(i) Draw the geometrical isomers of complex [Co(en)2Cl2]+ .
(ii) On the basis of crystal field theory, write the electronic configuration for d4 ion if Δ0>P.
(iii) [NiCl4]2− is paramagnetic, while [Ni(CO)4] is diamagnetic, though both are tetrahedral. Why? (Atomic number of Ni = 28)
(i) Geometrical isomers of [Co(en)2Cl2]+ :
(ii)If Δ0>P, it becomes more energetically favourable for the fourth electron to occupy a t2g orbital with configuration te.
(iii) In [NiCl4]2− , Ni is in the +2 state. Cl− is a ligand which is a weak field ligand which does not cause pairing of unpaired 3d electrons. Hence, it is paramagnetic.
In [Ni(CO)4], Ni has 0 oxidation state. CO is a strong field ligand, which causes pairing of unpaired 3d electrons. No unpaired electrons are present in this case. So, it is diamagnetic.