Werner’s experiments

1. Werner’s experiments
Dr. Mithil Fal Desai
Shree Mallikarjun and Shri Chetan
Manju Desai College Canacona Goa
Alfred Werner
Noble prize in 1913

2. Experiment 1 and Observations
CoCl3 + 6NH3
CoCl3 + 5NH3
CoCl3 + 4NH3
CoCl3 6NH3
CoCl3 5NH3
CoCl3 4NH3
A
B
C

3. CoCl3 5NH3
CoCl3 4NH3
AgNO3
AgNO3
AgNO3
CoCl3 6NH3
Solution + 3AgCl
Solution + 2AgCl
Solution + 1AgCl
Experiment 2 and Observations

4. Conclusions
A. Werner was able to explain the nature of bonding in complexes. He
concluded in complexes the metal ion shows two kinds of valency:
Primary valency is number of charges on metal ion (non directional).
Secondary valency is number of ligands around the metal ion (directional).
CoCl3
.6NH3
Three primary valencies and six secondary valencies

5. Old and New representation of complexes
CoCl3 5NH3
CoCl3 4NH3
CoCl3 6NH3
[Co(NH3)6]Cl3
[Co(NH3)5Cl]Cl2
[Co(NH3)4Cl2]Cl

6. Possible shape for complexes with six
secondary valencies

7. What could be the
correct shape of the
complexes with six
secondary valencies?
Complex
Observed
isomers
Theoretically predicted structures
Trigonal prism Hexagonal Octahedral
[MX6] 1 1 1 1
[MX5Y] 1 1 1 1
[MX4Y2] 2 3 3 2
[MX3Y3] 2 3 3 2