It is quite difficult to give a sound reply without knowing what complex are you referring to. This said, generally speaking, if a metal complex is poorly polar, it will be soluble in chlorinated solvents. This is the case of many complexes featuring organic ligands, especially if the global charge is neutral.

Massimiliano Arca Thank you, sir. My complex is a bipodal ruthenium arene complex. I understand "This is the case of many complexes featuring organic ligands, especially if the global charge is neutral". My query is why does this happen?

In a nutshell, solubility is the result of two competing factors, i.e. the stability of the compound in the solid state (evaluated thermodynamically by means of the lattice enthalpy & Born-Mayer model for ionic compounds) and the interactions with the solvents (salvation free energy & Born model for ionic compounds).

A neutral complex is stabilized in the solid state only by VdWand medium weak non-covalent interactions, such as H-bonds and - possibly in your case - pi-pi interactions.

Interactions with solvents with low polarity are typically weak but the chlorine atom of CH2Cl2 and CHCl3 may well form local interactions, as frequently found in the solid state, where these solvents are often found co-crystallized.

As for solvation, theoretical calculations (DFT, I'd suggest) may help you evaluate the dipole moment of your compound. If this is small enough, solvents with a low polarity (dielectric constants in the range 2-8) may well solubilize it. On the contrary acetonitrile (dielectric constant 37.5) could be too a polar solvent for your compounds.

Dear Srividya Swaminathan many thanks for posting this very interesting technical question on RG. In addition to the experts answers provided by Massimiliano Arca let me just add a few personal observations. Chlorinated solvents, particularly DCM (dichloromethane) are often very good solvents for neutral (and sometimes even salt-like) organometallic complexes. Classical complexes such as [Co(NH3)6]Cl3, however, are soluble only in water but insoluble in all chlorinated organic solvents. Thus one cannot say that metal complexes in general are highly soluble in chlorinated solvents. In the case of certain platinum group organometallic complexes it can even happen that chlorinated solvents react with the metal complexes in the sense of an oxidative addition. In that case toluene is a good alternative. Finally, I'm not surprised to hear that the solubility behavior of your complexes in acetonitrile is completely different. I remember that we occasionally had organometallic complexes which were highly soluble even in n-pentane and n-hexane, but at the same time insoluble in acetonitrile. However, the solubility in acetonitrile can increase significantly upon heating, so that acetonitrile is often a very good solvent for getting single-crystals.

Good luck with your work and best wishes, Frank Edelmann