The Valence Bond Theory (VBT) explains with reasonable success, the
formation, magnetic behaviour and geometrical shapes of coordination compounds It, however, fails to provide a quantitative interpretation of magnetic behaviour
and has nothing to say about the optical properties of these compounds The Crystal Field Theory (CFT) to coordination compounds is based on
the effect of different crystal fields (provided by the ligands taken as point charges),
For example, impure nickel is converted to [Ni(CO)4], which is
decomposed to yield pure nickel •
Coordination compounds are of great importance in biological
systems