I have a Ru(III) complex with Ered = -0.36 V, and I would like to isolate the Ru(II) complex by reducing Ru(III) chemically, does any one know a suitable reducing agent?
Why didn't you try by electrolysis at a fixed potential ? To my opinion, this is the most powerful tool for a redox transformation. Another interest of such a procedure lies in that you do not add potential ligand (such a phosphine) in your reactor...
Dear Manuel, I already tried some zinc dust but it didn't work, I think the cause is that my complex is Ru(III) charged but not neutral, and the redox potential differs betwwen the charged and neutral complexes even they are Ru(III), and consequently it differs from the potential of Zn dust
If think is not enough, you can use Magnesium turnings. Alternativelym if you want an efficient homogeneous reducing agent, you can try sodium naphtalenide in THF. Once you establish the concentration of the solution of NaNaph, you adjust the amount depending on the number of electrons that you want to reduce. In your case, is one electron reduction. The green color of NaNaph disappears upon reaction, so the rective is also self-indicator that the reduction has occured.
I have been using Zn or H3PO2 to generate Ru(II) in situ from RuCl3 and they both worked well. But be sure to have a ligand to "catch" the Ru(II) once is formed.
Zn works well, usually. However it strongly depends on the ability of your ligand(s) to stabilize Ru(II). Moreover, Zn is safer and easier to handle than many other reducing agents.
Depending on how valuable is the ligand sphere for you: There is an old publication from Stephenson and Wilkinson, where they make triphosphanedichlororithenim from ruthenium trichloride hydrate. So a non-innocent ligand as reducing agent.
If you are working with polypyridine ligands the following answer would help you otherwise pls ignore.
Inmost of the Ru(II) polypyridine complex formation RuCl3 is used as the metal salt by just using ethylene glycol as solvent and carrying out reflux the reduction can be effected. In the case of ligands like terpyrdine the Ru(III) to Ru(II), can be carried out by using few drops of N-methyl morpholine as the mild reducing agent during complexation in low boiling solvents.