Do ligands in ionisation isomerism interchange? The text says:


  This form of isomerism arises when the counter ion in a complex
  salt is itself a potential ligand and can displace ligand which can
  then become the counter ion.


For other structural isomers that I studied in coordination compounds I simply thought that those  compounds (structural isomers) separately exist. In fact I think of structural isomers in coordination chemistry this way only that these are independently existing with different properties but same molecular formula so we study them.

But the text above is confusing it seems that they convert like resonating structures or conformation isomers.

What is true? If they do interchange then isn't this a contradiction to Werner's theory that postulates that secondary valencies are non ionisable.

note:the below problems is related to one of the comments:


  
    Please Consider this problem-"Give evidences that [Co(NH3)5Cl]So4 and [Co(NH3)5 So4]Cl are ionisation isomers".
  
  
  Here we test by dissloving them in water and reacting them separately
  with silver and barium ions  to test for counter ions.One gives
  AgCl and other BaSo4 as ppt. .Now if there is equlibrium like keto-
  enol tautomerism then only one of the two isomers should be stable in water 
  then why such kinds of evidences are given?
Actually, in the ionisation isomerism the ligands do not interchange. They get displaced. Thus one ion becomes counter ion for the other. When one has look at the molecular formula it seems the ligands in the coordination sphere are interchanged with the ligands outside the sphere. So, this does not cross out Werner’s theory as there is displacement of ion and not just interchange.