Q11 of 36 Page 1

Out of [CoF6]3- and [Co(C2O4)3]3-, which one complex is

(i) diamagnetic


(ii) more stable


(iii) outer orbital complex and


(iv) low spin complex?


(Atomic no. of Co = 27)


The Oxidation state of Co in both the complexes is +3

[CoF6]3-


F- is a weak field ligand, the cation Co3+ does not allow to pair electron in its excited state hence there is no pairing takes place, so it is paramagnetic, high spin complex, outer orbital complex with sp3d2 hybridisation.



[Co(C2O4)3]3-As the oxalate have -2 charge and is a strong field ligand, it allows to pair electron of Co in its exited state hence there is pairing of electrons which makes it more stable, so it is diamagnetic, low spin complex, inner orbital complex with d2sp3 hybridisation.



Therefore, from the above information, we can conclude


(i) Diamagnetic complex= [Co(C2O4)3]3-


(ii) More stable complex= [Co(C2O4)3]3-


(iii) Outer orbital complex= [CoF6]3-


(iv) Low spin complex= [Co(C2O4)3]3-

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