An octahedral complex of Co 3 + is diamagnetic. The hybridisation involved in the formation of the complex…

${}_{27}{\text{Co}}^{3+}$ has 24 Electrons i.e 6 electrons in inner 3d orbital of central metal ion for diamagnetic behaviour these d⁶ Electrons have to be paired and due to pairing two inner d-orbitals get empty and hybridisation is ${\mathrm{d}}^2{\mathrm{sp}}^3$.