Ethylenediamine tetraacetate  $\left({\mathrm{EDTA}}^{4-}\right)$ is one of the most important chelating agent used in co-ordination chemistry. Find the number of ${\mathrm{sp}}^2$ hybridised carbon atoms in  ${\mathrm{EDTA}}^4$ is given as:

 

EDTA is a multidentate ligand because it can donate six pairs of electrons - two pairs from the two nitrogen atoms and four pairs from the four terminal oxygen atoms of the ${\mathrm{COO}}^{-}$groups. A divalent chelate's structure  ${\mathrm{Co}}^{3+}$ Each N has four $\mathrm{N}-\mathrm{CO}-\mathrm{O}$ thus totaling eight bonds $\mathrm{N}-\mathrm{Co}-\mathrm{O}$ bonds.