If the complex is formed by use of inner d-orbitals for hybridisation (written as \ d^2sp^3) ,it is called inner orbital complex.in the formation of inner orbital complex , the electrons of the metal are forced to pair up and hence the complex will be either diamagnetic or will have lesser number of unpaired electrons. Such complexes are Low Spin Complexes.

For example, [math]\left[Fe\ \left(CN_6\right)3^-\right][/math] is inner orbital complex.

If the complex is formed by use of outer d-orbitals for hybridisation (written as sp^3d^2) ,it is called as outer orbital complex.outer orbital complex will have larger number of unpaired electrons since the configuration of the metal ion remains undisturbed. Such complex is also called high spin complexes.

For example, \left(Fe\left(H_2O\right)_63^+\right)is outer orbital complex.

•ligands such as H_2O and halides have high spin and there is no overlapping of electrons in orbitals of metal.