Warner's theory

  • Werner is 1893 gave a theory to Explain the structure of coordination compounds .The fundamental postulates of this theory are-

1)Metals possess two types of valency:,

a) Primary valency or ionizable valency
    
  • This corresponds to the valency or oxidation state of the metal in it's simple salts.

b) Secondary valency or non -ionic

This corresponds to the coordination number of the metal in the complex salts .

  • 2) There is a central metal atom around which natural molecules or anions are coordinated . The natural molecules or anions are called as ligands and the number of coordinate bonds formed by these ligands is known as coordination number .
  • The sphere enclosing the central metal atom and ligands is known as coordination sphere.
  • 3) Each element has a tendency to satisfy both it's primary ans secondry valencies are satisfied by negative ions ,whereas secondary valencies are satisfied either by negative ions or by neutral molecules .


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Warner's theory

  • In certain cases ,the nagative ions may satisfy both the primary and secondary valencies of same metal ions are as follows.

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Warner's theory 



4) The ligands can be arranged in different ways in space and hence, these compounds are capable of showing the phenomenon of isomerism.

5) The total charge on the complex ion is the resultant of the charge of Central metal atom and ligands.

Cr3+   + 6NH3                [Cr(NH3)6]3+

Total charge on complex ion =+3+6×0=+3

Experimental verification


  •  Warner applied his theory to give the structures of complex of Cobalt and Platinum with ammonia which are as follows

1] Cobalt III Amine complex compounds

a) Luteo cobaltic chloride , CoCl3.6NH3


  •  It is an Orange yellow crystalline solid.
  • On treatment with AgNO3, all three chlorine atoms are principitated as  AgCl.this indicates that all the three chlorine atoms are attached to the metal with ionic bond and are present outside the coordination sphere.
  • The conductivity measurement shows the presence of four ions.
  • On the basic of the above facts ,structure of the complex may be given in figure.
  • The primary valencies are represented by solid lines and secondary valency are represented by dotted lines.

b) Roseo Cobaltic chloride,CoCl3.5NH3.H2O

  •  It is pink crystalline solid.
  • On treatment with AgNO3, all the three chlorine atoms are precipitated as AgCl .
  • This indicates that all the three chlorine atoms are attached to the metal with and ionic bond and are present outside the coordination sphere.
  • The conductivity measurement shows the presence of four ions.

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Warner's theory 


  • On the basic of facts the structure of the complex given as follows.

C)Purpureo Cobalt chloride ,CoCl3.5NH3

1) It is violet crystalline solid.
2)On treatment with AgNO3 ,only to chlorine atoms are precipated as AgCl.
This indicates that only two clorine atoms are attached to the metal with an ionic bond and are present outside the Coordination sphere .
3) The conductivity measurement shows the presence of three ions.

d) Praseo cobaltic cloride ,CoCl3 .4NH3

  • It is a great crystalline solid.
  •  On treatment with AgNO3 only one chlorine atom is precipitated as AgCl this indicates that only one chlorine atom is attached to the metal with an ionic bond and is present outside the coordination sphere .
  • On treatment with concentrated H2 SO4, only one chlorine atom  is last as HCl .this indicates that all the 4 ammonia molecules and 2 chlorine atoms are attached to the metal with strong bond and are present in the coordination sphere.
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Warner's theory 
  • The conductivity measurement shows the presence of two ions .On the  basic  of above facts  the structure of the complex may be given.


2] Platinum (4) Ammine complex compounds

  • On treatment with  AgNO3 , all the four chlorine atom are precipitated AgCl .This indicates that the four chlorine atoms are attached to the metal with an ionic bond and are present outside the coordination sphere.
  • On treatment with concentrated H2SO4 all the four chlorine atoms are last as HCL and no (NH4)2)SO4  is obtained. 
  • This indicates that all the six ammonia molecules are attached to the metal with strong bond and are present in the coordination sphere.
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Warner's theory

  • This conductivity measurement shows the presence of five ions .
  • On the  basic of above facts the structure of the complex may be  given.