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Question
On the basis of crystal field theory explain why Co(III) forms paramagnetic octahedral complex with weak field ligands whereas it forms diamagnetic octahedral complex with strong field ligands.
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Solution
With weak field ligands; ∆0 < p, the electronic configuration of Co (III) will be \[\ce{t^4_{2g} e^2_g}\] and it has 4 unpaired electrons and is paramagnetic. With strong field ligands, ∆0 > p, the electronic configuration will be \[\ce{t^6_{2g} e^0_g}\]. It has no unpaired electrons and is diamagnetic.
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The correct statements are:
On the basis of Crystal Field theory, write the electronic configuration for the d5 ion with a strong field ligand for which Δ0 > P.
On the basis of Crystal Field Theory, write the electronic configuration of d4 ion if Δ0 > P.
