the free ligand can become more active than the metal complex
The question is not professional and does not have an answer. What means "active?" Which ligand of what complex?
Yurii V Geletii, I totally agree with you (LOL). We are not sure at all the "activity" is biological, catalytic or even thermal reactivity etc. We can answer nothing.
Why the free ligand can become more "activity" biological, than the metal complex ??
An example of biologicaly active ligand, compare potassium cyanide and iron hexacyanide. Find the answer yourself.
Metal complexes often are much more stable than ligand itself and if you looking for reason then you should check the gibbs free energy and Coordination complex enthalpy.
Dear Hussein Ali Kadhim Kyhoiesh in order to get a qualified answer to your technical question I think you should be more specific. In what sense do you mean "active"? Are you talking about ligands in coordination chemistry or in biochemistry? I strongly sggest that you have a closer look at the very instructive example provided by Yurii V Geletii. The free cyanide ion e.g. in potassium cyanide, KCN, is very "active" in the sense of highly toxic. When it forms coordination compounds with iron, the "activity" depends on the oxidation state of iron in these compounds. The yellow iron(II) complex K4[Fe(CN)6] is so stable that it is not significantly toxic any more despite the presence of six cyanide ligands. Red K3[Fe(CN)6] is kinetically less stable in solution. Thus the iron(III) complex is much more toxic because it can dissociate free CN– ions. The opposite in terms of stability is also possible. Free chloride ions are indefinitely stable, while hexachloro complexes of the rare-earth (RE) elements, [RECl6]3–, are difficult to isolate. Given the vast number of possible ligands and complexes it would greatly help if you would narrow down and specify your original question.
With best wishes, Frank Edelmann
I think you need to rewrite the question in more detail. Good luck!
M( Metal )+Ln ( Ligand )= MLn ( Chelate complex ) . Since Chelate complex is more stable than free ligand so free ligand is more reactive .This is called ligand -field stabilisation energy ( LFSE ) .
Dear Dr Hussein Ali Kadhim Kyhoiesh . This depends on :
1. Type of ligand.
2. Type of metal complex.
3. The conditions. Thank you.
The more basic is the ligand, the more easily it can donate electron pairs to the central ion, and hence more easily it can form complexes of greater stability. The ligand that binds H+ firmly form stable complexes with metal ions.Dec 18, 2021
https://www.embibe.com › exams
Stability of Coordination Compounds: Determination, ...
In metal cations, higher oxidation state forms more stable complex than lower oxidation states with ligands such as NH3, H2O, etc. Even few exceptions are there like CO, PMe3, o-phenanthroline, bipyridyl, CN−, which form more stable complex with lower oxidation state metals.
https://www.intechopen.com › chapt...
Stability of Metal Complexes | IntechOpen
The most important characteristics of the central atom, determining the stability of the complex compound, are the degree of oxidation (charge on the central ion in the case of ionic complexes), the dimensions, and the electronic structure.
https://link.springer.com › chapter
Factors Determining the Stability of Complex Compounds in Solution
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