Coordination Compounds

Coordination Compounds

Question

Name of the following coordination entities and describe their structure:

(i) [Fe (CN)6]4-

(ii) [Cr (NH3)4Cl2]+

(iii) [Ni (CN) 4]2-

(Atomic numbers Fe = 26. Cr = 24, Ni = 28

Answer

(i) [Fe (CN)6]4-

IUPAC name: Hexacyanoferrate (II)

Structure: Oxidation state of iron is + 2

Fe2+: Electronic configuration is 3d6 4s° 4p°

Orbitals of Fe2+ ions:

 

As CN- is a strong field ligand, it causes the pairing of unpaired 3d electrons

 

 

Since there are six ligands around the central metal ion, the most feasible hydrization is d2sp3.

d2sp2 hybridized orbitals of Fe2+ are:

 

 

6 electron pairs from CN-1 ions occupy the six hybrid d2sp3 orbitals

Then,

 

Hence, the structure of [Fe (CN)6]4- is octahedral.

(ii) [Cr (NH3)4Cl2] +

Name: Tetraamminedichlorido chromium (III)

Electronic configuration of Cr: 3d4 4s2

Electronic configuration of Cr3+: 3d3

 

 

Structure is octahedral with d2sp3 hybridization.

(iii) [Ni (CN) 4]2-

Name: Tetracyanonickelate (II)

Structure: Here oxidation state of Ni is + 2

Ni + 2: Electronic configuration is 3d8 4s0 4p0

Orbitals of Ni2+ ion

 

 

As CN-1is a strong field ligand, it causes the pairing of unpaired 3d electrons.

 

 

Since, there are four ligands around the central metal ion, the most feasible hybridization is dsp2

 

 

4 electron pairs from CN-1 ions occupy the four hybrid dsp2 orbitals

Then,

 

 

Hence, the structure of [Ni(CN)4]2- is square planar.

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