A complex ion has a metal ion or atom surrounded by a number of other molecules, atoms or ions. These molecules, ions or atoms which donate one or more electrons or share their electrons with the central ion or atom are called complexing agents or ligands. Ligands can be a part of positively charged or negatively complex ions. Ammonia in [CO(NH3)6]3+and chloride ions in [ptCl6]2- are examples of ligands or complexing agents. Foliar sprays of micronutrients such as Fe-EDDHA or Cu-EDTA contain the ligands EDDHA and EDTA.
