Give the oxidation state, d orbital occupation and coordination number of the central metal ion in the following complexes:

(i) K3[Co(C2O4)3] (iii) (NH4)2[CoF4]


(ii) cis-[CrCl2(en)2]Cl (iv) [Mn(H2O)6]SO4

(i) Overall charge balance:

X + 3(-2) = -3


X = + 3


Oxidation state of Co is + 3.


As there are 3 oxolate ion and being bidentate, coordination no. Of complex is 6. So it is octahedral complex.


d orbital occupation: t2g6eg0(oxolate ion is weak field ligand , does not cause pairing of electron as the energy required for pairing of electron is more than CFSE).


(ii) Overall charge balance:


X + balance4(-1) = -2


X = + 2


Oxidation state of Co is + 2.


As there are 4 fluoride ion , coordination no. Of complex is 4 i.e. Tetrahedral complex.


d orbital occupation: eg4t2g3(fluoride ion is weak field ligand , does not cause pairing of electron as the energy required for pairing of electron is more than CFSE).


(iii) Overall charge balance:


X + 2(-1) + 2(0) = + 1


X = + 3


Oxidation state of Cr is + 3


Coordination no. Of complex is 6. (-en is a bidentate ligand). Octahedral complex.


d orbital complex: t2g3


(iv) Ovearll charge balance:


X + 6(0) = + 2


X = + 2


Oxidation state of Mn is + 2.


Coordination no. Of complex is 6. Octahedral complex.


d orbital occupation: t2g3eg2(water is weak field ligand, does not cause pairing of the electron).


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