Write down the IUPAC name for each of the following complexes and indicate the oxidation state, electronic configuration and coordination number

(i) The complex is an anion with chromium as central atom, 2 water molecules and 2 oxolate ions with -2 negative charge each. Balance overall charge as 0, we get oxidation state of Cr as: 

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

X=+3.

Name of compound: potassium diaquadioxolatochromate(III) trihydrate.

Electronic configuration of Cr: 3d3 , t2g3

Co-ordination no. Of complex: 6 ( as oxolate ion is bidentate ligand)

As both the water molecule and oxolate ion are weak field ligand , so they do not cause pairing up of electron.

µ=[n(n+2)]1/2

µ=[3×5]1/2

µ=4BM.

(ii) The complex is a cation with cobalt as central atom, five neutral ammonia molecules and one chloride ion. Balance overall charge as 0, we get,

X+5(0)+1(-1)=+2

X=+3.

Oxidation state of cobalt is +3.

Name of compound is pentaamminechloridocobalt(III) chloride.

Coordination no. is 6.

Electronic configuration of cobalt: 3d6

As ammonia is a strong field ligand so it causes pairing of the electron. No. Of unpaired electrons:0

µ=[n(n+2)]1/2

µ=[0]1/2

µ=0BM.

(iii) The complex is neutral with chromium as central atom, three chloride ions and 3 pyridine molecules which are neutral.

Name of compound is trichloridotripyridinechromium(III).

Balance overall charge as 0.

X+3(-1)+3(0)=0

X=+3.

Oxidation state of chromium is +3.

Electronic configuration:3d3

Coordination no. Is 6.

As chloride ion and pyridine molecule botha re weak field ligand so they do not cause pairing of electron.

µ=[n(n+2)]1/2

µ=[3×5]1/2

µ=4BM

(iv) The complex is anion with iron as central atom, and 4 chloride ions. Balance overall charge:

X+4(-1)=-1

X=+3

Oxidation state of Fe: +3.

Electronic configuration:3d6

Name of compound: Caesium tetrachloridoferrate(III).

Coordination no. is 4.

As chloride ion is weak field ligand ,it does not cause pairing of electron.

µ=[n(n+2)]1/2

µ=[4×6]1/2

µ=5BM

Steriochemistry is optically inactive as it is a tetrahedral complex and the relative position of each ligand will be same in all condition.

(v) The complex is anion with manganese as central atom , and six cyanide ions with each unit ngative charge. Balance overall charge

X+ 6(-1)=-4

X=+2

Oxidation state of Mn=+2

Electronic configuration of Mn:3d3

Name of compound: potassium hexacyanoferrate(III)

Coordination no. Is 6.

As cyanide ions are strong field ligand , they cause pairing of electrons.

No. Of unpaired electrons is 1.

µ=[n(n+2)]1/2

µ=[1×3]1/2

µ=1.732BM.

Steriochemistry: optically inactive .