File:Chapter-21 Coordination Chemistry (Introduction) pp 174-178.pdf

In coordination compounds there is a 3rd bracket. The space within the 3rd bracket is to be treated as coordination sphere contains metal and non metals (ligands). The space outside the 3rd bracket treated as ionization sphere contains ions. Non metallic part (Lewis base) donates electrons and metallic part (Lewis acid) accepts those electrons in their vacant s, p and d orbitals. In this way, non metallic part ligated to the metallic part through coordinate bond. Thus, non metallic part within the coordination sphere is to be treated as ligand. So, shortly we can say, coordination complex is the product of a Lewis acid-Lewis base reaction in which neutral molecules or ions (ligands) bond to a central metal atom (or ion) through coordinate covalent bonds. Coordination compounds are those molecular compounds which retain their identities even when dissolved in water or any other solvent and their properties are completely different from those of the constituents.