Main Postulates

I) The metal ligand bond arises by donation of pair of electrons by ligands to the central metal atom.

II) To accommodate these electrons the metal ion must possess requisite number of vacant orbitals of equal energy. These orbitals of the metal atom undergo hybridisation to give hybrid orbitals.

III) Sometimes the unpaired (n-1)d orbitals pair up before bond formation making (n-1)d orbitals vacant. The central metal atom makes available number of d-orbitals equal to its co-ordination number.

iv) The metal ligand bonds are thus formed by donation of electron pairs by the ligands to the empty hybridized orbitals. These bonds are equal in strength and directional in nature.

v) Octahadral, square planar and tetrahedral complexes are formed as a result of d²sp³ (or sp³ d²), dsp² and sp³ hybridization respectively.