The reaction between N-S bidentate/ONS tridendate ligand (TSC) and cis[RuCl2(DMSO)4] in ethanol by reflux is complete as seen from TLC chromatography. But removing the excess solvent through evaporation is not yielding the powdery precipitate. How to isolate the pure Ruthenium DMSO complexes from the reaction mixture?
First - how you manage the DMSO during storage, during reaction prep and during the reaction itself is important. DMSO is strognly hydroscopic so there will be some % of water present. I cannot say how this will affect your reaction, if at all, however, water does affect evaporation / boiling properties of DMSO and ethanol.
To remove the ethanol, dry it under a really deep vacuum in a really good evaporator. Most rotary evaporators are not good enough, they leak too much and the pumps are too weak. you need to be achieving vacuum levels consistently below 0.5mBar to get this kind of sample really dry. For that, you will need an oil based mechanical pump (not recommended as the solvent will kill it) or a dry vacuum pump, scroll type (recommended). Yes, they are expensive.
Whichever drying system you use, ensure that ALL the components are compatible with all your solvents used. If you plan on using a freeze dryer, you will need one with a refrigerated shelf to guarantee a good result. Watch out on all freeze dryers as many have plastic parts, which do not mix well with DMSO.
Kind regards,
Rob
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