[firzzy87]

Can a very acidic solution effect the ability of bidentate ligand to form a complex formation of iron (III) ion >

[haozhm]

i think the impacts of formation of complexes are very much, such as temperature, solvents, ratio, PH and so on. for the question you quetoed, i think the acidity has a little impact on the formation of complex. and you can have a try firstly!

[Yggdrasil]

Which bidentate ligand are you talking about?  Some ligands, such as those with amines, may be affected by pH because protonation of the amine at low pH would tie up the lone pair which forms the bond with the metal ion.

[firzzy87]

i mean a bidentate ligands like oxalate ion

[Borek]

High pH - iron is precipitated by OH^-, low pH - oxalate gets protonated. Both processes may prevent complex formation. All depends on the equilibrium constants.