Question

What is flexidentate ligand? Give examples with structures.

Answer 1

Flexi-dentate ligands are the poly-dentate ligands that do not use all its donor atoms to get coordinated to the metal ion. In some complexes they use a different number of donor atoms while in some, a different. 
For example, ethylene diamine tetraacetic acid (EDTA). It can bind by its two amines and four oxalates giving hexadentate character. However it can show flexi-dentate character as well

This ligand acts as a hexadentate ligand in [Fe (EDTA)]
As a pentadentate ligand in [Cr (OH) (HEDTA)]2- [Co (Br) (HEDTA)]2-
As a tetradentate ligand in [Pd (H2EDTA)]

Answer 2

Answer :

Flexidentate ligands : There are many ligands which have more than one donor atoms (polydentate ligands).

All these ligands have two donor atoms. When these ligands get coordinated to the metal atom or ion, they give rise to the formation of two types of complex compounds. In one type they get linked to the metal atom through one donor atom only while in the formation of another type of the complex compound, they get coordinated to the metal atom through both of its donor atoms.

The examples of such ligands are $SO_4^{2-}$ (both negatively-charged O-atoms are donor atoms), $CO_3^{2-}$ (both negatively-charged O-atoms are donor atoms), $N_2$ (both N-atoms are donor atoms).