What type of isomerism exists in compounds containing two or more complexes, each of which contains a different set of ligands that can in principle be replaced with a ligand of the other complex?

Coordination isomerism

The correct answer is option 1.  Coordination isomerism.

The type of isomerism that exists in compounds containing two or more complexes, each of which contains a different set of ligands that can, in principle, be replaced with a ligand of the other complex is called Coordination Isomerism. Therefore, the correct option is: Coordination Isomerism