Is there any common methods to replace anions from the metal complexes. Eg: [M(L)6]X2 into [M(L)6]X2 , L = Pyridine / Triazole Ligands. X = Boron trifluoride, perchlorate, nitrate, Trifluoromethane sulfonate etc., Especially small size anions into bigger size anions.
By the usual method in X2 that you want to replace, X is a halide. Thus you react your halide complex with 2 equiv AgX', where X''=BF4-, CF3SO3-, PF6-,etc or with 1 equiv AgX''2, were X"2 is a NO3--, SO4--, etc and simply filter off the separated Ag-halide salt. If you don't need clean complexes or isolate, you can also use alkali metal salts (Li, Na) instead of Ag with your starting halide complex
Thankful Prof., Which kind of the solvent is preferable ? On the conversion time, Is there any possibility of water molecule in the unit cell crystal or not.
Preferably in non-protic but polar solvents. You can chose the one, which solves your cationic complex best. THF, acetone, dioxane,CHCl3, CH2Cl2 etc. Occasionally, you can also use MeOH if others are not suitable. If you use dry solvents you won't expect water in the crystal.
To exchange anions in presented salt (if the complex cation is stable i solution) is also to use ion-exchange resin. The ion-exchange resin should be in form of anion You require to be or in OH form and than, after passing the complex, You can neutralize it with acid with required anion.
Yes, there are some common reactions with Silver salts.
Kindly check your indicated chemical formula.
DK DUTTA
Indeed, anion exchange resins can also be used for replacing anions of some transition metal salts or complexes. However, in case of such sensitive complexes as the ones Ray has drawn, this is not a viable option (decomposition is expected by the required strong acids). Furthermore by using ion-exchange resin in some cases (at least partial) immobilization can take place, i.e. portion of the transition metal (complex) can stick on the resin.
Precipitation reactions, the largest concentration of second anion (law of mass action), electrolysis, and others.
If the ligand to replace is a halide, the way described by Imre Toth is perfectly feasible. AgBF4, AgCF3SO3, AgPF6 or AgNO3 in different non-protic solvents work almost equally fine in many cases.
If you have a complex like e.g. [Re(CO)3Cl3]2- you can even selectively remove 1, 2 or all 3 haldides (and replace them by other ligands).
If in your formula X2 is the counter-ion, then crystallisation with an excess of the desired anion should work. The same principle would work if you add an excess of the desired second anion and then try to extract your complex in a (suitable) two-phase system. (Preparative) HPLC/Ion-exchange chromatography can do a good job if the complex is stable enough (taylor-made HPLC gradient system depending on the compound).
If your complex is soluble in relatively nonpolar solvents such as acetone or dichloromethane, you can often use sodium tetraphenylborate or sodium tetrafluoborate for a metathesis reaction, as sodium chloride isn't very soluble in such solvents.
As Imre wrote, a precipitation method can be used very well, but do not forget to take into consideration, that some complexes with large cations and anions are sparingly soluble- depending on the nature of ions in them - and AgCl or AgX halides will contaminate them. In this case, concentrated solutions of well-soluble sodium salts (NaClO4, NaMnO4, NaBF4) may also be used instad of silver salts, with cooling the reaction mixture, and the precipitated complexes cna be recyrstallized with temperature gradient repeatedly.
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