The most amazing field of modern inorganic chemistry is co-ordination chemistry. From last four decades, co-ordination chemistry created its own identity in the Inorganic chemistry. The co-ordinate compounds also referred as complexes is a combination of ligand or chelating agent with metal ions through co-ordinate bonds. Ligands are covalent bonded organic molecules containing lone pair or lone pairs of electrons on heteroatom in the organic moiety. As metal ions are electron deficient so these form co-ordinate bonding between metal ion and ligand. The behaviour of metal ion with different ligands depends upon the sterric hindrance, structure, various substituent and nature of bonding present in ligands as well as screening effect, Kernal effect, atomic number oxidation state of metal ion. It was also observed in complexes that there are primary as well as secondary valencies.