A complex in chemistry is a structure composed of a central metal atom or ion surrounded by a number of negatively charged ions or neutral molecules possesing lone pairs.
The ions/molecules surrounding the metal are called ligands.
The basic procedure for naming a complex:
- Write the number of ligands surrounding the central metal ion/atom using: mono-, di-, tetra-, penta-, and hexa.
- Write the name of the ligands (in alphabetical order) appending an o for anions: fluoro, chloro, cyano. Neutral ligands keep their original name.
- Name the central atom/ion appending -ate if the atom is negative. Neutral or positive atoms/ions keep their original name.
eg. [NiCl4]2- = tetrachloronickel (II) ion
Transition metals make good central ions for complexes.