On the basis of valence bond theory explain the nature of bonding in [CoF6]3 ion.
The oxidation state of cobalt in this complex is +3. Hence, we have
F− ion provides a weak ligand field and is unable to pair up the unpaired electrons of the 3d orbitals. Hence, six equivalent hybrid orbitals are obtained by mixing of one 4s, three 4p and two 4d orbitals. Six empty sp3d2 hybrid orbitals are filled up by six electron pairs provided by F− ion. The highly paramagnetic nature of the complex further confirms the presence of four unpaired electrons.
As d-orbitals of the outermost shell take part in hybridisation, the complexes thus formed are called outer orbital complexes.