedron 62(2013) 51-60
[A [2x2] Cu4 molecular grid and a Mn5 cluster derived from a 1-(2-pyridyl)pyrazole based polytopic ligand – Synthesis, structure, magnetic properties and catalytic activity in the allylic oxidation of cyclohexene]
Hi
Toluene should be dried and distilled before use. Use nitrogen atmosphere and mangan(II)acetate. Slightly basic medium is favorable for this type of Mn ion complex formation.
Ashis Ranjan Bandyopadhyay thank you for your suggestion, I will have it tried. But will the salts dissolved in toluene too ?
Atanu Jana by aq. Et3N do you mean aqueous solution of Et3N (Et3N diluted in water) ? or the Et3N itself? thank you...
Devina Wijaya Et3N should be diluted with water. This diluted aq Et3N will help you to create the desired pH.
Devina Wijaya
Please have in the back of your mind the following two points, that might be contributing towards making this problem a complex one.
(a) One of the components in this case is an aldehyde, which is capable of giving
rise to products out of Aldol condensation.
(b) The aldehyde contains a hydroxy group, which is capable of making a complex with the metal atom.
Please note further the following points as well. These are with respect to your response to my earlier answer.
(1) I would rather use anhydrous MnCl2 in this reaction.
(2) Please carry out the reaction in freshly distilled dry toluene (distilled over
Na-wire).
(3) The above-mentioned anhydrous manganese salt is likely to be soluble in dry
toluene. Please check this by adding powdered salt of Mn into dry toluene
and observe carefully while stirring.
I would also like to request you to search for many earlier discussions on this topic in Researchgate This will definitely enrich your knowledge on this.
With best wishes,
ARB
Yes, Mn(II) is stable but very much sensitive on pH medium. I think you can try the same thing by changing solvent polarity. You may can take help of binary mixture of solvent, in addition to that you may can try with Ionic liquid.
You may try below reaction for your synthesis.
1) MnCl2 + KSCN + Schiff base [try CH3OH OR CH3CN as solvent]
1) MnCl2 + NaN3 + Schiff base [try CH3OH OR CH3CN as solvent]
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