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Examples Based on Postulates of Werner’s Theory:


Werner’s study structures of various cobalt ammines and form a series of complex which is called Werner’s series and it is given below:

Cobalt has a primary valency (oxidation state) of three and exhibit secondary valency (coordination number) of 6. The secondary valencies are represented by thick lines and the primary valency is represented by broken lines.

(1) CoCl3.6NH3 ComplexIn this compound, the coordination number of cobalt is and all the 6 secondary valencies are satisfied by NH3 molecules (the black solid lines). The 3 primary valencies are satisfied by chloride ions (represented by dotted line). These are non-directional in character. These chloride ions are instantaneously precipitated on the addition of silver nitrate. The total number of ions in this case is 4, three chloride ions and one complex ion. The central ion and the neutral molecules or ions satisfying secondary valencies are written in a square bracket while writing the formula of the compound. Hence the complex may be written as [Co(NH3)6]Cl3 and as shown as in fig. 
(2) CoCl3.5NH3 complex: In this compound the coordination number of cobalt is also 6 but the number of NH3 molecule is decreased to 5 from 6 and one remaining position is now occupied by chloride ion. This chloride ion exhibits the dual behaviour as it has primary as well as secondary valency. Secondary valency is shown by full line and the primary valency is shown by dotted line in the fig. This structure satisfies the 3 primary and 6 secondary valencies of cobalt. Hence the complex formed may be formulated by writing five ammonia molecules and one chloride ion inside the square brackets and the two chloride ions outside the brackets [CoCl(NH3)5]Cl2.
(3) CoCl3.4NH3 complex: In this compound, two chloride ions exhibit dual behaviour of satisfying both Primary and Secondary Valencies. This compound will give precipitate with silver nitrate corresponding to only one Cl- ion and the total number of ions in this case is 2. Hence it can be formulated as [CoCl2(NH3)4]Cl.
(4) CoCl3.3NH3 complexIn this compound, three chloride ions satisfy primary as well as secondary valency. No Cl- will be precipitated on the addition of silver nitrate at room temperature. Therefore, the complex compound behave as neutral non conducting molecule. It may be formulated as [CoCl3(NH3)3].

Colour Coordination compounds of CoCl3 with NH3: The important aspect of the structure of five different complexes of CoCl3 with ammonia prepared by Werner is shown in table.


SN
Werner Complex
Colour of complexes
Naming of complexes based on colour
1
CoCl3.6NH3
[Co(NH3)6]Cl3
Luteo complex
2
CoCl3.5NH3
[Co(NH3)5Cl]Cl2
Purpureo complex
3
CoCl3.4NH3
[Co(NH3)4Cl2]Cl
Praseo  complex
4
CoCl3.3NH3
[Co(NH3)3Cl3]
Violeo complex


Coordination compounds of CoCl3 with NH3:
SN
Werner Complex
Modern Formula
Number of Cl- Ions precipitate  with AgNO3
Total number ions formed
1
CoCl3.6NH3
[Co(NH3)6]Cl3
3
4
2
CoCl3.5NH3
[Co(NH3)5Cl]Cl2
2
3
3
CoCl3.4NH3
[Co(NH3)4Cl2]Cl
1
2
4
CoCl3.3NH3
[Co(NH3)3Cl3]
0
0 (Non electrolyte)



Coordination compounds of PtCl4 with NH3:
The important aspect of the structure of five different complexes of PtCl4 with ammonia prepared by Werner is shown in table.

SN
Werner Complex
Modern Formula
Number of Cl- Ions precipitate  with AgNO3
Total number ions formed
1
PtCl4.6NH3
[Pt(NH3)6]Cl4
4
5
2
PtCl4.5NH3
[Pt(NH3)5Cl]Cl3
3
4
3
PtCl4.4NH3
[Pt(NH3)4Cl2]Cl2
2
3
4
PtCl4.3NH3
[Pt(NH3)3Cl3]Cl
1
2
5
PtCl4.2NH3
[Pt(NH3)2Cl4]
0
0 (Non electrolyte)

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